## How to calculate the wave node number of expansion joint

The expansion has been calculated:

• Expansion = total thermal expansion length x temperature difference x safety factor x expansion coefficient

How to calculate the wave node number of expansion joint according to the expansion amount?

According to the expansion, the wave number of the corrugated compensator is calculated. According to the wave height and wave distance of each manufacturer, the wave number is uncertain.

## How to calculate the weight of expansion joint?

The pressure and compensation of the expansion joint are different, and the weight will be different.
The factory can calculate the theoretical weight according to the specific parameters of the design, and there is a slight deviation between the actual weight and the theoretical weight.
Which is more expensive, nonmetal expansion joint or metal expansion joint?

Conventionally speaking, non-metallic expansion joints are cheap, because they are all made of fabric. They are certainly not as expensive as stainless steel. But some non-metallic fabric expansion joint structure is more complex, more expensive than metal.

## Is the inlet of absorption tower metal expansion joint or nonmetal expansion joint?

Metal expansion joint and non-metal expansion joint can be used at the inlet of absorption tower. Depending on its own situation, Hongsheng non-metal expansion joint is mainly made of multi-layer soft materials, which has many advantages such as high temperature resistance, high pressure resistance, strong corrosion resistance, good flame retardant performance, sound absorption and shock absorption, good flexibility and so on. The fabric compensator has a long service life, and compared with the traditional metal bellows, it avoids the rigid force transmission caused by the connection, eliminates the pipeline vibration, solves the problem of the compensation amount of the thermal expansion and cold contraction of the fan and the unavoidable position deviation of the metal parts. And can play in the accident to the fan, the pipeline, the boiler and so on the protection function. And it is much better than metal expansion joint in transportation, installation, cost, maintenance and many other aspects.
The length of tube joint is not less than 300. Why, is it suitable for the middle tube joint of expansion joint?
In order to make the weld on boiler and pressure vessel evenly distributed and avoid the superposition of welding residual stress, the number and arrangement of weld are specified in relevant boiler and pressure vessel regulations.

• (1) When splicing the cylinder, the length of the shortest cylinder segment shall not be less than 300 mm for medium and low pressure boilers and 600 mm for high pressure boilers; the number of longitudinal welds for each cylinder segment: when the inner diameter of the cylinder is di ≤ 1800 mm, the number of splicing welds shall not be more than 2; when Di > 1800 mm, the number of splicing welds shall not be more than 3; the outer arc length between the center lines of two longitudinal welds for each cylinder segment is longer than that for medium and low pressure boilers It shall not be less than 300 mm for high-pressure boiler and 600 mm for high-pressure boiler; the longitudinal welding seams of adjacent cylinder sections shall be staggered with each other, and the outer arc length between the center lines of two welding seams shall not be less than 3 times of the thickness of steel plate and shall not be less than 100 mm.
• (2) The head and tube sheet shall be made of integral steel plate as far as possible. If splicing is necessary, when the inner diameter of head and tube sheet di ≤ 2200mm, there shall be no more than one splicing weld; when Di > 2200mm, there shall be no more than two splicing weld; the distance between head splicing weld and head center line shall not exceed 0.3di, and shall not pass through the edge pulling manhole, and shall not be arranged on the edge pulling arc of manhole; the whole splicing weld on tube sheet shall not be arranged on the edge pulling arc, and shall not pass through the edge pulling arc For the convex head composed of central circular plate and sector plate, the weld direction is only allowed to be radial and circumferential. The minimum distance between radial welds shall not be less than 3 times of the wall thickness and not less than 100 mm.
• (3) The requirements for the splicing weld of the furnace are the same as those of the cylinder. The splicing weld of U-shaped lower apron must be arranged radially, and the shortest arc length between the two weld center lines shall not be less than 300 mm.
• (4) The butt weld of the pipe shall not be arranged in the bending part of the pipe. For medium and low pressure boilers, the distance from the center line of butt weld on the straight section of heating surface pipe to the starting point of pipe bending (or the outer wall of drum, header, or the edge of pipe support). At least 50 mm, for high pressure boiler, the above distance is at least 70 mm; the distance between the center line of pipe weld within the scope of boiler and the starting point of pipe bending shall not be less than the outer diameter of pipe, and shall not be less than 100 mm; the distance between butt welds on the straight section of heating surface pipe shall not be less than 150 mm.
• (5) The main welding seam and its adjacent area of pressure parts should avoid welding parts. If it cannot be avoided, the weld of welding parts can pass through the main weld, instead of stopping in the weld and its adjacent area.
• (6) Holes, welds and corners should be staggered. The distance between the edge of the opening and the weld shall not be less than 3 times of the actual wall thickness at the opening, and shall not be less than 100 mm. When a hole is opened on a convex head, the projection distance between the edge of the hole and the periphery of the head shall not be less than 10% of the outer diameter of the head. The opening and weld are not allowed to be arranged at the corner of the part or on the edge pulling arc, and should be away from a certain distance.

## Rectangular metal bellows expansion joint

The expansion joint of rectangular metal corrugated pipe adopts rectangular section and fillet wave. The single expansion joint in the pipe bears two-dimensional displacement. Elbow joint pipe composed of two expansion joints can bear three-dimensional displacement. The rectangular fillet metal corrugated expansion joint has full height, half height type, according to the flue size, the stress-strain requirements of the user can choose multiple wave joints.

• 1. After the user selects the appropriate compensator according to the thermal displacement of the pipe system, at least the circulating medium in the pipe, the design pressure of the flue gas duct, the maximum temperature during operation, the shape dimension (length and width) of the cross section of the flue gas duct are selected (the total height is 216mm, the half height is 108mm) and the wave number (the single wave number of single wave of single wave of single wave is not more than 6 waves), so as to carry out the structure of the compensator Design and manufacture.
• 2. Maximum allowable expansion per wave: full height type △ α = ± 24mm half height type △ α = ± 12mm.
• 3. Ash baffle: the air duct or the pipe with less dust can not be used, and the dust baffle plate shall be used for the flue with more dust.
• 4. In order to reduce the number of corrugated pipe joints, cold pull should be considered 50%.
• 5. The compensator is suitable for the case where the cross-section area is less than 4.6 square meters and the outer dimension of the flue gas duct is less than 1.5m but greater than 0.6mm. Standard all height bellows compensator is suitable for all air ducts.

Due to the constraints of various aspects, it is quite complicated, but any complex pipe system can choose several fixed supports to choose different settings in different parts, and divide them into several relatively simple shape separate pipe sections, Z-shaped pipe section and π type pipe section, and determine the deformation and compensation amount of each pipe section respectively. Due to the variety of compensator, the correct selection of the type is made It is very important, so in the overall design of the pipe system, the design of the pipeline direction and support system (including fixed pipe support, guide sliding pipe frame, etc.) and the design of the compensator should be considered comprehensively, so as to achieve the best combination of safety, rationality, applicability and economy.
Rectangular metal bellows expansion joint is a flexible component with bellows as the core, and it can be compensated in three directions, namely axial, transverse and angular. Axial compensator is used to reduce the self excitation of medium. There is no inner sleeve in the product, which limits the radial compensation capacity to a large extent. Therefore, it is generally used to absorb or compensate the axial displacement of the pipeline (if a small amount of radial displacement is required in the pipe system, the maximum diameter displacement can be explained when ordering): the transverse displacement compensator (large tie rod) mainly absorbs the transverse displacement perpendicular to the axis of the compensator, and the lateral displacement of the small tie rod is mainly absorbed The compensator is suitable for absorbing transverse displacement, and can also absorb the combination of axial, angular and arbitrary displacement in three directions: hinge compensator (also known as angular compensator). It is used with two or three compensators (single hinge compensator has no compensation capacity), which can absorb transverse deformation in one-way plane. Universal hinge (angular) compensator is used by two or three matching devices, which can absorb the deformation in three-dimensional direction.

Source: China Expansion Joints 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.)