# NTSB Safety Recommendation P-18-004

- **operation:** document
- **citation:** P-18-004
- **title:** NTSB Safety Recommendation P-18-004
- **source type:** guidance
- **agency:** National Transportation Safety Board
- **status:** guidance
- **official:** true
- **published on:** 2018-06-25
- **effective on:** 2018-06-25
- **summary:** TO HONEYWELL: Specify in your PermaLock mechanical tapping tee assembly installation instructions a not-to-exceed torque limit for Nylon bolts and have that value checked and adjusted with a torque wrench immediately after installation.
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- **app url:** https://regulus.evalyn.ai/document/ntsb-recommendation-p-18-004
- **source url:** https://data.ntsb.gov/carol-main-public/sr-details/P-18-004
**body:**

NTSB safety recommendation P-18-004.

TO HONEYWELL: Specify in your PermaLock mechanical tapping tee assembly installation instructions a not-to-exceed torque limit for Nylon bolts and have that value checked and adjusted with a torque wrench immediately after installation.

Priority: CLASS II

Overall Status: Closed - Acceptable Alternate Action

Issued Date: 2018-06-25

Adopted Date: 2018-06-15

Overall Date Closed: 2022-07-26

Synopsis: The National Transportation Safety Board (NTSB) is providing the following information to urge the Pipeline and Hazardous Materials Safety Administration (PHMSA) and Honeywell to take action on safety recommendations intended to prevent the incorrect installation of PermaLock mechanical tapping tee assemblies in gas distribution systems. These recommendations are derived from our ongoing investigation of a fatal accident involving a natural gas explosion and fire in Millersville, Pennsylvania. The NTSB is issuing two recommendations to PHMSA and two recommendations to Honeywell.

Probable Cause: The National Transportation Safety Board determines that the probable cause of the natural gas explosion at 206 Springdale Lane was an improperly installed mechanical tapping tee that leaked and allowed gas to migrate into the house where it ignited.

Keywords: Hazmat

Ntsbnumber: DCA17FP006

Report Number: PSR-18-01

Addressee Name: Honeywell International, Inc.

Addressee Status: Closed - Acceptable Alternate Action

Addressee Date Closed: 2022-07-26

Addressee Organization Type: P-Private Industry

Communication Date: 2018-06-25

Communication Type: Transmittal Letter

Communication Contents: The National Transportation Safety Board (NTSB) is an independent federal agency charged by Congress with investigating every civil aviation accident in the United States and significant accidents in other modes of transportation—railroad, highway, marine, and pipeline. We determine the probable cause of the accidents and issue safety recommendations aimed at preventing future accidents. In addition, we carry out special studies concerning transportation safety and coordinate the resources of the federal government and other organizations to provide assistance to victims and their family members affected by major transportation disasters. On June 18, 2018, the NTSB adopted its safety recommendation report Installation of PermaLock Mechanical Tapping Tee Assemblies, PSR-18/01. This report is based on our ongoing investigation of a fatal accident involving a natural gas explosion and fire in Millersville, Pennsylvania, on July 2, 2017. The details of the ongoing investigation and the resulting safety recommendations may be found in the attached report, which can also be accessed at http://www.ntsb.gov. Among the Safety Recommendations are two recommendations issued to Honeywell, which can be found on page 9 of the report. The NTSB is vitally interested in these recommendations because they are designed to prevent accidents and save lives. We would appreciate a response within 90 days, detailing the actions you have taken or intend to take to implement these recommendations. When replying, please refer to the safety recommendations by number. We encourage you to submit your response to correspondence@ntsb.gov. If it exceeds 10 megabytes, including attachments, please e-mail us at the same address for instructions. Please do not submit both an electronic copy and a hard copy of the same response.

Addressee Organization Type: P-Private Industry

Communication Date: 2018-08-22

Communication Type: Official Correspondence

Communication Contents: -From Edward Myszka, Vice President and General Manager: Honeywell1 acknowledges and appreciates the substantial efforts of the National Transportation Safety Board's (the "Board") staff in connection with its response to Incident #DCA 17FP006, its investigation of the causes thereof, and its efforts to address and enhance industry safety. Honeywell's Perfection business has supported and cooperated fully with the Board and its staff throughout this process and commits to continue to do so in the future. In particular, Perfection commits to work collaboratively with the Board and its staff in regards to Recommendations P-18-3 and P-18-4. Our commitment to health, safety and the environment is an integral aspect of our design of products, processes and services. Honeywell's Health, Safety, Environmental, Product Stewardship and Sustainability (HSEPS) Management practices are managed by a global team of trained professionals with extensive knowledge and hundreds of years of collective experience. We support the spirit behind the recommendations (i.e ., improving safety) and include herewith revised installation instructions for Perfection Permalock® tapping tees - we've made enhancements in the interest of continuous improvement and refinement; however, we maintain that our instructions were not and have never been inadequate in any way. Further, we believe it beneficial to offer clarification concerning some of the Board's findings and suggestions. This letter addresses: 1) Federal Regulations and corresponding installer qualification requirements that have come into existence since the installation of the tees in question 2) The fact that the installer appears to have disregarded the written instructions provided with the tees 3) Specific concerns with respect to Recommendations P-18-3 and P-18-4 Updates to Federal Regulations As acknowledged by the Board, since the 1998 installation of the tee at issue, new federal regulations concerning operator qualification and training were adopted. The Operator Qualification (OQ) rule was adopted into the Code of Federal Regulations under Subpart Nin 49 CFR Part 192 and Subpart Gin 49 CFR Part 195. Under the rule, each pipeline operator is responsible for developing an OQ program, following their written OQ plan, establishing a covered task list applicable to their system, and defining the training and qualification requirements for personnel performing covered tasks on their pipeline facility. It is the operator's responsibility to ensure their contractors and vendors comply with their program requirements. 49 CFR Part 192 was passed in 1999 and amended in 2005. The stated objective of this rule was to reduce the risk of accidents on pipeline facilities attributable to human error. It is intended to provide an additional level of safety by requiring operators of pipelines and natural gas distribution systems to develop qualification programs to evaluate an individual's ability to perform covered tasks. The qualification programs should also ensure that personnel can recognize and react to abnormal operating conditions that may occur while performing covered tasks. As noted in the report, " ... when the tee assembly involved in the accident was installed in 1998, federal regulations concerning operator qualification training standards for installation of tee assemblies did not exist, and UGI did not have a training program for installing them ... " The Operator Qualification rule, designed to reduce casualty incidents, was not in effect when the Permalock® tee was installed. Disregard of Written Instructions In 1998, UGI was relying solely on each of its individual installers to follow the written installation instructions shipped with the tee assembly2• The report states: "NTSB examination of the Permalock® tee assembly involved in the accident has revealed that the tee assembly was incorrectly installed. Although the cutter tool pierced a hole in the main, the locking sleeve did not progress down far enough into the tower to form threads in that hole. As a result, the locking sleeve was not attached to the main." In other words, the installer of the tee in question did not follow the written installation instructions, at a minimum Step 6 of the instructions (set forth below) was omitted. The depth tube was not used, and as a result, the steel locking sleeve never engaged the main. This was evidenced by the lack of formed threads through the entire crosssection of the pipe wall. The punched bore through the exhumed pipe was smooth. During a proper installation, the sleeve always produces a double-lead thread form in the pipe wall. The steel locking sleeve is designed to serve as the primary anchor to the main; preventing radial, lateral and rotational movement. If the instructions were followed, and the depth tube utilized, this incident would not have occurred. Written instructions, no matter how detailed or clearly presented, are only useful if the installer follows them. Specific Concerns with Respect to Recommendations The recommendations made by the Board were: 1. Update your Permalock® mechanical tapping tee assembly installation instructions to specify the exact tools that should be used during installation and explain what an installer should sense while using those tools throughout the installation process. (P-18-3) 2. Specify in your Permalock® mechanical tapping tee assembly installation instructions a not-to exceed torque limit for Nylon bolts and have that value checked and adjusted with a torque wrench immediately after installation. (P-18-4) Prescribing Exact Tool Size A general description of tool length may provide some benefit. However, using a shorter wrench is subjective rather than objective and does not guarantee or increase the likelihood of a proper installation. Therefore, while we don't think it's necessary, we have added guidance in the updated instructions submitted with this letter. Installers Should Follow Written Directions and Not Rely on Sense The use of a depth tube to verify the proper installation of the cutter sleeve is included in both the previous and current installation instructions. This removes the need for subjective sensory input, such as the torque changes between the punching of the main line, and the installation of the cutter sleeve. As mentioned above, the failure of the installer to follow instructions and use the depth tube was the cause of the incorrect installation. The installation instructions which were reviewed during this investigation were p/n 37575 revision level F, which was the active revision level at the time of installation. These instructions are currently at revision level R. The modifications that have been made to the installation instructions were either made to offer increased clarity to the end user, or to due to design changes to the Permalock® tapping tee which required clarification of the instructions. The installation instructions (both current and previous revisions) explicitly and objectively state the following: • Revision F , Step 6: Place DEPTH TUBE on top of the CUTTER ASSEMBLY. Thread CUTTER ASSEMBLY downward using a 5/16" hex wrench. Continue threading the CUTTER ASSEMBLY downward until it becomes snug. The DEPTH TUBE will be flush to 1/8" above the top of the TEE TOWER. • Revision R4 , Step 1: ... NOTE: A blue colored depth tube is required for 1 1/4 IPS main installation, and a white colored depth tube is required for 2-4 IPS main installation. If you do not have the proper color depth tube, DO NOT install the fitting. • Revision R, Step 6: Place DEPTH TUBE on top of the CUTTER ASSEMBLY. Thread CUTTER ASSEMBLY downward using a 5/16" hex wrench. Continue threading the CUTTER ASSEMBLY downward until it bottoms in the tower. The DEPTH TUBE is a visual guide and will be approximately flush with the top of the Tee Tower when the cutter is engaged. As dem

Addressee Organization Type: P-Private Industry

Communication Date: 2022-05-17

Communication Type: Official Correspondence

Communication Contents: -From Dionne Hamilton, General Counsel, Smart Energy, Honeywell International, Inc.: Thank you for your May 2nd correspondence to the President/CEO of Honeywell International Inc. (“Honeywell”), Darius Adamczyk, with respect to Safety Recommendation P-18-4. I have been asked to obtain the relevant information and respond to the letter. The letter references Honeywell’s position that a not-to-exceed bolt position is a better alternative than a not-to-exceed torque limit, and the NTSB’s response that Honeywell’s position would satisfy the recommendation if an engineering tolerance analysis and bolt stress analysis were performed. The NTSB wished to ensure the tapping tee’s performance while maintaining nylon bolt stress below the critical stress for slow crack growth. The letter asked if Honeywell had additional information to provide. In response, we would like to share with you the findings of a July 6, 2021, report by Fusion Engineering (“Fusion”), attached hereto. The analysis undertaken by Fusion included bolt torque testing, which demonstrated that threading the bolts into the base until the corners touch results in consistent force applied on the bolt, regardless of surface or temperature conditions, whereas relying on torque readings is difficult because the amount of torque required to produce the same amount of tension on the bolt varies widely in different conditions (see pages 8 and 9 of the Fusion Report). Fusion also determined that the bolt load decreases by approximately 30% after installation due to viscoelastic relaxation, and that moisture/softening of the material over time does not result in sufficient strain to fracture the bolts (see pages 12-14 of the Fusion Report). Proper positioning of the bolts is important because it prevents the installer from stripping the base (see page 8 of the Fusion Report). Other significant findings/opinions of Fusion: - Threading the bolts into the tapping tee base results in approximately 48 in-lbs of torque, but once threaded into the base, the bolts do not fracture even at torques up to 140 in-lbs. (see page 15 of the Fusion Report) - When the bolts are threaded until the corners of the tapping tee are in contact, the force on the bolt is only 235 lbs., which is well below the fracture strength of the bolt of 1788 lbs. (see page 15 of the Fusion Report). In light of the Fusion Report, we trust you will agree that having the installer visually confirm the bolt position is preferable to having the installer visually review a torque reading that might not result in proper bolt position. Please let us know if you have any further questions. Thank you.

Addressee Organization Type: P-Private Industry

Communication Date: 2019-03-12

Communication Type: Official Correspondence

Communication Contents: We note that you disagree with specifying a not-to-exceed torque limit for the nylon bolts. Your letter discussed the numerous variables that could impact torque readings, including friction level variations due to sand, precipitation, dirt, and other environmental particulates, as well as temperature differences. Further, because plastic materials such as nylon are viscoelastic, they are highly sensitive to loading rate. The speed at which the bolts are driven, and the main pipe’s roundness, age, material, and manufactured tolerances will also affect a torque reading. Because of these factors, you believe that including torque values in the instructions would be detrimental to installation, and that it is far more accurate—and requires less training and tooling on the part of the end user—to use a visual indicator instead. We discovered fractured nylon bolts in the Millersville accident, as well as in several other accidents and incidents we have investigated involving PMTTs. We believe that plastic materials such as nylon are susceptible to fracture by slow crack growth, and that without some control of tension preload, it is difficult to assure that the bolts are not overtightened. We concur that the factors you mentioned can affect the applied and measured torque values when a PMTT is installed outside of a controlled environment. Prior to Revision R of your installation instructions, bolts were required to be tightened until the mating halves of the tee assembly made contact with each other, but the bolts could have been tightened in a manner that would have allowed the bottom of the threads to extend far below the bottom of the PMTT base, allowing a large range of stresses to be applied to the bolt. Revision R contains additional language, stating “The bolts should be flush with the bottom of the base. Do not tighten further.” This control method (not-to-exceed bolt position) places the nylon bolts into a prestressed state, which can be translated by engineering models into prestressed loads, such as a force or a torque value. Therefore, limiting the installed length of the bolt so it doesn’t protrude below the base can limit the amount of stress that is applied to the nylon bolts. This may represent an alternative method of satisfying Safety Recommendation P-18-4 if you have performed engineering tolerance analysis and corresponding bolt stress analysis to ensure that the PMTT performs as designed while maintaining nylon bolt stress below the critical stress for slow crack growth. Please tell us if you have performed such analysis or have additional information regarding this issue. Pending further correspondence on this question, Safety Recommendation P-18-4 is classified OPEN—ACCEPTABLE ALTERNATE RESPONSE.

Addressee Organization Type: P-Private Industry

Communication Date: 2022-05-02

Communication Type: Official Correspondence

Communication Contents: In an August 22, 2018, letter, signed by Mr. Edward Myszka, former Vice President and General Manager, Honeywell disagreed with specifying a not-to-exceed torque limit for the nylon bolts, but proposed an alternative of a not-to-exceed bolt position that places the nylon bolts into a prestressed state, which can be translated by engineering models into prestressed loads, such as a force or a torque value. The not-to-exceed bolt position would be implemented by limiting the installed length of the bolt so it does not protrude below the base. On March 12, 2019, we replied that this may represent an alternative method of satisfying the recommendation if you have performed an engineering tolerance analysis and corresponding bolt stress analysis to ensure that the PMTT performs as designed while maintaining nylon bolt stress below the critical stress for slow crack growth. We have not received any additional information from Honeywell regarding this recommendation in the past 3 years. Please tell us if you have performed such an analysis or if you have additional information regarding your actions to implement the recommendation. Safety Recommendation P-18-4 is currently classified OPEN-- ACCEPTABLE ALTERNATE RESPONSE.

Addressee Organization Type: P-Private Industry

Communication Date: 2022-07-26

Communication Type: Official Correspondence

Communication Contents: On March 12, 2019, we said that your proposed solution of a not-to-exceed bolt position may be an acceptable alternative to our recommended action when installing your PMTT assemblies in gas distribution systems. We asked if you had performed engineering tolerance analysis and corresponding bolt stress analysis to ensure that the PMTT performs as designed while maintaining nylon bolt stress below the critical stress for slow crack growth. We note the information in your letter about the bolt torque testing and engineering tolerance analysis that you completed, and that you determined that the not-to-exceed bolt position solution is preferable. This installation procedure satisfies the intent of our recommendation. Accordingly, Safety Recommendation P-18-4 is classified CLOSED-- ACCEPTABLE ALTERNATE ACTION.
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