NIBCO Fire Protection Gate Valves - Manual (Page 5)

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5
2.0 INSTALLATION
2.1
PRELIMINARY INFORMATION
Gate valves should preferably be installed with the stem pointed vertically upward.
However, it is normally acceptable to have the valve stem pointed in a horizontal position
either in vertical or horizontal piping.
Although a gate valve will function satisfactorily in an inverted position it is not generally
recommended because it allows fluids to become trapped in the bonnet cavity resulting
in contamination and inability to fully drain the system. This is critical in water lines
exposed to freezing temperatures.
Valves are shipped in the closed position to prevent damage to the seating surfaces.
There is no internal blocking used for shipment.
2.2 HANDLING AND INSTALLATION
Each valve should be handled only with apparatus that will safely support the valve
weight. Slings should never be placed around the handwheel, stem, or gland adjustment
parts. First raise the valve to the vertical position and block it. Reposition the slings and
lift the valve vertically. Remove the expendable end protectors, if present, and install the
valve according to the piping layout.
For installation of valves into pipelines, flange bolting and gaskets, are governed by the
applicable code for pipeline specification. While the valve is being installed, it should be
kept in the closed position; and care should be taken to prevent foreign material from
entering the valve. For flange bolting data, refer to appendix.
After installation and during system testing, the gland nuts should be tightened uniformly,
if necessary, until leakage through the packing is stopped. Tighten the nuts just enough
to prevent leakage. Excessive tightening may cause difficult operation of the valve,
damage the stem, and shorten packing life (this applies to O.S.&Y. metal-seated gate
valves only. Resilient-seated gate valves incorporate split, flat rubber-washers seals for
stem sealing).
CAUTION: Care should be taken during handling, installation, and operation to prevent
personal injury and damage to valve components, especially seating surfaces.
3.0 OPERATION
Gate valves should never be used for throttling purposes. They should be fully opened
or fully closed. If the valves were only slightly opened, wire drawing and erosion of the
wedge and seats would result. It is not recommended valves be back-seated tightly, as
line contamination can build up over a long period of time and may lock up the valve
during operation.