NIBCO Check Valve Automatic Stop F869B - Manual (Page 6)

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14. Before reassembly make sure all the components are thoroughly clean, particularly
gasket surfaces. Check carefully inside the valve body (still mounted on the boiler). It is
very important that all foreign particles and residue be removed from the valve. A light
lubricant such as kerosene or fuel oil may be used very sparingly for parts difficult to
reassemble. A drop or two is plenty.
15. Two new identical gaskets are required – one on top of and one under the lip of the
dashpot. The top one will seal against the bonnet and the bottom one will seal against
the body of the valve. Carefully replace the cylinder in the valve body with one gasket
under the lip. Carefully reinstall the disc-piston assembly into the valve making sure the
disc pilot pin is through the pilot pin hole in the seat ring cage. Use aligning markings put
on earlier. Make sure the piston-disc can slide up and down freely before going any
further. This can be done by grasping the piston and pulling up and down. Use two vise
grips on the flange and dashpot cylinder to keep the dashpot from moving. Don’t forget
to use a tongue depressor or the like under the vise grips to keep from damaging the
flange and dashpot lip.
16. Carefully place the bonnet and one gasket on top of the valve body making sure the
stem of the dashpot adjustment can move freely. Align with markings put on earlier.
Make sure the valve stem is well open (by turning the handwheel counterclockwise) so
the stem is not pressing on the piston. Damage can be caused when the bonnet-body
bolts are being tightened if this is not done.
17. Make sure that the body and bonnet bolts are thoroughly cleaned and lubricated before
fastening down the bonnet. Check each threaded hole carefully. Install all bolts finger
tight then torque to the figure indicated in foot pounds on the attached sheet and use the
tightening sequence indicated.
18. Operate the stem up and down by turning the handwheel counterclockwise then
clockwise to make sure nothing is preventing the piston from rising.
19. When the boiler is brought back up and steam is flowing through the valve, it is a good
idea to check for complete operation of the automatic feature. This would require closing
off then reopening. The valve should then open automatically. With pressure in the
header, if the boiler is shut down, the valve should close automatically. (The handwheel
should be in the wide open position to operate in the full check position).
CAUTION: When doing these final checks, your specific system may require additional
operation for safe performance and to prevent damage to boiler or piping components.
These steps are suggestions to check out the valve only – the operator must keep in mind
the characteristics of his own system and check out the valves using the steps based on
these characteristics.