Flowserve Swing Check Valves 2.5-24 - Manual (Page 11)

Swing Check Valves FCD ADENIM0013-00
10
4.0 VALVE MAINTENANCE
(Continued)
4.1 Inspection
The most important aspect of valve maintenance is periodic inspection. The early detection of a malfunction
can, in many cases, prevent a minor defect from becoming a major problem. It is very important that leakage
from any of the major seals (disc/seat, body-bonnet) be addressed immediately. The smallest weepage can
quickly become a major problem if it is not treated promptly. Some other areas that should be included in a
periodic inspection program are:
1. Cleaning: Pressure Seal Area and Body-Bonnet Studs
2. Bolting: Body-Bonnet and Hinge Pin Cover
4.2 Cleaning
The frequency and extent of cleaning will depend on the valves' location and service conditions. Do not allow
water or dirt to collect in the body neck bore area above the pressure seal of pressure seal valves. The build up
of corrosion or extraneous material may interfere with removal of the bonnet. For the same reason, excessive
rust should not be allowed to build-up on the body-bonnet bolting of bolted bonnet valves.
4.3 Bolt Torquing
At regular intervals, not more than six months, check the tightness of all bolting. Bolted bonnet valves should
have the body-bonnet bolting torqued to the valves shown in Table 2.
4.4 Refinishing Sealing Surfaces
Minor discontinuities in both the disc and seat sealing surfaces, which may cause leakage, can, in many cases,
be removed by lapping. Major defects such as cracks or deep gouges will generally require replacement of the
part.
(NOTE: Lapping is a polishing process in which a sealing surface is ground with an abrasive held in place by a
special fixture. The abrasive is commonly found in paste form or bonded to a paper backing. Detailed
instructions on the use of lapping abrasives and fixtures, normally supplied with such equipment, should be
adhered to). In addition to the following lapping materials manufacturers' recommendations, the following
precaution should be observed. Anchor/Darling swing check valves are supplied with a crowned sealing
surface on the seat in order to provide precise seat width and tight sealing. Lapping of the seat will cause the
sealing band width to be significantly increased.
Subsequent to all seat refinishing operations, the seat width must be checked against dimensions supplied in
Table 1 and reduced if necessary. Failure to do so may create leakage problems, particularly at low pressures.