Countermeasures against jamming of gas regulating butterfly valve

What is a regulating butterfly valve?

A regulating butterfly valve is a common flow control valve that is shaped like a butterfly wing and can be used to regulate the flow of fluid. A regulating butterfly valve usually consists of a circular butterfly plate, which rotates to regulate the flow. Regulating butterfly valves are commonly used to convey a variety of fluids such as water, gasoline, oil and gas, gases, powders, and they can be used in both high and low pressure systems. The main advantage of regulating butterfly valve is its high accuracy of flow adjustment, which can control the flow of fluid more precisely, and its simple structure, easy to maintain and use.
(Regulating butterfly valve is widely used in gas pipeline network to realize the pressure adjustment of the pipeline network and the adjustment of the user’s dosage and calorific value, which is an essential equipment in the operation of the system, and there is no other better alternative) Because of the influence of gas moisture and impurities to the valve body during its operation, the regulating butterfly valve often has the phenomenon of jamming) The jamming of the regulating butterfly valve will lead to the inability to balance the system pressure, and the jamming at the user end will lead to low user dosage or calorific value. (Can not meet the production needs, and even lead to the occurrence of media interruption accidents such as user flameout) The jamming of the regulating butterfly valve will cause damage to the execution structure, and even lead to motor burnout, increasing the motor scrap rate and increasing the operating cost of the enterprise equipment) From the analysis of the use of the regulating butterfly valve in the past two years, a total of 11 regulating butterfly valve problems have occurred, of which 9 can not be put into use due to jamming. The problem of jamming accounts for 81.8% of the failure of the regulating butterfly valve.
Through the investigation of the butterfly valve site and the existing problems, the regulating butterfly valve jamming is the bottleneck problem that restricts the production and supply, the butterfly valve jamming seriously threatens the regulation of the gas system network pressure and gas supply, and also increases the frequency of daily butterfly valve maintenance and increases the valve maintenance cost.

Cause analysis

In view of the above problems, the online regulating butterfly valve jamming and its effects are analyzed, mainly the following problems.

  • (1) The regulating butterfly valve is uninterrupted operation and does not move for a long time, which is easy to cause the shaft and sleeve gap destruction and sleeve rusting and sticking to the shaft.
  • (2) The internal structure of the regulating butterfly valve is different, through the analysis of the structure of the regulating butterfly valve on site, the valve body mainly has two types, single sleeve and double sleeve) as shown in Figure 1, the left figure is the single sleeve structure, the right figure is the double sleeve structure.

20221227025933 67119 - Countermeasures against jamming of gas regulating butterfly valve

Figure.1 Regulating butterfly valve two types of valve body structure

  • (3) Different manufacturers of the valve, there is a difference in the selection of the valve body sleeve material, the better sleeve using copper or copper base material coated with self-lubricating composite materials, so that the possibility of rusting of the shaft and sleeve will be greatly reduced because of the different sleeve materials.
  • (4) The valve is not regularly test rotated on a daily basis, and the butterfly valve is regularly test rotated according to the amount of dust and saturated water contained in the conveyed medium to avoid the destruction of the sleeve gap caused by dust and water.
  • (5) The aging failure of the valve body shaft head pressure flange packing, causing the pressure flange to increase the friction of the shaft, resulting in over torque valve body does not act.
  • (6) Temperature difference and pressure difference between the two sides of the valve, causing uneven deformation of the valve plate, uneven force can not rotate or inflexible rotation.
  • (7) Incorrect installation direction, the valve plate shaft is not installed parallel to the ground, easy to cause ash accumulation on the shaft head, moisture gathering corrosive shaft.

Solutions

From the above causes such as stuck rotation inflexibility, butterfly valve stuck causes more, which increases the difficulty of judging the valve body failure.
So the daily inspection and maintenance of the valve body is more important, in order to ensure the normal operation of the valve body, mainly from the following aspects to solve the problem of valve body jamming.

  • (1) The selection of the valve body in the premise of meeting the requirements of the use of the sleeve material is preferred to copper or self-lubricating composite material regulating butterfly valve, steel sleeve easy to rust, copper material because the material with the shaft is two different materials or composite material with self-lubricating properties, the possibility of rust adhesion is very small.
  • (2) From the viewpoint of valve body structure, it is more energy-saving to choose single sleeve butterfly valve for rotation than double sleeve butterfly valve. The torque of the regulating butterfly valve is equal to the torque times the torque. In the case of a certain torque, the size of the torque is proportional to the size of the torque. The magnitude of torque is proportional to the magnitude of friction, and the friction is proportional to the friction coefficient, thus verifying that sleeve gap destruction, sleeve rusting and sticking, or packing aging will cause the friction coefficient to change, thus causing the torque to increase. In addition, it is confirmed that the friction coefficient is different for different materials of bushings, and the friction force is different for different contact areas.
  • (3) From the daily management, the valve body should be regularly test rotation. The packing of the shaft head pressure lang should be replaced regularly, and graphite packing should be selected to avoid the increase of friction caused by the aging and hardening of the grease packing or oil-free packing.
  • (4) Valve body operation to ensure that both sides of the valve pipeline temperature, pressure balance, to avoid temperature differences, pressure differences caused by uneven deformation and unbalanced force caused by the valve stuck.
  • (5) For the dust and moisture in the gas, as far as possible to control the low limit, conducive to the operation of the valve body, the valve body should be installed so that the valve body shaft parallel to the ground, so as to avoid the shaft and sleeve clearance damage caused by water and ash accumulation at the shaft head caused by vertical installation of the shaft.
  • (6) For avoiding the shaft and sleeve gap damage, sleeve rust adhesion on the shaft, shaft and sleeve gap has been a slight gap damage or has been a slight snagging problem, you can take in the shaft head hole installation oil injection hole method to the sleeve and shaft lubrication, to solve the snagging, the depth of the hole is just through the sleeve does not hurt the valve plate shaft is good. After the hole is opened, the oil injection nozzle is installed and a high-pressure oil gun is used to inject thin oil to achieve the purpose of lubrication) Figure 2 shows the example of the oil injection nozzle in the actual jam.

20221227030639 89534 - Countermeasures against jamming of gas regulating butterfly valve

Figure.2 Shows an example of oiling nozzle in the actual jam.

Effect evaluation

Through a comprehensive analysis of the causes of butterfly valve jamming, the main causes of butterfly valve jamming are the number of bushings, the material of bushings and the destruction of bushings and shaft clearance. For the valve body already on line, it is impossible to change the number of bushings and the material of bushings online, and the problem of jamming can only be solved by solving the problem of damage to the clearance between the shaft and the bushings. The feasible way is to add oiling hole, this method does not need butterfly valve shutdown offline, need to process oiling nozzle in advance, prepare high pressure oiling gun can be implemented simple operation, after the implementation of no new problems and the introduction of risk, can be carried out online, no need to stop gas treatment gas) through the shaft head to add oiling hole, can ensure that the shaft and sleeve clearance is not destroyed (sleeve does not occur rust adhesion, to avoid the increase in friction caused by The valve body is stuck due to the increase of torque caused by the increase of friction.

Conclusion

The above is a comprehensive analysis of the causes of the regulating butterfly valve jamming, thoroughly identified the causes of the electric regulating butterfly valve jamming, for each reason proposed the corresponding countermeasures, can effectively solve the butterfly valve jamming problem, to ensure the long-cycle operation of the equipment, reduce the occurrence of media supply interruption accidents, reduce the maintenance labor intensity, focused on the summary analysis of the main causes of jamming, for the main causes proposed the shaft head to add the solution of oil injection hole). (The above-mentioned is not only applicable to the gas pipeline network regulating butterfly valve, the method can also be extended to the related valve body rotation part fault judgment, processing, to solve similar problems.

Source: China Butterfly Valves Manufacturer – Yaang Pipe Industry Co., Limited (www.sfutube.com)

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