7 replies to this topic

[SGAJSE]

Hello all,

 

I have a problem in a Ethylene back-up pump (J. C. Carter pumps). These pumps are suffering from trip frequency problems during normal operation.

 

Ethylene backup pumps tripped when the level in the tank between 3 – 7 m, this was the case since the start of ethylene storage operation.

 

During the last test of the pump, the pump pot’s level was dropped rapidly to the pump trip level on LCZA-171 at pot suction pressure of (0.6 kg/cm2g) and tank level of 6.3 m. this was due to partial vaporization of ethylene liquid in the pot where the pressure is further reduced.

 

Please let me know if additional information is needed.

 

Regards,

Edited by SGAJSE, 19 July 2020 - 02:15 AM.

[Chemitofreak]

I guess the problem in your case is that the suction piping is gaining heat from the ambiance (especially in summers). Try insulation the line, that might help you  

[breizh]

Hi ,

 

You should consult the vendor : https://www.nikkiso....submerged.html 

 

Consider the following link with similar issue : https://www.eng-tips....cfm?qid=284608

 

my view

Breizh 

Edited by breizh, 19 July 2020 - 03:09 AM.

[SGAJSE]

I guess the problem in your case is that the suction piping is gaining heat from the ambiance (especially in summers). Try insulation the line, that might help you  

 

Hi Chemitofreak

Thank you for your response. 

the suction line is very long and complex but we rather believe that the problem is related with other thing, because the suction line is shared with another pump (loading pump).

we don't experience any cavitation problems with the ethylene loading pumps which are located in the same area, having the same NPSHr, operate with similar conditions and have equally complex and very long piping section. the loading pump can operate with a tank level as low as 1 m.

[Chemitofreak]

 

I guess the problem in your case is that the suction piping is gaining heat from the ambiance (especially in summers). Try insulation the line, that might help you  

 

Hi Chemitofreak

Thank you for your response. 

the suction line is very long and complex but we rather believe that the problem is related with other thing, because the suction line is shared with another pump (loading pump).

we don't experience any cavitation problems with the ethylene loading pumps which are located in the same area, having the same NPSHr, operate with similar conditions and have equally complex and very long piping section. the loading pump can operate with a tank level as low as 1 m.

 

 

Long and complex suction line for a boiling liquid is not a good idea.

 

Although the NPSHr for both the pumps is the same is the NPSHa for both the pumps same ?

 

I guess you are using the canned pumps, compare how deep both the pumps are located below the ground.

[SGAJSE]

 

 

I guess the problem in your case is that the suction piping is gaining heat from the ambiance (especially in summers). Try insulation the line, that might help you  

 

Hi Chemitofreak

Thank you for your response. 

the suction line is very long and complex but we rather believe that the problem is related with other thing, because the suction line is shared with another pump (loading pump).

we don't experience any cavitation problems with the ethylene loading pumps which are located in the same area, having the same NPSHr, operate with similar conditions and have equally complex and very long piping section. the loading pump can operate with a tank level as low as 1 m.

 

 

Long and complex suction line for a boiling liquid is not a good idea.

 

Although the NPSHr for both the pumps is the same is the NPSHa for both the pumps same ?

 

I guess you are using the canned pumps, compare how deep both the pumps are located below the ground.

 

 

"Long and complex suction line for a boiling liquid is not a good idea." That was the design of the ethylene plant by Stone & Webster since 1986.

 

the net positive suction head available for both pumps are nearly the same, the difference only in the pump capacity (different velocity).

 

yes, the pumps type is vertical multistage pot mounted submerged motor pump.

[Chemitofreak]

 

 

 

I guess the problem in your case is that the suction piping is gaining heat from the ambiance (especially in summers). Try insulation the line, that might help you  

 

Hi Chemitofreak

Thank you for your response. 

the suction line is very long and complex but we rather believe that the problem is related with other thing, because the suction line is shared with another pump (loading pump).

we don't experience any cavitation problems with the ethylene loading pumps which are located in the same area, having the same NPSHr, operate with similar conditions and have equally complex and very long piping section. the loading pump can operate with a tank level as low as 1 m.

 

 

Long and complex suction line for a boiling liquid is not a good idea.

 

Although the NPSHr for both the pumps is the same is the NPSHa for both the pumps same ?

 

I guess you are using the canned pumps, compare how deep both the pumps are located below the ground.

 

 

"Long and complex suction line for a boiling liquid is not a good idea." That was the design of the ethylene plant by Stone & Webster since 1986.

 

the net positive suction head available for both pumps are nearly the same, the difference only in the pump capacity (different velocity).

 

yes, the pumps type is vertical multistage pot mounted submerged motor pump.

 

 

Pump capacity will have an impact on NPSHA as more flow will lead to more frictional loss (assuming the pipe diameter is the same in both the cases)

 

Is your issue based on the ambient weather conditions ? I mean summer and winter 

Edited by Chemitofreak, 20 July 2020 - 06:25 AM.

[Bobby Strain]

Insufficient NPSHa doesn't usually overload a pump motor. I would usually look for pumping a greater volume which requires more power. But, then, you didn't tell us very much that is helpful. You also didn't attribute the trip to motor overload. So, we need a lot more information if you want help.

 

Bobby

Edited by Bobby Strain, 20 July 2020 - 04:43 PM.