Intermediate strength bolts on B16.5 and B16.47 flanges
Para. 5.3.3 of B16.5 and B16.7, states that intermediate strength bolts may be used on flanges provided user verified integrity. Is there any method or code or standard or procedure for verification of joint? Please advise.
Hugo Julien ASME PCC-1!
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Anilkumar Panchal, CEng Is it Appendix O in ASME PCC-1?
Jörg A. Is ASME PCC-1 a Pseudo Panacea? Not really but...
Whereas the PCC-1 "guidelines" undisputedly do indeed provide useful guidance, some believe that they are flawed.
Task Forces or Advisory Boards which have been formed to answer specific industry-related concerns often include individuals from supplier organisations. It is naive to think that those participants have volunteered (or have paid!) only for altruistic reasons. Rather, they are there to promote their own commercial agenda. The most effective of these lobbyists are rewarded by published endorsements which promotes their agenda either directly or indirectly.
Having said the above, by all means review the PCC-1 guidelines, take value from some of the great recommendations therein. But, do it with an open cynical mind so that you can separate the wisdom from the commercial chaff.
to be continued
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Jörg A. Anilkumar, there are a number of factors which contribute to the reliability of critical flanged joints and hence, which should be verified. These include material specs (flanges, studs, nuts, washers), seal specs (gaskets, rings), geometry (flange surface condition, perpendicularity), installation procedures and, the proverbial icing on the cake: bolt stress.
It is important to note that the use of calibrated wrenches to apply increasing levels of torque in esoteric patterns does not verify bolt stress. It only verifies how much INPUT force was applied. The RESULT of this effort remains unknown. Likewise, neither does applied tensioner pressure guarantee specific residual bolt stress values.
Valid verification methods are, however, available. All have their own pros and cons: http://www.heviitech.com/verification/
While not in every case (because such precision isn't always required), we find the use of ultrasonic bolt elongation measurement to be quite suitable.
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Warren Brown Anilkumar Panchal, CEng it is a bit open to interpretation as to what "verified" means. However, I would suggest that you interpret it as performing a PCC-1 Appendix O calculation with a view to determining if the joint integrity will be limited by maximum permissible bolt stress if a lower strength bolt is used. You will see that if the selected bolt stress must be reduced according to equation O-4.
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Warren Brown Jörg Albrecht ... seriously! you criticize those who volunteer, claim that they push their agenda and then in the same post blatantly push your own agenda! If you or any of the other "some believe" individuals would like to actually improve PCC-1 then you have the opportunity to be involved as an interested party and/or have the opportunity to provide comment during the public comment period prior to the release of each revision (next one coming later this year for PCC-1). However, if you do get involved then don't expect any rewards, since ASME specifically do not "endorse any product or service" and there will also be a bunch of keyboard critics to deal with... The other opportunity to contribute (versus simply criticizing) would be to write a technical paper for publication detailing the perceived issues, I've done that before and it does bring change. Bonus is you might also learn something along the way..
Jörg A. Warren, I had expected that my post would elicit such a response. Nevertheless, I do stand by it. We simply need to remove the emotional response and stand back a few steps from the issue to recognise the bias. Take for example, the case of bolt preload. I don't think that anyone would dispute that it is one of the pillars upon which the integrity of a bolted joint rests. Yet, PCC-1, implies that is okay to "guess" that the residual load of critical fasteners is in accordance with design - whether the fasteners are torqued or tensioned. Of course, in some cases such "guesses" are probably sufficient. But in others, I think you can agree that we need more than to guess or hope that the fasteners are tightened properly.
to be continued...
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Jörg A. Indeed, Warren, I did push my own agenda: It is that of "verification" versus conjecture. I prefer to know that my fasteners are tightened properly rather than rely upon chance.
There are many means of verification available. It just so happens that based on our extensive experience in this field, measurement of fastener elongation using ultrasonic technology is the one which we find is the most suitable.
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Jesús lionel Mondragón Alexis Good afternoon Sirs, I read all the post, in some points I am agree like " These include material specs (flanges, studs, nuts, washers), seal specs (gaskets, rings), geometry (flange surface condition, perpendicularity), installation procedures and, the proverbial icing on the cake: bolt stress." but the real deal of the question (I mean Aplication) is regarding to wrenching (normally the gasket is weakest element) or stress force transmitted to the flange itself
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Warren Brown Jörg I suggest you read PCC-1 more closely. It contains reference to several different methods for elongation verification, section 10.2 outlines elongation verification calculations and Table 3 indicates elongation measurement as the preferred load-control method for Critical Service joints. In addition to that, Appendix K addresses inaccuracy of Torque control. I understand that by being controversial you bring more attention to yourself and hope to generate more work, but this time I felt compelled to call you out on it. I will renew my call to you and anyone else to contribute (either by being directly involved or by writing peer-reviewed technical papers) rather than simply criticizing. By the way... the word "guess" does not appear in any section of PCC-1.
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Jörg A. Indeed, Warren, the word "guess" does not appear anywhere in PCC-1. Therein sits the problem. A guess can be a dangerous thing, particularly when somebody in the course of an investigation is asked "how do you know that the bolts were 'tight enough' (sic)?". Answers such as "because we explicitly followed the torquing patterns as per PCC-1", "because we used a calibrated torque wrench", or "because we recently calibrated our tensioner pump gauges" stand on very feeble ground since they are all clearly based on guesses. Yet since, other than suggested in footnotes, fine print or appendixes, the methods are not -clearly- described as such in these highly-regarded guidelines, they imply credibility.
As per our communication of many years ago, I would be very happy to contribute in any way possible. Based on our unique perspectives, I'm sure that a joint (hah: a pun!) effort to collaborate on a technical paper would be quite effective.
More can be found @ https://www.linkedin.com/groups/4439477/4439477-6264422244752166912
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