Selection of common pipe fittings for dairy production lines
Dairy production line is a kind of food production line, modern dairy/beverage/wine/pharmaceutical industry is actually a branch of the chemical industry, and the production line has a great commonality.
Chemical industry is a “sex change” process, different from the “shape change” of machine processing, the equipment is relatively simple, and all the production lines are “tubes, pipes and tanks”, i.e. for reaction (tanks) and process transport (pipe), which is also the main work of the dairy engineering enterprises. Used for conveying (pump), online processing (separation, homogenization, sterilization), providing reaction conditions (heat exchange) and packaging machines, the actual does not belong exclusively to the small industry of dairy machinery, but the specialized adaptation of general equipment.
This article will start with the selection of pipe fittings.
Process piping materials used for materials and CIP need to meet the requirements of food-grade stainless steel, commonly used are.
AISI (American Iron and Steel Industries Association standards) 304 and 316L. 304L and 316 are also in line with food requirements, but generally difficult to buy. This may be related to domestic thinking, either the most basic and cheapest, or the most high-grade and most expensive, the middle of all do not want.
Stainless steel that does not come into contact with food, such as platforms, brackets, bridges, distribution cabinets, insulation shells and the like, you can use AISI202, AISI430.
304, 316 is austenitic stainless steel, theoretically no magnetism, but because of mechanical processing may be brought on the magnetic, so can not be magnetic as the only criterion to determine the “stainless steel”. 202 only slightly magnetic, it is also austenitic, but corrosion resistance does not reach food grade standards, 430 is a ferritic stainless steel, can not be used for Food contact surface, can meet the general production plant moisture requirements. I often say, “design is to highlight and compromise, not simply a pile of advanced technology”, the choice of materials is also the same reason, as long as the air is not filled with thick acid fumes, with 316L insulation shell, bracket, platform is meaningless, only to show that “I have money “Just (it is recommended that the platform and bracket etched on a large “316L”). Of course, the use of 202, 430 stainless steel to deceive customers is 304, is to cut corners.
Dairy production line is a complex combination, not only need to use non-metallic materials (mostly for sealing), but also because of the performance required (often impact resistance requirements), have to use non-stainless steel metal materials, such as the locking ring inside the separator, homogenizer / high-pressure pump plunger, check valve, etc.. It is necessary to inform the pipe fittings and valves supply manufacturers of the type and characteristics of the material, which is likely to affect the selection of sealing materials (temperature resistance, pressure resistance, resistance to acid, alkali, grease corrosion).
Pipes are mainly divided into two categories: seamless steel pipes and welded steel pipes.
The expression of seamless steel pipe is “outside diameter x wall thickness”, which has n more outside diameters to choose from, but also with n more wall thickness, the length is also “variable”, when ordering, you need to specify: material (or standard number), the length of each steel pipe, outside diameter and wall thickness, polishing requirements etc.. The industry is mostly used for steam pipes. When buying more by weight, so that both sides are more fair.
Seamless steel pipe needs to be used with standard Dn specification valve fittings, so seamless steel pipe in the selection should be as close as possible to the standard Dn specification of the outside diameter (such as 32 with Dn25, 48 with Dn40, 57 or 60 with Dn50, 76 with Dn65, 89 with Dn80, 108 with Dn100, a few millimeters short of the welding to find it. (Hardware Manual” are Dn specification standards), these are also the most readily available specifications on the market (seamless steel pipe wall thickness do not go with the Dn pipe, it is too wasteful, huh . ), do not have to choose special specifications for theoretical calculations of the flow of the pipe, a little difference will not have any impact, the pipe fittings manufacturers will not produce a batch specifically for your project.
“Low-pressure fluid welded pipe” and “galvanized steel pipe” is a standard diameter and wall thickness with the (Dn) series, the general length of the steel pipe is 6m, that is, “fixed size”. They are mostly used in the industry for water and ice water pipes. Because the outer diameter, wall thickness is a fixed specification, the weight per unit length is also fixed, so when buying more by the number of meters, but also pay attention to check whether the diameter and wall thickness is sufficient, or by weight pricing.
Commonly used “stainless steel welded steel pipe” has a relatively much simpler “specification series” (that is, a higher degree of stereotypes), but at the same time there are multiple standard series, the domestic industry commonly used ISO (International Standards Committee standards) specifications (it seems that only GEA Company with the German standard), the actual “imperial standard”, that is, 1 inch (25.4mm) as the standard unit of external diameter, fixed wall thickness of the pipe standard. Food pipe polishing requirements are generally “inside mirror outside matte”, do not advocate “outside mirror”, not conducive to visual protection, certain special purposes for heat transfer can be “inside mirror outside pickling “, that is, the outer surface is not polished. The most common length specification of steel pipe is 6 meters, not specially proposed, that is, the default.
Commonly used ISO style food grade, low pressure fluid welded stainless steel pipe OD series are:
- 3/4 inch – 20mm.
- 1 inch – 25mm.
- 1-1/2 inches – 38mm.
- 2 inches – 51mm.
- 2-1/2 inches – 63mm.
- 3 inches – 76mm.
- 4 inches – 102mm.
ISO standard no 1 1/4 inch (32 pipe) and 3 1/2 inch (89 pipe), the design should be avoided to prevent the difficulty of purchasing matching valve fittings, but also optimize the procurement and spare parts.
Frequently encountered problems also.
The so-called “points”, that is, 1 inch into 8 parts, “4 points of the pipe” that is 4/8 (1/2) inch specifications, “6 points of the pipe” that is 6/8 (3/4) inch specifications.
The so-called “Dn/nominal diameter” is found in “carbon steel welded pipes for low pressure fluid transportation” and “galvanized pipes”, whose outer diameter and wall thickness are completely fixed in the matching series. However, the nominal diameter is not the outside diameter or inside diameter, but only a general name in the early days (presumably related to the earliest British standards of mold, weight and so on), and has been used since. It is 1 inch as the standard unit of diameter, often said Dn50 pipe, the actual “two-inch pipe”.
The reason why the pipe is more British system, is undoubtedly the embodiment of the authority of the British Empire at that time . the United States to the British immigrants mainly established, of course, also used and expanded the scope of application; and Germany, Russia standards are often limited to their own country, the industry in the early years of the use of stainless steel pipe (such as the old equipment 40, 50 cold-drawn stainless steel pipe) had according to the seamless pipe specifications (once that the seamed pipe can only be used as a decorative pipe, because at that time welding Poor quality, huh . ), but because of technological advances and the widespread use of imported equipment, ISO system style has become mainstream.
Common process valve
1. Butterfly valve
Butterfly valves are quick and convenient to open and close, have a certain rough adjustment effect (but can not be used for real adjustment occasions), better hygiene, is the most common valve on the process pipeline of dairy production line.
When installing, it is important to remember that the valve handle is in the same direction as the valve plate, and the vertical pipeline direction is off, and the pipeline passage direction is open.
When multiple butterfly valves are installed intensively to form a valve group, attention must be paid to the valve handle activity space not to interfere.
2. Ball valve
The process pipeline of food production line is not recommended to use ball valve, because when it is opened, the contact surface of the ball and the shell cannot be cleaned. If you must use, you should choose to use the passage detachable two-piece or three-piece sanitary ball valve, the common “pipe ball valve” should be strictly prohibited for material piping (of course, water generally does not matter . ). When the ball valve is fully open, there is no resistance, the switch is more laborious but also can roughly adjust the flow.
3. Plug valve
Old production line common, but because the spool and shell grinding, easy to fall off the chip, the bottom of the sealed existence of cleaning dead ends, the bottom of the open must be disassembled and cleaned, is now rarely used.
In the use of three-way ball valve or plug, note that the direction of the valve handle is sealed, while the other three directions for circulation.
4. Check valve
One-way valve generally has a spring type, ball two.
Spring-type check valve forward through, overcome the spring force, through the gap between the valve plate and the shell over the material, the reverse will be the valve plate and interface to push the strict seal, can not be over the material.
Check valve is divided into two types, one is straight type, one interface is large, one interface is small, the diameter of the ball inside between the two, forward when the ball is topped to the large mouth can pass the material, reverse when the ball sealed the small mouth can not pass the material; one is Y type, forward when the ball is pushed to the Y branch, reverse when the ball is topped to the small mouth.
Because the internal structure is quite complicated, check valve should be avoided for material pipeline, must be used, before and after should be installed live knot, in order to disassemble cleaning.
Now more spring type check valve, is because the ball check valve ball and interface grinding wear, use a period of time after the leakage law is higher, for the ball material, processing accuracy and valve body interface processing accuracy requirements are very high, while the spring type only the valve plate and interface only axial friction, wear can rely on the spring force to make up for the material, accuracy requirements are slightly lower, the service life is also longer.
In fact, the Y-type ball check valve has the smallest fluid resistance, almost negligible, spring-type check valve must be strictly controlled the number of tandem, the best a pipeline only 1, at most 2, otherwise the pump head must be increased.
In the CIP return pipeline, the check valve must be installed at the end of the branch pipeline is not necessary, the location is often in mid-air, installation and maintenance is very inconvenient, and since the installation is inconvenient, the installation error may be larger, often affecting the closure of the check valve.
Check valve before and after the best section of “no pipe straight section”, in order to allow a smooth flow of fluid to the center, for resistance, life, closure are good.
5. Seat valve
Although many of the pneumatic valves in the automated production line are seat valves, which can achieve a variety of circulation, but I do not recommend the use of manual seat valves for switching occasions (recommended for regulating occasions).
The simplest L-type seat valve is actually a kind of shut-off valve, rely on the rotation of the handle to raise / lower the valve plate, increase / reduce the flow area, handle mechanism, valve plate, valve seat for specialized transformation, is a regulating valve. The remaining T-type, F-type, etc. are commonly used for switching between multiple pipelines.
The manual seat valve is used for switching operation, not only is it slow, but it is often difficult to confirm whether it is “fully” open or closed when the handle is turned, often resulting in malfunctions and even cascading accidents. Pneumatic seat valves are pneumatically actuated by a cylinder that moves the stem quickly and can be fitted with a top control unit to monitor the stem position, eliminating this concern.
Seat valve resistance, not recommended for high-pressure, viscous material pipeline, if you also want more than one seat valve in series, then …… pray that God blesses you pump it .
6. Safety valve / pressure relief valve / back pressure valve
The principle of these three is almost the same, are pre-loaded through the spring or compressed air force, through the role of the cylinder / cavity, to the fluid “pre-set” a resistance, when the material to overcome this force, through / discharge, to ensure the basic stability of the pressure in the pipeline. These three valves are less common, lazy nonsense.
7. Live knot
Live knot is divided into threaded head (or called 1/3 live knot), flat head, threaded sleeve (these two together can be called 2/3 live knot) and sealing ring composition, used in the need for pipe disassembly occasions. In order to save costs, in the need to use only 1/3 live knot (such as the distribution of each joint of the pipe plate) or 2/3 live knot (this is rare, unless the equipment manufacturers do not have a full set of interface live knot), the occasion should be specified when ordering, otherwise you are left with that half in addition to expanding the internal demand is of little use.
Hygienic live knot should be butt-welded, not the old-style plug welding, should be a round thread to avoid cutting workers’ fingers, while contaminating material.
The whole line of live knot should be as far as possible to maintain the same system (such as SMS specifications), may be a particular equipment live knot specifications, do not toss the supply department in order to match it, cut down, weld a standard forget. Of course, it is best to request when ordering equipment and instruments, “each interface must be matched with a complete set of live knot / sanitary chuck”, some Manufacturers at this time, such as the price is too high, simply set the “welded interface”, after the arrival of their own welding live junction.
Even if it is a sanitary live junction, it is also a possible point of contamination, so you should avoid using too much, to meet the maintenance requirements can be. Some old ideas often want to “disassemble flexible”, for modern medium and large production lines, is often flexible enough to deform? Do new production lines have to consider the demolition requirements? Oh . and the old idea often want to “disassembly cleaning”, but the CIP system is already a standard configuration of medium and large production lines, unless the production line design is not reasonable, the installation is not qualified to “disassembly” well . even if the habit of disassembly and cleaning once a month, there is no need to The production line into the “parts state” well .
Of course, the necessary live knot or have to be installed, otherwise it does not become a jerry-built well, huh. I think the following occasions need to live knot:
- 1. equipment interface, including the various interfaces of the tank.
- 2. closely installed valve group, the total interface of the valve array.
- 3. important, high value, the need to disassemble and clean the valve, the interface of the online instrumentation.
- 4. the interface of the distribution pipe plate.
Other occasions, all do not install live knots, so in the selection of valve fittings, should also always choose “welded interface” of the valve fittings, and then separately welded live knots when needed. The welding is not welded, is jerry-building; should not be welded but welded, is ignorant waste, the former is a moral issue, the latter is a technical problem.
Pharmaceutical production line commonly used instead of live knot chuck, hygiene a little better, but the disadvantages are also very obvious: disassembly is more trouble, don’t look like a manual butterfly nut tightening, the actual installation error often need to use tools; remove the set is easy to lose; often need two people to operate (one to the pipe, one tightening), while the live knot only one person; locking firmness is poor, especially the large diameter.
It is not advisable to use “concentric reducer”, it looks beautiful, but when used for horizontal installation, it will cause the large mouth end of the pipe stock, vertical installation, although there is no such problem, but why purchase two specifications of the reducer? In case the eccentric is not enough, concentric can not be replaced, and vice versa, so all choose the “eccentric reducer” well.
Standard reducers are two adjacent levels of caliber (such as 38/51, 51/63), when jumping applications, it is best to use two reducers welded to maintain the versatility of the entire production line / project, if the jump 2 two levels, may not be very beautiful (in fact, who deliberately to look ah, ha ha . -), it is necessary to customize, the ordering cycle will be slightly longer.
As the branch is likely to weld the butterfly valve, in order to reduce the dead space for cleaning, “short neck” tee should be used. It is recommended to purchase “short neck” tee, and then reduce the diameter of the branch circuit when additional reducers are needed, so that the versatility of the fittings is better. In the case of cleaning requirements must be used “reducer short neck” (middle port reduction) reducer, must be specifically pointed out, processing custom, and additional storage.
In some special occasions, the standard tee may need to be transformed to meet the requirements, so it can not be completely “standardized” trapped thinking, but the optimization of transformation, should be carried out on the standard tee.
Common food-grade stainless steel elbow radius of curvature is often between 1.2 to 1.5D, the manufacturers may vary slightly.
When inspecting the goods, pay attention to the roundness of the interface and four elbows can be put together into a complete circle.
As the food-grade pipe fittings are mirror polished inside, the pipe friction resistance is negligible, except for the gravity caused by the height of the pipe, fluid resistance is mainly concentrated in the valve and elbow. In the encounter of viscous, high-pressure materials, the common right-angle elbow will appear to be resistance, may also trigger the pipeline vibration, should be customized large radius of curvature elbow, such as 3 – 5D, 8 – 10D.
If you need to use to non-90-degree elbow, the amount of small, scattered use, direct transformation of the standard 90-degree elbow can be. In fact, the two halves of the 90-degree elbow, whether or not exactly 45 degrees, anyway, just can be spelled 90 degrees, in some occasions (space or equipment limitations) is very applicable. The use of two 45-degree elbows (with sufficient straight pipe section transition in between), than a 90-degree elbow resistance is smaller, suitable for viscous materials.
Common carbon steel valve selection
This detail is very complicated, here is only a brief description.
1. Clear fluid medium
Perhaps do not have to get the material of each part, but must be clear fluid media, different media itself has different requirements for the valve material.
2. Clear fluid pressure
Carbon steel valves have different pressure levels, expressed in Pn. For example, Pn10, Pn16, Pn25, Pn40, etc., the number that is the upper pressure limit, the unit is 1 engineering atmospheric pressure (commonly known as 1 kg/pc) / 1 bar (imperial units).
Flanges also have different pressure levels, pay attention to the selection with the valve.
Valve body is generally divided into cast iron and cast steel, is the boundary of Pn16/Pn25, the price will increase exponentially (or even several times).
3. Determine the use of valves
Regulation, switching, safety, hydrophobic, etc.
4. Determine the specifications of the valve model
Due to the continuous updating of technology, the selection samples of each manufacturer should be used to determine the specifications of different manufacturers may vary a lot.
And a certain food fluid is often only one flow rate different (often the upper limit of the flow rate of non-destructive materials), water, steam and other fluids are multi-stage optional and correspond to the pressure / differential pressure, that is, when elected to a different pressure / flow rate, the pipe / valve fittings fittings specifications and interfaces will have a large change.
Therefore, in the selection, you must first find out the pressure/differential pressure/flow rate conditions, and then, according to the flow rate, to determine the specific model of the valve (see manufacturer’s sample), specifications (mostly expressed as interface specifications (Dn)) and special parameters.
Different structure/model of the valve may have the applicable range of pressure, temperature and flow rate, which should be noted when selecting the model.
Valve interface may not be the same as the diameter of the main pipe, in fact, many valves tend to increase feedback sensitivity and reduce the interface diameter, pressure reducing valves, regulating valves, safety valves, water evacuation may be one or more than the diameter of the main pipe smaller. Therefore, do not see the necking on the cry of “cutting corners”, but should be samples and instructions for reference, subject to the actual effect.
5. The valve interface form
In general, the use of pressure less than 4bar, diameter less than Dn50, you can choose the wire connection, the pressure is higher, the diameter is larger, the best choice of flange.
I’m in construction, pressure less than 4bar, diameter less than Dn25, before you think about whether to use the wire connection, because it may be necessary to repeatedly wrap a few times to do, save that little money is not enough workers tossed it, but also affect my construction image . anyway, the team of welders more, on the welding chant, certainly a full work . plumbing more wire connection, but only because of their industry history early, when welding or high precision Technology (welding technology between World War I and World War II to reach engineering practical) is not commonly used.
Source: China Pipe Fittings Manufacturer – Yaang Pipe Industry (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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