What would happen if a pump works with its discharge valve closed for 1.5 hours?

Question

Pump specifications:

Type: Centrifuge-Horizontal
Flow Rate: 31 m3/hr
Differential Pressure: 2.5 barg
Type of liquid: Water

i would be glad if you tell me any standards or writings about this situation.

Answer 1

OPERATION OF CENTRIFUGAL PUMPS AGAINST A CLOSED DISCHARGE VALVE :
"How long can a particular centrifugal pump run against a closed discharge valve without damage to the pump?" While the answer to this question varies with the size of the pump and the motor driving it, the calculations are relatively simple. The first requirement is a family curve on the pump showing the horsepower required by the various impeller diameters at shut off.
From the curve(TDH VS GPM), it can be seen that a 5" diameter impeller will draw 1-1/2 break horsepower when the pump is operating at no flow. The next thing you must know is the capacity of the pump casing in pounds of water. Let us assume our pump holds 8 pounds.

Now, since the horsepower of the motor has no hydraulic work to do with a closed valve, that is, no water is being transported, then the shut off horsepower must be converted to heat. While some of this would be dissipated by radiation of the casing the majority goes to heat up the water in the casing.

Remembering our high school physics for a moment, the BTU is by definition the heat required to raise one pound of water one degree Fahrenheit. Also one horsepower converted into heat corresponds to 42.4 BTU's per minute. Therefore, the temperature rise of the water in the casing would be given by the formula:
RISE=SHUT-OFF HP*42.4 / #WATER IN THE CASING

From the above, you can see that operation of this pump for about twenty five minutes would vaporize the water. If the unit had close clearances, it would then seize up and damage the pump.

One more word of caution, never operate a pump with closed discharge and suction valves. Several years ago, a large double suction pump driven by a 150 horsepower motor was being occasionally operated against a closed discharge valve. Unfortunately, one night the suction valve was also closed. The resulting explosion damaged property and injured plant personnel. The closed suction and discharge valves turned the pump casing into a boiler with no relief valve and as the 150 connected horsepower was converted to heat, the pressures increased to the explosive level.

I think now,it will be easier to estimate your situation.

Answer 2

Probably not much depends on the horsepower. Centrifugal pumps aren't very efficient so a lot of the horsepower winds up as heat. With the discharge valve shut off the temperature of the water will increase as a result of the power input from the motor. First thing I'd worry about is over heating. Could melt the elastomers in the seal and allow the seal to blow. 2nd thing that will happen is you will have conciderable wear on the impellar. No pumps are really designed for continuous deadhead operation.

Most pump manufacturers list the minimum flow requirement for their pumps. You can't simply deadhead a centrifugal pump indefinitely. I accidently deadheaded a pump operating at about 17 bar with a 150 horsepower motor. The pump got so hot (in a few seconds) the solder on the inlet piping gave way and the suction piping blew off the pump as the water inside flashed to steam. I was lucky no one was hurt.

The rule of thumb is that the minimum flow required for a centrifugal pump is 20% of the pump flow at its best operating point (highest efficiency). You'll need a pump curve to check that.