SOLDERING AND SILVER BRAZING Analyze the application to determine which valve is best suitedfor installation, keeping in mind the service for which the valveis recommended. Before installing the correct valve, review theinstallation instructions to prevent damage to the valve and assureits maximum efficiency.
1. Cut tube end square. Ream, burr and size.
2. Use sand cloth or steel wire brush to clean both tube and cutto bright metal. Steel wool is not recommended.
3. Apply flux to outside of tube and inside of solder cup.Surfaces to be joined must be completely covered. Use fluxsparingly.
4. Be sure that valve is fully open. Apply heat to tube first.Transfer as much heat as possible through tube into valve. Avoidprolonged heating of valve itself.
4a. Silver Brazing Method:
Assemble parts to be brazed. If fluxed parts are allowed tostand, the water in the flux will evaporate; and dried flux isliable to flake off, exposing metal surfaces to oxidation. Assemblejoint by inserting tube into socket hard against the stop. Theassembly should be firmly supported so that it will remain inalignment during the brazing operation.
NOTE: On one inch and large valves, it is difficult to bringthe whole joint up to temperature at one time. It will frequentlybe found desirable to use a double tip torch to maintain the propertemperature over the large area. A mild pre-heating of the wholesocket area is recommended. Apply heat to parts to be joined. Thepreferred method is by oxy-acetylene flame. Heat tube first,beginning one inch from edge of valve. Sweep flame around tube inshort strokes up and down at right angles to run of tube. To avoidburning through tube, the flame should be in continuous motion andnot allowed to remain on any one point.
Apply flame to valve at base of socket. Heat uniformly,sweeping flame from valve to tube until flux on valve becomesquiet. Avoid excessive heating of valve.
When flux appears liquid and transparent on both tube andvalve, start sweeping flame back and forth along axis of joint tomaintain heat on parts to be joined, especially toward base ofvalve socket.
5. Use just enougn solder: with wire solder, use 3/4" for a 3/4"valve, etc. If too much solder is used, it may flow past tube stopand clog sealing area. When joint is filled, a continuous run ofsolder or brazing alloy will be visible.
5a. Silver Brazing Method:
Apply brazing wire or rod at point where tube enters valvesocket. Keep flame away from rod or wire as it is fed into thejoint. Move flame back and forth as alloy is drawn into joint. Whenthe proper temperature is reached, alloy will flow readily intospace between tube outer wall and valve socket. When joint isfilled, a continuous rim of brazing alloy will be visible.
6. Remove excess solder with small brush while plastic, leaving afillet around end of valve as cools. SILVER BRAZING The strength of a brazed joint does not vary appreciably withthe different brazing materials, but depends to a large extent uponthe maintenance of proper clearance between the outside of the tubeand the valve socket. The interior dimensions of silver brazingvalve sockets are machined to the closest tolerances and finishedsmooth to promote full capillary attraction.
NOTE: Care should be observed in cleaning and in removingresidues of the cleaning medium. Attempting to braze a contaminatedor improperly cleaned surface will result in an unsatisfactoryjoint. Silver brazing alloys will not flow over or bond to oxides.Oily or greasy surfaces repel fluxes, leaving bare spots whichoxidize and result in voids and inclusions. THREADING Grid, dirt or any foreign matter accumulated in the pipe canhinder efficient valve operation and seriously damage vital valveparts. Thoroughly clean pipe internally with air or steam.
When threading pipe, gauge pipe threads for size and length toavoid jamming pipe against seat and disc. Thoroughly clean threadedend to remove any harmful steel or iron deposits. For a good joint,use teflon tape or pipe dope. If pipe dope is used, apply sparinglyon pipe threads, never on valve threads. Do not allow any pipe dopeinto valve body in order to avoid damage to disc and seat.
Before installation, check line of flow through valve so thatvalve will function properly. Close valve completely beforeinstallation. Apply wrench to hex next to pipe and guard againstpossible distortion. After installation of valve, support line; asagging pipe line can distort the valve and cause failure. FLANGED There are several steps to follow to make sure that a flangedjoint will be properly assembled. First clean the joint carefully.Then loosely assemble the joint by putting in the bottom two orthree bolts. Then carefully insert the gasket into place. Thebottom bolts will help locate gasket and hold it in position. Theninsert the rest of the bolts into place and tighten all of thebolts evenly - not in rotation, but by the cross over method toload the bolts evenly and eliminate concentrated stresses. Thebolts should be checked for tightness after an appropriate intervalof use and retightened if necessary. |
