High Pressure Heater

[VaughnQ]

I would like information on the reuse of studs in the closing of High Pressure Heaters.

The working pressure of the heater is approximately 400psi.
The stud size is 1-1/4".

The studs have no visible damage, nor did the vessel(s) come down for leaks

Can these studs be reused, what is the limitation?
Is there a code which dictates their usage?

LQ

 

[unclesyd]

I would clean and give the studs a general physical inspection and reuse them.

As longs as there are no detrimental physical defects you can reuse the studs as long as they have stayed within the allowable temperatures of the stud material.

If there is any doubt about defects a quick wet magnetic particle inspection will clear this up.

 

[VaughnQ]

Thanks man, useful info.
Is there a code [ASME, etc] that dictates the steel usage?

LQ

 

[unclesyd]

Yes, all codes have tables or recommendations for the maximum operating temperature of the different fastener materials based on chemistry and physical properties.

Come back with your specific bolting material you will get the specific recommended temperature.

 

[MJCronin]

vaughn..

Studs, nuts and other hardware that were supplied with an ASME pressure vessel, are part of the vessel.

Almost all of the bolting material that I have encountered for feedwater heaters has been ASME SA193 and ASTM SA194.

There is no "code requirement" to replace bolting material every time that a component is broken down (although I am aware that a lot of organizations require this).

I believe that the wholesale replacement of vessel hardware is sort of an "outage insurance policy" to try to eliminate at least one cause, should the component leak at a critical time. The cost of new bolting material is, in many cases, as much as the integrity test mentioned above.

My opinion/recollections only......

-MJC

 

[VaughnQ]

unclesyd:

The bolt spec is ASTM A-193, Grade B-7 all thread bolts, with ASTM A-191 Grade 2-H, heavy hex nuts.


Thanks for the help guys.

LQ

 

[rmw]

I'd like to restate something that MJCronin said just with different words. He said "....are part of the vessel." I'd like to say it this way. The bolting is part of the pressure boundary. Be sure to use equal or better to avoid code problems.

rmw

 

[unclesyd]

I would like to make add an additional qualifier to my statement concerning reuse of fasteners especially around steam, condensate or treated water for boiler. If you ever see the fastener encrusted with any material especially if off white or grayish all studs in that set should be discarded. This is a sign that you have had a leak and the integrity of the fastener may be compromised.
Adding a little more if you ever need the services of one of the leak repair companies inspect the flange in question and if the any of the studs are encrusted or even broken no online repair should be attempted.


Here are the specifications for your fasteners under the ASTM banner. To get the allowable stress values to use for design you will have to change the Specification to SA193 B7 for the studs and SA194 2H for the nuts.

The ASTM Specifications are available individually while I don't presently know about the SA Specs. It was that you had to get a great big expensive book with everything. Your designer of the bolted connection should have ASME Section II Materials which will give you the allowable stress values of your fasteners.

http://www.astm.org/cgi-bin/SoftCar...EDLINE_PAGES/A193A193M.htm?L+mystore+jqmc7085

http://www.astm.org/cgi-bin/SoftCar...EDLINE_PAGES/A194A194M.htm?L+mystore+jqmc7085

 

[GenB]

studas specially cheaper ones as the vaughn is usig, many times are replaced because they are already stressed out and compromise their integrity. no knowing the condition and because of time consuming in testing and "certification" it is cheaper replacing for new ones.
again depend of the aplication if for just 100 to 200 psi sat steam, it will be wise just to vissual inspect,
PT for assurance and put the4m back.
genb