Category: Valve

Socket-Welding Procedure

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The procedure for making a socket weld is as follows:

1. Cut the pipe end square, making sure the diameter is not undersize or out of round.
2. Remove all burrs with a metal file.
3. Clean the pipe end, valve joint, and the inside of the valve socket with a degreasing agent to remove any oil, grease, or other foreign material.
4. Insert the pipe end into the valve socket and space by backing off the pipe after it hits against the shoulder inside the spacing collar. Tack weld in place.
5. Make certain the valve is in the open position before applying heat. Valve bonnets should be hand-tight to prevent distortion or damage to the threads. Nonmetallic discs should be removed before applying heat.
6. The valve and pipe should be supported during the welding process and must not be strained while cooling.
7. Preheat the welding area 400°F to 500°F .
8. A socket weld can generally be completed in two to four passes, depending on the welding method used. Make sure the first pass is clean and free from cracks before proceeding with the second pass. Avoid excessive heat because it may cause distortion to the valve bonnet.
9. Use a wire brush and a clean cloth to remove discoloration.

Butt-Welding Procedure

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The procedure for making a butt weld is as follows:

1. Machine the pipe ends for the butt-welding joint.
2. Clean the pipe ends, valve joint, and the inside of the valve socket with a degreasing agent to remove oil, grease, or other foreign materials.
3. Align by means of fixtures, and tack weld in place.
4. Make certain the valve is in the open position before applying heat. The valve bonnet should be hand-tight to prevent distortion or damage to the threads. Nonmetallic discs should be removed before applying heat.
5. The valve and pipe should be supported during the welding process and must not be strained while cooling.
6. Preheat the welding area 400°F to 500°F .
7. Depending on the welding method used (gas, arc, and so on), a butt weld is normally completed in two to four passes. The first pass should have complete joint penetration and be flush with the internal bore of the pipe. Make sure the first pass is clean and free from cracks before proceeding with the second pass. The second pass should blend smoothly with the base metal and be flush with the external diameter. Avoid excessive heat because this can cause distortion and possible malfunctioning of the valve.
8. Use a wire brush and a clean cloth to remove discoloration.

Soldering or Silver-Brazing Procedure

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The basic procedure for soldering or silver-brazing pipe or tubing to valves is as follows:

1. Cut the tube or pipe end square, and make sure the diameter is not undersize or out of round.
2. Remove all burrs with a metal file.
3. Clean the pipe or tubing end (at least to the depth of the socket) and the inside of the valve socket with steel wool and
a cloth to wipe away the residue.
4. Clean all surfaces with a suitable solvent and wipe dry.
5. Apply solder flux or silver-brazing flux to the inside of the valve socket and the outside of the pipe or tubing.
6. Insert the pipe or tubing into the valve socket until it seats against the shoulder within the socket.
7. Turn the valve and the pipe or tubing once or twice to evenly distribute the flux.
8. Make certain the valve is in open position before applying heat. A nonmetallic disc should be removed before the heat is applied. After removing the disc, the valve bonnet or bonnet ring should be replaced hand-tight to prevent distortion to the threaded sections when heating the valve.
9. Make certain the valve and pipe or tubing are properly supported during the soldering or silver-brazing process. Any strain on the joint while cooling will weaken it.
10. Apply flame evenly around piping or tubing adjacent to valve ends until solder or brazing alloy suitable for the service flows upon contact.
11. Soldering: Apply solder to the joint between the pipe or tubing and the end of the valve socket. Apply the flame toward the bottom of the valve socket until all the solder is absorbed. Control the direction of the flame away from the valve body to avoid excessive heating, which causes distortion and improper functioning of the valve.
12. Silver brazing: Apply brazing alloy to the joint between the pipe or tubing and the end of the valve socket. Wave the flame over the valve hexes to draw the metal alloy into the socket, leaving a solid fillet of brazing alloy at the joint. Control the direction of the flame away from the valve body to avoid excessive heating, which causes distortion and improper functioning of the valve.
13. Remove all excess and loose matter from the surface with a clean cloth or brush.

Valve Installing Pointers

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Unless valves are installed properly, they will not operate efficiently and can cause problems in the system. There are certain precautions you should take when installing valves that will improve their performance and minimize the possibilities of a malfunction. These precautions may be summarized as follows:

1. Always clean out a valve before installation because dirt, metal chips, and other foreign matter can foul it. This can be done by flushing the valve with water or blowing it out with compressed air.
2. Clean the piping before installing the valve. If you cannot flush or blow out the foreign matter, the ends of the pipes
should be swabbed with a damp cloth.
3. Only apply paint, grease, or joint sealing compound to the pipe threads (that is, the male threads). Never apply these
substances to the valve body threads because you run the risk of their getting into the valve itself and interfering with its operation.

4. Install valves in a location that can be reached conveniently (see Figure 9-47). If the valve is placed so that it is awkward to reach, it sometimes may not be closed tightly enough. This can eventually cause leaks to develop in the valve.

valve installation Valve Installing Pointers

5. When necessary, support the piping so that additional strain is not placed on the valve. Small or medium-size valves can be supported with hangers placed on either side. Large valves should always be independently suspended.

6. Sufficient clearance is particularly important when rising stem valves are used. Failure to ensure proper clearance
before installing the valve may cause damage to the disc sealing surface.

Damaged Valve Stems

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Sometimes the threads on valve stems become worn or damaged, making the valves inoperable. When this occurs, the stems must be replaced. Before the stem can be replaced, however, all pressure must be removed. Then, with pressure removed, disconnect and remove the bonnet and upper valve assembly. The remainder of the procedure depends on the type of stem used (that is, rising or nonrising stem) and other design factors. Basically, the procedure may be summarized as follows:

1. Run the stem down by turning it in a clockwise direction.
2. Rotate the stem in a clockwise direction until the stem threads are completely out of the threaded portion of the upper bushing.
3. Pull the stem out of the stuffing box.
4. Remove the wedge or disc from the stem.
5. Replace the old stem with a new one.
6. Reassemble in reverse order with new packing and gasket (when applicable).

Valve Seat Leakage

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Leakage of water from the valve body is usually an indication that the wedge, disc, or seat ring needs replacing. For most valves, the procedure for doing this may be summarized as follows:

1. Open the valve.
2. Remove the bonnet and other components of the upper valve assembly.
3. Run the stem down by turning it in a clockwise direction.
4. Remove the wedge or disc from the stem and replace if necessary.
5. Remove the seat ring with a seat ring wrench and replace if necessary.
6. Reassemble in reverse order.

The disc, disc assembly, and ball are all possible sources of seat leakage in check valves. Access to these components is gained by removing the valve cap (counterclockwise), side plugs, and pins. Reassembly is in reverse order.

Valve Stuffing-Box Leakage

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Leakage around the valve stuffing box is usually an indication that the stuffing must be adjusted or replaced. This leakage does not occur when the valve is completely opened or closed. Therefore, an absence of leakage is not necessarily an indication that the valve is functioning normally.

Once you have detected leakage, check first to determine whether or not adjusting the packing will stop it. If it is a bolted bonnet valve, turn the packing gland nuts (or gland stud nuts) clockwise alternately with no more than 1?4 turn on each until leakage stops. If you are dealing with a screwed and union bonnet valve, turn the packing nut clockwise until the leakage stops. If the leakage will not respond to adjustment, the packing must be replaced.

The procedure for replacing the packing in most valves may be summarized as follows:

1. Remove the handwheel nut and the handwheel.
2. Remove the packing nut.
3. Slip the packing gland off of the stem.
4. Replace the packing.
5. Reassemble in reverse order.

The procedure used with bolted bonnet outside screw and yoke valves is a little more complicated. On Y valves of this type, it is necessary to remove the gland flange and gland follower before replacing the packing. On globe and angle valves, the stud nuts and upper valve assembly must be removed.

Because of their design and construction, the problem of stuffingbox leakage does not occur with check valves.