1 Current situation
The electric regulating butterfly valve is widely used in the gas pipeline network to realize the pressure adjustment of the pipeline network and the adjustment of the user's consumption and calorific value, which is an indispensable equipment in the operation of the system, and there is no other better alternative) The regulating butterfly valve is often stuck due to the influence of the gas moisture and impurities to the valve body during its operation) The stuck regulating butterfly valve will cause the system pressure to be unbalanced, and the stuck user side will lead to low user consumption or low calorific value to meet the production needs. (The jamming of the regulating butterfly valve will cause damage to the execution structure and even lead to the burnout of the motor, which increases the scrapping rate of the motor and increases the operation 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 are caused by jamming and cannot be put into use. 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 to supply, the butterfly valve jamming seriously threatens the regulation of gas system network pressure and gas supply, also increases the frequency of daily butterfly valve maintenance and increases the valve maintenance cost.
2 Cause analysis
In response to the above problems, the online regulating butterfly valve jamming and its effects are analyzed, and the main problems are as follows.
(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 differences, through the analysis of the structure of the regulating butterfly valve on site, the valve body mainly has two types, single-axis sleeve and double-axis sleeve) as shown in Figure 1, the left figure is a single-axis sleeve structure, the right figure is a double-axis sleeve structure.
Figure 1 Regulating butterfly valve two types of valve body structure
(3) the valve manufacturer is different, the valve body sleeve material selection differences, the better sleeve using copper or copper base material coated with self-lubricating composite materials, so that the possibility of shaft and sleeve rust 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 corrosion of the shaft.
3 Solution countermeasures
From the above reasons such as stuck rotation inflexibility, there are more causes of butterfly valve stuck, which makes it more difficult to judge 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 is 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 the temperature and pressure balance of the pipeline on both sides of the valve, to avoid uneven deformation and unbalanced force caused by temperature and pressure differences 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 vertical installation of the shaft head water and ash accumulation caused by the shaft and sleeve clearance damage.
(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.
Fig. 2 Example of adding oiling nozzle in actual jamming
4 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 damage of the bushings and shaft clearance. For the valve body already on line, it is impossible to change the number of bushings and bushing material online, and the problem of jamming can only be solved by solving the problem of shaft and bushing clearance damage. The feasible way is to add oil injection holes, this method does not require the butterfly valve shutdown offline, you need to process the oil injection nozzle in advance, prepare high-pressure oil injection gun can be implemented simple operation, no new problems and the introduction of risk after implementation, can be carried out online, do not need to stop gas treatment gas) by adding oil injection holes in the shaft head, 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.
The above is a comprehensive analysis of the causes of the adjustment butterfly valve jamming, thoroughly identify the causes of electric adjustment butterfly valve jamming, and put forward corresponding countermeasures for each cause, which can effectively solve the problem of butterfly valve jamming, ensure the long-cycle operation of the equipment, reduce the occurrence of media supply interruption accidents, reduce the maintenance labor intensity, focus on the summary analysis of the main causes of jamming, and put forward the solution of adding oil injection holes to the shaft head for the main causes. (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.