3 replies to this topic

[confusedchamp]

Fuel gas is being heated in system by LP steam. If the gas is trapped due to blocked isolation valves on fuel gas side and heat is continuous, then there can be over pressure due to thermal expansion.

 

I don't know whether this is a credible scenario. Can some one by their experience advice on the the way to proceed with relief calculation.

[fallah]

Hi,

 

Appears you are discussing about a heat exchanger. If so, please specify the side in which the fuel gas is passing to exchange the heat with the LP steam. However, regardless of fuel gas to be in tube or shell side, if the pressure of the fuel gas in trapped condition (while LP steam continue to pass) wouldn't be exceeded the design pressure of relevant side the overpressrue scenario due to thermal expansion cannot be credible.

[confusedchamp]

Apologies for half information.

Yes its Heat Exchanger indeed. This exchanger comes online only when the supply fuel gas is at low temperature and shall be heated to meet the process conditions. Normally its a once in a year operation.

 

The fuel gas is on tube side. I have presently considered both the inlet and outlet valves closed (operator fault). The inlet steam temperature is somewhere around 137 Deg C. 

I have considered that the maximum temperature that fuel gas can achive in blocked in condition is 137 Deg C.

The fuel gas initial temperature when its trapped is 5 Deg C. I was suspecting that this will pressurise the system when heated to 137 Deg C.. The system is designed for 50kg/cm2g.

 

Hence was evaluating relief valve for thermal protection.

Edited by confusedchamp, 04 June 2013 - 06:07 AM.

[fallah]

Hi,

 

Then, if the final pressure (with T=137C) of the fuel gas would be lower than 50 kg/cm2g, then the overpressure scenario isn't credible...