thermmech
Mechanical
- Dec 13, 2004
- 103
I need help with troubleshooting leakage on 22 x 240 "DEU" TEMA heat exchanger.The service is "Anti-Hydrate Heater", it is using saturated steam at 300# to preheat inlet natural gas from 15C to 30C during the winter. Location is Middle East. Material of construction is CS.
The high pressure nat. gas is on the tubeside, hence TEMA type "D" where tubesheet is integral with the channel. Channel is very heave and the center of gravity is probably very close to tubesheet. Shellside op. pressure is 200+ psig.
As preheating is not required during better part of the year, the unit is flooded with a condensate backflow from the condensate pot downstream.
The exchanger has a history of leakage on the girth flange. It has been in service more than 10 years, but the identical exchanger only 4 years old started leaking almost immediately upon installation. The original gasket was DJNAF. We tried to stop the leaks by machining the gasket contact faces and replacing the DJNAF gasket with Kammprofile. It didn't help.
The channel is VERY thick and heavy and it was believed that the distortion of the flange could be caused by the excessive moment that the weight of the channel was putting onto the girth flange. However, the newer exchangers in the same service were provided with 2 channel supports and have developed the leaks nevertheless.
The shellside fluid is clean steam/condensate; pressure and temperature vary over the course of the year. Yesterday the temperature on the shell side was 45C instead of 180C.
I would appreciate any pointers on the cause of the leaks, and suggestions for fixing it. Hopefully I will have some mechanical software installed tomorrow and be able to check the original design. I will provide some feedback at that time.
Thanks in advance (apologies for a haphazard posting).
The high pressure nat. gas is on the tubeside, hence TEMA type "D" where tubesheet is integral with the channel. Channel is very heave and the center of gravity is probably very close to tubesheet. Shellside op. pressure is 200+ psig.
As preheating is not required during better part of the year, the unit is flooded with a condensate backflow from the condensate pot downstream.
The exchanger has a history of leakage on the girth flange. It has been in service more than 10 years, but the identical exchanger only 4 years old started leaking almost immediately upon installation. The original gasket was DJNAF. We tried to stop the leaks by machining the gasket contact faces and replacing the DJNAF gasket with Kammprofile. It didn't help.
The channel is VERY thick and heavy and it was believed that the distortion of the flange could be caused by the excessive moment that the weight of the channel was putting onto the girth flange. However, the newer exchangers in the same service were provided with 2 channel supports and have developed the leaks nevertheless.
The shellside fluid is clean steam/condensate; pressure and temperature vary over the course of the year. Yesterday the temperature on the shell side was 45C instead of 180C.
I would appreciate any pointers on the cause of the leaks, and suggestions for fixing it. Hopefully I will have some mechanical software installed tomorrow and be able to check the original design. I will provide some feedback at that time.
Thanks in advance (apologies for a haphazard posting).
