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KEYSTONE Figure 990/991 ButterFly valves
InstallatIon, operatIon and maIntenance InstructIons
ExISTINg SYSTEm
1. spread the flanges with the adequate tooling.
insert some flange bolts to bear the valve.
2. Open the valve and remove the flange spreads.
3. Close the valve clockwise, return to open position
and cross-tighten all bolting.
Installation in a new system (see diagrams)
it is common practice to use the valve to help in alignment of the flanges
prior to welding the flanges into the pipeline. in such cases, the following
instruction applies:
1. Open the valve until the disc is free of the seat but still contained
within the face to face of the valve.
2. align both mating flanges with the valve center line and secure in
position using the flange bolts.
3. Position the flange/valve/flange assembly in the pipeline.
4. tack weld the flanges to the pipeline.
5. remove the flange bolts and the valve.
6. Finish weld the flanges to the pipeline and allow to cool fully.
7. Follow the procedure for installation in an existing system.
NEW SYSTEm
1. Center a flange-valve-flange assembly between
the pipes.
2. tack weld the flanges to the pipes.
3. remove the valve and finish weld. install the valve
according to the procedure in the left column.
WarNINg
Do not finish weld the flanges to the pipeline with the valve still assembled
to the flanges as this will result in serious damage to the valve seat.
3
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