What is a copper pipe

What is a copper pipe?

Copper pipe refers to seamless pipe made of copper by pressing or drawing. Copper pipe has the characteristics of good conductivity and thermal conductivity. It is the main material of conductive accessories and heat dissipation accessories of electronic products, and has become the first choice for modern contractors to install tap water pipes, heating and refrigeration pipes in all residential commercial houses. Copper pipe has strong corrosion resistance, is not easy to oxidize, and is not easy to react with some liquid substances, so it is easy to bend. Because of its strong and wear-resistant characteristics, it is often used in electrical, industrial and construction industries. Copper pipes can be produced by extrusion method, continuous casting and rolling method and up drawing method. Copper tube is an important raw material for the processing and manufacturing of refrigeration devices. It is mainly used for two purposes:

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Characteristics of copper pipe

Copper tube has light weight, good thermal conductivity and high low temperature strength. It is commonly used in tap water pipeline, heating and refrigeration pipeline, and can be used in different environments. Copper pipes with small diameter are often used to transport pressurized liquids (such as lubrication system, oil pressure piping system, etc.) and pressure measuring pipes used as instruments. Copper pipe integrates the advantages of metal and non-metal pipe. It is the best connecting pipe in the cold and hot water system. Copper pipe is fire-resistant and heat-resistant. It can still maintain its shape and strength at high temperature without aging.
The pressure resistance of copper pipe is several times or even dozens of times that of plastic pipe and aluminum plastic pipe. It can withstand the highest water pressure in today’s buildings. In hot water environment, with the extension of service life, the pressure bearing capacity of plastic pipe decreases significantly, while the mechanical properties of copper pipe remain unchanged in all thermal temperature ranges, so its pressure bearing capacity will not be reduced and aging will not occur.
The linear expansion coefficient of copper pipe is very small, which is 1/10 of that of plastic pipe. It will not lead to stress fatigue fracture due to excessive thermal expansion and cold contraction.
The strength of copper pipe is greater, and the outer diameter is smaller under the requirement of ensuring the effective inner diameter, which is more suitable for concealed burial.

  • 1. Because the copper pipe is easy to process and connect, it can save materials and total cost during installation, has good stability and reliability, and can save maintenance.
  • 2. Copper is light. For twisted pipe with the same inner diameter, the thickness of ferrous metal is not required for copper pipe. When installed, the transportation cost of copper pipe is smaller, the maintenance is easier and the occupied space is smaller.
  • 3. Copper can change shape. Because copper pipe can bend and deform, it can often be made into elbows and joints. Smooth bending allows copper pipe to bend at any angle.
  • 4. Copper is easy to connect.
  • 5. Copper is safe. No leakage, no combustion support, no toxic gas and corrosion resistance.

Copper pipe is high temperature resistant and can be used in a variety of environments. Compared with this, the disadvantages of many other pipes are obvious. For example, the galvanized steel pipe commonly used in residential buildings in the past is very easy to rust, and the problems such as yellowing of tap water and smaller water flow will occur after a short service time. The strength of other materials will decrease rapidly at high temperature, which will cause unsafe hazards when used in hot water pipes. The melting point of copper is as high as 1083 ℃, and the temperature of hot water system is insignificant to copper pipes.

Classification of copper tubes

Common copper pipes can be divided into the following types:

  • Copper condensing tube, mold copper tube, air conditioning copper tube, all kinds of extruded and drawn (reverse extruded) red copper tube, iron white copper tube, brass tube, bronze tube, white copper tube, beryllium copper tube, tungsten copper tube, phosphorus bronze tube, aluminum bronze tube, tin bronze tube, imported red copper tube, etc.
  • Thin wall copper pipe, capillary copper pipe, hardware copper pipe, special-shaped copper pipe, small copper pipe, pen copper pipe, pen copper pipe, etc;
  • According to the needs of users, square and rectangular mold copper pipes, D-type copper pipes and eccentric copper pipes are processed and produced according to the drawings.

Air conditioning copper pipe

Ordinary air conditioner: the thickness is generally 2 points, 3 points, 0.5mm, 4 points, 0.6mm, 5 points and 6 points, 0.7mm. Mainly used for R22.
Degreasing air conditioning copper pipe: also known as “degreasing air conditioning copper pipe”, it is 0.8mm thick for 2 points and 3 points, and 1.0mm thick for 4 points, 5 points and 6 points. It is mainly used for r410 and other refrigerants.
Specific classification of air conditioning copper pipe materials:

  • Oxygen free copper: including high-purity oxygen free copper (tu0, TU1, TU2) and phosphorus deoxidized copper (TUP, TP1, TP2, etc.), which is characterized by very little oxygen content and a small amount of deoxidizer remains in deoxidized copper;
  • Aerobic copper: it mainly includes ordinary pure copper (T1, T2, T3, etc.) and ductile copper, which is characterized by high oxygen content;
  • Special copper: arsenic copper, silver copper, tellurium copper, etc. it is characterized by adding different trace alloy elements to improve the comprehensive properties of the material.

Now let’s focus on red copper and brass.
Red copper tube: the copper tube used in our refrigeration industry is red copper, with copper content of more than 99.90%. It has the good characteristics of copper metal, a high-quality basic metal. It is widely used in various industrial and civil fields and plays an important role. It mainly includes TP2, T2 and TU1.
TP2 is phosphorus deoxidized copper, containing 0.015-0.04% phosphorus. It has good welding and cold bending performance. It is widely used in the manufacturing fields of air conditioning refrigeration connecting pipe, stove gas path connecting pipe, electric heating pipe and so on.
T2 is pure copper with copper content higher than 99.90%. T2 copper pipe will be the first choice when users have high conductivity requirements for materials.
TU1 is oxygen free copper, with copper content ≥ 99.97%, extremely low oxygen and impurity content, high purity, excellent conductivity and thermal conductivity, good ductility, good processability, welding, corrosion resistance and cold resistance. Because of its high requirements and high cost, its product price is much higher than that of other types of copper tubes.
Brass pipe: copper zinc alloy pipe. The number after the letter H in the brand often represents the middle value of its copper content, and the zinc content is its surplus. Brass pipes of different grades show better quality and elongation with the increasing copper content. It is mainly used as a connector for water pipes and wading.

Processing technology of copper pipe

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General requirements for copper tubes

  • Sealed refrigerant system requires that the internal surface of pipe fittings shall be clean, free of oxidation, water, oil, etc;
  • Cracks, out of round deformation, distortion, visible sand holes, inkjet (defective marks detected by the copper pipe factory) and blackening (oxygen) are not allowed
  • Copper pipe with defects such as chemical).

General requirements for copper tube processing

  • The pipeline shall be processed according to the design drawings, and the shape and size shall meet the design requirements;
  • The diameter change at the fracture shall be within 2% of the standard diameter of copper pipe, and the fracture shall be free of flash and burr;
  • The pipe fittings shall be degreased, decontaminated, free of copper chips, and the internal and external surfaces shall be smooth without oil stain, scar and oxide scale;
  • Nitrogen must be filled for protection during welding. After welding, blow the inside with 2.8 – 3.0MPa dry compressed air.

Blanking and deburring of copper pipe

Equipment and operation requirements

  • Tools used: pipe cutter, effective ruler and positioning block. Measure the corresponding length with straight according to the size and pipe diameter required in the drawing, and place the positioning block;
  • After the copper pipe is positioned and fixed, it shall be removed with a cutter to ensure that the cutting opening is flush and free from deformation;
  • Gloves are not allowed during operation, but gloves can be worn for deburring to prevent wool from entering the copper pipe;
  • During the cutting process, the copper pipe is fed evenly to ensure that the pipe orifice is smooth;
  • When the pipe diameter is less than (equal to) Φ 12mm, multiple pieces (no more than 10 pieces) can be cut together; When the pipe diameter is greater than copper pipes with a length of Φ 12mm or less than Φ 60mm must be cut separately;
  • After blanking, the port must be deburred. The wire grinder shall be used for deburring. The size of the frequency converter shall be adjusted according to different pipe diameters to control the machine speed. See Table 1 below for details.

Table 1

Pipe diameter D DΦ7 Φ7DΦ9.52 Φ9.52DΦ19 Φ19DΦ30 DΦ30
Value of frequency converter 19±2 22±2 27±2 35±2 46±2

After deburring, the copper chips and sundries inside and outside the pipe must be blown off with 2.8 – 3.0MPa dry compressed air.

Technical requirements

The blanking length (L) is shown in the technical requirements of the drawing, and the calculated length can be based on the statistical table of copper pipe blanking size and weight calculation.
The dimensional tolerance of blanking length is shown in Table 2 below.
Table 2

Size of blanking 10100 100400 4001000 10002000
Tolerance range ±0.8 ±1.2 ±1.5 ±2

Bending of copper pipe

Equipment and operation requirements

Manual pipe bender: select the appropriate pipe bender (left-hand pipe bender or right-hand pipe bender) according to the drawing and the shape of copper pipe.
CNC pipe bender, turn on the power supply and check that the compressed air pressure is within the range of (0.4 – 0.6) MPa (right-hand pipe bender).
Remove all sundries that may affect the operation of the pipe bender within the scope of the pipe bender to ensure the smooth operation of the equipment.
Before each bending, the die or parameters shall be adjusted, and the idle bending test shall be carried out. The processing shall be carried out after confirming that the equipment is normal.
Refer to table 3 below for the bending radius of general copper pipe and the limit distance between two bends (see Appendix I for capillary bending):
Table.3 bending radius of copper pipe and limit distance between two bends

Specification of copper pipe Automatic pipe bender Manual pipe bender Bending radius is preferred Distance of profiling
Bending radius Clamping distance Limit distance of straight section between two bends a Bending radius Clamping distance Limit distance of straight section between two bends a
φ6×0.6 / / /     R15 15 15 R15 /
φ7×0.6 / / / R10, R15 15 15 R15 /
φ8×0.75 R20,  R25 20 20 / / / R20 60
φ9.52×0.75 R15, R20 25 25 R15, R20 18 18 R20 50
R25, R30 25 25 R25, R30 28 28 / /
φ12×0.8 R25, R30, R35 30 30 / / / R25 60
φ12.7×0.75 R25 30 30 / / / R25 60
φ16×0.8 R30, R35, R40 40 40 R40 45 45 R35 80
φ16×1.0
φ19×0.8 R40, R45, R50 45 45 / / / R40 190
φ19×1.0
φ22.2×1.0 R45, R50 55 55 / / / R45 210
φ28.6×1.0 R50, R60 70 70 / / / R60 250
φ28.6×1.2
φ31.75×1.2 / / / R55 85 85 R55 250
φ34.93×1.5 R55, R70 85 85 / / / R70 290

Note: 1. The limit distance between two bends of copper pipe is shown in figure (1) below, dimension a;

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Explain:
1. The straight section distance of the bending end of copper pipe shall ensure more than 2/3 of the corresponding clamping distance shown in table (3).
2. The copper pipe end ruler shall ensure that:

  • a. If the product has one bend, the straight section size of the end size shall ensure more than 2/3 of the corresponding clamping distance shown in table (3).
  • b. If the product has more than two bends (including) and the last bend is 90 degrees, the end size shall be above the clamping distance + bend radius (if it is not 90 degrees, it shall be lengthened appropriately).

Technical requirement

  • For pipe fittings with a diameter of no more than 16mm, smooth collision pits of more than 1.3mm are not allowed within 1000mm; For pipe fittings with a diameter greater than 16mm, smooth collision pits exceeding 2.0mm are not allowed within 1000mm.
  • The out of roundness of the bending part of the copper pipe shall not exceed 15%, and the specific calculation formula is: |b-a|/ ф* 100%, as shown in figure (2) above.
  • Bending angle tolerance of copper pipe: ± 2 °.

Flaring/necking

Equipment and operation requirements
Open the air source and ensure that the air pressure is (0.3 – 0.7) MPa.
Select appropriate expanding and shrinking die and clamping block according to the drawing requirements, and adjust the stroke of punch to meet the drawing requirements. Install the expanding and shrinking die and clamping block on the expanding and shrinking machine, and adjust the position of tooling and punch so that their centers are in a straight line.
The copper pipe must be dipped in volatile oil before expanding or shrinking.
See table (4) for the list of expanding and shrinking tooling (Note: if the straight pipe is required to expand and shrink, the shortest limit distance of pipe clamping is 60).
Table (4) list of expanding and shrinking tooling in copper pipe workshop (piping connection)

Specification of copper pipe Expansion and contraction specification Ф D Pipe clamping allowance Port depth L Flare height A Elongation Use equipment
φ6×0.6 Expand inside φ6 85 10 2 -2 Bench drill
Overspend φ8 85 10 3 -2 Bench drill
Overspend φ9.52 85 10 5 -3 Bench drill
Retraction φ2.6 85 10 2 3 Bench drill
Retraction φ3.0 85 10 2 2 Bench drill
Retraction φ3.5 85 10 2 2 Bench drill
Retraction φ4 85 10 2 1 Bench drill
φ7×0.6 Overspend φ8 85 12 2 -2 Bench drill
Overspend φ9.52 85 10 5 -3 Bench drill
Extrasystole φ3.5 85 10 2 3 Bench drill
Retraction φ4.5 85 10 2 3 Bench drill
Retraction φ6.5 85 12 2 2 Bench drill
φ8×0.75 Expand inside φ8 160 12 2 -2 Pneumatic
Extrasystole 7.8 85 12 2 2 Bench drill
φ9.52×0.75 Expand inside φ9.52 160 12 3 -4 Pneumatic
Overspend φ12 150 12 3 -4 Spinning
Overspend φ12.7 160 12 4 -3 Pneumatic
Retraction φ3.0 85 12 3 4 Bench drill
Retraction φ3.5 85 12 3 3 Bench drill
Retraction φ4.0 85 12 3 3 Bench drill
Retraction φ4.5 85 12 3 3 Bench drill
Retraction φ6 85 12 2 2 Bench drill
Retraction φ6.35 150 12 2 2 Spinning
Extrasystole φ7 85 12 2 2 Bench drill
Extrasystole φ6 85 12 2 2 Bench drill
Extrasystole φ8 150 12 2 2 Spinning
Extrasystole φ7.94/Extrasystole φ7.4 Bench drill
Extrasystole φ8.9 85 12 2 2 Bench drill
φ12×0.8 Expand inside φ12 160 14 2 -2 Pneumatic
Expand inside φ12.7 150 14 2 -1 Spinning
Overspend φ12.7 160 14 3 -1 Pneumatic
Overspend φ14.4 150 14 4 -2 Spinning
Retraction φ4.0 150 14 8 2 Spinning
Retraction φ4.5 150 14 7 6 Spinning
Retraction φ9.52 150 14 4 3 Spinning
Extrasystole φ9.52 150 14 4 2 Spinning
φ12.7×0.75 Expand inside φ12.7 160 14 2 -2 Pneumatic
Extrasystole φ9.52 85 14 2 2 Bench drill
φ16×0.8 Expand inside φ16 160 16 3 -2 Pneumatic
Expand inside φ19 150 16 4 -3 Spinning
Overspend Ф17.2 150 16 3 -2 Spinning
Retraction φ8 150 16 8 6 Spinning
Retraction φ9.52 150 16 7 6 Spinning
Retraction φ12 150 16 4 4 Spinning
Extrasystole φ12 150 16 4 4 Spinning
Extrasystole φ12.7 150 16 4 4 Spinning
Retraction φ12.7 150 16 4 4 Spinning
Extrasystole φ14.4 150 16 2 2 Spinning
φ19×0.8 Expand inside φ19 160 18 3 -3 Pneumatic
Overspend φ22.2 150 18 4 -4 Spinning
Retraction φ8 150 18 6 6 Spinning
Retraction φ9.52 150 18 6 6 Spinning
Extrasystole φ9.52 150 18 6 4 Spinning
Retraction φ12 150 18 6 4 Spinning
Extrasystole φ16 150 18 6 4 Spinning
φ22.2×1.0 Expand inside φ22.2 60 22 3 -2 Spinning
Overspend φ25.4 60 22 3 -2 Spinning
Retraction φ9.52 60 22 6 4 Spinning
Retraction φ16 60 22 6 4 Spinning
Extrasystole φ16 60 22 6 4 Spinning
Retraction φ19 60 22 6 4 Spinning
Extrasystole φ19 60 22 3 4 Spinning
φ28.6×1.2 Expand inside φ28.6 60 22 4 -3 Spinning
Expand inside φ31.6 60 22 6 -3 Spinning
Overspend φ34.93 60 22 6 -2 Spinning
Retraction φ22.2 60 22 4 6 Spinning
Extrasystole φ25.4 60 22 4 6 Spinning
Extrasystole φ22.2 60 22 4 6 Spinning

Technical requirement

  • The flare roundness shall not be greater than 0.10mm.
  • The concentricity of flare shall not be greater than 0.20mm.
  • The roundness of necking shall not exceed 0.20mm.
  • The concentricity of necking shall not exceed 0.30mm.
  • For pipe fittings with diameter less than 22mm, the pinch mark depth shall be ≤ 0.15mm; For pipe fittings with a diameter of not less than 22mm, the pinch mark depth shall be ≤ 0.3m.

The port processing tolerance requirements of various types of copper pipe expansion and contraction are as follows:

  • Expansion (contraction) is controlled by outer diameter: ≤ ф The tolerance of 22.2 is -0.01 – -0.08, > ф The tolerance of 22.2 is -0.10 – -0.18;
  • Expansion (contraction) is controlled by inner diameter: ≤ ф The tolerance of 22.2 is + 0.16 – + 0.24, > ф The tolerance of 22.2 is + 0.20 – + 0.32.

Turn (drill) hole

Equipment and operation requirements

  • Adjust the drilling machine speed when the drilling diameter is ≤ Φ At 12 o’clock, use the bench drilling machine and adjust the speed to level 3. The speed is 1400R/min. when the drilling diameter is > Φ At 12 o’clock, use the radial drilling machine and adjust the speed to 800r/min.
  • When drilling a copper pipe with a bench drill, the copper pipe must be fixed with tooling to ensure that the pipe fittings do not rotate and move relative to the operation limit of NC flanging when drilling or turning the hole.
  • During flanging, the minimum spacing L1 of flanging holes is greater than D + 10mm (D is the diameter of flanging holes). See figure (3) and figure (4) for details.
  • The distance L2 between the copper pipe orifice and the first flanging hole is ≥ 38. See the following figures (3), (4) and (5) for details.

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The minimum distance L3 between the flanging hole and the bending position of the copper pipe shall meet the requirements of table (5) below (see Fig. 3 and Fig. 5)

Pipe diameter ф12 ф16 ф19 ф22.2 ф28.6 ф34.93 ф41.28
L3 30mm 30mm 48mm 50mm 55mm 58mm 65mm

If the shape and flanging direction of the bend are shown in the above figure (3), L4 ≥ 100mm; if the shape and flanging direction of the bend are shown in the above figure (4),
Then L4 has no limit.
If the bend shape and flanging direction are shown in the above figure (6), and bend from the left end to the right end, L5 > profiling distance + (half of the aperture). If the flanging direction is downward or upward, only inner flanging can be used.
See table (6) for the list of NC flanging hole molds.
Table (6) list of NC flanging dies

Serial number Piping Φ3.5 Φ4.5 Φ6 Φ7 Φ8 Φ9.52 Φ12 Φ16 Φ19
Main pipe
1 Φ12×0.8
2 Φ16×0.8
3 Φ19×0.8
4 Φ22.2×1.0
5 Φ28.6×1.2

Operating limit of manual flanging:
In order to improve efficiency, numerical control flanging is preferred. Manual flanging is adopted only when numerical control cannot flanging. Basically, there is no operating limit (special treatment in case of special circumstances).
The list of manual flanging dies is as follows:
Table (7) list of manual flanging dies

Serial number Piping Φ3.5 Φ4.5 Φ6 Φ7 Φ8 Φ9.52 Φ12 Φ16 Φ19
Main pipe
1 Φ12×0.8
2 Φ16×0.8
3 Φ19×0.8
4 Φ22.2×1.0
5 Φ28.6×1.2

Note: “★” indicates manual external flanging and “●” indicates manual internal flanging
Technical requirement

  • The height of flanging hole is 2mm.
  • The drilling must be deburred with a scraper, and the burr must also be deburred after flanging. The whole can be cleaned with a steel brush first, and then the residual burr can be scraped with a scraper.

Degrease

Equipment and operation requirements

  • Turn on the cooling water circulating pump in the water pump room.
  • First open the water pressure valve on the horizontal degreasing furnace, then open the natural gas valve, turn on the main power switch, and finally open the degreasing furnace.
  • When the degreasing furnace is just started, it takes about 30 minutes to raise the temperature. The product can only be sent to the degreasing furnace when the 1# temperature control and 2# temperature control temperature rise to the set temperature.
  • After the heat exchanger and piping are discharged from the oven, 2.8-3.0mpa dry compressed air must be used to blow away the sundries inside and outside the heat exchanger and piping.
  • After degreasing, the heat exchanger shall be removed from the conveyor belt in time to prevent other heat exchangers from stopping for too long in the furnace due to the stop of the conveyor belt.
  • When degreasing the piping, pay attention to evenly separate the copper pipes and do not stack them.

Technical requirement
The degreasing parameters of various types of heat exchangers and piping are shown in the table below.

Main parameter 1# temperature control 2# temperature control Spindle speed r/min Timemin)
Heat exchanger degreasing 140 170 1015 79
Piping degreasing 120 150 2025 45
Heat exchanger drying 100 130 25(Max 4

Welding

Equipment and operation requirements

  • Adjust the oxygen gauge pressure of welding to (0.3 – 0.6) MPa.
  • Nitrogen filling protection must be done during welding. The nitrogen filling pressure is (0.02 – 0.05) MPa. After welding, it shall be cooled for at least 10 seconds before removing the nitrogen filling pipeline( Air cooled tooling must be used for tooling positions with air cooling)
  • Some welding shall be protected with wet cloth to prevent damage to internal parts of high and low voltage switches and needle valves.
  • Solder paste is not allowed for primary welding, and a small amount of solder paste can be used for secondary welding.

Technical requirement

  • All internal surfaces shall be clean, bright and free from oxides and other foreign matters.
  • During welding, the molten electrode shall be fully penetrated, and the welding spot shall be full and smooth without defects such as sand hole, false welding, weld bead, weld plug, etc.
  • Piping assembly shall be carried out in strict accordance with the requirements of process documents or drawings.
  • For general requirements of welding, refer to Kanban for welding points.

Heat treatment process of copper pipe

The difference between copper tube heat treatment process and steel pipe: annealing requires rapid cooling with water to reduce hardness. This is just the opposite of the heat treatment of steel pipe.

Heat treatment method of copper alloy

  • 1. Solution quenching
  • 2. Aging heat treatment
  • 3. Recrystallization annealing
  • 4. High temperature homogenization annealing
  • 5. Low temperature stress relief annealing
  • 6. Low temperature strengthening annealing (such as tin phosphorus, zinc white copper)

Annealing process of copper tube

The annealing process of red copper pipe is divided into the following types: intermediate annealing, finished annealing and stress relief annealing.

  • 1. Homogenization annealing process of copper tube: heat the copper tube to a temperature slightly lower than the solidus temperature (150-300 ℃ above AC3 or ACM), hold it for a long time (10-15h), and then cool it with the furnace to homogenize the chemical composition and structure of the copper tube. This simple process is uniform annealing.
  • 2. Intermediate annealing process of copper tube: the intermediate annealing requires full recrystallization, the heating temperature is higher than the recrystallization temperature, and the holding time is based on the principle of ensuring the uniform temperature of copper tube. That is, recrystallization annealing for the purpose of softening between two cold working deformations (cold rolling or stretching), also known as softening annealing. The normalization treatment mainly refers to the heat treatment process of heating the workpiece to 40-60 ℃ above A3 point and maintaining it for a period of time, so that the structure of the steel becomes a uniform vostian structure, and then cooling it to room temperature in still air. After cold deformation, the alloy produces work hardening and the yield strength increases sharply. It is necessary to overcome large deformation resistance when continuing processing. After heating the copper tube above the recrystallization temperature and cooling slowly after holding for a certain time, the fully broken structure of cold deformation is recrystallized and the grain structure of copper tube is refined, so as to obtain good plasticity and low deformation resistance, so as to continue cold processing deformation.
  • 3. Finished product annealing process of red copper pipe: finished product annealing is carried out to meet the product states required by the standard, such as o state, 1/4h state, 1/2h state, etc., and also includes stress relief annealing. That is, after the cold deformation is processed to the size of the finished product, the annealing with different states and properties can be obtained by controlling the annealing temperature and holding time. After heating at 450-600 ℃ below A1 point for a period of time, and then slowly cooling to room temperature, the residual stress generated in the stamping, cutting and casting process of steel can be eliminated. That is, after the cold deformation is processed to the size of the finished product, the annealing with different states and properties can be obtained by controlling the annealing temperature and holding time.
  • The purpose of copper tube annealing process is to reduce hardness and improve machinability; Eliminate residual stress, stabilize size and reduce deformation and crack tendency; Refine the grain, adjust the structure and eliminate the structural defects.

Types of heat treatment of copper alloys

1. Homogenization annealing
The main purpose is to eliminate the component segregation of ingot during casting. The diffusion rate of solute is directly proportional to the diffusion coefficient D, d = d0exp (- Q / RT), [R gas constant, Q activation energy, d0 frequency factor cm2 / S], Q represents the energy required for atoms to move from one position to another, and the atomic movement must overcome the energy barrier. The activation energy of pure phase is large and the diffusion coefficient is small, but if only the concentration is uneven, the relative q is small. With the increase of temperature, the number of atoms overcoming the energy barrier is increasing with the help of thermal fluctuation. The vacancy at high temperature is also conducive to atomic diffusion. Generally, the homogenization temperature is 100 ℃ higher than the annealing temperature. The diffusion rate has a parabolic relationship with time, that is, R2 = KT (r diffusion distance, K constant). Generally, tin bronze has a large crystallization range and serious component segregation, so it needs homogenization annealing.
2. Intermediate recrystallization annealing
The main purpose is to eliminate work hardening. The intermediate annealing temperature is above the recrystallization temperature, and the softening degree of the material depends on the cold working rate, annealing temperature and holding time. Generally, high-temperature annealing is adopted at the initial stage of processing and lower temperature annealing is adopted at the later stage of processing to ensure the uniformity of grain size.
Empirical formula of alloy recrystallization temperature: T = 0.4t melting (k) = 0.4t melting – 164 (℃)
3. Low temperature annealing
Brass cold working produces residual stress, which will lead to stress corrosion and seasonal fragmentation. The main purpose of low-temperature annealing is to eliminate residual stress, so the low-temperature annealing temperature should be as low as possible to avoid material softening. For Tin Phosphorus and zinc white copper, low temperature annealing can also significantly improve the hardness.
4. Age hardening
The purpose of aging heat treatment is to precipitate solute atoms to strengthen the alloy after solid solution and quenching. The aging temperature is strictly required, and the furnace temperature must be kept as uniform as possible.
5. Solution quenching

It is a heat treatment process before aging. Its purpose is to keep warm at the solid solution temperature and then cool rapidly to obtain the maximum supersaturated solid solution. It is usually used together with aging precipitation heat treatment to improve the material properties.

Cleaning process flow of copper pipe

Causes of copper pipe pickling

The function of pickling is to remove the oxide scale and rust on the copper surface with acid solution. Is a method of cleaning metal surfaces. It is usually carried out together with cleaning the pre membrane. The pickling effect also depends on the temperature. When the temperature of the pickling solution increases to 50 ℃, the dissolution rate of copper increases at first and then decreases rapidly. The dissolution rate of zinc changed little with temperature. The temperature should be about 30 ℃. After pickling, it will be all right after cleaning with clean water, and there will be no toxic substances left. Through pickling, our metal materials can be restored as new.

Purpose of copper pipe pickling

In engineering, pickling and passivation are usually carried out to give greater play to the ground corrosion potential of copper pipes. Generally, thorough cleaning, including alkali cleaning and pickling, and then passivation with oxidant are required to ensure the integrity and stability of the passivation film. One of the purposes of pickling is to create favorable conditions for passivation treatment and ensure the formation of high-quality passivation film. Because a layer of copper pipe surface with an average thickness of 10 microns is corroded by pickling, and the chemical activity of the acid solution makes the dissolution rate of the defective part higher than that of other parts on the surface, pickling can make the whole surface tend to be uniform and balanced, and some hidden dangers that are easy to cause corrosion are removed. But more importantly, through pickling and passivation, the oxides of iron and iron are preferentially dissolved than those of chromium and chromium, and the chromium poor layer is removed, resulting in the enrichment of chromium on the surface of stainless steel. The composition and structure of this chromium rich passivation film improve the corrosion resistance of copper. Copper surface cleaning, pickling and passivation not only maximize corrosion resistance, but also prevent product pollution and obtain beauty.

Process flow

Pickling – > water washing – > polishing – > water washing – > passivation – > water washing
Container material: plastic or FRP
Tank liquid management

Serial number Working procedure Product Name Temperature () Timeimemin Remarks
1 Pickling Pickling Normal atmospheric temperature 28 Each washing process is flushed with overflow water
2 Washing Tap water Normal atmospheric temperature 12
3 Polishing Polishing agent Normal atmospheric temperature 0.56
4 Washing Tap water Normal atmospheric temperature 12
5 Passivation Passivator Normal atmospheric temperature 25
6 Washing Tap water Normal atmospheric temperature 12

Operating procedures
1. Pickling (cleaning)
The treatment time shall be properly controlled according to the workpiece material, surface condition and treatment temperature; Remove the oil stain on the surface in time to avoid secondary contamination of the workpiece; When the pickling solution has too many impurities or the treatment effect is not ideal, it shall be replaced with a new solution.
2. Washing
Flush with overflow water, and the next process can be started only after the workpiece is cleaned; The water quality must be changed frequently to avoid polluting the tank liquid of the next process.
3. Polishing
The treatment time shall be properly controlled according to the workpiece material, surface condition and treatment temperature; Remove the oil stain on the surface in time to avoid secondary contamination of the workpiece; When the polishing effect is not ideal, the groove shall be inverted and new liquid shall be added; It is forbidden to bring in other impurities to pollute the tank liquid.
4. Washing
Flush with overflow water, and the next process can be started only after the workpiece is cleaned; The cleaned workpiece shall enter the next process immediately; The water quality must be changed frequently to avoid polluting the tank liquid of the next process.
5. Passivation (closed)
Strictly control the processing time for 2 – 5 seconds; If the passivation effect is not ideal, the tank shall be reversed and new liquid shall be added. It is forbidden to bring in other impurities to pollute the tank liquid.
6. Washing
Flush with overflow water. The water must be completely clean, otherwise the workpiece surface is uneven and scratched; The washed workpiece shall be dried in time.
Precautions

  • 1. Each washing must be thoroughly clean and replaced frequently.
  • 2. If the treatment effect of the treatment solution is not ideal, it shall be supplemented or replaced in time.
  • 3. Operators should pay attention to safety and wear protective articles (acid resistant gloves, long rubber boots, protective glasses, work clothes, etc.). If they accidentally splash on the skin or eyes, they must wash with a large amount of water or send them to medical institutions.
  • 4. At present, considering the number of copper pipes to be cleaned and process conditions, it is temporarily cleaned at room temperature and then dried. This process document will be further modified after the copper tube drying oven is put into use.

Storage of copper tubes

The products of semi-finished products or finished products warehouse must be sealed with rubber plugs conforming to the specifications of pipe orifice and covered with dust-proof cloth.
The products in the semi-finished products or finished products warehouse shall be placed neatly and beautifully, and shall not be mixed.
The product accounts, materials and cards of semi-finished products or finished products warehouse are consistent.

Other appearance defects of copper pipe during processing

It is not allowed to hurt hands due to clamping injuries and clamping marks caused by pipe processing and clamping.

  • For pipe fittings with diameter less than 22mm, the depth of pinch damage and pinch mark shall not exceed 0.15mm; For pipe fittings with a diameter of no less than 22mm, the depth of pinch damage and pinch mark shall not exceed 0.3mm;
  • For pipe fittings with diameter no more than 16mm, smooth collision pits no more than 1.32mm are allowed;
  • For pipe fittings with a diameter greater than 16mm, smooth collision pits not exceeding 2.0mm are allowed.

Processing method of copper pipe

There are three processing methods for copper pipes:

  • 1. Explanation of copper tube extrusion process: the definition of extrusion process is that the copper germ tube is extruded by the copper tube extruder, so that the density distribution and wall thickness of the copper tube are more uniform, so as to achieve stronger compressive capacity.
  • 2. Explanation of copper tube continuous casting and rolling process: the definition of continuous casting and rolling process is continuous casting and rolling, so as to pour the liquid copper burned at high temperature into the continuous caster and roll out the copper billet (called continuous casting billet), and then directly heat it in the soaking furnace for a certain time without cooling, and then directly enter the hot continuous rolling unit for rolling. Continuous casting and rolling process can skillfully combine casting and rolling processes. Compared with the previous traditional process of casting copper billet first, heating in heating furnace and then rolling, it has the advantages of simplifying process, reducing labor force, increasing metal yield, saving materials, enhancing continuous casting billet quality and producing energy-saving and environment-friendly copper products, which directly realizes mechanization Advantages of programming and automation.
  • 3. Explanation of copper pipe upward drawing process: the original feature of upward drawing continuous casting copper pipe is “no oxygen”, that is, the oxygen content is less than 10ppm. Electrolytic copper is melted into copper liquid at high temperature. In the whole process after hardening, charcoal reduction, flake graphite covering and oxygen isolation are adopted. Oxygen in molten copper liquid is a new type of copper oxide and cuprous oxide. Charcoal can deoxidize itself under the action of high temperature to make its oxygen content less than 10ppm. The co shielding gas produced in the process of chemical reaction and the oxygen isolation effect of flake graphite make the graphite no longer oxidized in the crystallization process, so as to achieve the effect of up drawing process.

Copper pipe processing methods: hot processing and cold processing
There are many processing methods for copper pipes, but they can be divided into hot processing and cold processing. Such as extrusion, cross rolling and piercing, the tube blank is heated to a temperature much higher than the recrystallization temperature of copper for deformation processing, so as to obtain the tube blank. The tube blank is made into tube by cold rolling and cold drawing at room temperature. This traditional craft has remained unchanged for many years and is still used today.
At present, the extrusion billet supply method is mainly used, which is a traditional red copper tube billet supply method. Its production process is to melt and cast electrolytic copper into a solid round ingot, then heat it in the heating furnace to more than 850, enter the extruder one by one and extrude it into a tube billet, and then cold rolling or multi pass linear stretching to the tube billet required for disc stretching. Extrusion can be divided into high extrusion ratio and low extrusion ratio, both of which have fine grain structure and good surface quality. The tube billet extruded with high extrusion ratio has small specification and thin wall thickness, which can be processed directly on continuous direct machine or disc drawing machine; For low extrusion ratio extrusion, large billet can be extruded from large ingot, and then extended by cold rolling mill. For ingots with the same size and specification, the extrusion tonnage required for high extrusion ratio is large, and the wall thickness tolerance of extruded pipe is large.
At present, the continuous casting and rolling billet supply method is very popular in China. It is a new billet supply method rising in the 1990s. Its production process is to cut the milling surface of the horizontal continuous casting hollow tube billet to a fixed length and directly send it to the three roll planetary tube mill to roll out small-diameter thin-walled copper tubes. Because the three roll pipe mill can make the rolled copper pipe without rotation, it is easy to take up the coil on line. It is characterized by short production process and canceling reheating and extrusion processes. It has advantages in saving energy, reducing equipment investment and reducing cost. Continuous casting and rolling can provide tube billets greater than 1500 kg/disc, which can not be done by extrusion method anyway. The large coil heavy tube blank creates a very favorable condition for the drawing process of the subsequent process to improve the efficiency. The continuous casting and rolling production line has experienced ups and downs, experiences and lessons from the initial R & D to putting into production, from only producing thick wall tubes to becoming the main billet supply process of thin wall tubes. With the efforts of relevant practitioners in China, this process is gradually becoming perfect and mature.

Dimension of copper pipe

Nominal Pipe Size inches O.D. I.D. Wall Thickness
Type
K* L** M*** DWV**** K L M DWV
1/4 0.375 0.305 0.315 0.035 0.030
3/8 0.500 0.402 0.430 0.450 0.049 0.035 0.025
1/2 0.625 0.527 0.545 0.569 0.049 0.040 0.028
5/8 0.750 0.652 0.666 0.049 0.042
3/4 0.875 0.745 0.785 0.811 0.065 0.045 0.032
1 1.125 0.995 1.025 1.055 0.065 0.050 0.035
1-1/4 1.375 1.245 1.265 1.291 1.295 0.065 0.055 0.042 0.040
1-1/2 1.625 1.481 1.505 1.527 1.541 0.072 0.060 0.049 0.042
2 2.125 1.959 1.985 2.009 2.041 0.083 0.070 0.058 0.042
2-1/2 2.625 2.435 2.465 2.495 0.095 0.080 0.065
3 3.125 2.907 2.945 2.981 3.030 0.109 0.090 0.072 0.045
3.5 3.625 3.385 3.425 3.459 .120 .100 .083
4 4.125 3.857 3.897 3.935 4.009 .134 .114 .095 .058
5 5.125 4.805 4.875 4.907 4.981 .160 .125 .109 .072
6 6.125 5.741 5.845 5.881 5.959 .192 .140 .122 .083
8 8.125 7.583 7.725 7.785 .271 .200 .170

*K, thick walled, underground residential, commercial and industrial uses.

**L, medium walled, residential and commercial uses

***M, thin walled, above ground residential and light commercial uses.

****DWV, Drain/Waste/Vent, non-pressurized

Calculation formula of weight and length of copper pipe:

  • Weight per meter (kg/m) = 0.02796 × Wall thickness (mm) ×( Outer diameter – wall thickness (mm)
  • Length per kilogram (m/kg) = 1/weight per meter

Standard for copper pipe

At present, the commonly used standards of copper pipes and fittings in China mainly include American standards, European standards and Chinese national standards.

American Standard ASTM B88-1996

The standard was last revised in 1996. Compared with the old standard, it has basically no changes. It stipulates the specifications, dimensions and deviations, pressure, quality inspection methods, etc. of 1/4 “- 12” copper pipe. Among them, “K” type is copper pipe suitable for underground pipeline, high pressure and high temperature or other higher requirements“ L “type is copper pipe suitable for non underground pipeline but with high pressure“ M “type is a surface economic and practical copper pipe, which is suitable for general water supply and heating pipelines (this standard is widely used in China)“ DWV “type is used for non pressure drainage (it is not used in China at present). The matching copper pipe standard is ASME/ansib16, which specifies the inspection methods such as material, specification, size and deviation of 1/4 “- 12” pipe fittings.

European standard EN1057-1996

The current European standard replaces the original British standard BS2871-1971, its content is basically the same as the original standard, the inspection terms are the same as the American Standard, but the caliber range is smaller than the American Standard. The “Y” series (from 6mm to 108mm) is used for underground pipelines and general purposes“ X “series (from 6mm to 267mm) is economical and practical, which is widely used in China and Hong Kong. The matching pipe fitting standard is EN1254.
3. Chinese standard GB/T 18033-2000 (replaces the original standard GB1527-87)
The current national standard is very different from the original national standard. The new standard basically refers to European and American standards, and stipulates that DN15-200mm wall thickness is divided into three types of copper pipes: A, B and C.

  • A. The pipe is thick wall type, which is suitable for high purpose;
  • B. Type pipe is suitable for general purpose;
  • C. The type pipe is thin-walled copper pipe, which is basically equivalent to EN1057-x.

The outer diameter deviation is divided into ordinary grade and higher precision grade, but both are lower than foreign standards. At present, only a few small-diameter copper tubes produced by domestic manufacturers can meet the requirements of the new standard. Other technical indicators of the new national standard are basically the same as foreign standards, but at present, no domestic manufacturer can strictly implement this standard to produce copper water pipes. In terms of supporting pipe fittings, the latest domestic standard is GB/T 11618-1999. However, the size can not be matched at all, and the technical indicators are far behind the foreign standards. The fitting gap with the pipe fittings is large, the socket depth is very small compared with the foreign standards, and there is no clear provision on the material. The standards in this regard must be further revised. At present, the most chaotic market in China is the market of copper accessories. The prices at home and abroad are very different. For the same domestic products, the price difference is 2-3 times due to different materials and sizes. The safety and service life of copper pipe system are closely related to accessories. If we do not pay attention to the standards and quality of accessories, the quality of pipeline can not be guaranteed.

Technical requirements for copper pipe welding

General requirements for welding: ensure that the pipeline does not leak, the welding pipeline is horizontal and vertical, and the welding fluid is evenly distributed in the weld. Ensure that the functions of all components are intact, and pay attention to the directionality of all valves.

Copper pipe blanking

a. Tools: pipe cutter, tape measure, wire marking pen, file.
b. Steps:

  • ① Measure the corresponding length with a tape measure according to the size and pipe diameter required by the drawing, and note the position with the wire number.
  • ② The thicker copper pipe shall be fixed and then removed with a cutter to ensure that the cutting opening is flush and not deformed.
  • ③ File the rough edge of the cutting edge with a file and wipe it clean with a rag.

Welding process

a. Tools: welding gun, acetylene cylinder, oxygen cylinder, nitrogen cylinder.
b. Steps:

  • ① Check whether the quantity in the oxygen cylinder and acetylene cylinder is sufficient.
  • ② Welding shall be carried out according to the drawing requirements.
  • ③ When welding the solenoid valve, remove the coil of the solenoid valve to prevent damage, and pay attention to its flow direction
  • When welding other parts, such as liquid mirror, expansion valve, check valve, etc., pay attention to heat damage during welding. If necessary, remove the removable parts and wrap the welded valve body with wet cotton cloth.
  • ⑤ During welding, low-speed nitrogen shall be introduced into the welded pipe to prevent oxidation.
  • ⑥ After welding, cool and clean the oxide and welding slag in the pipe with dry nitrogen.

Welding rod

For the welding of red copper and red copper, silver electrode without silver or 5% silver shall be selected, and flux shall not be used. For other welding not necessarily, the welding rod shall be selected according to its technical description or requirements.
2.0 insertion depth and clearance between same pipe joint and copper pipe.

Surface cleaning before welding

Except for the welding of red copper and red copper, all pipe fittings shall be cleaned with emery cloth or stainless steel wire brush before welding to expose the bright metal surface( The inner surface shall be cleaned, and the metal chips and sand particles shall be cleaned)

Flux

The welding base shall be kept clean and free of oxides, metal chips, dust and other inclusions. Flux shall be applied immediately after cleaning and welded as soon as possible, each for no more than 2 hours. Excess welding shall be removed in time. It can be wiped with wet cloth or steel wire brush dipped in water before the weld is cooled, or it can be washed with water. However, in order to avoid cracks, this work shall be carried out 10-15 seconds after welding.
In order to avoid the formation of oxides, such as welding pipes and pipe fittings into the pipeline, inert gas shall be filled, and the protective flow channel shall be long enough and connected by the air outlet.
Welding: during welding, the gas welding flame shall not directly heat the welding rod. Valves, pipe fittings and sight glasses that are easily deformed by heat shall be removed and wrapped with wet cloth during welding.
Cleanliness: the surface shall be free of oxides and residues, otherwise it shall be removed with steel wire brush or abrasive cloth, but the weld shall not be damaged.
Appearance: the weld shall be smooth and uniform, and the color shall be golden yellow or silver white. There shall be no flowing particles and particles. Fillet welds shall not be too high.

Welding operation instruction

Objective
The materials used for welding and some welding methods are specified to ensure the quality of welding and no leakage point in the system.
Requirement
Brazing is adopted for the welding of red copper pipe. The brand of electrode is bag10cuzn and the flux is borax. Brass electrode is used for the welding of different materials. The specification of electrode shall be determined according to the size of weldment.
All plug-in welding in this process shall be welded according to the requirements in the figure below. Clearance after welding and before welding: 0.1-0.25mm h ≈ D note: H refers to insertion depth and D refers to pipe diameter
During welding, when the copper pipe is annealed after welding, the annealing temperature shall not be lower than 300 ℃.
Repair welding shall be carried out where leakage is found during the pressure test. During the repair welding, the nitrogen of the system shall be discharged, and the pressure test shall be carried out again after welding.
Before repair welding, the oxide layer on the surface shall be wiped with gauze. After repair welding, the oxide scale shall be removed. After quenching in water, the copper pipe shall be dried without water droplets.
After all welding, purge the system with nitrogen.
The joints that are not allowed to be welded due to technical requirements shall be connected with bolts or flanges.
Corresponding protective measures shall be taken for parts that are easy to deform and damage under high temperature conditions. For example, the angle valve, evaporator and condenser shall be welded after the interface is wrapped with wet gauze. For solenoid valve, expansion valve and liquid mirror, those that can be disassembled must be disassembled and welded. The above measures shall be taken for those that cannot be disassembled.

Installation of copper pipe

1. Copper pipe installation shall meet the following requirements:

  • (1) The pipe can be cut manually or mechanically, and oxygen acetylene flame cutting is not allowed. During cutting, the pipe deformation caused by improper operation shall be prevented, the end face of the pipe notch shall be perpendicular to the pipe axis, and the burr at the notch shall be cleaned.
  • (2) File or beveling machine shall be used for pipe beveling, and oxygen acetylene flame cutting shall not be used. Both sides of the jaws of bench vises for clamping copper pipes shall be padded with wood pads.

2. During pipe prefabrication, the correct actual pipe length shall be measured and installed after prefabrication on the ground. If possible, the elbow directly bent by copper pipe shall be used as far as possible. When multiple pipes are parallel, the bending parts shall be consistent to make the pipes neat and beautiful.
3. The pipe shall not be simmered hot. Generally, the pressed elbow or welded elbow shall be used when the outer diameter is less than 108mm. The straight edge length of copper elbow shall not be less than the outer diameter of the pipe and not less than 30mm. The processing of elbow shall also be determined according to the material, diameter, design and other conditions of the pipeline.
4. When copper pipe is used to process the compensator, the compensator shall be prefabricated before installation. When the sleeve type or bellows type compensator of the finalized product is adopted, it should also be prefabricated into pipe sections with adjacent pipes before installation, especially when the compensator of different materials such as stainless steel needs to be brazed with copper pipe is selected, generally, the compensator and copper pipe should be prefabricated into pipe sections before installation. The supports and hangers required for pipeline laying shall be processed and prefabricated according to the form and quantity indicated in the construction drawing.
5. Mechanical connection and welding connection of copper pipe shall meet the following requirements:

  • (1) Before brazed connection of copper pipe, confirm whether the specifications and dimensions of pipe and pipe fittings meet the connection requirements. According to the pipe length measured on site in the drawing, the blanking shall be correct.
  • (2) The brazing strength is small, and the general welded junction adopts the form of lap joint. The overlapping length is 6 – 8 times of the pipe wall thickness. When the outer diameter D of the pipe is less than or equal to 28mm, the overlapping length is (1.2 – 1.5) d (mm).
  • (3) Before welding, the outer wall of copper pipe and the inner wall of pipe fittings shall be rubbed with fine sandpaper, steel brush or cloth sandpaper containing other abrasives to remove surface oxides.
  • (4) During welding, the welding nozzle shall be properly selected according to the pipe diameter, and the welding position and electrode shall be heated evenly. Overheating shall not occur. After the solder seeps into the weld, stop heating immediately and keep it still. Natural cooling.
  • (5) When welding between copper pipe and copper alloy pipe fittings or between copper alloy pipe fittings and copper alloy pipe fittings, flux shall be used at the welding position of copper alloy pipe fittings, and the residual flux on the outer wall of the pipe shall be removed after welding.
  • (6) During the welding of plastic coated copper pipe, the bare copper pipe with a length of not less than 200mm shall be stripped, and wet cloth shall be wound at both ends. After the welding, the plastic coated layer shall be restored.
  • (7) The brazed pipe fittings must be cleaned within 8h to remove the residual flux and slag. The joint is usually painted with boiled alum aqueous solution containing 10% – 15% or citric acid aqueous solution containing 10%, and then washed with water.
  • (8) Inverted welding shall be avoided during welding and installation.

6. The copper pipe shall be connected by ferrule and shall meet the following requirements:

  • (1) The pipe orifice section shall be vertical and flat, and shall be rounded or flared with special tools.
  • (2) Adjustable spanner or special spanner shall be used. It is strictly prohibited to use pipe wrench to tighten the nut.
  • (3) Secondary assembly should be adopted for the connecting parts. When it is completed at one time, the nut shall be tightened by 1 – 1 / 4 turn after the torque surge point to make the ferrule edge cut into the pipe, but it shall not be too tight.

7. Cold pressing connection of copper pipe shall meet the following requirements:

  • (1) Special crimping tools shall be used.
  • (2) The nozzle section shall be vertical and flat, and the nozzle shall be free of burrs.
  • (3) When the pipe is inserted into the pipe fitting, the sealing ring shall not be distorted.
  • (4) During crimping, the end face of the caliper shall be perpendicular to the axis of the pipe fitting, and shall be extended for 1 – 2S after reaching the specified clamping pressure.

8. PTFE raw material belt should be used for the threaded connection between brass fittings and accessories. During the connection, 2 – 3 threads should be screwed by hand, and then tightened by wrench at one time. It is not allowed to screw backwards. 2 – 3 threads should be left after tightening.
9. Various loose flanges specifications shall meet the design requirements, and the gasket can be temperature resistant cloth rubber plate or copper gasket. Galvanized bolts shall be used for flange connection and tightened symmetrically.
10. The installation of supports and pipes shall meet the following requirements:
(1) When the pipeline passes through the wall, floor slab and buried wall for concealed installation, it shall cooperate with the civil engineering to reserve holes and slots, and the size of the reserved holes and slots can be implemented according to the following provisions:
1) The hole size should be 50 – 100mm larger than the outer diameter of the pipe.
2) The width of the wall groove of the buried pipe can be the outer diameter of the pipe plus 50mm, and the depth is the outer diameter of the pipe plus 15 – 30mm.
3) The clearance at the top of overhead pipe shall not be less than 200mm.
4) When the pipeline passes through the outer wall of basement or underground structure, waterproof casing shall be embedded and waterproof measures shall be taken.
5) For the installation of exposed pipes, the clear distance between the outer wall or the outer surface of the insulation layer and the decorative wall should be 10 – 15mm.
6) The distance between the concealed pipeline (including trench, ceiling, pipe well, etc.) and the wall and column surface shall be determined according to the installation requirements of the pipeline support and the fixation requirements of the pipeline. The distance between the pipeline center and the wall and column surface can be determined according to the data in table 4.3.9.10. (1).
Table 4.3.9.10. (1) maximum distance from pipe center to wall and column surface (mm)

Nominal inner diameter DN Light tube Thermal insulation pipe
15 90 130
20 95 135
25 100 140
32 110 150
40 115 155
50 120 160
65 130 175
80 145 185
100 155 195
125 170 210
150 180 225
200 210 260

7) The spacing of copper pipe fixed supports shall meet the design requirements. The distance between fixed supports of hot water pipe shall be determined according to the expansion amount of pipeline and the allowable expansion amount of expansion joint. The fixed support should be set at the reducer, branch, interface and both sides passing through the load-bearing wall and floor slab.
8) The distance between movable supports of copper pipes can be determined according to table 4.3.9.10. (2).
Table 4.3.9.10. (2) spacing of copper pipe movable support

Nominal inner diameter DN Vertical pipe spacing (m) Horizontal pipe spacing (m)
15 1.8 1.2
20 2.4 1.8
25 2.4 1.8
32 3 2.4
40 3 2.4
50 3 2.4
65 3.5 3
80 3.5 3
100 3.5 3
125 3.5 3
150 4 3.5
200 4 3.5

9) The pipe support should be made of copper alloy. When steel support is used. A soft spacer shall be set between the pipe and the support.
10) The open position where the piping system is installed intermittently shall be blocked in time.
11) Pipes shall not be used as lifting, pulling and climbing parts.
12) The support installation shall be flat and firm, and the spacing and specification shall meet the design requirements. Steel casing shall be added when the pipeline passes through the wall and floor, and the gap between the casing and the pipeline shall be filled with flame-retardant dense materials and waterproof ointment.
11. The installation of compensator shall meet the following requirements:
(1) When the square (circular) compensator is installed horizontally, it shall be consistent with the slope of the pipeline; When installed vertically, the high point shall have exhaust device.
(2) The compensator shall be pre tensioned according to the design requirements. If there are no design requirements, the pre stretching of casing compensator shall meet the requirements of table 4.3.9.11. (2). The pretension length of the square compensator is half of its elongation. When installing the copper corrugated compensator, the straight pipe length shall not be less than 100mm.
Table 4.3.9.11. (2) pretension length of casing compensator

Compensator specification (mm) 15 20 25 32 40 50 65 80 100 125 150
Pull out length (mm) 20 20 30 30 40 40 56 59 59 59 63

12. Valve installation shall meet the following requirements:

  • (1) Before installation, check whether the model and specification meet the design requirements. Check whether the valve rod and disc are flexible, whether there is jamming and external inclination, and the disc must be closed tightly.
  • (2) Before installation, the valve must be tested for strength and tightness, and installation shall not be carried out if it is unqualified.

13. Pipeline pressure test shall meet the following requirements:
(1) Water pressure or air tightness test shall be carried out according to the design requirements. When there are no design requirements, the test pressure shall be 1.5 times of the working pressure of the pipeline system, but shall not be less than 0.6MPa.
(2) Before the test, safe and effective fixing and protection measures shall be taken for the pressure test pipeline. Pipe joints shall be exposed.
(3) After the hydraulic test is qualified, the subsequent civil construction can be carried out. During the hydrostatic test, records shall be made and confirmed by the supervising engineer for future reference or filing.
(4) The hydrostatic test shall be carried out according to the following steps:

  • 1) Plug the end of the test pipe, inject water slowly, and discharge the gas in the pipe at the same time.
  • 2) After the pipeline system is filled with water, conduct tightness inspection. After reaching the test pressure, stop pressurization, observe for 10min, and the pressure drop shall not exceed 0.02MPa; Then reduce to the working pressure for inspection, and it is qualified if there is no leakage.

14. After passing the hydrostatic test, the pipeline for domestic drinking water shall be washed with clean water, disinfected and then washed with drinking water. It can be used only after passing the inspection of relevant departments.
15. For pipes requiring insulation as specified in the design, the insulation construction shall be carried out after the hydrostatic test is qualified. The type and thickness of thermal insulation materials used must meet the design requirements, and the construction method shall meet the requirements of the thermal insulation materials.
16. Quality requirements
I main control items

  • (1) The model, specification and quality of pipes, components and welding materials must meet the design requirements and the requirements of this chapter and section. Inspection method: inspection certificate, acceptance or test record.
  • (2) The specification, model, strength and tightness test of valves and valves requiring disassembly inspection must meet the design requirements and relevant provisions of this chapter.
  • (3) The hydrostatic test must meet the design requirements and relevant provisions of this chapter. Inspection method: check section and system test records.
  • (4) The weld surface shall be free of cracks, burn through, nodulation, serious slag inclusion, pores and other defects. Welded junctions with special requirements must comply with relevant regulations. Inspection method: observe with a magnifying glass. For welded junctions with special requirements, check the test records. Spot check 10% according to the system, but not less than 5.
  • (5) The flanging surface of the pipe orifice shall be free of wrinkles, cracks, scratches and other defects. Inspection method: observation inspection. Spot check 10% according to the system, but not less than 5.
  • (6) Pipes, components, gaskets and fillers degreased with different oil must meet the design requirements and relevant regulations after degreasing. Inspection method: check the degreasing record. Check all according to the system.
  • (7) The surface of the bend shall be free of cracks, delamination, pits, overburning and other defects. Inspection method: spot check 10% according to the system, but not less than 3 pieces.
  • (8) Weld flaw detection: the radiographic detection of brass gas welding welds must be inspected according to the design or relevant regulations. If the working pressure is above 10MPa, it must comply with the provisions of item 2 of table 4.3.9.16.1; The working pressure below 10MPa must comply with the provisions of item 3 of table 4.3.9.16.1. Inspection method: check the flaw detection records. If necessary, spot check 10% of the number of welded junctions inspected according to the regulations.
  • (9) Inspection of welding mechanical properties: the mechanical properties of welded joints must comply with the provisions in table 4.3.9.16.2. Inspection method: check the test records.
  • (10) The cleaning and purging of the pipeline system must be carried out according to the design requirements and relevant regulations. Inspection method: check the cleaning and purging records. Complete inspection according to the system.

II General Items

  • (1) The installation position of support, hanger and bracket shall be correct, flat and firm. The support and copper pipe shall be separated by asbestos rubber pad, soft metal pad or wood pad, and shall be in close contact. The movable surface of the movable support is in good contact with the supporting surface and moves flexibly. The hanger rod of the hanger shall be vertical, with complete screw thread and good anti-corrosion. Inspection method: pull and observe by hand. Spot check 10% according to the system, but not less than 3 pieces.
  • (2) The slope of the pipeline shall meet the design requirements and relevant provisions of this chapter. Inspection method: check with a level ruler. According to the system, spot check 2 sections every 50m of straight pipe section and one section less than 50m.
  • (3) When installing the compensator, the two arms shall be straight without distortion, and the outer arc shall be uniform. When installed horizontally, the slope shall be consistent with the pipe. The installation direction of corrugated and packing compensator shall be correct. Inspection method: observe and check with a level ruler. Check all according to the piping system.
  • (4) The installation position and direction of the valve shall be correct, and the connection shall be firm, tight and flexible. Valves with special requirements shall comply with relevant regulations. Inspection method: observe and make opening and closing inspection or inspection and test records. Spot check 10% of all valves according to the system, but not less than 2. All valves with special requirements shall be inspected.
  • (5) The flange connection shall be tight, parallel, coaxial and perpendicular to the center line of the pipeline. The bolt shall be stressed evenly, 2 – 3 threads of the nut shall be exposed, and the gasket shall be installed correctly. The flanging bend of loose flange nozzle is rounded, and the surface is free of wrinkles, cracks and scratches. Inspection method: try tightening with a wrench, observe and check with a ruler. Spot check 10% of the piping system, but not less than 3 places. All flanges with special requirements shall be inspected.
  • (6) The allowable deviation of copper pipe installation shall comply with the provisions of table 4.3.9.16.3.

17. Quality problems needing attention

  • (1) The cutting and groove processing of copper pipe must be carried out by cold processing.
  • (2) The internal and external surfaces of pipes shall be smooth and clean, free of pinholes, cracks, wrinkles, delamination, roughness, raceways, inclusions, bubbles and other defects. Brass pipes shall be free of green rust and serious dezincification.
  • (3) The out of roundness of copper pipe shall not exceed the allowable deviation of outer diameter. The end of copper pipe shall be flat without burr. The inner and outer surfaces of copper pipes shall be free of local pits, scratches, pressed objects, bumps and other defects exceeding the allowable deviation of outer diameter and wall thickness.
  • (4) The pipes connected by flanging shall be coaxial, and the deviation is: when DN ≤ 50mm, it shall not be greater than 1mm; DN > 50mm, not more than 2mm.

18. Finished product protection

  • (1) Pipes and pipe fittings shall be properly kept and stacked separately during construction, and shall not be confused and damaged. Contact with other pipes, etc. shall be avoided.
  • (2) When the construction is interrupted, the pipe orifice shall be blocked. When installing again, check whether there is foreign matter in the pipe.
  • (3) For the pipeline laid in the trench, the sundries in the trench shall be cleaned before construction; It is strictly prohibited to step on the installed pipeline, and the trench cover plate shall be covered in time.
  • (4) Elbow work shall be carried out after thread processing, and thread protection measures shall be taken.
  • (5) The supports installed on the wall, concrete column and trench should cooperate with reserved holes or embedded iron parts during civil engineering construction, and should not be drilled arbitrarily.
  • (6) During pipeline installation, the pipeline surface shall be prevented from being scratched by sand or other hard objects.
  • (7) Before handover and acceptance, the construction unit shall specially organize finished product protection personnel to be on duty for 24 hours. Ensure safety.
  • (8) Effective protection measures shall still be taken for the pipes after pickling, purification or degreasing.

Surface quality requirements for copper pipes

1. The inner and outer surfaces of copper pipes shall be smooth and clean, and there shall be no defects affecting the use, such as delamination, pinhole, crack, peeling, bubble, rough scratch (pull), inclusion and green rust.
2. The surface of the pipe is allowed to have slight and local fine scratches, pits, pressed objects, spots and other defects that do not make the outer diameter and wall thickness of the pipe exceed the allowable deviation. Slight straightening and turning marks, ring marks, oxidation color, darkening, water marks and oil marks shall not be used as the basis for scrapping.
3. If there are special requirements for the surface quality of pipes (such as pickling, degreasing, etc.), they shall be determined by the supplier and the demander through negotiation and indicated in the contract.
4. The copper pipe to be polished in the next process shall be subject to trial polishing inspection. During trial polishing, it shall be sanded and polished, and the depth of one side shall be 0.02mm – 0.04mm. After polishing, the product shall meet the following requirements:

  • (1) Sand hole and pinhole impurity points (maximum 0.2mm): no more than 4 are allowed within 200mm of the product.
  • (2) Bruise (max. 0.3mm) × 0.8mm): no more than 2 places are allowed within the 200mm length of the product.
  • (3) No more pull (scratch) marks, cracks, peeling and other defects are allowed.
  • (4) The total number of sand holes, pinholes and bumps within any 200mm length shall not exceed 6.

How to judge the quality of copper pipe

  • 1. Generally, it is necessary to observe the appearance of copper tubes to judge during procurement. The first thing is to look at the color of copper tubes. Judge different colors according to the type of copper tubes purchased, such as purple copper tubes. Generally, red copper with red color is good copper, and there are impurities in poor copper.
  • 2. Generally, good copper pipes are processed from pure copper, which will have better extensibility, so high-quality copper pipes will have a deep line. If the inside of the copper tube is the same as the outer wall, it indicates that the overall quality of the copper tube is relatively high. However, if the color or other aspects are different, it is likely to add some substances similar to iron. However, more good copper tubes are used in military industry and its special industries.
  • 3. Generally, copper pipes processed and formed are mainly divided into hard state, semi-hard state and soft state. The flexibility of different forms is also different. Generally, it can be determined by bending copper pipes. High quality copper pipes are very easy to bend, but if it is difficult to bend or cracks will appear after bending, it indicates that the quality of copper pipe parts is not very good.

Packaging and marking requirements for copper tubes

  • 1. The thin-walled copper pipes that are easy to be deformed and damaged during shipment and storage can be packed in tile cartons or in wooden boxes after being separately packed in paint bags (or plastic bags). The quantity, brand, specification and model of copper pipe and the manufacturer of copper pipe shall be marked outside the packing box.
  • 2. Copper pipes with thick pipe wall and not easy to be deformed and damaged during transportation and storage can be packed in bundles according to a certain number, wrapped with woven bags or paper, and bound with adhesive tape outside the wrapped woven bags or paper. When using this method for packaging, the two ends and the middle of the bundled copper pipes shall be bound at least. Bundles of copper pipes shall be marked with the number, brand, specification, model and manufacturer of copper pipes.
  • 3. Pipes with a diameter (or edge to edge distance) of no more than 10mm can be packaged in coils (rolls) with a length of no less than 4m. The coiled (rolled) copper pipe shall be marked with the name, specification, model, brand, weight and manufacturer of the copper pipe.
  • 4. For copper pipes with large wall thickness, it is allowed not to use packaging supply on the premise of ensuring quality. For copper pipes supplied in bulk, the specification, model, brand, etc. of copper pipes shall be marked on each copper pipe.
  • 5. The supplier and the demander can negotiate according to the actual situation and adopt other packaging methods to ensure the quality of copper pipes.
  • 6. Regardless of any packaging method such as bundle, disc (roll) or box. It is not allowed to supply copper pipes with different names, specifications, models and brands, nor is it allowed to supply copper pipes in bulk.

Source: Network Arrangement – China Copper Pipes Manufacturer – Yaang Pipe Industry Co., Limited (www.steeljrv.com)

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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