JOHNSON CONTROLS
61
SECTION 3 - SYSTEM COMPONENTS DESCRIPTION
FORM 160.67-O2
ISSUE DATE: 10/9/2020
3
POWER PANEL
All motor contactors and circuit protectors, the com-
pressor oil pump variable speed drive and the control
power transformer are contained in an enclosure in-
stalled adjacent to the OptiView™ control center. A
main power disconnect switch is supplied which pro-
vides the termination points for customer’s single point
power supply wiring.
STEAM CONDENSER PACKAGE
The steam condenser system is furnished fully pack-
aged. It consists of a steam condenser, single hotwell
(condensate) pump and single vacuum pump which are
standard, (with an option for standby pumps for both
with automatic switchover controls), hotwell conden-
sate level control system, and an atmospheric steam
relief valve. The hotwell is the collection well under
the steam condenser where condensate collects and
serves as a reservoir for the hotwell pump. Condensate
level in the hotwell is controlled by a level control sys-
tem with two (2) pneumatic automatically controlled
valves located in the hotwell pump discharge piping.
One valve, (named as recirculation valve on drawings),
is for recirculation back to the steam condenser and the
other, (named as overboard valve on drawings), is for
removal of condensate from the hotwell. This conden-
sate is typically piped back to the boiler feedwater cir-
cuit.
The recirculation valve is used primarily during startup
since very little steam is condensed and it is neces-
sary to recirculate the condensate to ensure stable op-
eration of the hotwell pump. As the turbine comes up
to speed more and more condensate will be produced
until at some point the operating level set point will
be exceeded and the level control will modulate the
overboard valve open and modulate the recirculation
valve closed. Because the condensate in the hotwell is
at saturation steam temperature/pressure the hotwell
pump is subject to possible cavitation if the conden-
sate level in the hotwell becomes too low. The hotwell
pump requires a Net Positive Suction Head, (NPSH) of
at least 2 feet. For this reason the level in the hotwell
is very important. If the level is too low the pump will
cavitate. If the level is too high some of the tubes in
the condenser will be covered with condensate which
will reduce the capacity of the condenser causing the
exhaust pressure of the turbine to rise.
All key control and monitoring parameters are inte-
grated with the chiller control panel. In addition, auxil-
iary pressure gauges are located at the condenser steam
inlet and hotwell pump discharge piping. Temperature
gauges are located at the steam inlet, cooling water in-
let and outlet, and the hotwell.
Piping is fitted with unions at suitable break-points.
Steam Condenser
A steam condenser is provided to condense the steam
exhausted from the steam turbine. Cooling water sup-
ply for the steam condenser is piped from the outlet of
the refrigerant condenser. This eliminates the need for
a separate water supply and is designed to minimize
water pressure drop for energy savings. The steam
condenser is a shell and tube heat exchanger with 3/4”
OD (19mm) prime surface copper tubes. Steam con-
denses on the outside of the tubes. Condensing water
flows inside the tubes. Tubes are roller-expanded into
the tube sheets. Subcooling sections in both ends of
the condenser cool non-condensibles, (mainly air), suf-
ficiently below the condensing temperature thereby
reducing the required capacity of the vacuum pump.
Water side is suitable for a maximum working pressure
of 150 psig, (1030 kPA). Cooling water end plates are
provided on each end of the steam condenser so that
tubes may be accessed without having to disturb the
water piping connections.The steam side of the system
is protected by an atmospheric relief valve. Refer to the
following "Atmospheric Relief Valve section."
Atmospheric Relief Valve
The steam side of the system is protected by an atmo-
spheric relief valve mounted on the steam condenser.
Since there is no valve in the steam discharge piping
this relief valve provides protection not only to the
steam condenser but the turbine as well. The relief
valve is sized per HEI and is mounted on the shell side
of the steam condenser. It is set to open at 1-2 psig,
(7-14 kPA), and will prevent the system pressure from
exceeding 10 psig, (69 kPA). The relief valve is a water
seal type relief valve. Water is used to cover and seal
the closed port of the relief valve during operation. The
relief valve is furnished with water supply and an over-
flow connection that assures the correct depth of water
is maintained. During operation a small trickle of water
should be maintained to ensure that the water that seals
the closed relief port on the valve does not evaporate
over a period of time. The steam condenser operates
under a high vacuum pressure. Any leaks, even very
small, through the relief port would cause air to leak
into the steam condenser causing the condensing pres-
sure to rise, reducing efficiency and power of the tur-
bine and eventually shutting the system down.
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