Valve maintenance and operation of the valve electric device six choices

Valve maintenance and operation of the valve electric device six choices

Do not rely on the valve to support other heavy objects and do not stand on the valve. Stem, especially thread parts, should be wiped frequently, the lubricants have been dirty dust to replace the new, because dust contains hard debris, easy to wear thread and stem surface, affect the service life. Open and close the valve, the force should be smooth, not impact. Some impact opening and closing of high pressure valve components have taken into account the impact force and the general valve can not wait. For the steam valve, before opening, it should be heated in advance and the condensed water should be excluded. When opening, it should be as slow as possible to avoid the phenomenon of water strike.
Valve maintenance, can be divided into two cases; One is storage maintenance, the other is use maintenance.
(I) Storage and maintenance
The purpose of storage and maintenance is not to damage the valve in storage, or reduce the quality. In fact, improper storage is one of the important reasons for valve damage.
Valve storage, should be in good order, small valves on the shelf, large valves can be neatly arranged on the warehouse ground, not disorderly stacking, do not let the flange connection surface contact the ground. This is not only for aesthetics, mainly to protect the valve from damage. Due to improper storage and handling, handwheel broken, stem tilt, handwheel and stem fixed nut loose loss, etc., these unnecessary losses should be avoided.
For the valve that is not used temporarily in the short term, asbestos packing should be removed to avoid electrochemical corrosion and damage to the stem.
The valve just into the warehouse, to check, such as in the process of transportation into rain or dirt, to wipe clean, and then to storage.
The valve inlet and outlet should be sealed with wax paper or plastic sheet to prevent dirt from entering.
The valve processing surface that can rust in the atmosphere should be coated with anti-rust oil to protect it.
The outdoor valves must be covered with rain proof and dustproof materials such as linoleum or tarp. The warehouse where the valve is stored shall be kept clean and dry.
(2) Use and maintenance
The purpose of use and maintenance is to extend the service life of the valve and ensure reliable opening and closing.
Stem threads, often with stem nut friction, to apply a little yellow dry oil, molybdenum disulfide or graphite powder, for lubrication.
Do not often open and close the valve, but also to regularly turn the hand wheel, add lubricant to the stem thread, to prevent biting.
For outdoor valves, protective sleeves should be added to the valve stem to prevent rain, snow, dust and rust.
If the valve is mechanical, add lubricating oil to the gearbox on time. Always keep the valve clean.
Inspect and maintain the integrity of other valve components frequently. If the fixed nut of the handwheel falls off, it should be matched and can not be used properly, otherwise it will grind the square part of the upper part of the valve stem, gradually lose the reliability and even can not start.
Do not rely on the valve to support other heavy objects and do not stand on the valve. Stem, especially thread parts, should be wiped frequently, the lubricants have been dirty dust to replace the new, because dust contains hard debris, easy to wear thread and stem surface, affect the service life.
operation
For valves, not only must be able to install and maintain, but also to operate.
(a) manual valve opening and closing
Manual valve is the most widely used valve, its hand wheel or handle, is designed in accordance with ordinary manpower, taking into account the sealing surface strength and the necessary closing force. So you can’t use a long lever or a long spinner. Some people are used to using the wrench, should pay strict attention to, not too much force, otherwise easy to damage the sealing surface, or plate broken hand wheel, handle.
Open and close the valve, the force should be smooth, not impact. Some impact opening and closing of high pressure valve components have taken into account the impact force and the general valve can not wait. For the steam valve, before opening, it should be heated in advance and the condensed water should be excluded. When opening, it should be as slow as possible to avoid the phenomenon of water strike. When the valve is fully open, the handwheel should be reversed a little, so that the thread between tight, so as not to loose damage.
For pole-stem valves, remember the position of the stem when fully open and fully closed, to avoid hitting the top dead point when fully open. And it is convenient to check whether it is normal when fully closed. If the valve does fall off, or between the spool seal embedded large debris, the position of the stem will change when fully closed.
When the pipeline is first used, there are more internal dirt, the valve can be slightly opened, the high-speed flow of the medium can be used to wash it away, and then gently closed (not fast closed, fierce closed, to prevent residual impurities from clamping the sealing surface), open again, so repeated many times, wash the dirt, and then put into normal work. Normally open the valve, there may be dirt on the sealing surface. When closing, the above method should also be used to wash it clean, and then formally close.
If the handwheel and handle are damaged or lost, they should be completed immediately, and can not be replaced by movable plate hands, so as not to damage the stem quartet, opening and closing is not effective, resulting in accidents in production. Some media, cooled after the valve is closed, so that the valve parts shrink, the operator should be closed again at the appropriate time,
Let the sealing surface leave no seam, otherwise, the medium flowing from the seam at high speed, it is easy to erode the sealing surface.
During operation, if it is found that the operation is too laborious, the cause should be analyzed. If the packing is too tight, it can be properly relaxed, such as the valve stem skew, should inform the personnel to repair. Some valves, in the closed state, the closed parts are heated expansion, resulting in opening difficulties; If it must be opened at this time, the cover can be unscrewed half a circle to a circle to eliminate stem stress, and then the plate to start the wheel.
(2) Matters needing attention
1, 200℃ above the high temperature valve, due to the installation at room temperature, and after normal use, temperature rise, bolt heat expansion, gap increase, so must tighten again, called “hot tight”, operators should pay attention to this work, otherwise prone to leakage.
2. When the weather is cold, the water valve should be closed for a long time, and the water should be removed after the valve. Steam valve after steam, also want to exclude condensate. The bottom of the valve is silky and can be opened to drain.
3, non-metallic valves, some hard and brittle, some low strength, operation, open and close force can not be too large, especially can not make strong force. Also take care not to knock things.
4, when the new valve is used, the packing should not be pressed too tightly, so as not to leak, so as not to pressure the stem too much, accelerate wear, and hard to open and close
Six choice basis of valve electric device
The correct selection of valve electric device should be based on:
1. Operating torque: Operating torque is the main parameter to select the valve electric device. The output torque of the electric device should be 1.2 ~ 1.5 times of the large torque of the valve operation.
2. Operation thrust: there are two main machine structures of valve electric device, one is not equipped with thrust plate, and the torque is directly output at this time; The other is equipped with a thrust disc, in which the output torque is converted into output thrust through the stem nut of the thrust disc.
3. Rotation number of output shaft: the number of rotation number of output shaft of the valve electric device is related to the nominal diameter of the valve, valve stem pitch and the number of threads, calculated according to M=H/ZS (in the formula: M is the total rotation number that the electric device should meet; H is the opening height of the valve, mm; S is the pitch of the valve stem drive thread, mm; Z is the number of stem threads.)
4. Stem diameter: for multi-rotation type of open stem valve, if the large stem diameter allowed by the electric device can not pass the valve stem, it can not be assembled into an electric valve. Therefore, the inner diameter of the hollow output shaft of the electric device must be greater than the outer diameter of the stem of the open stem valve. For some rotary valves and multi-rotary valves in the dark rod valve, although do not consider the stem diameter through the problem, but in the selection should also be fully considered stem diameter and keyway size, so that the assembly can work normally.
5 output speed: the valve opening and closing speed is fast, easy to produce water strike phenomenon. Therefore, according to different conditions of use, choose the appropriate start and close speed.
6. Installation and connection mode: installation mode of electric device includes vertical installation, horizontal installation and ground installation; Connection mode: thrust plate; The valve stem through (stem multi-turn valve); Dark rod multiple rotation; No thrust plate; Valve stem does not pass; Part of the rotary electric device is widely used, is to realize the valve program control, automatic control and remote control indispensable equipment, which is mainly used in the closed circuit valve. However, the special requirements of the valve electric device must be able to limit the torque or axial force. Usually the valve electric device uses a torque limiting coupling.