Lapping Seats - Fisher HPA Instruction Manual

Instruction Manual
D101634X012

Lapping Seats

Key numbers referenced in this procedure are shown in figure 17, 18, or 19, except where indicated.
A certain amount of leakage should be expected with metal‐to‐metal seating in any valve body. If the leakage
becomes excessive, however, the condition of the seating surfaces of the valve plug and seat ring can be improved by
lapping. (Deep nicks should be machined out rather than ground out.) Use a good quality lapping compound of a
mixture of 280 to 600‐grit. Apply the compound to the bottom of the valve plug.
Figure 7. Typical Unbalanced TSO Trim Assembly, Small Port Designs (0.8125 Inch Port Diameter)
A7111
OUTER PLUG
PIN
INNER PLUG
PROTECTED SOFT SEAT
HP and HPA Valves
July 2017
17