11" X 15" Elliptical Handhole Gasket Failure 1

[mab75]

Hello,

I have two R-22 liquid chillers with a pressure vessel that has an 11 X 15 ASME Code elliptical handhole assembly (bolt & yoke type) on one end. Two 1" bolts are used to pull the cover up against the inboard face of the mating ring. The original gasket used is a Topog-E standard material type.

We have experienced several failures of the handhole gaskets in the last 3-4 years. The failures are sudden and have occured after as little as 6 weeks and as many as 18 months in service. Some of the failed gaskets are shredded in the area between the two mating surfaces and sometimes the gasket is intact except for large splits. I have made some changes (gasket types, belleville washers, new cover) without success.

Has anyone else run into this problem? Are there alternatives to the current door design that I should be looking at? If need be, are there formulas for designing bolted elliptical flanged joints?


Thanks

 

[puigi]

Seat taper and seating area overlap are important dimension on that design may-way. If you have or could obtain the original drawings with the man-way seat and door dimension that would be helpfult to determine if excessive seat taper is the cause of your problems. Ensuring that the door is centered on the seat before tightening is also very important to ensure a long service life.
Finally, does Topog-E recommend a miminum or maximum compression for their gaskets? If so I would follow it. I've had better luck with graphite impregnated spiral wound gasket for that type of door.

 

[mab75]

Thanks Puigi,

The Topog-E instructions are for boilers and they say to make the nuts hand tight, tighten 1/4 turn, raise internal pressure, and tighten as needed. Not very useful.

I have an extra door. I can have it checked for flatness while the machines remain in operation.

As far as the spiral wound gasket, I am concerned about how much force will be needed to seal the joint. The standard door design doesn't look like it will withstand much bolt force.

When using the spiral wound gaskets, have you had to beef up the doors to handle the higher bolt loads?

 

[puigi]

Mab:

I have not had to re-enforce any doors. If you are concerned that the door may not be able to take the force required to achieve the necessary compression for the spiral wound gasket material, there are some other wire impregnated graphite gasket materials that may meet your needs, grafoil and graph-lock come to mind.

 

[Duwe6]

Spiral-wound 'Garlock' and grafoil gaskets need more sealing pressure than the 2 yokes that an oval manway has. It takes the internal pressure from the vessel to cause these gaskets to 'crush' and seal up the hole. Endemic with that M/W design.

Unless your compressor is being run at a greatly reduced pressure, compared with mfr's recommended pressure, puigi appears to have diagnosed the problem. Only other possibility is a misinstalled gasket -- misaligned, or a bunch of adhesive or tape used to hold the gasket in position while the M/W is swung shut and the yokes tightened. Tape or dissolved glue creates a leakpath. Watch the entire installation process next time.

 

[GenB]

the gasket material have to be good for cold environment, the current gasket may become brittle, contact Top-OGee and ask the min gasket temp and if they have a diff material.