NIBCO Check Valve Automatic Stop F869B - Manual (Page 4)

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4
Guidelines for Disassembly and Cleaning
NIBCO
®
F-869-B Automatic Steam Stop Check Valves
The NIBCO F-869-B automatic steam stop check valve is the preferred type of valve used on
discharge nozzles of steam boilers in multiple boiler installations. The ANSI/ASME Power Piping
Code B31.1 makes reference to this in Section 122.1.7A.
Periodically it may become necessary to perform maintenance on these valves to keep them
performing at their best. Depending on the water used, conditioners used in the water, as well
as other characteristics of the piping system, accumulation of scale and other foreign materials
may interfere with good operation of the valve.
After some years of operation, it would be wise to disassemble the valve and inspect for buildup
of scale, damage to seating surfaces or any other cause that may interfere with good operation.
This can be done during normal shutdown and is not a complicated or expensive job if done
properly. Normally, insulation will not have to be removed. Insulation is usually limited to the
body portion of the valve. The body should not have to be removed from the system in the
majority of cases. In an effort to improve maintenance efficiency, some large multiple boiler
installations with four or more boilers keep a spare valve on hand and change one valve every
year. This gives the maintenance staff the opportunity to renew one valve each year at their
convenience. The following will be a step-by-step guide for this purpose. Also included will be
guidelines for renewing the seat and disc surfaces.
CAUTION: A valve shop can do this type of work if they are competent. You may want to check
with others in your locale to find out if there is a competent valve shop in your area; but in no
case undertake this work yourself or assign this work to others if you have any doubts
concerning safety and/or possible damage to the valve or the piping system.
1. Shut down, isolate and drain the portion of the system where the valve is located. Let the
system cool off before starting any work on the valve.
2. Mark the body and the bonnet of the valve with chalk or an ink marker in three or four
places at the bonnet-body joint to serve as aligning marks during reassembly. Open the
valve main operating stem all the way with the handwheel.
3. Remove the valve bonnet-body bolts.
4. Remove the bonnet assembly from body. This must be done very carefully to avoid
damaging the main operating stem or the dashpot adjustment stem. The dashpot
adjustment stem sticks down into the dashpot without much clearance. Jerking or quick
release of the bonnet may result in damage. It may be necessary to loosen the gasket
between the bonnet and the dashpot in the body with a putty knife or some similar tool
before lifting off the bonnet. Be careful to lift the bonnet straight up until the dashpot
adjusting stem clears the dashpot. Take care when setting the bonnet down not to
damage or bend the dashpot adjusting valve stem.
Mark the position of the dashpot adjustment assembly on the bonnet if you remove it
from the bonnet. You may want to mark the open and closed position of the dashpot
adjustment valve permanently by using a small punch mark on the top of the bonnet.