Overpressure Protection and the Downstream User

C. David Slavin

► May, 21 , 2015

Agenda

►Transmission Pipeline Definition

►Overpressure Protection Requirements

►Transient Conditions

►Solutions

Learning Objectives

►Bring Awareness to “Downstream” Pipeline operators and engineers about the definition of a Transmission Pipeline and Overpressure Protection Requirements.

Transmission Pipelines

Scope Diagram: ASME B31.8

Source: U.S. Energy Information Administration

CFR 192.3 Transmission Pipeline Definition Transmission line means a pipeline, other than a gathering line, that: (1) Transports gas from a gathering line or storage facility to a distribution center, storage facility, or large volume customer that is not down-stream from a distribution center; (2) operates at a hoop stress of 20 percent or more of SMYS; or (3) transports gas within a storage field.

NOTE: A large volume customer may receive similar volumes of gas as a distribution center, and includes factories, power plants, and institutional users of gas.

Transmission Vs. Distribution

1. Transports Gas to a “Large Volume Customer”

“OR” 2. Operates above 20% SMYS

Overpressure Protection Requirements

CFR 192.195 Overpressure Protection • 192.195 Protection against accidental

overpressuring. • (a) General requirements. Except as provided in §

192.197, each pipeline that is connected to a gas source so that the maximum allowable operating pressure could be exceeded as the result of pressure control failure or of some other type of failure, must have pressure relieving or pressure limiting devices that meet the requirements of §§ 192.199 and 192.201.

Case Study/ Example

►Company Y was cited for no inspection records on their pipeline for overpressure protection, they commented that the were relying on the upstream supplier to provide overpressure protection

DOT Response: ►“Under the pipeline safety regulations, each

operator is responsible for ensuring that its pipeline is protected from pressure control failures and must therefore either maintain its own overpressure devices, or monitor it supplier’s device recording the type, location, and inspection date for each device” [record]

Interconnection Agreements

“The Parties further agree that Customer's Facilities will accommodate pressures up to Company’s X mainline pressure which has a design maximum allowable operating pressure ("MAOP") of XXXX psig, and Customer shall adhere to Part 192.195 of the Department of Transportation regulations. Customer expressly agrees that Company X is not responsible for the over-pressure protection of Customer's Facilities, and that Customer or its designee is solely liable for damages due to inadequate over-pressure protection.”

Transient Pressure Conditions

Pressure Surge Causes

Pressure Surge ► Valve Closure

► Compressor Start and

Stop

► Failed Overpressure

Protection

http://www.ogj.com/articles/print/volume-111/issue-11/transportation/transient-analysis-helps-im-for-crater-type.html

1 4

► Speed of Sound in Methane (@ 60 Deg F): 1521 ft/s

► Speed of Sound in Water (@ 60 Deg F): 4871 ft/s -Engineering Tool Box

Pressure Surge ► Wave Speed

► Compressibility/Bulk

Modulus

► Distance to Valve

Pressure Surge Conditions

Overpressure Protection Solutions

Overpressure Requirements (B31.8.845)

(1) Overpressure protection shall be provided by the use of ►(a) a monitor regulator in series with a

controlling regulator (each regulator run) ►(b) adequately sized relief valve(s) downstream

of the controlling regulator(s) ►(c) overpressure shutoff valve(s) upstream or

downstream of the controlling regulator(s). Installation of alarm devices which indicate primary (controlling) regulator failure are useful and should be considered for monitor regulator systems.

Suitable Protection

ALBERTA ENERGY AND UTILITIES BOARD Reference Tool for Interpreting Pipeline Pressure Control and Overpressure Protection Requirements March 2007

Unsuitable Protection

Monitor and Working Regulator

►Advantages • Uninterrupted Service • Pressure Control • No Venting, Easy Testing

►Disadvantages • Cost • Larger Footprint • System Failure

-Mooney Flowgrid Regulator

Relief Valve

►Advantages • Most Reliable (No Blockage) • Reasonable in Cost • Uninterruptible

►Disadvantages • Noise (Could be an Advantage) • Release to Atmosphere Hazard • Can become unstable (Open

and Close)

Note: Must be sized for full flow.

Shutoff Valve

►Advantages • Nothing Vented • Assures Safety

►Disadvantages • Interrupts Service • System Failure

-Pietro Fiorentini (SBC 782)

ASME B31.8 Interpretations ►Question (2): Can gas pipelines be designed to have

transient overpressures up to 10% above MAOP, similar to ASME B31.4?

►Reply (2): No

ASME B31.8 Interpretations ►Question (4): Are gas pipelines allowed to operate

at transient overpressures up to 10% above MAOP when MAOP is equal to the Design Pressure?

►Reply (4): No.

2 4

► DOT Regulated “Transmission” Pipeline • If you operate above 20% SMYS

• “or” if you are a Large Volume Costumer

► Overpressure Protection Records are Required!

Summary & Review

Questions