(a) Water Hammer. Severe shock to piping and equipment may occur if cold
water is injected into HTW lines too rapidly and without precaution. This
must be remembered when placing idle pumps and circulating lines in operation.
(b) Blending. When possible, use bypass valves to blend cold water with
h o t water; allow sufficient time to heat the equipment valve. If no bypass
valves are provided, slowly open main valves to permit gradual blending until
temperatures are stabilized; then open as required.
( c ) V e n t s . Check vents and see that any air accumulated in the high
points of the system is discharged.
( d ) Draining Equipment. Check operation of draining equipment (pumps,
steam ejectors) in sump pits and manholes.
(e) Manholes, Tunnels, and Trenches. Make sure manhole vents are
unrestricted, and tunnels and trenches are kept dry and properly ventilated.
(f) Aboveground Systems. Make certain that supporting structures do not
s e t t l e o r s h i f t p o s i t i o n . Insulation covering must maintain its mechanical
a n d watertight protection, and insulation must remain dry and in good physical
5 SYSTEM SHUTDOWN. Notify the generating plant and the HTW consumers before
shutting down the system. When shutting down, proceed as follows:
(a) Shut down the HTW generator.
(b) Keep the water circulating through the HTW g e n e r a t o r until inlet and
outlet water are at the same temperature.
(c) Close inlet water valve of HTW generator.
(d) Close outlet water valve of HTW generator. Open bypass valve of
o u t l e t valve to relieve the pressure until water in generator has cooled; then
( e ) If line is to be drained to sewers and the water temperature is
higher than permitted by local ordinances, make provis i o n s to cool the water
in a sump or by other means.
(f) When aboveground systems are used in cold climates, drain the lines
to prevent freezing if the system is to be out of service for a prolonged
p e r i o d of time.
( g ) If system is to be drained, keep drain and vent valves wide open to
maintain the lines in a dry condition.
(h) In underground systems, keep draining equipment in service to remove
any filtration water.