JOHNSON CONTROLS
57
SECTION 3 - SYSTEM COMPONENTS DESCRIPTION
FORM 160.67-O2
ISSUE DATE: 10/9/2020
3
The leak-off steam is commonly piped to a sewer or
open header. If this line becomes partially clogged, or
the back pressure builds up for any reason, steam will
blow out around the shaft at the packing gland.
Some machines may be equipped with an optional
gland condenser which condenses the gland leakage as
well as steam leaking from other leak-off connections.
The condensate from this gland condenser can be re-
turned to the feed water system.
Gland Leak-Off Condenser - Optional Supply
by Special Quotation
This equipment may be specified for use on high back-
pressure applications, those turbines operating with a
high pressure differential across the glands, and those
which must operate for long periods of time between
shutdowns (some low pressure turbines may also use
this equipment).
The condenser is piped to the outer leak-off connec-
tions of the glands. It creates a slight vacuum on the
outer leak-off areas, assuring that leakage will leave
through leak-off piping and not past inactive seals.
The most common configuration is the gland condens-
er and ejector. The gland condenser is a shell-and-tube
type heat exchanger in which cooling water is used to
condense steam leakage from the glands. The ejector
is a steam nozzle which creates a low pressure area to
remove any air which has leaked into the system and
thus maintains the vacuum in the leak-off areas.
This equipment is available for all types of leak-off
flows, large or small. The condensed leakage steam
and cooling water can be recovered and returned to the
boiler. Note that the condenser tubes and ejector both
require periodic cleaning.
Vacuum Breaker Solenoid Valve
The vacuum breaker solenoid valve is located on the
turbine exhaust connection and is identified as FCV-
173 on schematic drawings. This valve is closed during
turbine operation and is opened at shutdown whether
planned or emergency to allow air to enter the turbine
exhaust piping and steam condenser to help slow the
turbine more quickly by increasing the exhaust pres-
sure on the turbine. The entrance of air into the sys-
tem necessitates the operation of the vacuum pump to
evacuate the air before the next startup may occur.
Steam Nozzle Valves
Steam nozzle valves are furnished to provide added
efficiency as load conditions change on the turbine.
The nozzle valves regulate the amount of steam and
steam pressure entering the turbine. The turbine oper-
ates more efficiently at higher entering steam pressures
since the flow is reduced at higher steam pressures.
The turbine should not be run with the steam nozzle
valves wide open all the time. This does not allow the
turbine to have any backup power in case the load is
increased relatively rapidly. The steam nozzle valves
are manually adjustable on the standard system design
with Manual Start. The valves are controlled automati-
cally when the Auto Start design is furnished.
Sentinel Warning Valve
The sentinel warning valve is a small relief valve lo-
cated on the turbine exhaust. It is not a true relief valve
as it is too small but is used to provide a warning that
turbine exhaust pressure has become too high. The
valve is set to open at 5 psig on the standard YST Con
-
densing Turbine. On a special non-condensing turbine
it is set at 10-15 PSIG above the normal back pressure.
The opening of this valve will release steam giving an
indication of excessive pressure.
Do not under any circumstances pipe the
discharge of the Sentinel Warning Valve
away from the turbine.
If the valve leaks air into the system during normal op-
eration it should be opened manually a few times to
blow out any foreign material that may have collected
around the seat. If this fails, the valve should be re-
moved and repaired or replaced.
Steam Ring Drain
All YST chillers are provided with a tapped drain open-
ing in the turbine steam ring for getting rid of excess
moisture that accumulates in the steam ring when the
turbine casing is cold at startup. The drain line is fitted
with a check valve and solenoid valve. The line must
be piped to a sewer or any other low point that permits
the waste to drain off by gravity. The location of this
opening is shown in top
.