Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
Master Pump Minimum Flow Control Valves<br />
When a motor or turbine-driven boiler feedwater discharge<br />
flow. some of the energy generated from the pumping action is<br />
converted to heat. if the pump discharge flow falls below a set<br />
minimum level there is a rapid increase in both temperature and<br />
pressure within the pump. This increase can cause mechanical<br />
pump damage due to caviattion or excessive pressures. To guard<br />
condenser<br />
deaerator<br />
tank<br />
Boiler Feed Pump<br />
condenser<br />
discharge<br />
deaerator<br />
storage tank<br />
Feedpump<br />
Minimum Flow<br />
or recirc. Valve<br />
Main<br />
supply<br />
to Boiler<br />
Or reactor<br />
MiniMuM FlOW ValVe requireMents:<br />
against this problem, a minimum flow line is used downstream of<br />
the pump charge. The minimum flow line takes the full discharge<br />
pressure from the pump and passes a set minimum flow to either<br />
the deaerator(deaerator tank) or the condenser. The feedwater<br />
valve cannot serve this purpose as the full head of the boiler is on<br />
the feedwater valve outlet at start-up.<br />
For a valve to be successful in the service with high differential pressures, it must be<br />
able to deal with four general problems.<br />
• The valve must be able to protect its trim from cavitation damage between initial valve<br />
opening and full valve opening.<br />
• The valve must be able to deal with foreign matter and pipe scale entrained in the flow<br />
stream. Foreign matter will cause problems to the valve trim.<br />
• The valve must able to provide zero leakage as any leakage in the service will cause<br />
wire-drawing across the seat and trim failure occur.<br />
• The valve must be able to maintain zero leakage throughout a normal service life. This<br />
is the most difficult requirement for a pump minimum flow control valve.<br />
Pump Minimum Flow control Valve be designed to meet the above requirements.<br />
One of the severe potential problems in pump<br />
minimum flow line is the intrusion of foreign dirty<br />
particles.<br />
Trim technology cover well known brand trims<br />
over the world based on a velocity profile and<br />
pressure profile. In case dirty water or containing<br />
impurities fluid service the use of pressure<br />
profile trim is most primary selection. But very<br />
high differential pressure drop service primary<br />
selection of the trim should be based on a velocity<br />
profiles. But all the case the pump minimum flow<br />
control valve shall be no seat leakage trim.<br />
We know the severe duty service trim<br />
technology that you prefer & familiar valve<br />
manufacturers. We can solve the problems of<br />
those valves and serve for customers with more<br />
better solution in valve product.<br />
<strong>Descaling</strong> <strong>ValVes</strong><br />
For pump minimum flow control, the valve have to<br />
be satisfied against severe cavitation phenomenon<br />
due to high differential pressure across the valve<br />
trim. the trim is designed and analyzed by ingenious<br />
design tools such as cFd. above is a sample<br />
figure of cavitating analysis of the trim of minimum<br />
flow control valve.<br />
9
Change language