What is a compensator?
Compensator is also known as expansion joint, or bellows expansion joint. The utility model is composed of a bellows (an elastic element) constituting the main body of the bellows and accessories such as an end pipe, a bracket, a flange, a conduit, etc. The utility model belongs to a compensation element. The effective expansion deformation of bellows is used to absorb the size changes of pipelines, conduits and containers caused by thermal expansion and cold contraction, or to compensate the axial, transverse and angular displacements of pipelines, conduits and containers. It can also be used for noise reduction and vibration reduction. It is widely used in modern industry. In heating, in order to prevent pipeline deformation or damage caused by thermal elongation or thermal stress during heating, compensators need to be installed on the pipeline to compensate the thermal elongation of the pipeline, thereby reducing the stress of the pipe wall and the force acting on the valve or support structure.
|Types of Compensators|
|Effect of compensator|
|Installation pressure test|
(1) Corrugated compensator
1. The meaning of the corrugated compensator:
The corrugated compensator is a compensating device that utilizes the effective telescopic deformation of the elastic member of the bellows to absorb the dimensional change caused by the expansion, contraction or the like of the pipeline, the duct or the container, and belongs to a compensating element.
2. Classification of corrugated compensators:
The corrugated compensator (bellows bexpansion joint) is classified according to the displacement form and can be basically divided into an axial type, a transverse type, an angular type and a pressure balanced type bellows expansion joint (corrugated pipe).
According to whether it can absorb the pressure thrust (blind plate force) generated by the pressure of the medium in the pipeline, it can be divided into unconstrained corrugated expansion joints (bellows bexpansion joints) and constrained corrugated expansion joints (bellows bexpansion joints).
According to the waveform structure parameters of the corrugated compensator, it can be divided into U-shaped, Ω-shaped, S-shaped, V-shaped corrugated expansion joints (corrugated pipes). At present, the expansion joints (corrugated pipe) products at home and abroad adopt U-shaped waveform structure. Mostly.
3. Advantages of the corrugated compensator:
The utility model has the advantages of compact structure, less space occupation and direct burying; the disadvantage is that the manufacturing is difficult, the pressure resistance is low, and the compensation ability is small. The compensation capacity is related to the outer dimensions, wall thickness and diameter of the corrugated tube: the higher the pressure, the thicker the wall, the smaller the diameter, the greater the rigidity, and the smaller the compensation capacity. Waveform compensator is generally used for applications where the nominal pressure is ≤1.0MPa and the nominal diameter is ≥150mm. It can also be used for large diameter pipes with normal pressure and low pressure. It can be used in boiler flue gas ducts up to DN4000mm.
4. The disadvantages of the corrugated compensator:
The corrugated compensator has a thin wall that cannot withstand torque and vibration, and has poor safety; high equipment investment, strict design requirements, high construction and installation accuracy, and often fail to reach the expected life; axial corrugated compensator generates pressure thrust on the fixed bracket, resulting in The fixed bracket has a large thrust and is therefore expensive.
5. Application conditions of corrugated compensator:
The corrugated compensator cannot bear the weight and should be hoisted separately. Unless the corrugated compensator is used for reinforcement, the corrugated compensator should not be hoisted together with the pipe after welding. In the installation, the degree of the corrugated compensator should be correctly designed according to the data recommended by the manufacturer. Under any circumstances, the bellows cannot be stretched or compressed or twisted to compensate for the installation deviation, so as not to affect the normal function of the corrugated compensator, reduce the service life and increase The piping, equipment, and support members are loaded. There should be enough space around the expansion joint to ensure that the expansion joint can move freely within the design range.
(2) Rotary compensator
1. The advantages of the rotary compensator
- (1) High product safety performance: The product structure is reasonable, and the rotary compensator adopts a double seal form, one end is end seal and one side is ring seal;
- (2) Convenient design: When designing the heating network, the conditions for compensation of the bellows compensator are harsh. The five golden principles must be followed. The sleeve compensator should be “strictly found” and consider the bellows compensator and sleeve. The stress of the compensator, the blind plate force, and the like. The types of rotary compensators are various, and the compensation problem of the pipeline can be solved by selecting the appropriate type of rotary compensator according to the direction of the pipeline;
- (3) Long product life: the life of the product can reach more than 20 years;
- (4) Large compensation amount: the compensation amount can reach 1800 mm (other compensators, such as the compensation amount of the bellows compensator, the maximum compensation amount is 300-400 mm). For pipelines above DN 200, the unilateral compensation amount can be reached. 130~200 m, for pipelines with ≤ DN 200, the unilateral compensation amount can reach 100-130 m, which can be used for long-distance transmission steam pipeline compensation;
- (5) High economical operation of the pipeline: using the rotary compensator compensation, because the compensator compensates for the distance increase, the elbow is reduced compared with the natural compensation and the sleeve compensation, thereby reducing the pressure drop and reducing the tube loss of the heating network as a long distance conveying. One of the main compensation methods for the heat network;
- (6) Installation method and type diversification: According to the direction of the pipeline, combined with the topography of the site, the type of compensation of the rotary compensator is selected to solve the compensation problem of the steam pipeline. The installation is convenient, no need for cold drawing, pre-tightening and other construction processes. Welding can be;
- (7) Investment province: Due to the long compensation distance of the rotary compensator, the number of compensators used is reduced, and the thrust of the fixed pier for civil construction is small, the number of fixed piers is relatively small, and the scale of the fixed pier is relatively small, which greatly saves the civil works. Compared with other compensators, the total investment of the project should be saved by 20% to 40%, and the economic benefits are considerable.
2. Application conditions of the rotary compensator:
The rotary compensator is generally installed on the pipeline in groups of 200 to 500 m (determined according to natural terrain), and there are more than 10 installation forms, which can be determined according to the direction of the pipeline. After adopting this type of compensator, the distance between the fixed brackets is increased, and the guide brackets should be appropriately added to avoid the deflection of the pipe sections; in order to reduce the frictional resistance of the pipe sections, a rolling bearing should be installed on the sliding brackets.
(3) Square compensator
1. The meaning of the square compensator
The square compensator is also called a square expansion force or a expansion force bend, and the elastic deformation bent by the tube absorbs the thermal expansion of the pipe. To make a square compensator, a seamless quality steel pipe must be used. The whole compensator is preferably made of a single pipe.
2. The advantages of the square compensator:
- (1) It is convenient to manufacture and install. Compared with the sleeve compensator and the corrugated compensator, the axial thrust acting on the fixed bracket is small, and the thermal compensation amount is large, which is suitable for various pressure and temperature conditions;
- (2) High safety, no maintenance in normal operation, no need to set up inspection wells.
3. Application conditions of square compensator:
When installing the square compensator, in order to reduce the deformation elastic force and improve the compensating ability of the compensator, the outer arm must be pre-pulled for a certain length and then installed on the pipeline.
In the design of piping compensation, the most economical way is natural compensation. Natural compensation is to compensate the thermal displacement by the flexibility of the natural bending shape of the pipeline. Obviously, the ability of natural compensation is limited. When natural compensation can not meet the requirements, it is usually necessary to consider installing metal bellows expansion joints and other compensation devices.
The main loads of the piping system are external loads (self weight of pipes and flowing medium, internal pressure, wind load, earthquake load, etc.) and displacement load. The purpose of setting up the pipe compensator is to eliminate the force acting on the equipment or pipe, and separate the complex pipe into a relatively simple and independent expansion section to ensure the best use effect of the expansion joint. The pipeline compensator can compensate the axial, transverse and angular thermal deformation of the absorption pipeline, absorb the vibration of the equipment, reduce the influence of the vibration of the equipment on the pipeline, and absorb the deformation amount of the earthquake and ground subsidence on the pipeline. The compensator is applied to the inlet and outlet of the hot and cold piping system, iron and steel plant, thermal power plant, flue gas desulphurization, dust removal equipment, air heating, auxiliary air blower and so on. Therefore, various compensators are widely applied.
- Compensation to absorb the axial, lateral and angular thermal deformation.
- Corrugated compensator is convenient for installation and disassembly of valve piping.
- Absorb the equipment vibration, reduce the impact of equipment vibration on the pipeline.
- Absorb earthquake and subsidence to the deformation of pipeline.
- After selecting suitable compensator according to the thermal displacement of piping system, users should at least provide the flow medium in the pipe, the design pressure of the flue duct, the maximum temperature at operation, the wave shape selected by the shape dimension (long and wide) of the cross section of the flue duct (full height 216mm, half high 108mm) and wave number (a single corrugation number of no more than 6 waves), so as to carry out the structural design and manufacture of the compensator.
- Maximum permissible expansion per wave: full high delta alpha = + 24mm half high type delta = = 12mm.
- Ash tray: the air duct or dust less pipe can not be used, for the dusty flue should be used ash board.
- In order to reduce the waviness of bellows, cold drawing 50% should be considered.
- The compensator is suitable for occasions where the sectional area is less than 4.6 square meters and the size of the flue duct is less than 1.5m but larger than 0.6mm. The standard full height corrugated compensator is suitable for all smoke channels.
- (1) High elastic limit, tensile strength and fatigue strength to ensure normal operation of bellows.
- (2) Good plasticity, which is convenient for forming the bellows and can be obtained through the subsequent treatment process (cold hardening, heat treatment, etc.) hardness and strength.
- (3) Better corrosion resistance to meet the requirements of bellows in different environments.
- (4) Good welding performance to meet the welding requirements of bellows in the manufacturing process.
- For the heat pipe network laid out by the trench, rainwater or accidental sewage will be immersed in the bellows when the pipeline of the compensator is low. The materials with stronger corrosion resistance, such as iron nickel alloy and high nickel alloy, should be chosen. Because of the high price of such materials, it is possible to add only one layer of corrosion resistant alloy to the surface of the bellows when making bellows.
Source: China Compensator 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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