How does a pressure gauge ( discharge & suction ) behave in a crude oil tanker? how to make best use of it in order to decide correct use of centrifugal pump from bulk discharge to stripping level?
Suction pressure depends upon the tank level. When tanks level are high , suction pressure is high and vice versa. The height of cargo divided by 10 shall be your approx suction pressure.
Sometimes when you prepare for cargo discharging and fill separators, you get less suction pressure because of vapour lock in cargo pump separators. The solution is simple.
1. Open discharge valve of pump.
Let's take an example of VLCC.
Discharge pressure depends upon various factors.
1. Shore pipe line length
Discharge pressure is maintained as per charter party requirements or as per company SMS. The pressure is always given at ship's manifold. Eg. My vessel can discharge cargo with a maximum manifold pressure of 10.0 kg/cm2.When you are discharging and tank levels get low, the first indication that tanks are not getting enough oil is fluctuating discharging pressure. As soon as discharging pressure fluctuates, pump RPM can be reduced, if required further, pump discharge valve can be throttled.
How to use the pressure to take tanks to stripping level.
1. As soon as discharging pressure fluctuates, reduce pump RPM