In all my Process Safety courses, we discuss the key RAGAGEPs for Primary Containment (ASME B31.3, ASME Section VIII, etc.). I am always taken aback by how many safety professionals tasked with managing PSM/RMP-covered processes know so little about these critical standards. I am not teaching them to be piping or pressure vessel SME’s; but enough to know what should be happening during their installation/field erection. One of the phrases I learned and stuck in my head in a 1994 training course was “Three-Threads Showing“. It’s a catchy, easy-to-remember phrase that’s even easier to identify in the field. It plays a key role in flange and manway joinments. SAFTENG members can read the dozen or so articles I have written about this topic, or the AICHE CCPS Beacon from 2012. But for those who say this phrase is outdated and has no place in process safety, I wanted to share with you a case where an organization was actually cited for the “three threads showing.
VIA ELECTRONIC MAIL
June 13, 2023
XXXXXXXXX
Senior Vice President of Operations
XXXXXXXX
2626 Cole Avenue, Suite 900
Dallas, Texas 75204
CPF 4-2023-053-NOPV
Dear Mr. XXXXXXX:
From January 24 to May 20, 2022, a representative of the Pipeline and Hazardous Materials Safety Administration (PHMSA), Office of Pipeline Safety (OPS), pursuant to Chapter 601 of 49 United States Code (U.S.C.) was onsite and inspected XXXXXXXXXXXXXXX (XXXXXXXX) pipeline construction project in Oklahoma and Texas. As a result of the inspection, it is alleged that XXXXXXXXXX committed a probable violation of the Pipeline Safety Regulations, Title 49, Code of Federal Regulations (CFR). The item inspected and the probable violation is:
- § 195.202 Compliance with specifications or standards.
Each pipeline system must be constructed in accordance with comprehensive written specifications or standards that are consistent with the requirements of this part. XXXXXXXX failed to construct each pipeline system in accordance with comprehensive written specifications or standards that are consistent with the requirements of Part 195 in accordance with § 195.202. Specifically, Navigator failed to follow its written procedure, Flanged Pipe and Equipment Bolting (Revision A; 1/7/2019), Section 3.0 Bolting Materials, which stated that “a minimum of three threads shall protrude beyond the nut face after the nut is completely torqued” and Section 6.0 Gasket Installation and Bolt Torquing Procedure which stated that XXXXXXXXX must “[u]se rotational tightening until all nuts do not move under 100% torque. There shall not be less than three threads showing on the outside of each nut after they are completely torqued.”
During the field inspection on March 10, 2022, PHMSA observed that Navigator used the incorrect length of bolts (studs and nuts) at the Ruby and Marshall pump stations, resulting in less than three threads showing on multiple flange fittings and on multiple valves. At these locations, PHMSA observed multiple bolts with less than three threads protruding beyond the nut faces as required by Navigator’s procedure. Navigator failed to ensure that a minimum of three threads protruded beyond the nut face.
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