Site : BTenggrara
Pump Model : 65 x 40 -200
Duty : 25 m3/hr at 5 bar
Pump Speed : 2900 rpm
NPSH R : 2.0 Meter
Operating Pressure is 5 bar when temperature is below 150 C , but temperature at 180 C and above
pressure drops to 2 bar
Cuase :
as temperature increase . the oil vapour pressure increase, as mentioned by customer oil
seem boiling at expansion tank
The drop in pressure is due to pump cavitating .when the vapour pressure increase
the suction head or NPSH avialable is reduced to a very low level ,possible below the
NPSH required of the pump.Thus the pump is cavitating and cavitation reduces the flow seriously
Solution
a) increase suction head by raising the Inlet tank level
b) Increase suction line diameter ,to 100 mm from 65 mm ~this reduces the friction head
check suction strainer for blockage
c) upgrade pump , with pump operating on the left of the curve where the NPSH R is about 1 .0 Meter
The above rectification will help ,
Determine the Vapour pressure at 180 C . check with the Thermal Oil supplier and recalculate
the NPSH avaialable in the system
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