"What is the Highest tensile strength fasteners I can use in h3S"


"We make hot tapping and plugging equipment for servicing pipelines without disrupting service. We are nearing completion of testing a new type of flange bore plug and have now discovered some of the key "pressure retaining hardware" is too hard for NACE. We are scrambling to find some new "off the shelf" hardware that is reasonably priced, so we don't have to completely re-test. Lower UTS would mean other things might have to change to accomodate bolt diameter changes. I am looking for an off-the-shelf fastener particularly shoulder screws (with around 160 ksi UTS.) Currently the Shoulder Screws must meet the following spec....Heat treated ALLOY steel, Rc 36-43, 160 ksi, Unbrako or equivalent. Sizes will vary depending on the size of the plug. If these (bolts) fail, it could lead to a catastrophic failure. Do any of you know of some fair priced bolts with high UTS that are approved by Nace for use in Sour gas?


NACE MR0175 sets the hardness (strength)requirements for metals and alloys in sour service, including fasteners. The precipitation hardening alloys (17-4PH) will get you close to HRC 36, but not quite. You will find it difficult to select a bolt at hardnesses greater than HRC 36 that meet MR0175 requirements. Two that you might consider include alloy 718 and MP35N.


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