2 replies to this topic

[meanyunny]

My plant has a vacuum deaerator tower (deaerates by reducing the seawater [partial] pressure in the tower using vacuum pump while seawater flows through packing, where entrained air will evolved from the water). The water discharge from the tower is connected to a HP centrifugal water pump. System has been running for around 3 years.

 

Lately we discovered that the discharge line of the tower (suction line of the water pump) shows vacuum condition after few minutes starting up the tower's vacuum pump; i.e. We opened up a sampling point at the pump suction line, initially before vacuum pump is running (while water pump is running), water continuously flows out from the sampling point. However few minutes after starting up the vacuum pump and as tower's pressure drops to ~0.05bar (normal operating pressure of tower), the water flow from the sampling point gradually decreases and eventually vacuum is observed (suction could be felt at the sampling point). While this was happening, however, all parameters remained and maintained at normal operating condition, i.e. the inlet water flowrate of the tower, tower pressure, the bottom water level of the tower, and the discharge of the water pump (flowrate and pressure). 

 

We would like to know if this is possible or normal? Is it possible that the pressure of the water in the tower discharge line is so low that water would not be able to flow out from the sampling points (2 points - 2inches and 3/4inches; sampling outlet to atmospheric)? But yet in fact there is actually still continuous flow of water in the pipelines?

Previously, water has always been able to flow out from the sampling point, until recently after a servicing of the vacuum pump. we are unsure if these events are related.

[Bobby Strain]

So, is the water properly deareated and flowing without any evidence of problems? If so, then probably nothing is wrong.

 

Bobby

[meanyunny]

We cannot tell if the water is flowing normally inside the pipeline since the water would not flow out of the sampling points, which is exactly our concern right now as we are afraid there is disruption in the water flow which might cause the water pump failure.

However, the flowmeter at the pump discharge and flowmeter upstream of deaerator tower shows constant flowrate. There is no flowmeter at the tower discharge line (pump suction line).