Testing a backup pump resulted in the pump in use not being able to deliver flow
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We are an deasphalting unit, and when testing the spare pump for the feedstock pump, it caused the operating pump to fail to deliver flow. The standby pump had just completed its warm-up process about half an hour ago. Before testing, the standby pump, the warm-up line, the connection lines for the inlet and outlet, and the pump outlet valve were all in closed state. I was wondering, what could be the possible reasons?
This post was last edited by altpage on 2017-12-19 14:08. Where is the gas connection for the raw material buffer tank? Is it the torch route? What is the pipe diameter? Has the standby pump been purged with steam?
It is the line that connects the unit to the flare tower; it was purged, and it took two and a half hours to warm up. The inlet was opened half an hour before pump testing began
The reasons are as follows: 1. Residual steam and condensate from the purging remain inside the pump; when the pump is tested, these substances are carried out through the pump outlet and back to the tank via the return line or the pump warming line, causing the operating pump to become evacuated. 2 Since the gas phase line of the raw material buffer tank is connected to the flare, when both pumps are operated simultaneously (even though the standby pump’s outlet is not in use, there is definitely internal leakage in the valves at the outlet of the high-pressure pump), the inlet head pressure of the operating pump becomes insufficient, causing the pump to become vacuumed. Solution: 1 After steam purging, before attempting to run the standby pump, thoroughly displace the residual steam condensate in the pump chamber using feedstock – by directing feedstock from the outlet of the operating pump to the inlet of the standby pump, through the pump body of the standby pump, and then out to the sludge line. 2 Add a line that leads the external raw material to the pump inlet pipeline, using the thrust of this external raw material to activate the standby pump. This line is necessary; otherwise, switching pumps every time will result in vacuum conditions. At present, this line is not available, so when it is necessary to switch pumps, simply stop the operating pump for 1–2 minutes and then start the standby pump – the impact on the operation of the extraction tower is acceptable.
This post was last edited by altpage on 2017-12-23 10:54
This post was last edited by altpage on 2017-12-23 10:55
The first reason is that we pre-heated the pump before starting it; oil was fed in through the pre-heating line while waste oil was removed through another line, and the pump’s temperature reached over 100 degrees Celsius. Therefore, this possibility is low. The second reason is that our original design called for a feed buffer tank that was under pressure, but no further work was done on it, so now it’s a tank at atmospheric pressure. It’s likely that the insufficient inlet pressure, as you mentioned, is the cause of the low flow rate
Two pumps competing for flow. The pump inlet pipeline is narrow, resulting in high resistance; try increasing the liquid level in the container.