You can run a centrifugal pump at shut-off head for sometime
say 5-10 minutes but further running may increase the
temperature of the fluid due to churning and can cause
failure of gaskets and lube oil faiukre
First and the foremost thing it depends on the size of the pump. The main thing is that theoretically nothing will happen to the valve. But usually while the pump is running heat is developed due to the friction between the moving and static parts. This heat is usually dissipated to the fluid flowing through the pump. Hence on closing the discharge the heat dissipation is blocked and hence the temperature hikes up(churning effect of the pump impeller). This may lead to seal failure and impeller damage depending on how much time you are running the pump.
Running of the impeller will do work on the fluid...so the
temperature of the fluid increases according to first law
of thermodyanamics....as the process goes on the pressure
builds up in the impeller region,so the negative pressure
drop develops...so the energy given by the pump may not be
sufficient to keep the fluid in the impeller region....so
the fluid may flow in the negative
direction.....erosion,fouling depends on the properties of
the fluid and material of the pump
Discharge valve shutdown means , flow rate is zero and as from the pump characteristic curve we can see that for a zero flow rate there is still head developed in it, so pressure will be developed inside the pump without much affecting the centrifugal pump and cause damage in case of Reciprocating pump.
That depends on type of discharge valve if it is gate valve
fluid passes incase of globe valve fluid can't flow.Any
have if we close the discharge valve it can withstand till
reaching of shut off design pressure.As time passes line
get pressurised there is a chance of bursting of valve and
impellers get damaged due to churning of pump.
But finally i want to say is there won't be any effect on
centrifugal pump it keep on running.
by operating the centrifugal pump with discharge valve
close that effect the discharge bellows to burst and also
due to internal workdone it may cavitate..but upto some
extent that means till upto its shutoff pressure we can
respected sir,i have been selected in the written
examination(CHEMICAL) of IOCL Panipat held on 30 m1rch, So
please tell me which type of questions asked in this
interview frequently.Can u mail me some questions?