NIBCO Check Valve Bronze Swing - Manual (Page 5)

NIBCO Technical Services • Phone: 1.888.446.4224 • Fax: 1.888.336.4224
5
Attached to this report, in the Appendix, are proper instructions for soldering, brazing
and threading installation of valves.
In the event that it is necessary to remove the bonnet before the valve is put into a line
either for brazing, soldering or threading in, it is always essential that the bonnet be
removed with great care. The necessary steps to do this are that a good wrench with flat
jaws (not a pipe wrench) of the proper size be used to loosen the bonnet. Generally it is
best to loosen the bonnet with a slight impact to the wrench. After the bonnet is
loosened, it is absolutely necessary to make sure that no nicks or scars be put on the
body or bonnet seating surface.
When removing the disc, especially for brazing and valves which have PTFE or Buna-N
discs, it is first necessary to remove the bonnet then loosen the side plug and take it out.
After the hinge pin is removed the hanger and disc assembly can be taken out of the
bonnet area of the valve. While the PTFE and Buna-N disc are not very susceptible to
nicks, it is still wise to handle them with care so that they do not get damaged before
they are put back into the valve for reassembly.
When reassembling the valve, it is important to check the interior of the valve to see that
seats are totally clean and have not been damaged due to high temperature heat
applied during the brazing operation. If there is doubt about how much temperature has
been applied to the valve, it is a wise practice to take a flat disc and put blueing on it so
that it can be determined if there are any high spots on the seat. If there are high spots,
then a lapping operation should be done to bring the valve back into functional position.
After the hanger and disc are put in to place, the hinge pin should then be pushed into
position.
The side plug should be cleaned and reinstalled into its original position. Before putting
the bonnet onto the valve, a check should be made to assure that the disc and hanger
move freely.
When assembling the bonnet to the valve body, a slight amount of lubricant equivalent to
about 10 weight oil should be put on the bonnet joint sealing surface of the body and the
bonnet. (Some lubricants can be a serious contaminant to the line fluid. Consideration
must be given to the application when any lubrication is used). This gives lubrication so
that good tightening pressures can be applied. The wrench should be given a slight
impact for the final tightening.
After the valve has been installed, the valve should be tested to make sure that it opens
and closes easily and that the bonnet joints or pipe joints are not leaking.