Surge mapping procedures. 1

[rQuestionEngineering]

Anyone can share how surge mapping is conducted on site ?

How are the process valve setup ?
How the machine is brought to the surge points and so on ..?

 

[pmover]

well, describe the system or application.
some units are operated with the loop in partial or on full recycle. some units can be tested during start-up.
the objective is to increase the resistance across the compressor, maintaining constant rpm, IGV angle, thereby reducing the flow rate. flow and pressure data can be recorded/observed and once the compressor is near surge, the flow/pressure signals may start oscillate. another symptom is observing compressor vibration levels. sometimes, the unit suddenly surges with no warning or signals indicating a surge condition.
suggest having someone knowledgeable and experienced with this activity. this testing is not to be taken lightly as i've seen significant movement in 30" pipe.

 

[rQuestionEngineering]

How the flow rate can be reduced ?

 

[georgeverghese]

Seriously doubt your company operating managers will allow you to do this - most likely you will ruin this compressor's seals and bearings and bring untold misery upon yourself and your supervisors for the production loss and the cost of repairs.

Besides, the antisurge controller should trip this compressor some distance away from the surge point - no way your managers will give you approval to disable the surge trip function.

 

[rotw]

First the maps used for various engineering purposes during project maturation are not actual but predicted. This is common.
The controllers are set with preliminary parameters based on predicted maps.

When machine is performance tested at manufacturer works, the actual maps can be made available and then the controller parameters can be further tuned. Performance test is usually done based on PTC10 type 2 whereby the machine will not be running under real conditions in terms of gas, speed and power. At this point the controllers are normally reasonably tuned as for a first shot.

After the machine is commissioned at site and plant start up activity commence, in certain cases (not sure if it is always a rule) a surge testing is performed with the real gas. This is where the anti-surge valve is slowly closed by an experienced operator and the operating point gradually brought towards a near surge condition, point at which a measurement is taken. This is a coordinated procedure elaborated by experienced crews and that also generally requires several parties to attend at site, including compressor OEM, controller's manufacturer (when not provided by compressor OEM), site engineers, user/owner and contractor. This testing allows another layer of optimization of the parameters of the controllers at site.

The anti-surge control system is a proprietary one. In general any major compressor vendor would have not trouble delivering, testing and maintaining that.