4 replies to this topic

[flash]

This topic is only for a concept discussion.

I would like to discuss typically how long a thermal relief scenario lasts. Is it only for a few seconds where relief valve pops open, releases a small amount and then closes again and does this cycle frequently or it can stay open for many minutes or hours continuously until the entire expanded volume is released. I guess it will depend upon how big the boxed in volume is.

I understand the system has to release the expanded volume which will depend upon the pipe length but wonder about the phenomena in real situations.

 

Thanks,

[fallah]

flash,

 

I think the discussion in cluded in following link can help you out fro your query:

 

https://www.linkedin...016377874309122

[ankur2061]

flash,

 

Any relief valve pop-up will happen when set pressure is exceeded.

 

Almost all cases you will find that the TRV is installed on a pipe.

 

For heat exchangers (coolers) where cooling water is the cold fluid the TRV is installed on the CW outlet pipe and in bare pipes exposed to solar radiation and which can have trapped liquid between two isolation valves the TRV is mounted on the pipe at an easily accessible location.

 

In the above two typical cases, the TRV will pop for a few seconds due to pressure increase by thermal expansion and close when the pressure decreases below the reclosure pressure.Most TRVs on pipelines are set at the pipeline design pressure corresponding to the design temperature, which is generally very high. Thermal expansion due to thermal radiation is a rare phenomenon and even if it happens, it will be for a very short duration and discharge quantities will be very small. The coefficient of thermal expansion of the liquid also plays a role in the shorter and longer duration of TRV activation.

 

Main practical problem with TRVs is that often the seat of these valves gets plugged or damaged due to solid particles (rust) or corrosion  and they start leaking internally.

 

To conclude, TRVs in general are rarely found to be operating for long duration due to thermal expansion and practically are often a nuisance due to internal leakage.

 

Regards,

Ankur.

[flash]

Thanks Ankur and Fallah for the valuable comments. It was for a thermal relief valve installed on a pipe.

 

The reason I started this thread is to understand what should be the capacity of the Slop Tank that collects the discharged liquid hydrocarbon. Relief duration and therefore amount directly affect the volume of the Tank. If the relief is for short duration/s maybe an automatic liquid removal mechanism (linked with level) can be implemented to limit the Tank capacity.

[fallah]

If the relief is for short duration/s maybe an automatic liquid removal mechanism (linked with level) can be implemented to limit the Tank capacity.

 

flash,

 

Yes, mentioned mechanism can be applied to limit the tank capacity...