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Pipeline Safety Advisory Bulletin; Inspecting and Testing Pilot-Operated Pressure Relief Valves

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Office of Pipeline Safety (OPS), Pipeline and Hazardous Materials Safety Administration, DOT


Notice of advisory bulletin.


This notice announces a pipeline safety advisory bulletin about pilot-operated pressure relief valves installed in hazardous liquid pipelines. The bulletin provides pipeline operators guidance on whether their inspection and test procedures are adequate to determine if these valves function properly. Malfunctioning of a pilot-operated pressure relief valve was a contributing factor in an accident involving a petroleum products pipeline in Bellingham Washington.

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L.M. Furrow by phone at 202-366-4559, by fax at 202-366-4566, by mail at U.S. Department of Transportation, 400 Seventh Street, SW., Washington, DC, 20590, or by e-mail at

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After its investigation of an accident involving a 16-inch petroleum products pipeline operated by the Olympic Pipe Line Company in Bellingham, Washington, the National Transportation Safety Board (NTSB) made the following recommendation to the Research and Special Programs Administration: [1]

Develop and issue guidance to pipeline operators on specific testing Start Printed Page 46570procedures that can (1) be used to approximate actual operations during the commissioning of a new pumping station or the installation of a new relief valve, and (2) be used to determine, during annual tests, whether a relief valve is functioning properly. (P-02-4)

The recommendation arose from NTSB's evaluation of a test Olympic had done to check the pilot of a pilot-operated pressure relief valve in a pumping station at its new Bayview products terminal. NTSB found the test was inadequate to determine if the pilot was configured properly or if it was operating reliably. Furthermore, NTSB concluded that the DOT regulations governing the testing of relief valves and other safety devices on hazardous liquid pipelines provide insufficient guidance to ensure that test protocols and procedures will effectively indicate malfunctions of pressure relief valves or their pilot controls.[2]

According to NTSB's accident report [3] —available online at​Publictn/​P_​Acc.htm—Olympic installed pressure control devices to protect the Bayview terminal piping and components from overpressure by the 16-inch pipeline. These devices consisted of (1) a control valve to throttle back the inflow of product; (2) a downstream pilot-operated pressure relief valve designed to divert excess product if a set pressure was exceeded; and (3) upstream remotely controlled block valves that would stop the inflow if a pressure of 700 psig was reached inside the terminal.

The report explains that the pilot of the relief valve had been configured for low-pressure operation, with a set point of 100 psig. Consequently, during start-up of the Bayview terminal, the relief valve opened at a pressure lower than intended. To correct the problem, Olympic replaced the pilot spring (with an identical spring) and increased the set point to 700 psig. (Olympic did not consult the valve manufacturer's specifications and was unaware that a different piston, cover, and O-ring were necessary for high-pressure configuration.) The pilot was then tested in situ with a hydraulic pump rig to be sure the pilot valve opened at the correct pressure. Olympic used the same test procedure it used to test relief valves under DOT's regulations.

The accident investigation disclosed that increasing the set pressure of the pilot had compressed the pilot spring so much that rising inlet pressure could not lift the piston, making operation of the pilot completely unreliable. Although the pilot set point apparently had been tested, the test procedure did not reveal that the pilot had been configured for low-pressure operation and thus would not consistently open at the intended pressure. NTSB observed that if the relief valve did not open because of pilot malfunction and downstream pressure rose above 700 psig, a block valve would close and increase pressure in the 16-inch pipeline, which is what happened in the accident.

Advisory Bulletin (ADB-05-05)

OPS shares NTSB's concern that pipeline operators could be conducting in-service tests that do not identify unreliable pilot-operated pressure relief valves. Therefore, we are issuing the following advisory bulletin:

To: Operators of hazardous liquid pipelines regulated by 49 CFR part 195.

Subject: Inspecting and testing pilot-operated pressure relief valves.

Purpose: To assure that pilot-operated pressure relief valves function properly.

Advisory: Operators should review their in-service inspection and test procedures used on new, replaced, or relocated pilot-operated pressure relief valves and during the periodic inspection and testing of these valves. Operators can use the guidance stated below to ensure the procedures approximate actual operations and are adequate to determine if the valves functions properly.

Guidance: The procedures should provide for the following:

(a) During installation, review the valve purchase order (or comparable documentation), valve name-plate, and manufacturer's specifications. Verify that the valve is:

(1) Compatible with the material and maximum operating pressure of the pipeline;

(2) Compatible with or protected from environmental attack or damage;

(3) Compatible with the hazardous liquid transported at all anticipated operating temperatures and pressures;

(4) In conformity with the manufacturer's specifications for the valve model and type of service, and with the purchase order (or comparable documentation);

(5) Configured according to the manufacturer's specifications for the pilot and in-line valves; and

(6) Operable at the set pressure (i.e., activation of the pilot valve opens the in-line valve).

(b) If the pilot assembly of a previously installed valve is reconfigured or repaired “

(1) Do the work according to the manufacturer's specifications;

(2) Test the valve to ensure it is operable at the set pressure (i.e., activation of the pilot valve opens the in-line valve) or, if testing the in-line valve would be unsafe or environmentally hazardous, tests the pilot valve according to paragraph (d) below; and

(3) Document the work.

(c) Verify that the valve set pressure is consistent with “

(1) The design or configuration of the pilot valve and in-line valve; and

(2) Use of the valve as a primary overpressure protection device or as a backup safety relief device.

(d) Test the pilot valve at least twice and verify that it activates consistently at the intended set pressure.

(e) During periodic inspections and tests, review the valve installation to determine if it has been modified since the last inspection. If so, verify that the pilot sensor and valve inlet and discharge piping are properly sized and placed and that the installation is consistent with the intended design.

(f) Document all verifications, and sign, date, and keep for the operating life of the valve all documentation.

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Issued in Washington, DC, on August 4, 2005.

Stacey Gerard,

Associate Administrator for Pipeline Safety.

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1.  The Norman Y. Mineta Research and Special Programs Improvement Act (Pub. L. 108-426, 118; November 30, 2004) reorganized the Research and Special Programs Administration (RSPA) into two new DOT administrations: the Pipeline and Hazardous Material Safety Administration (PHMSA) and the Research and Innovative Technology Administration. RSPA's regulatory authority over pipeline and hazardous materials safety was transferred to PHMSA.

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2.  Under 49 CFR 195.262(c), the safety devices in each new pumping station must be tested under conditions approximating actual operations and found to function properly before the pumping station may be used. Also, under 49 CFR 195.428, each pressure limiting device, relief valve, pressure regulator, or other item of pressure control equipment must be inspected and tested annually to determine that it is functioning properly, is in good mechanical condition, and is adequate from the standpoint of capacity and reliability of operation for the service in which it is used.

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3.  Pipeline Rupture and Subsequent Fire in Bellingham, Washington, June 10, 1999, Pipeline Accident Report NTSB/PAR-02/02, October 11, 2002.

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[FR Doc. 05-15758 Filed 8-9-05; 8:45 am]