10 replies to this topic

[trungphu]

Hello everyone,

 

Have you ever encountered the problem as I described follow? The vibration of synthesis gas compressor in ammonia plant increases periodically. Its vibration increases up to a value that almost reach trip value, and then reduces to normal value. This phenomenon has repeated over two weeks. All operation parameters are kept normal.

 

Hope to receive your precious comments.

 

Trung Phu

Edited by trungphu, 12 December 2015 - 10:41 AM.

[manojkaila]

Trung Phu

 

1 Do you have the VFD on Motor or turbine. Any recent update or failure in VFD components. 

2 Just check that is it surging phenomena.

3 Any liquid carry over in suction,

4 How about suction strainer DP ?

5 Cross check the Anti surge deviation & actual opening of valve in field.

I hope this will help.

 

Regards, 

[Bobby Strain]

You need to monitor and review all the operating variables to troubleshoot. And note the time of day, too.

 

Bobby

[trungphu]

Thank you all. The compressor is driven by a turbine. We suspect the vibration caused by the turbine.

[trungphu]

The excessive vibration of turbine may be caused by high bearing lube oil temperature. Have you encountered this situation?

[manojkaila]

Dear,

 

As per my understanding hi lube oil temp will not create vibration. But if your bearing is damage due to poor lubrication it will lead the high vibration. Check the lube oil sample in Lab with all parameters like moisture etc... Check with your rotary team and confirm which bearing is giving more vibration that spec. Check your lube oil cooler condition and cooling water inlet and outlet temp. If your cooling water quality is not good it will create scaling in cooler & reduce heat transfer.

 

I hope something  from above will help.

 

Good luck

 

Manoj

[breizh]

Hi trungphu ,

did you check or do you have mean to control your vibrations sensors ? I had bad experience on MVR because of sensors and electronic associated ( Bentley nevada ) .

 

If bearings are the causes , the problem will amplify .

 

Hope this is of some help.

 

Breizh

[Ankit_Kumar]

Kindly check the composition of syn gas. It should be as per PFD value. In ammonia, u r maintining H2/N2 ratio after secondary reformer (plant without coldbox) or before suction of syn compressor (plant with cold box)??? 

 

As u said, all operating parameters are same so better to check it from machinery point of view. i.e. bearing and shaft .... In my previous industry, we were using old compressor (relocated plant) so we faced this problem several times until we went for complete overhauling of the compressor. Rotor balancing was the issue at our plant.

 

Supply of oil temp will only affect bearing temperature. Check the quality of oil by sampling it. Lube oil temp is normally to be maintained at 45-50 C. If it is same in your case, oil temperature will not affect temperature of bearing. 

[trungphu]

Thank you all so much for your valued comments.

 

Our maintenance department said that oil coking phenomenon at bearing is the cause of vibration. Do you think it possible?

[Satyajit]

Hi Trung Phu,

                      This is a very critical machine as you know. You have already received many important advices,suggestions and you have also inhouse opinions. It is not really easy for us to pinpoint the root cuase for vibration in the machine as we do not have all the information of your plant e.g. process parameters, steam parameters, cooling water details, climatic conditions, oil conditions etc. In one of my previous plants, the vibration in syngas machine used to increase in the night when it starts raining outside. By careful anaysis,we found that when the ambient temperature drops,ammonia vapor reaches its dew point quicker than expected and the excess condensation of ammonia starts. The ammonia separator was too small to handle the ammonia condensed.Hence carry over of ammonia liquid with recycle gas to the recycle stage starts and that causes heavy vibration and trips the machine. I can not say this could be the same problem in your plant as I know nothing about your plant.

 

I would therefore suggest you to take all the advices from this forum, initiate a root cause analysis in your plant with the support of machine manufacturer or expert and try to find out the root cause. Once you know the root cause, you should be able to remove the root cause and bring a permanent solution to your current  problem in the machine.

Good luck.

Kind regards,

Satyajit

Edited by Satyajit, 05 January 2016 - 04:28 PM.

[trungphu]

Thank you so much for your advice, Mr. Satyajit.

 

I will transfer all of helpful information on the forum to my superiors. Its my honor to receive process sharing and experiences from professionals in chemical engineering field.

 

With gratitude,

 

Trung Phu