The depth of engagement to form a leakproof connection is dependent on the pipe diameter and system pressure.
For general talking purposes per ASME B1.20.1, for NPT pipes, a 1.25" pipe is shown as having 11.5 threads per inch with the typical hand tightening limitation at 4.5 turns for a depth of 0.42 inches (<5 threads). Past that to get to full engagement requires the use of a wrench. Effective length of thread is shown as 0.707 inches. So it's amazing that with only two threads for engagement it didn't come apart under the pressure test and stayed in place for 15 years. I would wonder if there are any other connections in a similar condition. Craig Prahl | Jacobs | Group Lead/SME - Fire Protection | [email protected] | www.jacobs.com 1041 East Butler Road Greenville, South Carolina 29606 CONTACT BY: email or MS TEAMS -----Original Message----- From: Sprinklerforum <[email protected]> On Behalf Of Matt Grise via Sprinklerforum Sent: Wednesday, January 5, 2022 9:42 AM To: [email protected] Cc: Matt Grise <[email protected]>; Kevin Hall <[email protected]> Subject: [EXTERNAL] RE: Thread connection holding on one thread only If I recall from my book-learning days, there is a pretty well established minimum thread engagement that provides the full strength of a threaded connection. (maybe 3?). That may also only apply to bolts though. Matt -----Original Message----- From: Sprinklerforum <[email protected]> On Behalf Of Kevin Hall via Sprinklerforum Sent: Wednesday, January 05, 2022 8:33 AM To: [email protected] Cc: Kevin Hall <[email protected]> Subject: Re: Thread connection holding on one thread only I do not believe one is sufficient. I recall a project where the specification limited the maximum number of exposed threads to 2 or 3. I'd have to do some research to find the product/installation standard that was referenced. Kevin Hall, M.Eng., P.E., ET, CWBSP, PMSFPE Coordinator, Engineering and Technical Services American Fire Sprinkler Association [email protected] 214-349-5971 On Wed, Jan 5, 2022 at 2:16 AM Dan Arbel via Sprinklerforum < [email protected]> wrote: > Dear Forum Members > > I have a case where 1.25" NPT pipe nipple was connected to 1.25" BSP > (as per British standard) pipe. > > Sprinkler System in interstitial space. > > There was only 2 threads engagement. > > After about 15 years somebody touched the a pipe and the connection > disengaged. > > I would appreciated the members opinion on the allegation that even > one thread engagement is sufficient providing sufficient strength. > > Dan Arbel > Dan Arbel Risk Engineering Ltd > Mail: [email protected] > WEB SITE: > https://urldefense.com/v3/__https://linkprotect.cudasvc.com/url?a=http > s*3a*2f*2fwww.riskmanage.com__;JSUl!!B5cixuoO7ltTeg!XkU8cH2TMBKLQ2ZlRo > 1tisvmulk98nUEHNhgQ5Y2N2mjqKrtgbiQDgiMg-yghiPIMw$ > &c=E,1,rOBCJWaUiWX-Zi-j03j48v-ojODJ4zDjCTCn-XcTQUWSVSZzQRanv2vrdqlUogX > nkOECEYOqMT2eMuzN6PVEfyuVyVF6Hoz4BiV1VyGvBRCcljgZH2U,&typo=1 > Mobile: +972-52-6611337 > Tel: +972-4-8243337 > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > https://urldefense.com/v3/__https://linkprotect.cudasvc.com/url?a=http > *3a*2f*2flists.firesprinkler__;JSUl!!B5cixuoO7ltTeg!XkU8cH2TMBKLQ2ZlRo > 1tisvmulk98nUEHNhgQ5Y2N2mjqKrtgbiQDgiMg-zXS7SC2A$ > .org%2flistinfo.cgi%2fsprinklerforum-firesprinkler.org&c=E,1,RvPpy3ldS > C8kzu280ouAOq2QKBzNGfMu7REiocN-XOdCtouKzXB4EaUtnbHa1UoPns-R2H1fzQj-fW- > oIX3YW0Doh9ZL84fg3cNaQ0q1OQ,,&typo=1 > _______________________________________________ Sprinklerforum mailing list [email protected] https://urldefense.com/v3/__https://linkprotect.cudasvc.com/url?a=http*3a*2f*2flists.firesprinkler.org*2flistinfo.cgi*2fsprinklerforum-firesprinkler.org&c=E,1,wikZY07kLJSV87o86Ivs1Jsxm4l75jKdQbbfbZ7tVZifvQRGY33Wh20_IAQ7wACFTF9yFLpxM-xqELTjxDST6UJ7dCl0WTqJP_LkvfP8qA,,&typo=1__;JSUlJSU!!B5cixuoO7ltTeg!XkU8cH2TMBKLQ2ZlRo1tisvmulk98nUEHNhgQ5Y2N2mjqKrtgbiQDgiMg-w4GyP2OA$ _______________________________________________ Sprinklerforum mailing list [email protected] https://urldefense.com/v3/__http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org__;!!B5cixuoO7ltTeg!XkU8cH2TMBKLQ2ZlRo1tisvmulk98nUEHNhgQ5Y2N2mjqKrtgbiQDgiMg-w8lV3Y3w$ ________________________________ NOTICE - This communication may contain confidential and privileged information that is for the sole use of the intended recipient. Any viewing, copying or distribution of, or reliance on this message by unintended recipients is strictly prohibited. If you have received this message in error, please notify us immediately by replying to the message and deleting it from your computer. _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
