3 replies to this topic

[AMPIR]

Hi; 

As I know for the centrifugal compressors, the stonewall protection is an optional protection (is not mandatory same as Anti-surge protection). However operating in the stonewall condition also damage the compressor so I am thinking if there is no stonewall protection, maybe it should be just relied to the operator action to trip the compressor. In this basis I have two questions:

1) Does it need to trip the compressors in case of stone wall?

2) if yes and compressor does not have stonewall protection, which alarm will be activated for operation attention ( e.g. : high compressor vibration) ?

 

 

Many thanks

[souravkr]

For Stone wall effect prevention I have not yet seen any automation protection. Though there can be protection in terms of

 

1. Low discharge pressure trip of compressor based on minimum design pressure ratio

 

2. Installing Anti Choking valve at compressor discharge.

 

I would think share if any additional protection I find. 

 

High vibration trip for Centrifugal Compressor is a must for all compressors.

[AMPIR]

Hi Souravkr;

 

Thanks for your kind reply. 

 

As the compressor is working in a closed loop so the compressor head will be dropped not the discharge pressure. So unfortunately the LL discharge pressure protection cannot help to protect the system.

 

The compressor suction does not have any high alarm or trip.The system data I found a case which the suction pressure was so high ( close to discharge ) so it is clear that the compressor was worked at stonewall condition. I need to investigate the case to figure out what was the operational situation and then decide if it is possible to add a high suction pressure alarm.

 

Unfortunately there is no high vibration trip in C&E chart and vendor database is not available. I need to check with operation about high vibration.

 

Is the Anti Choking valve common at the centrifugal compressor discharge? 

 

Thanks 

[functionlake]

Hi AMPIR,

 

I know this reply has been a long time since your post, but I want to put it here for others who are finding an experience operating a gas centrifugal compressor in choke, overload or stonewall region.

 

I've experienced a compressor had been running continuously within overload region for more than 2 months due to the unavailability of the parallel compressor. Overload region mentioned here means that the operating point of the compressor falls to the right of the stone wall line of the recommended operating map. The compressor delivered more than the design flow by 2MMscmd which was a significant increase in its capacity.

 

All compressor parameters including bearing vibration, lube oil temperature, bearing temperature were within their alarms. However, there was only a parameter, thrust bearing temperature, increased dramatically up to its alarm of over 100degC. The oil additives in lube oil has their limitation, and it is 90degC for our case. Normally, it is below 70degC. Consequently, the thrust bearing temperature was only the limit for our compressor at that time. Three years later, the compressor has been fine.

 

Of course, operating the compressor in overload region induces inaccurate aerodynamics prediction and impact on mechanical integrity. The tip Mach number of this condition shall be checked by the OEM, it was 0.45 for our case.

 

Hope it helps.