Valve installation guide and practical connection method Method for external leakage treatment of power station valves

Valve installation guide and practical connection method Method for external leakage treatment of power station valves

Warm welding and silver brazing
It is important to remember the recommended valve use and analyze the application environment to determine which valve is best suited for installation. Before installing the correct valve, read the installation guide to prevent damage to the valve and to ensure full performance of the valve.
1. Cut the pipe vertically, trim and remove burrs, and measure the pipe diameter.
2. Brush the pipes and cutting parts with gauze or steel wire to make the metal surface shine. Steel velvet is not recommended.
3. Apply flux to the outside of the pipe and the inside of the welding cover. Flux must completely cover the welding surface. Please use flux sparingly.
4. Make sure the valve is open. Heat the pipe first. Transfer as much heat as possible from the pipe to the valve. Avoid prolonged heating time of the valve itself.
4A. Silver brazing method:
Assembly of parts to be brazed. If the flux-coated parts are allowed to stand upright, the moisture in the flux will evaporate, and dry flux will easily peel off, leaving exposed metal surfaces vulnerable to oxidation. In connection assembly, insert the pipe into the casing until it encounters obstruction. Assembly is to ensure that there is a firm support to maintain a straight position throughout the brazing operation.
Note: For valves of 1 “or greater nominal size, it is difficult to heat the connection to the required temperature all at once. In order to maintain a normal temperature over a large area, two welds are usually required. Proper preheating of the entire casing area is recommended. Acetylene flame is recommended for heating the connecting parts. Heat the pipe starting 1 inch from the valve, then flame the pipe up and down alternately a short distance around the pipe, turning the pipe at an appropriate Angle to avoid burning through the pipe. The flame must move continuously and not be allowed to stay at a single point.
Bake valve sleeve base with flame. Heat evenly and flame the valve and pipe until the flux on the valve no longer makes a sound. Do not overheat the valve.
When the flux is liquid and translucent on the pipe and valve, begin to bake the flame back and forth along the axis of the joint to keep the joint hot, especially at the base of the valve sleeve.
5. Use appropriate solder: if using wire solder, use 3/4 “solder for nominal 3/4″ diameter valves, etc. If too much solder is used, some of it may flow through the pipe barrier and clog the seal area. Solder and brazing alloys continue to flow as the joints are installed
5a. Silver brazing method:
Spot solder wire or rod on pipe socket in valve. Remove the flame from the rod or wire as it enters the joint. Move the flame back and forth as the alloy flows into the joint. When the right temperature is reached, the alloy will flow quickly and easily into the space between the pipe housing and the valve sleeve. When the joint is filled, the edges of the welded alloy are visible.
6. When solder is sticky, clean off excess solder with a brush. When the solder cools, place a strip around the end of the valve.
Silver brazing
The strength of the brazing joint may not be good if different brazing materials are used, depending on normal, extensive cleaning and maintenance between the casing and the valve sleeve. The mechanical tolerances and surface smoothness of the internal diameter of silver brazed valve sleeves are required to be very precise to ensure adequate adhesion.
Note: The residue of the cleaning medium should be carefully observed during cleaning and during the process. Soldering on surfaces that have been soiled or improperly cleaned is not satisfactory because silver brazing alloys do not flow over or adhere to oxides, and greasy surfaces and exposed surfaces tend to oxidize and cause voids and debris to reject the flux.
Threaded connections
Accumulation of slag, dirt, or any external material in the pipe line can interfere with the efficiency of the valve and seriously damage critical components of the valve. The inside of the pipe must be thoroughly cleaned with air or steam.
When tapping pipe, measure pipe thread size and length to avoid filling pipe with seat and disc.
Thoroughly clean thread ends for any harmful steel or iron deposits. If you want a stronger weld, use teflon tape or pipe adhesive. Pipe adhesive should be used sparingly on pipe threads, but not on valve threads. Do not allow any pipe adhesive into body to avoid damage to disc and seat.
Before installation, cut off flow through valve to allow valve to work properly. Close valve completely before installation. Place the wrench over the hex bolt head near the pipe to avoid possible distortion. After valve installation, support line: sagging line can distort valve and cause failure.
Flange connection
To ensure proper assembly of the valve cord, follow the following steps. First clean the joint carefully, then loosely install two or three bolts in the base. Next, carefully insert the gasket into the joint. Bottom bolts help to position the gasket and hold it in place. Insert bolts should then be cross-screwed, not loop-screwed, to help eliminate excessive concentration of pressure. After a period of normal use, check and verify that all bolts are tightened and re-tighten as necessary
Treatment method for external leakage of power station valve
1. Leakage of valve packing
Stem and packing will move with each other and this will be reflected in the use of the valve. The more times the valve is opened and closed, the more movement there will be. In addition, the effect of temperature, pressure and so on will greatly increase the possibility of leakage of the valve packing, during this time the pressure of the packing will gradually decrease, thus aging, elasticity will no longer exist. And the pressure medium will leak out from the contact gap between the packing and the valve stem. If this problem is not properly solved, with the passage of time, the condiment will be blown away and the valve stem will be separated from the groove, making the leakage surface bigger and bigger.
2. Leakage of flange
Flange leakage is often caused by more than one aspect, such as the sealing gasket pressure is not enough, the roughness of the joint surface and the requirements of a certain distance, gasket deformation, resulting in the sealing gasket and the flange did not reach full contact and the gap, leakage will then occur. At the same time, the flange surface sealing is not strict because of bolt deformation or elongation, gasket aging, resilience decline, cracking, etc., which can also produce leakage. In addition, human factors are also the flange leakage needs special attention. In addition, the valve body can also produce leakage problems due to space constraints, not described here.
3. Methods for handling external leakage of power station valves
Packing chamber leakage with pressure plugging treatment
There are many ways to deal with the external leakage of power station valves, among which the safety of injection type with pressure plugging technology is relatively high, which has been more detailed conclusions. This method uses a special fixture and hydraulic injection tools, the sealant is injected into the fixture and the leakage part of the outer surface formed by the sealing cavity, the remedial effect of leakage defects is better, and the time used is relatively short. When the injection pressure exceeds the pressure of the leakage medium, it will strongly stop the leakage, so that the injection from the plastic body into the elastic body, at this time the sealing structure has a certain elasticity, and there is a certain specific pressure of the working seal, the final formation of the secondary seal, which undoubtedly increases the good sealing performance. The following two kinds of sealing injection agents are widely used and promoted in China 1) heat curing sealing injection agent. The use of this injection needs to meet certain conditions, that is, the temperature, the temperature reaches a certain degree of the case, the injection agent is an elastic body, the general case is a solid. (2) non-heat curing sealing injection agent. Its scope of application is very wide, all kinds of temperature conditions can be operated, high pressure injection can also be installed, injection and filling are better, the valve switch function can also be well preserved. When the wall thickness of the valve packing box is more than 8 mm, the use of injection pressure to deal with the leakage problem can be directly set up in the valve packing box wall injection hole, sealing cavity is the valve packing box itself, sealing injection can play the same role and packing. Find a proper position to open a hole in the outer wall of the valve packing box with a diameter of 10.5mm or 8.7mm. It is important to emphasize that this hole should not be drilled through, with a distance of 1-3 mm. Pull out the bit and tap with an M12 or MIO tap. The valve should be in the open position and then a long rod bit, 3 mm in diameter, should be selected to drill through the remaining valve packing wall and leak will be eject in the direction of the bit. Drilling will have a certain risk, mainly because the temperature or pressure is too large or contains toxic substances ejected will give the staff to bring certain harm, light wounding, heavy will also threaten the safety of life, so this can not be ignored, before drilling with baffle is a better control method.
Flange leakage with pressure plugging treatment copper wire containment method
This method is applicable to the two flange gap is small, the gap is uniform, the leakage medium pressure is low with pressure plugging, bolt injection agent joint shadow placed on the removed bolt, two are low, should be more than two. Installation note agent joint don’t put all the nut screwed tight, but to loosen a and installed after a joint, then tighten the nut immediately, install the he joint injection agent, here is not to be highlighted will need the union nut loosen at the same time, because of the sealing gasket can reduce pressure, leakage increase, severe cases, leak material will blow away the gaskets, If this happens, remedies are hard to come by and the damage is incalculable.
Valve body leakage with pressure plugging treatment
1. The bonding method
If it is the pressure medium and small leakage of sand hole parts, you can first polish the metal luster around the leakage point, and then use taper pin to the leakage point, with appropriate strength to drive, mainly in order to reduce leakage or temporary plugging. Adhesives cure faster and can be used to coat the pin with adhesives to create a new solid seal that can prevent leaks to some extent. If high medium pressure, leakage is big, can seal operations, with the method of roof pressure tools, operating in the process of jacking mechanism fixed on one side of the valve, high pressure screw, make the top screw’s axial pressure is the leak point, rotating pressure screw, using jacking screw the end of the rivet holding pressure on the leak, it is also an effective way to stop the leak. If the top of the rivet is smaller than the area of the leakage point, a soft metal sheet can be placed under the rivet. When the leakage stops, the metal surface around the leakage point should be cleaned in time.
2. The welding method
If the body is the leakage of medium pressure is low, small amount of leakage and available diameter than the leak more than twice as large as nut, so that we can make the leakage of media from escaping from the nut, the nut welding on the valve body, with a bolts and nuts the same specifications, place a piece of rubber mat in the bottom of the nut or asbestos mat, will bolt wire on the top tape screwed into the nut, Can effectively reduce the occurrence of leakage. If the valve body leakage medium pressure is high, the leakage is large, then the drainage welding method is a better method. First with a piece of iron plate, open a round hole in the middle, a round hole with the diameter of the isolation valve welding in the round hole of the iron plate, open the isolation valve, the iron plate center hole aligned with the leak point fitted in the valve body, let the leakage medium flow out of the iron plate center hole and the isolation valve. For the laminating surface is not good, can be used in the laminating surface placed rubber or asbestos pad, and then the iron plate around the valve body welding, and then close the isolation valve, so that the sealing effect can be achieved is also better.