Gas Freeing, Purging & Leak Testing of Process Equipment (Excluding Tanks)

Petroleum Development Oman LLCRevision: DRAFTEffective: Dec-5

Petroleum Development Oman LLCRevision 4.1 Effective: Mar-11

Petroleum Development Oman L.L.C.

Document Title: Gas Freeing Purging and Leak testing Process Equipment and Pipework

Document IDPR-1073

Document TypeProcedure

SecurityUnrestricted

DisciplineEngineering and Operations

OwnerUOM - Functional Maintenance & Integrity Manager

Issue DateApril 2010

Revision4.1

This page was intentionally left blankDocument AuthorisationAuthorised For Issue April 2010

Revision HistoryThe following is a brief summary of the 4 most recent revisions to this document. Details of all revisions prior to these are held on file by the issuing department.

Revision No.DateAuthorScope / Remarks

Apr-11Robin Norman UOP6Added Section 1.7 ALARP

4.1Mar-11Robin Norman UOP6See Interim Amendment March 2011 (Rev 4.1)

4.0Apr-10Robin Norman UOP6See Addendum 2 for details

3.2Feb-10Robin Norman UOP6Minor Revision See Addendum 1 for details

3.1Jan-09Robin Norman UOP6Revised Section 3 Leak Testing to provide clarity and remove any confusion

1.0Sept 01UOP/1Reviewed and revalidated

Sept 98UOP/1OP-32 rewritten to new format.

Related Business ProcessesCodeBusiness Process (EPBM 4.0)

EP 72Maintain and Assure Facilities Integrity

Related Corporate Management Frame Work (CMF) DocumentsThe related CMF Documents can be retrieved from the CMF Business Control Portal.CP-114Maintenance CoP

CP-115Operate Surface Product Flow Assets - CoP

See Appendix 4TABLE OF CONTENTS1Introduction71.1Background71.2Purpose71.3Scope71.4Distribution / Target Audience71.5Changes to the Document81.6Step-out Approval81.7ALARP82Roles and Responsibilities93Gas-Freeing, Purging Process Equipment103.1General103.2Draining of Vessels and Pipework to Open Pits103.2.1Considerations When Draining Vessels and Pipework103.2.2Criteria for Using an Open Pit113.2.3Control Required for using Open Pits113.3Gas-Freeing and Purging123.3.1Preparation and Precautions123.3.2Gas Freeing143.3.3Atmospheric Pressure Method143.3.4Cyclic Pressure Purge Method143.3.5Water Displacement Method153.3.6Series Purging153.3.7Displacing To Air153.4Purging Following Inspection or Maintenance153.5Sampling164Leak Testing174.1Objective174.2Definitions for Leak Testing174.3Reinstatement Policy184.3.1Method Options in Order of Consideration184.4Planning Reinstatement Leak Test194.5Nitrogen Leak Testing of Systems214.5.1Bubble Forming Solution224.5.2Acceptance Criteria for N2 Leak Testing (Bubble Test)224.6Performing the In-Service Reinstatement Test224.7Vacuum Testing234.8Reinstatement Testing of Relief Valves Connected to the Flare or Relief Headers235Hazards245.1Draining and Flushing to Open Pits245.2Gas-Freeing and Purging245.3Leak Testing24Appendix 1 Working With Nitrogen Gas26Appendix 2 Method Statement29Appendix 3 - Abbreviations30Appendix 4 Reference Material31Appendix 5 - User Feedback Page32Addendum 1 Changes at Revision 3.233Addendum 2 Changes at Revision 4.034Interim Amendment March 2011 (Revision 4.1)35TABLES AND FIGURESTable 1 - Recommended Criteria Hydrocarbon / Nitrogen Purge16Table 2 - Inert Gas End Points for Purging Equipment Out of Service16Figure 1 Reinstatement Leak Testing Decision Chart19Table - Sample Checksheet for Testing of Pipework System30

IntroductionBackgroundProcess equipment in hydrocarbon services shall be subjected to periodic inspections and maintenance which may result in the pressure containment being broken. Such breaks in the pressure containment can result in explosive mixtures of air and hydrocarbon vapour being present. Therefore whenever pressure containment is broken measure must be taken to ensure that: An explosive atmosphere is not present during such times that work is being undertaken An explosive atmosphere is not present in the equipment prior to its return to hydrocarbon service Pressure containment is tested and confirmed before the equipment is returned to hydrocarbon serviceIMPORTANT: This procedure will be used for gas freeing, purging and leak testing process system and equipment that has been commissioned and is being operated as a production unit.PurposeThe purpose of this procedure is to detail the steps necessary to ensure that hydrocarbon process equipment is correctly gas-freed before the pressure containment is broken; purged of any explosive mixtures before being returned to hydrocarbon process service; and leak tested to ensure pressure containment is confirmed.This procedure may be used in conjunction with PR-1077 - Preparation of Static Equipment for Internal Maintenance and Inspection.ScopeThis scope of this procedure[footnoteRef:2] covers gas-freeing, purging and leak testing of hydrocarbon process equipment and pipework. [2: The procedure shall not detail removal of instrumentation lines where the volume of hydrocarbon vapour / gas / liquid is small and will therefore not present an explosion hazard. However safe working practice shall still be observed when undertaking this work.]

Specific plant / equipment level Work Instructions / Method Statements shall be developed prior to the work being undertaken. These shall form part of the Scope of Work.Distribution / Target AudienceThis procedure is intended for the use of Operations and Maintenance personnel and Contractor staff working with Operations and Maintenance involved in intrusive work on process equipment and pipework.

Changes to the DocumentResponsibility for the upkeep of the Document shall be with the Functional Production Team Leader UOP, the Owner. Changes to this document shall only be authorised and approved by the Owner.Users of the Document who identify inaccuracy or ambiguity can notify the Custodian or his/her delegate and request changes be initiated. The Requests shall be forwarded to the Custodian using the User Feedback Page provided in this Document.The Document Owner and the Document Custodian should ensure review and re-verification of this procedure every 3 years.Step-out Approval

Roles and ResponsibilitiesDelivery Team Leader Awareness of the Procedure Ensuring compliance to the Procedure

Production Coordinator Procedure compliance checks Approving monitoring Levels Approving use of flammable liquid / gas for in-service reinstatement leak testing

Production Supervisor Equipment selection Review and approve method statements. (Technical Authority level-2 required) Witnessing leak testing

Production Operators Process equipment & pipework isolation. Logging isolation details. Nitrogen purging operations. Gas testing. Leak testing. Process equipment & pipework reinstatement

Specialist leak Testing Contractor Preparing and undertaking all works required for specialist leak testing