# Memo: Internal — Pipeline Safety Interpretation

- **operation:** document
- **citation:** PI-79-034
- **title:** Memo: Internal — Pipeline Safety Interpretation
- **source type:** guidance
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** guidance
- **official:** true
- **published on:** 1979-09-20
- **effective on:** Not available
- **summary:** PI-79-034 response to Memo: Internal concerning 192.747.
- **machine formats:** - **json:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-034.json
- **markdown:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-034.md
- **app url:** https://regulus.evalyn.ai/document/phmsa-interpretation-pi-79-034
- **source url:** https://www.phmsa.dot.gov/sites/phmsa.dot.gov/files/legacy/interpretations/Interpretation%20Files/Pipeline/1979/PI79034.pdf
**body:**

<<<PAGE 1>>>

Interpretation of §192.747
Associate Director for Pipeline Safety Regulation, DMT-30
Chief, Southern Region, DMT-16
In your memorandum of December 19, 1978, you point out problems you find in trying to enforce
§192.747 "Valve maintenance; distribution systems" concerning the number of valves that must be
maintained as required in a given piping system having a well defined business district and class 1,
2, and 3 areas. You asked if one key valve will suffice as the emergency valve, assuming that the
valve controls the system supply and that multiple main valves do exist within the system. If one
valve will not suffice, what minimum number of key valves should suffice, and what systems areas
should they control?
After a thorough review, we have concluded that:
(a) Section 192.747 does not specify how many valves are necessary for the safe operation
of a distribution system. The regulation requires that any valves necessary for the safe operation
of a distribution system (key valves) "...be checked and serviced at intervals not exceeding 1
year." Section 192.181 which prescribed design standards for installation of key valves in pipeline
systems can be used as a guideline for identifying key valves in existing systems installed prior to
1971. On such existing systems, new valve installations can be required only if the existing
system is hazardous to life or property or as necessary to meet the requirements of the operators'
Inspection and Maintenance or Emergency Plans. In addition, the manual used by the
Transportation Safety Institute (TSI) in conducting the course on "Safety Regulation for Gas
Pipeline Systems" includes additional guidance in determining if one key valve will suffice as the
emergency valve on such a distribution system. The TSI manual states that key valves be
considered at each pressure regulating station, principal lines to business districts, and class 4
locations, as well as other criteria. Since the system to which you refer has a well defined
business district, class 1, 2, and 3 areas, as well as multiple main line valves. it appears that more
than one key valve may be required for the safe operation of that distribution system.
(b) We cannot establish the minimum number of key valves that would suffice"...for a
typical distribution system having a well defined business district, and class 1, 2, and 3 areas"
because the number would depend on the specific system design. Because if the various dwelling
densities of the system, it appears that several key valves can be identified using criteria set forth
in §192.181, such as the operating pressure, the size of the mains, and the local physical
conditions. Some additional criteria to ne considered in determining the location of key valves are
DB
C:\WP51\INTERPRT\192\747\79-09-20
1

<<<PAGE 2>>>

the size of the system, accessibility of each valve, and the capability of the operator to handle an
emergency. The TSI manual states that the key valves should be considered at the following
locations:
1. 2. 3. 4. Control valve(s) at each pressure regulator station.
Principal feed(s) to business districts and class 4 locations.
All single valves on mains within (2) above.
Valves that meet the following criteria.
(a) Reasonable for sectionalizing plan.
Consider - Number of customers
- Volume of gas
- Environment
- Response time/valve accessibility
(b) Necessary because of unsatisfactory maintenance
History of pipeline section
Consider - Leak history
- Types of failures
Cesar DeLeon
DB
C:\WP51\INTERPRT\192\747\79-09-20
2
- **truncated:** false
- **body characters:** 3561