Flange Bolting for moderate Pressures and Temperatures
Flange Bolting for moderate Pressures and Temperatures
(OP)
Greetings,
I have a few questions regarding bolt-up of 600# and 300# flanges in a 2" through 8" piping system that will see temperatures of 600deg F and upwards of 750psi. The system will be subject to frequent thermal cycling. It contains biosolids sludge in some places and Therminol heating oil in others. I have been looking all over (16.5, 31.1 etc.) for a guiding protocol to address the following questions:
1.Bolts and nuts vs. studs and double nuts
2.Smartest (most efficient) way to measure tension, measuring torque and/or angle seems to have too many variables to make it accurate
3.If an ultrasonic bolt tension gauge is used to ensure maximum gasket compression, can a lubricant be used on the bolts/studs to facilitate bolt-up since you are no longer relying on torque measurements to indicate tension?
4.Common materials for these types of stresses and material data (Young's modulus for A307?)
5.When measuring elongation for strain/stress in this scenario, what would be the effective length for original length, the thickness of the flange faces plus the gasket thickness?
Any help anyone can offer is appreciated, thanks for your time.
I have a few questions regarding bolt-up of 600# and 300# flanges in a 2" through 8" piping system that will see temperatures of 600deg F and upwards of 750psi. The system will be subject to frequent thermal cycling. It contains biosolids sludge in some places and Therminol heating oil in others. I have been looking all over (16.5, 31.1 etc.) for a guiding protocol to address the following questions:
1.Bolts and nuts vs. studs and double nuts
2.Smartest (most efficient) way to measure tension, measuring torque and/or angle seems to have too many variables to make it accurate
3.If an ultrasonic bolt tension gauge is used to ensure maximum gasket compression, can a lubricant be used on the bolts/studs to facilitate bolt-up since you are no longer relying on torque measurements to indicate tension?
4.Common materials for these types of stresses and material data (Young's modulus for A307?)
5.When measuring elongation for strain/stress in this scenario, what would be the effective length for original length, the thickness of the flange faces plus the gasket thickness?
Any help anyone can offer is appreciated, thanks for your time.





RE: Flange Bolting for moderate Pressures and Temperatures
2.) Never did anything more than a torque measurement.
3.) Can't figure out why you need lubed threads with or without untrasonics?
4.) Steel is around 29,000,000 psi, and sometimes varies 1e6, implying a possible difference of 3% in axial stress. How close do you need to be? ASTM A193? 307 is mostly used for structural anchor bolts.
5.) I would use an effective length = inside to inside of the nut/washer interface at the moment of beginning load up.
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RE: Flange Bolting for moderate Pressures and Temperatures
BigInch provided some good answers. I'll add some thoughts: First, I'll second the question of why the need for such accuracy in tensioning?
Your question 3. seems to indicate that you do not lube the studs/nuts when you torque them. Most folks who are worried enough to use a torque wrench would lube them, then use a factor of around 0.18 in the torque calc.
I'd suggest getting a copy of ASME PCC-1 at htt
I would highly recommend speaking with an engineer from your chosen gasket company and follow his recommendation for bolt torques. It just doesn't seem that your application is difficult enough to warrant the effort involved with strain measurements.
jt
RE: Flange Bolting for moderate Pressures and Temperatures
A little background, we use vaporized Therminol on very large scale jacketed pipe systems where the process is very cyclic and the each production unit requires an overhaul on 1-2 year basis.
Our piping code requires RTJ flanges in all Therminol Systems. This is for both the vapor and condensate system.
Studs are ASME A193 B-7 with ASME A194 2H nuts. No bolts are used. To preserve the nuts we require all mechanics to have the appropriate size box end wrench. We now allow channel locks as backup. No open ends or adjustable. We allow impact wrenches on the majority of the systems.
The studs and nuts are coated with DAG, a water based colloidal graphite. We have a replacement set of studs and nuts Dagged ready for rebuild. The fasteners taken out are cleaned and Dagged. After the Dagging each stud id made up with the 2 nuts so there will be no problem during their next use.
The RTJ gaskets are not reused on a routine basis.
There is no torquing procedure for the flange make up. The mechanics achieve an essential leak free system by watching the flanges remain parallel while tightening.
We test the assembled system using the Therminol system vacuum before the insulation is replaced. The maximum decay rate is 1#/hour. As most of our system in an enclosed space a decay rate approaching 1# we will charge the system to 20 psig with Helium and start checking flanges and valves.
One rule with the maintenance crew is that if you put one bolt in a Therminol flange you put them all in and tighten same even if you have to pee in your pants.
The process flanges on these system are all raised face with the fasteners being the same as the Therminol system.
We use spiral wound gaskets, mostly mica filled but the trend now is to go with graphite filled.
The flanges are made up the same as the Therminol flanges with the mechanic insuring that the flanges are kept parallel during makeup. We use impacts on all the process side bolting.
The process side isn't tested prior to admitting the product.
RE: Flange Bolting for moderate Pressures and Temperatures
The accuracy I require is just that of my own satisfaction. I've had extensive conversation with the gasket manufacturer and in order to achieve the gasket manufacturer's recommended compression, and especially with spiral wound graphite, I want to be at the upper limit of allowable gasket compression without compromising the gasket but ensuring a leak-free joint.
The purpose of the ultrasonic would be to cross-check the values I anticipate getting based on the hydraulic torque wrench settings. Our two-wrench setup uses an adjustable pressure relief valve on the pump to bypass hydraulic fluid to the wrenches. A chart correlating torque vs. pressure is "calculated" and provided by the wrench mfgr.
As far as lube goes, I should have specified that anti-sieze is a standard for us on everything and I wanted to account for its lubricating effect in making the flange. I appreciate the suggestion to use a water based colloidal graphite.
Following unclesyd's post I went back to 16.5-2003 and reviewed the allowable temperatures for stud materials ("low strength" is out) and it seems with A193-B7 is more readily available (through our suppliers, not in general) than the "intermediate strength" materials shown.
Thanks again for the responses, it's great being able to discuss technical items with one's peers.