Gas Freeing, Purging & Leak Testing of Process Equipment ...

Petroleum Development Oman L.L.C.

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

Document ID PR-1073

Document Type Procedure

Security Unrestricted

Discipline Engineering and Operations

Owner UOM - Functional Maintenance & Integrity Manager

Issue Date April 2010

Revision 4.1

This document is the property of Petroleum Development Oman, LLC. Neither the whole nor any part of this document may be disclosed to others or reproduced, stored in a retrieval system, or transmitted in any form by any means (electronic, mechanical, reprographic recording or otherwise) without prior written consent of the owner.

Petroleum Development Oman LLC Revision 4.1 Effective: Mar-11

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PR-1073 - Gas-Freeing, Purging and Leak Testing Process Equipment and Pipework

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The controlled version of this CMF Document resides online in Livelink®. Printed copies are UNCONTROLLED.


i Document AuthorisationAuthorised For Issue – April 2010


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ii 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.

Date Author Scope / Remarks

Apr-11 Robin Norman UOP6 Added Section 1.7 ALARP

4.1 Mar-11 Robin Norman UOP6 See Interim Amendment March 2011 (Rev 4.1)

4.0 Apr-10 Robin Norman UOP6 See Addendum 2 for details

3.2 Feb-10 Robin Norman UOP6 Minor Revision – See Addendum 1 for details

3.1 Jan-09 Robin Norman UOP6 Revised Section 3 ‘Leak Testing’ to provide clarity and remove any confusion

1.0 Sept 01

UOP/1 Reviewed and revalidated

Sept 98

UOP/1 OP-32 rewritten to new format.

iii Related Business Processes

Code Business Process (EPBM 4.0)EP 72 Maintain and Assure Facilities Integrity

iv Related Corporate Management Frame Work (CMF) Documents

The related CMF Documents can be retrieved from the CMF Business Control Portal.

CP-114 Maintenance CoP

CP-115 Operate Surface Product Flow Assets - CoP

See Appendix 4


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TABLE OF CONTENTS

1 Introduction....................................................................................................................... 7

1.1 Background................................................................................................................. 7

1.2 Purpose....................................................................................................................... 7

1.3 Scope.......................................................................................................................... 7

1.4 Distribution / Target Audience......................................................................................7

1.5 Changes to the Document............................................................................................8

1.6 Step-out Approval........................................................................................................8

1.7 ALARP........................................................................................................................ 8

2 Roles and Responsibilities.................................................................................................9

3 Gas-Freeing, Purging Process Equipment.......................................................................10

3.1 General.....................................................................................................................10

3.2 Draining of Vessels and Pipework to Open Pits..........................................................10

3.2.1 Considerations When Draining Vessels and Pipework..........................................10

3.2.2 Criteria for Using an Open Pit..............................................................................11

3.2.3 Control Required for using Open Pits...................................................................11

3.3 Gas-Freeing and Purging...........................................................................................12

3.3.1 Preparation and Precautions................................................................................12

3.3.2 Gas Freeing........................................................................................................14

3.3.3 Atmospheric Pressure Method...........................................................................14

3.3.4 Cyclic Pressure Purge Method...........................................................................14

3.3.5 Water Displacement Method................................................................................15

3.3.6 Series Purging.....................................................................................................15

3.3.7 Displacing To Air.................................................................................................15

3.4 Purging Following Inspection or Maintenance.............................................................15

3.5 Sampling...................................................................................................................16

4 Leak Testing................................................................................................................... 17

4.1 Objective................................................................................................................... 17

4.2 Definitions for Leak Testing........................................................................................17

4.3 Reinstatement Policy.................................................................................................18

4.3.1 Method Options in Order of Consideration............................................................18

4.4 Planning Reinstatement Leak Test.............................................................................19

4.5 Nitrogen Leak Testing of Systems..............................................................................21

4.5.1 Bubble Forming Solution......................................................................................22

4.5.2 Acceptance Criteria for N2 Leak Testing (Bubble Test).........................................22

4.6 Performing the In-Service Reinstatement Test...........................................................22

4.7 Vacuum Testing.........................................................................................................23

4.8 Reinstatement Testing of Relief Valves Connected to the Flare or Relief Headers......23


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5 Hazards.......................................................................................................................... 24

5.1 Draining and Flushing to Open Pits............................................................................24

5.2 Gas-Freeing and Purging...........................................................................................24

5.3 Leak Testing..............................................................................................................24

Appendix 1 – Working With Nitrogen Gas...............................................................................26

Appendix 2 – Method Statement.............................................................................................29

Appendix 3 - Abbreviations.....................................................................................................30

Appendix 4 – Reference Material............................................................................................31

Appendix 5 - User Feedback Page.........................................................................................32

Addendum 1 – Changes at Revision 3.2.................................................................................33

Addendum 2 – Changes at Revision 4.0.................................................................................34

Interim Amendment March 2011 (Revision 4.1)......................................................................35

TABLES AND FIGURESTable 1 - Recommended Criteria Hydrocarbon / Nitrogen Purge.......................................16

Table 2 - Inert Gas End Points for Purging Equipment Out of Service...............................16

Figure 1 – Reinstatement Leak Testing Decision Chart........................................................20

Table - Sample Checksheet for Testing of Pipework System...........................................30


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1 Introduction

1.1 BackgroundProcess 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 service

IMPORTANT: 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.

1.2 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.

1.3 ScopeThis scope of this procedure1 covers gas-freeing, purging and leak testing of hydrocarbon process equipment and pipework.

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.

1.4 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.

1 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.


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1.5 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.

1.6 Step-out ApprovalThis procedure is mandatory and shall be complied with at all times. Should compliance with the procedure be considered inappropriate or the intended activity cannot be effectively completed or safely performed, then step out authorisation and approval must be obtained in accordance with PR-1001e – Operations Procedure Temporary Variance, prior to any changes or activities associated with the procedure being carried out.

1.7 ALARPALARP is the acronym for ‘As Low As Reasonably Practicable’ which simplified means, ‘reducing the risk to a level at which the cost and effort (time and trouble) of further risk reduction are grossly disproportionate to the risk reduction achieved’. Full Compliance to PDO Standards and Procedures is a key element in achieving ALARP.

For more details refer to ALARP Definition


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2 Roles and ResponsibilitiesDelivery Team Leader Awareness of the Procedure

Ensuring compliance to the ProcedureProduction 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


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3 Gas-Freeing, Purging Process Equipment

3.1 General Gas-freeing – This is the process whereby a safe atmosphere is established

within the process equipment / pipework prior to opening. Gas-freeing will normally be undertaken in conjunction with the draining and flushing processes.

Purging – This is the process whereby the atmosphere within the process equipment / pipework is purged of air by an inert gas i.e. nitrogen prior to final leak testing and reinstatement.

The following procedures shall be referenced in conjunction with this Section and Section 3.

PR-1076 - Isolation of Process Equipment

PR-1077 - Preparation of Tanks and Vessels for Internal Work Procedure

PR-1086 - Locked Valve Control

PR-1148 - Confined Space Entry

PR-1154 - Gas Testing

PR-1172 - Permit to Work

3.2 Draining of Vessels and Pipework to Open PitsBefore vessels and pipework can be gas freed they require to be drained and flushed / cleaned of hydrocarbons. The preferred method for draining and flushing of vessels and pipework is via a closed drain system to a sealed drain tank. On a large number of facilities in PDO this means of safely draining hydrocarbons liquids was not provided in the design. Because of this draining and flushing in some instances is carried out to ‘open pits’.

3.2.1 Considerations When Draining Vessels and PipeworkThe following will be considered when draining vessels and pipework;

NOTE: The list is not limited to, there could be more

Volume of liquid;

Size of pipework and flanged sections etc.;

Type of medium i.e. hydrocarbon; hydrocarbon / water; oily water; H2S content etc.;

Pressure;

Location;

Concurrent activities;

Type of work to be undertaken;

Hazard and Associated Risks of the operation identified (Risk Assessment required)

NOTE: When draining and flushing to an ‘Open Pit’ a ‘Risk Assessment’ reviewed and signed by the appropriate authority shall be required.


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3.2.2 Criteria for Using an Open PitIt shall be a mandatory requirement to ensure that the following criteria are met before draining or flushing operations can be carried out to an Open Pit.

The liquids to be drained shall not contain NORM, H2S, or Mercury

The Residual Risks associated with the draining / flushing operations are LOW (after putting controls in place as part of the Risk Assessment)

All hazards identified can be managed safely

The systems, equipment, vessels or pipe work is depressurised to atmospheric

A detailed Job Safety Plan has been developed and approved

A TRIC Discussion is held and a TRIC Card completed before the operation is commenced

Hydrocarbon monitoring instruments are within calibration and certification

The operation is continuously supervised by the appropriate Area Authority

Failure to meet the above criteria shall require a Variance to be raised in accordance with PR-1001e – Operations Procedure Temporary Variance.

3.2.3 Control Required for using Open PitsDraining / flushing to ‘Open Pits’ in the most part will have common risks attached to it and therefore the following require to be adhered to

Open Pits

Open pits shall be no larger than 3m x 3m x 1m (deep). Liquid levels in the open pit shall be maintained as low as possible.

Open pits shall be lined with ‘thick gauge PVC’ covered with firefighting foam to reduce evaporation of hydrocarbon to atmosphere.

Hazardous Areas

A hazardous Zone 1 will be established 1m above the pit and 3m around the pit. The pit itself shall be Zone 0

All electrical equipment that does not meet the specification for operation within these Zone ratings shall be isolated

Vacuum Tankers

Vacuum tankers shall meet PDO Specification SP-1207 – Specification for Vacuum Tankers.

Vehicle Access and Control

Vehicles shall be not be allowed to within 5m of the pit.

Continuous gas testing will be required if vehicles such as mobile cranes and vacuum tankers are required to be run in the vicinity of the pit.

Local gas testing shall be required before other vehicles are allowed to enter or are restarted in the vicinity of the pit.

General

When breaking flanges sufficient bolts will be retained to enable the flanges to be ‘closed’ in the event of uncontrolled draining.


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3.3 Gas-Freeing and PurgingAs general guide process equipment containing 96% nitrogen by volume shall be considered (hydrocarbon) gas free.

The key steps in the process of gas-freeing and purging with Nitrogen are:

Isolate from all other equipment.

Reduce pressure.

Remove hazardous liquids.

Remove hazardous vapours by depressurisation.

Flush with water if appropriate.

Purge with nitrogen.

Purge with air, if necessary.

Nitrogen for purging purposes shall be supplied in ‘quads’ or for large operations tankers or portable high volume tanks. The nitrogen tanks and associated equipment are normally supplied by a contractor, who will also supply competent personnel to operate the equipment. However, this does not remove the responsibility of the PDO Operations staff for the overall supervision and the safe completion of the work under the PDO PTW System.

3.3.1 Preparation and PrecautionsThe following shall be taken into account in the preparation of gas-freeing and purge procedures:

Hired equipment shall be inspected to confirm compliance with PDO standards, particularly for diesel engines and electrical equipment.

Personnel, whether PDO staff or Contractors, shall be competent in the use of the equipment being used for the purge.

Personnel must be in attendance whenever purging is taking place to monitor system pressure and purging equipment.

Notwithstanding the classification of the hired equipment, it should be located outside and in a non-hazardous area where possible.

All low temperature equipment must be cordoned off and appropriate warning signs fitted. Entry shall be restricted to authorised personnel only.

Any low temperature equipment must be kept clear of decking or other structural members and be provided with drip trays at joints. For details refer to Appendix 1

Where equipment is located such that any spillages of nitrogen liquid may cause structural damage, charged fire hoses must be available to deal with any spillage.

All nitrogen hoses shall have current pressure test certification, be visually checked for condition.

Great care shall be taken with the choice of location to which temporary vent lines are directed, due to the hazardous nature of the vented gas. Vent lines should be vented external of closed modules / areas. Temporary vent lines must also be secured against movement, especially where the gas released may be under pressure.


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NOTE: Consideration should be given to installing permanent supply and vent lines for activities that are carried out regularly.

Prior to starting the purging operation, with the exception of the flare system which may be required to complete the purge activity, the equipment being purged shall be isolated from all other equipment.

If venting is into a common flare system, Operations staff should be aware of the possibilities of gas being vented, or leaking across PCV's from another system and thus recontamination the purged vessel.

When discharging nitrogen to the flare system, considerations shall be given to the possibility of extinguishing a lit flare.

If nitrogen is being supplied by cylinders, a two-gauge regulator control, which indicates cylinder and flowing pressure, shall be used, fitted directly onto the manifold.

CAUTION: At no time, irrespective of the relative volumes of the operation and the cylinder(s), shall nitrogen be used without a regulator.

If the nitrogen is being supplied by `quads', the cylinders shall not be removed from the frame and the lifting slings shall not be altered in any way.

To avoid reverse flow of product into the nitrogen supply, the line up shall be equipped with check valves.

CAUTION: Where temporary hoses are used for purging and re-pressurisation these should be secured in position at 3m intervals to prevent ‘whipping’. Where temporary hoses are fitted with ‘crow’s foot’ type connections these must be fitted with ‘R’ clips and whip checks. Temporary hose connections and tie-in points shall be blanked off when not in

use and for all tie-in points an isolation valve shall be fitted. Where the connection is envisaged as being required to operate against a pressure in the vessel, the connection to the vessel shall comprise a hose connection coupling, a bleed valve, a check valve and a block valve.

All temporary connections and vent points shall be controlled under the PTW system. Labels should be fitted to identify all nitrogen purge points and regular checks carried out to identify the valve status. This status should be recorded on an Isolation Certificate (IC).

During periods when large numbers of temporary connections are in use (i.e. during shutdown or startup) regular checks shall be carried out, referring to a checklist, on all nitrogen utility points in service, in order to identify their status.

PVC or leather gloves must always be worn when handling anything that contains, or has been in contact with, cryogenic liquids. These gloves should be loose fitting so that they may be easily removed if liquid is splashed onto or into them.

Where spraying or splashing may occur, a face visor must be worn to protect the face and eyes.

Before the arrival of any temporary nitrogen equipment on site, the dangers of nitrogen in both liquid and gaseous form should be discussed at a safety meeting. Refer to Appendix 1.

It is very difficult to totally gas free a hydrocarbon vessel by nitrogen purging, even if flushing with water is part of the procedure. It is therefore most important that any hotwork in the vicinity of the vessel to be opened up is stopped prior to the removal of any manway doors, access hatches etc.


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The possible leakage of nitrogen in confined spaces/modules, whether permanent or temporary (habitats), MUST be considered in the planning of purging operations.

3.3.2 Gas FreeingBefore starting the purging operation, the nature and the properties of the substances to be purged must be taken into account.

a. Where practicable, liquid hydrocarbons must be cleared prior to purging. Relatively small quantities of hydrocarbon liquid will produce signif icant volumes of gas if vaporised.

b. Where recontamination by solids or sludge is likely, the purge procedure, where possible, should be preceded by a water flushing operation if purging efficiency is not to be impaired.

c. The relative densities of the gases to be purged must be considered. Where possible, propane or heavier gases should be displaced by downflow purging, and ethane or lighter gases should be displaced by upflow purging.

NOTE: Certain equipment, particularly filter beds, may require to be purged in one direction only. Generally this will be in a direction toward the support structure, but at all times the manufacturer's instructions should be followed.

Several methods of nitrogen purge are available which are described briefly below. Under normal conditions, a combination of these methods is generally used.

3.3.3 Atmospheric Pressure MethodThe principle of this method is the displacement of system contents by a flowing nitrogen purge.

This technique is most effective when applied to pipework. The volume of nitrogen should be a minimum of 120% of the pipework volume.

Great care should be given to the routing of the vent gas. It should remain at, or near to, atmospheric pressure to allow flow to take place.

In cases where the system is more complicated, some mixing of the nitrogen and the purged gas occurs and a reduction of the concentration of any component of the purged gas takes place, to a greater or lesser extent, by dilution rather than by displacement.

The effectiveness of the purge operation is governed at all times by the sampling procedure.

3.3.4 Cyclic Pressure Purge MethodIn this method, the equipment to be purged is pressurised with nitrogen and a period is then allowed for complete mixing. The pressure is then released and the cycle repeated until satisfactory samples are obtained.

This technique is most effective when applied to vessels and plant where baffles and convolutions render flow purging inefficient or where a pressure is required to displace residual liquids.

This method is restricted to equipment, which can withstand the necessary pressure, although a relatively low pressure is required for suitable mixing of the gases.

The volume of nitrogen required may be estimated by a simple pressure / volume relationship:


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If a hydrocarbon system at zero pressure is pressurised to 1bar (g) with nitrogen, the hydrocarbon element will be 50%.

Four times one bar cycles require four volumes of nitrogen and results in 6.25% hydrocarbons, whereas a single purge to nine bars will require nine volumes of nitrogen and results in 10% hydrocarbons.

Care must be taken that low-pressure instrumentation is not damaged by the purge.

In a typical case, the required purge will be obtained by use of successive purges, the number required being based upon experience of the operation but governed at all times by the sampling procedure.

3.3.5 Water Displacement MethodIn this method the equipment is flushed with water initially, and any vessels filled to allow oil to be floated off at a high point. The contents are then driven out and replaced by nitrogen.

This technique is most effective when applied to oil process trains where the flushing water is driven from vessel to vessel through the normal oil flow path.

The nitrogen pressure only requires being sufficient to overcome the head of liquids. There is very little mixing so the concentration of nitrogen is not diluted. The volume of nitrogen required need be only 100% of the process equipment volumes.

When considering utilising this method, checks must be made to ensure that the additional weight incurred due to the process being filled with water will not exceed structural design limits.

NOTE: This method may not be suitable in situations where water could enter into gas compression equipment.

3.3.6 Series PurgingWhere vessels or plant can be pressure purged in series, significant economies in time and nitrogen can be made by passing each cycle purge forward to the next vessel before releasing to the vent or flare. Can be used in conjunction with 2.3.5.

3.3.7 Displacing To AirFollowing purging, it is normal to displace the nitrogen in the vessel or system with air to ensure that it is safe to work on. Care must be taken, as with the nitrogen, that the purge method used is appropriate to the conditions and to the system.

WARNING: AT NO TIME SHALL AIR BE PURGED INTO A LIVE FLARE OR VENT SYSTEM.

3.4 Purging Following Inspection or MaintenanceWhen a vessel or pipework system has been opened up, it shall be purged with nitrogen to remove the oxygen prior to re-introducing hydrocarbons.

As with the purging for removal of hydrocarbons, the purging for removal of oxygen can use any, or a combination, of the methods described in: Purging for Gas Freeing

The main difference is that the sampling is for a different gas and to ensure that the vent lines are not discharging an explosive mixture.

WARNING: THE INTRODUCTION OF HYDROCARBONS INTO A SYSTEM THAT HAS NOT BEEN INERTED SHALL BE RISK ASSESSED. CALCULATIONS SHALL BE CARRIED TO ENSURE THAT IT IS NOT POSSIBLE FOR THE OXYGEN


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CONTENT TO REMAIN ABOVE 2% AFTER HYDROCARBONS HAVE BEEN RE-INTRODUCED. WHERE IT IS NOT POSSIBLE TO GUARANTEE THIS THE SYSTEM WILL BE N2 PURGED.

3.5 SamplingWhen purging hydrocarbons using nitrogen, it should be noted that the detector used must be capable of measuring a hydrocarbon gas in an inert atmosphere. The MSA Tankscope and Neotronics Digiflamm are examples of detectors that can be used.

For both flowing and cyclic purges the checks should be made at not only the recognised vents but also at any dead legs in the system.

When purging the nitrogen out of the system with air, it is equally important that representative checks are carried out. If the vessel or system is going to be entered, conditions for the entry are as defined in PR-1148 Confined Space Entry .

The recommended criteria to give safe conditions when purging a mixture of hydrocarbon gases with nitrogen are shown in Table 1.

Table 1 - Recommended Criteria Hydrocarbon / Nitrogen Purge

Mode O2 Level Hydrocarbon Level N2 Level

HC to Inert - <_ 4 % >t 96%

Air to Inert <_ 4% - >t 96%

For specific criteria when purging individual hydrocarbon components with nitrogen, refer to Table2.

Table 2 - Inert Gas End Points for Purging Equipment Out of Service

Purge Medium Nitrogen Nitrogen Nitrogen Nitrogen

Combustible Percentage Inert Gas required to render mixtures non-flammable when air is added in any amount

Purging end points with 20% Safety Factor

Percent of Combustible below which no mixture is flammable when air is added in any amount

Purging end points with 20% Safety Factor

Hydrogen 95 96 5 4

Carbon Monoxide

81 85 19 15

Methane 86 89 14 11

Ethane 93 95 7 5

Propane 94 95 6 5

Butane 95 96 5 4

Iso-butane 95 96 5 4

Pentane 97 98 3 2

Hexane 97 98 3 2

Gasoline 96 97 4 3


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Ethylene 94 95 6 5

Propylene 96 97 4 3

Benzene 96 97 4 3


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4 Leak Testing

4.1 ObjectiveThe objective of this section is to guarantee the integrity of process equipment and / or pipework that has been reassembled after inspection, maintenance, repairs, modifications or replacement, prior to it being returned to operation. This is required in order to eliminate the loss of containment of process fluids, thereby protecting the safety of all personnel either involved with, or in the vicinity of, the plant and maintaining the integrity of the Installation.

4.2 Definitions for Leak TestingVacuum Test A test to prove that the equipment does not suffer from

ingress of fluid from external sources. Normally required for any equipment that is designed to operate under vacuum conditions.

Reinstatement Test A pressure test, carried out at 95% of the Relief Valve setting, prior to returning an item of plant into service after the pressure containment envelope has been breached, to check integrity of the system and confirm absence of leaks. For hydrocarbon systems, this test is normally performed with the use of nitrogen.

Gross Leak Check A pressure test carried out at a positive pressure, approximately 2 - 10 bar(g), for gross leak identification.

Sensitive Leak Test A Nitrogen Leak Test carried out with a Nitrogen/Helium mixture, using Helium Sensing instruments to monitor for leakage from potential leak paths (flanges, seals etc.)

In-Service Reinstatement Test

A pressure test carried out using the service fluid under its maximum operating conditions and a leak search carried out.

Method Statement A specific document or procedure produced to cover a unique situation.

Operating Pressure (OP) The OP is the gauge pressure which prevails inside equipment and piping during any intended operation. The OP is determined by the process engineer

Maximum Operating Pressure (MOP)

The MOP shall be determined by the process engineer in consultation with the process control engineer.

The MOP is typically 105 % of the OP in order to provide sufficient flexibility for the control of the intended operations. The MOP shall be not less than 1.0 bar above the OP, except in pressurised LPG storage facilities, where the MOP is equal to the vapour pressure at the derived maximum operating temperature and assessed LPG composition.

If this margin is not sufficient for control, starting up, shutting down or other specific operations, a higher MOP shall be specified. The reason for this increased MOP shall be stated in the pertaining documents.


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Design pressure (DP) The DP (sometimes referred to as the upper design pressure, UDP) is the gauge pressure at the top of the equipment in its operating position that is taken to determine the minimum thickness of equipment parts at the DT.

The DP is initially selected by the process engineer and finally determined in close consultation with the mechanical design engineer.

Since the DP is related to the top of the equipment, for other parts or elements of the equipment the designer shall establish the associated design pressures taking into account the maximum pressure drop caused by flow through the equipment, plus the fluid static head.

NOTE: The definitions for pressure were taken from DEP 01.00.01.30-GEN Definitions of Temperature, Pressure and Toxicity Levels - December 2008 (DEP Circular 14/09 has been incorporated)

4.3 Reinstatement PolicyThis section address the decision making process to determine the testing that is required, prior to reintroducing the process fluid into a system after intrusive inspection, maintenance and / or engineering work.

The Standard is to carry out testing using Inert Medium or Sensitive Leak2 testing using Nitrogen/Helium mix if assessed as necessary.

In-service Leak Testing may be utilised only if achieving the Standard is ‘Not Practicable’ and has been Risk Assessed as acceptable. Minimum In-service Reinstatement pressure is Maximum Operating Pressure as defined in 4.2 above and shall be used for ‘Low Risk’ scenarios where 5 or less flanges have been disturbed.

IMPORTANT NOTE: It is a deviation from this Procedure, if In-service Leak testing is proposed or carried out to Operating Pressure as defined in 4.2 above.

4.3.1 Method Options in Order of Consideration 1. Sensitive Leak Test using N 2 /He to 95% RV pressure.

2. Nitrogen Testing to 95% RV pressure - Acceptance criteria is 15 minutes holding pressure.

The PDO Standard is Sensitive Leak Testing for Sour Service and Nitrogen for Sweet Service. Option 3 below shall only be considered if Options 1 & 2 are ‘Not Practicable’, the affected flanges are 5 or less and a Risk Assessment has been conducted. Refer to Section 4.4 for more detail.

3. Gross Leak Check (10% of MOP or 10bar maximum), followed by In-service Leak Test to MOP.

2 On facilities where High H2S levels are encountered i.e. Harweel, Sensitive Leak testing shall be enforced.


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4.4 Planning Reinstatement Leak TestIn order to determine the testing required prior to restart of a process system reference shall be made to Figure 1 – Reinstatement Leak Testing Decision Chart.

Figure 1 – Reinstatement Leak Testing Decision Chart


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1. Prior to the reinstatement of items of plant, all connections that have been disturbed (flanges, clamps etc) shall have been reinstated in accordance with SP-2020 – Flange Connection Bolt Torquing.

Any replaced or modified item of equipment, which forms part of the pressure envelope, must have previously undergone a successful strength pressure test prior to installation. Also, any repairs to equipment shall have been carried out in accordance with the design specification and in its original location.

2. If the above cannot be satisfied, a hydrostatic or pneumatic strength test must be carried out using a safe medium. The boundaries of this test shall ensure that all previously untested items of equipment have been incorporated.

3. The PDO Standards for reinstatement leak testing are;

For Sour Service - N2 / He at a pressure equal to 95% of the RV setpoint for the system or equipment being tested

For Sweet Service – N2 at a pressure equal to 95% of the RV setpoint for the system or equipment being tested

Where it can be clearly demonstrated that achieving the Standards above are not ‘reasonably practicable’ inservice leak testing using the service medium will be considered. A Risk Assessment requires to be completed and control put in place to mitigate any risks that could be encountered by stepping out of the Standard.

4. Is the Process Medium Sour or Sweet Service?

5. Sour service shall require that all reinstatement leak testing on process systems containing or exposed to H2S or Toxics be carried out using a nitrogen with a helium trace to a pressure equal to 95% of the RV setpoint for the system or equipment.

6. This method of testing also referred to as ‘sensitive’. Reinstatement leak testing of this kind requires specialist equipment and shall normally be carried out by a contract company.

7. Operations shall obtain quotations for the work from an approved contractor, based on the scope of work. The quotation should also have a method statement detailing how the work shall be undertaken and all safety considerations. Operations shall agree Terms and Conditions and authorise the work.

8. Sweet service shall require that all reinstatement leak testing on process systems containing hydrocarbons be carried out using nitrogen to a pressure equal to 95% of the RV setpoint for the system or equipment.

9. If it is demonstrated that testing using N2 is not ‘practicable’ and that the potential for an ‘uncontrolled leak’ after a Risk Assessment is Low the leak testing shall be considered as detailed in 13.

10. If it cannot be demonstrated then reinstatement testing shall continue using N2 to a pressure equal to 95% of the RV setpoint for the system or equipment.

11. The volume and pressure of N2 required to undertake the testing will be dependant on the system or equipment. Large volums of N2 can be supplied as liquid and then ‘vaporised’. This method is ideal for gas freeing and purging and can also achieve reinstatement testing requirements at the lower pressures. For small volume, higher pressure testing ‘N2 quads’ can be used. Where large volume and high pressure is required this will require putting the work out to a specialist contractor equipped with equipment to pump-up the system. For this work refer to the 6 and 7 above.


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12. If the N2 reinstatement testing is to be carried under the control of Operations a method statement will be required from the persons undertaking the work. As for 7 above the method statement should cover how the testing will be carried out, the boundaries and all safety precautions to be taken.

13. Before authorisation can be obtained to conduct ‘inservice leak’ testing, the number of ‘leak paths’ will be identified. Inservice leak testing shall only be considered as an option if there are five or less adjacent disturbed flanges which can be monitored simultaneously. If this criterion cannot be met then UOP requires to be consulted.

As for N2 reinstatement testing undertaken by Operations a method statement shall be required.

14. Gross leak test the system / equipment with N2 or a suitable inert medium before introducing the inservice medium. The gross leak test requires to be undertaken at a pressure of 10% of MOP up to a maximum of 10bar, whichever is achieved first.

15. The reinstatement or inservice leak test can be carried out using the prescribed test medium, to the required pressure and as detailed in the approved Method Statement.

16. Introduce process medium in accordance with the agreed start-up procedures and bring the process to steady state.

4.5 Nitrogen Leak Testing of SystemsThe purpose of the N2 reinstatement leak test is the same as that of the commissioning N2 / He sensitive leak test, i.e. to render the production equipment and pipework safe for the introduction of hydrocarbon gases and liquids, but is used for smaller scale testing.

It will not always be possible, or practicable, to use a contractor and / or the N 2 / He sensitive leak test equipment for the replacement / reinstatement of piping and valves and, in such circumstances, this sensitive leak bubble test should be used instead, utilising Operations / Maintenance personnel and on site N2 supplies.

The N2 reinstatement leak test3.is the direct pressure technique of bubble leak testing to locate leaks in a pressurised component, by the application of a solution that will form bubbles as leakage gas passes through it.

For this leak test, 100% nitrogen gas supplied from cylinders or a compressor shall be used for purging, testing and blanketing. When purging, the oxygen content should be reduced to the order of 1%, so that it is well below the lower limit that will form an explosive mixture. Oxygen levels may be measured using an Intrinsically Safe Oxygen Analyser. The test shall be performed at a pressure equal to 95% of stage RV setting or the maximum dead head pressure of any pump in the system not protected by a relief valve. Prior to examination, the test pressure shall be held for a minimum period of 15 minutes.

On completion of the N2 reinstatement leak test, the N2 shall be depressurised to approximately 2 psi (g) for inert blanketing the system.

3 N2 leak testing shall be performed by trained and experienced technicians. PR-1073 - Gas-Freeing, Purging and Leak Testing

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4.5.1 Bubble Forming SolutionThe bubble forming solution shall produce a film that does not break from the area being tested and the bubbles formed shall not break rapidly due to air drying or low surface tension. Household soaps or detergents are not permitted as substitutes for bubble testing solutions. If surface conditions give cause for concern in respect of the establishment of a coherent soap film on the area of investigation, the technique / procedure should be demonstrated in another area.

The bubble forming solution shall be compatible with the temperature of the test condition. As a general rule, the temperature of the surface of the parts to be examined should not be below 7°C or above 50°C, throughout the examination. Local heating or cooling is permitted, provided that temperatures remain within the range 7°C to 50°C during examination. Where it is impracticable to comply with the foregoing temperature limitations, other surface temperatures may be allowed provided that the procedure is demonstrated satisfactorily.

The bubble forming solution shall be applied to the surface to be tested by flowing, spraying or brushing the solution over the examination areas. The number of bubbles, produced in the solution by application, should be minimised to reduce the problem of masking bubbles caused by leakage.

4.5.2 Acceptance Criteria for N2 Leak Testing (Bubble Test)The presence of continuous bubble growth on the surface of the material indicates leakage through an orifice passage(s) in the region under examination. The area under test is acceptable when no continuous bubble formation is observed.

When leakage is observed, the position of the leak(s) shall be marked and recorded. The system will then be depressurised for remedial action. After repairs have been made, the repaired areas shall be retested in accordance with this procedure.

4.6 Performing the In-Service Reinstatement TestIn-service testing incorporates the testing for leaks, with the re-commissioning activity of reintroducing the process medium. This method of reinstatement may be adopted only when ALL the criteria, as determined by the Figure 1, are satisfied.

In all instances where there is a proposal to utilise a flammable fluid to perform an in-service reinstatement leak test, that proposal must be endorsed by the Production Coordinator at the planning stage.

The In-service Reinstatement test must be carried out to the ‘Maximum Operating’ pressure. The process medium must be introduced slowly. The pressure shall be increased in stages of not more than 20% of the maximum pressure obtainable or 10 bars (g), whichever is the greater, up to 80% of the maximum pressure obtainable and thereafter in 10% or 10 bar (g) stages.

At each stage of pressurisation, all disturbed joints / flanges shall be monitored for leaks, both visually and using appropriate gas meters. Production Supervisor must satisfy himself / herself that there are no signs or detection of process fluid at any of the relevant areas, for the test to be accepted.


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4.7 Vacuum TestingSome systems are designed for vacuum service and must be tested for this service. It is most important to determine that any equipment so tested is designed for vacuum conditions4, and isolated properly before testing. The vacuum should be of the order of 0.1 bar absolute and this should be held for a period of time after the eductor has been shut off.

If the equipment is in hydrocarbon service, it should be remembered that any appreciable leak inwards, of air, may create the possibility of an air / hydrocarbon explosive mixture.

In addition to the vacuum test, items for vacuum service will be tested to a positive pressure of 1.0 bar (g) with either nitrogen or air.

4.8 Reinstatement Testing of Relief Valves Connected to the Flare or Relief HeadersThe removal for replacement, repair and recalibration of system “relief valves” requires that the flanges on the process and flare / relief sides of the valves be subject to a reinstatement leak test. On the process side this can be achieved by subjecting the flange to 95% of the relief valve set point using N2 or an acceptable inert medium. The flare / relief flange is normally subjected to atmospheric pressure which is not ‘practicable’ on an open ended systems such as the flare and relief headers. In this instance it is acceptable to carry out the following;

1. Ensure that SP-2020 – Flange Connections Bolt Torquing and Tensioning is adhered to, ‘flange make-up certificates’ are issued and the flange break register updated;

2. Flange shall be ‘masked’ and a ‘single’ hole made for testing;

3. Normal operating conditions (temperature & pressure) must be achieved;

4. The flange shall be ‘sniffed’ from the single hole and measured for the presence of hydrocarbons using the appropriate type of gas detector;

Provided that the above is complied with a waiver (step-out) is not required.

4 Items for vacuum service should be tested with a vacuum. The reason for this is that applying a pressure test to vacuum equipment does not necessarily detect places where there can be leakage in the opposite direction, e.g. a gasket fault.


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5 Hazards

5.1 Draining and Flushing to Open Pits Release of hydrocarbons to the atmosphere due to evaporation

Exposure of personnel to hydrocarbon vapours

Fire or explosion from uncontrolled ignition sources and flammable vapours in and around the open pit

Environmental contamination due to uncontrolled draining and flushing

5.2 Gas-Freeing and Purging Entry of air into contaminated plant containing hydrocarbons can result in

subsequent fire or explosion where a source of ignition is present (e.g. static electricity, pyrophoric materials).

Entry of hydrocarbons into a system that contains air (oxygen) creating a flammable/explosive mixture.

If pure nitrogen is inhaled, only a few breaths will fully exchange the air in the lungs to nitrogen and unconsciousness will rapidly ensue.

Cryogenic liquids have rapid cooling properties and consequently, flesh coming into contact with un-insulated pipework or vessels containing these liquids may stick fast due to the moisture in the skin.

Cryogenic liquids have low boiling points and quickly produce clouds of vapour or gas at ambient temperatures, prolonged exposure to which can damage the lungs.

Short exposure of the eyes to liquids or vapours quickly results in damage whilst exposure of other skin tissues produces similar effects to a burn and prolonged exposure may result in frostbite.

5.3 Leak Testing Failure of the equipment during the test, causing immediate release of

hazardous materials or dangerous amounts of energy.

Fire or explosion arising from the use of flammable fluids for in-service leak testing.

Damage to the equipment during test, causing a weakness which might result in a subsequent failure.

Failure or damage to the equipment during test might arise from:

o Use of an excessive test pressure, due to either faulty calculation or faulty pressure control equipment.

o Testing at too low a temperature.

o Local over pressurisation, due to water freezing.

o Overloading, due to the weight of the test medium.

o Drawing an unacceptable vacuum when removing the test Medium.

o Corrosion, due to use of unsuitable hydraulic test medium.


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o Internal explosion created by presence of explosive mixture and heat source, as a result of compressions.

When carrying out pressure tests, consideration shall be given to adjacent systems operating under pressure. For example, if the system undergoing test were to fail, the adjacent pressurised system could suffer damage, thereby increasing hazards.


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Appendix 1 – Working With Nitrogen Gas

ObjectiveThis Appendix will identify the precautions and procedures that should be observed when working with nitrogen, and when inerting systems using nitrogen gas for purging.

WARNING: NITROGEN IS AN ASPHYXIANT AND WILL NOT SUSTAIN LIFE.

GeneralNitrogen is the main component of breathable air and, as such, is often wrongly considered not to be a personal hazard. It is provided for use either in a gaseous form in `quads' or from a nitrogen- producing skid, or in a liquid state in cryogenic bulk tanks where it is stored at a temperature below its boiling point of -196°C.

If undiluted nitrogen is breathed, not only is the blood passing through the lungs not replenished with oxygen, but also much of the residual oxygen in the blood passes out into the lungs. The effect is therefore much worse than holding one's breath or re-breathing air. In practice it will take only a few breaths to fully exchange the air in the lungs for nitrogen, and unconsciousness will rapidly ensue. There is no warning because the normal stimulus to respiration is the build up of carbon dioxide, not lack of oxygen. Carbon dioxide will not build up while breathing continues if the gas being breathed is nitrogen.

Fatalities and serious injuries have occurred when performing activities on equipment that has recently contained nitrogen. This has happened when, in order to make progress with the work, sheeting, tarpaulins, boarding etc have been used to screen or protect the work site, and a confined area has been created around the equipment. Great care must be taken to ensure that a confined space is not created, whether deliberately or inadvertently, which might allow the uncontrolled build up of nitrogen and the consequent exclusion of oxygen. Where it is deemed necessary to operate within a confined space that has recently contained nitrogen, an oxygen meter shall be used to continuously monitor the atmosphere.

Liquid nitrogen, released into the atmosphere in an uncontrolled manner, will quickly change form to a gas, thus producing an asphyxiation hazard from the nitrogen-enriched atmosphere.

PrecautionsPrior to using nitrogen in either a gaseous or cryogenic form, an assessment of the risks to both personnel and equipment, from leaks or spills, shall be carried out. Particular attention should be paid to:

Provision of drain paths for spills and leaks.

Routes for temporary hoses.

Provision of First Aid equipment and competent persons to use it.

Written procedures for the operation, including emergency procedures for dealing with spills and leaks.

All work involving the use of nitrogen shall be controlled by the Permit to Work (PTW) System. Barriers and warning notices shall be erected around the work area. All openings, man ways, pipe ends etc must be clearly marked, and oxygen monitoring and rescue equipment provided. All personnel involved in the operation shall be instructed in the hazards associated with nitrogen operations and the types and functions of monitoring equipment being used.


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Where habitats or partial enclosures are required, these shall be treated as Confined Spaces, and the controls and precautions associated with Confined Space entry shall be applied.

Cryogenic Liquids - OccurrenceCryogenic liquids are defined as those that are manufactured, stored or handled at, or below -85 ° C. Liquid nitrogen is the cryogenic liquid in common use within the oil industry.

Handling materials at low temperatures requires specialised procedures and safety precautions, due to the hazards from spills or accidental damage to cryogenic tanks and associated pipework.

Cryogenic Liquids - Personal ProtectionPVC or leather gloves must always be worn when handling anything that contains, or has been in contact with, cryogenic liquids. Such gloves should be loose fitting so that they may be easily removed if liquid is splashed onto or into them.

Where spraying or splashing may occur, a face visor shall be worn.

Coveralls should be worn outside gloves and boots to ensure that liquid contamination will run off and not become trapped.

Cryogenic Liquids - Mechanical HazardsThe physical properties of materials at low temperatures are markedly different from those at ambient temperatures. This change, not a gradual one, takes place over a short temperature range, resulting in an increased brittleness of the material at lower temperatures. In this state, normal stresses or shock can result in brittle fracture, which can be both sudden and extensive.

In the event of spillage of liquid nitrogen over a steel deck, the resultant drop in temperature could cause the steel to crack. In such circumstances, the deck should be flooded with copious amounts of water, which should assist the spilled liquid to `boil off'.

Wooden boards or rubber mats should be positioned under cryogenic tanks and hoses to prevent them contacting the deck.

Drip trays are to be positioned under all cryogenic hose connections to catch any minor spills.

Cryogenic Liquids - General HazardsWarming, to ambient temperature, of vessels initially containing a cryogenic liquid may result in high pressures.

When introducing cryogenic liquids to a system at ambient temperatures, care must be taken with respect to the rate of flow of the liquid since sudden cooling may result in fast contraction of pipework, which will stress joints thus causing damage.

Before cool down of plant, it is essential that all parts that may contain free moisture are carefully dried as water freezing in the pipework may expand to a sufficient degree to cause rupture.

Vapour fog clouds can form during draining of systems containing cryogenic liquid. This vapour fog is composed of atmospheric water vapour condensed by the cooling effect of the liquid being vaporised.

The fog should also be assumed to contain a possible hazardous concentration of the vaporised liquid. This can, depending on the quantity of product being vaporised, create asphyxiation and a visibility hazard.


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Cryogenic Liquids - Fire HazardAt equal pressure the boiling point of some cryogenic liquids, especially liquid nitrogen, is lower than that of liquid air. Air will condense on the external surfaces of pipework containing liquid nitrogen at an equilibrium pressure less than 1.5 bar(a) if the vessels are either unlagged or lagged with a porous cellular type insulant that has not been properly vapour sealed.

The liquid air produced can result in oxygen enrichment of the atmosphere local to the equipment and, if the insulant is combustible there is a serious risk of fire. Special care must therefore be taken before any maintenance or repair work is started, particularly where the use of naked flames or other potential sources of ignition is intended.


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Appendix 2 – Method StatementA Method Statement must be prepared, and approved by the Production Supervisor, for all Reinstatement Pressure Testing Operations, and such operations must be controlled by the Permit to Work System.

The Method statement shall be fit for purpose and be attached to the Work Permit or as a separate statement or document.

The Method Statement shall consider and include where necessary:

Details of the boundaries of the test including pressures, maximum and minimum temperatures, test medium, method of filling, venting and, if applicable, the method of draining the test medium from the system;

Drawings showing the relative positions of blanks, drains and vents, indicating where valves have been removed, defeated or mechanically locked;

Checklists of all system components. Refer to example Table - Sample Checksheet for Testing of Pipework System

The Method Statement shall detail the checks to be carried out which should include, but not be limited to:

Checklist for the equipment refitted.

Flange make-up checksheet, to include a tagging system for

All flanges disturbed.

Valve position for test.

Additional blanks/spades for test.

Steps and precautions during the test.

The test pressure.

Steps to be followed after the test.

Valve position.

Steps and precautions to be taken.

Marked-up drawings, showing plant to be tested and boundary of safety barriers.

Detail of all safety precautions.

Risk Assessment, including an appropriate Task Risk Assessment from the PTW Activity Risk Assessment Tool.

Table - Sample Checksheet for Testing of Pipework System

Flange No. Joint No.(tick)

Bolts toCorrect Torque (tick)

Test Leak Rate

Re-TestLeak Rate (if required)

NOTE: Flanges to be identified by suitable code number on attached P&ID.


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Appendix 3 - AbbreviationsThe following abbreviations are used in this Procedure.

ALARP As Low As Reasonably Possible

He Helium

IC Isolation Certificate

N2 Nitrogen

PCV Pressure Control Valve

PTW Permit to Work

RV Relief Valve


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Appendix 4 – Reference MaterialPDO Procedures

PR-1001e – Operations Procedure Temporary Variance

PR-1076 - Isolation of Process Equipment

PR-1077 - Preparation of Static Equipment for Internal Maintenance and Inspection.

PR-1078 Hydrogen Sulphide Management

PR-1081 The Buddy System

PR-1086 - Locked Valve Control

PR-1148 - Confined Space Entry

PR-1154 - Gas Testing

PR-1172 - Permit to Work

PR-1515 – Onsite Mercury Management Procedure

PR-1721 Shutdown Management

PDO StandardsSP-1005 HSE Specification - Emissions to Atmosphere

SP-1006 HSE Specification - Aqueous Effluents

SP-1170 Naturally Occurring Radioactive Materials (N.O.R.M.)

SP-1207 – Specification for Vacuum Tankers

SP-2020 – Flange Connections Bolt Torquing and Tensioning

SP-2087 – Specification for Onsite Mercury Management


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Appendix 5 - User Feedback Page

PR-1073 – Gas-Freeing, Purging and Leak Testing Process Equipment and Pipework User Feedback Page

Any user who identifies an inaccuracy, error or ambiguity is requested to notify the custodian so that appropriate action can be taken. The user is requested to return this page fully completed, indicating precisely the amendment(s) recommended.

Name:

Ref ID Date:

Page Ref: Brief Description of Change Required and Reasons

UOP7

Custodian of Document Date:


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Addendum 1 – Changes at Revision 3.2

Page Description of Change

17 Section 3.3 added footnote “ On facilities where Very High H2S are encountered i.e. Harweel, Sensitive Leak testing shall be enforced”

18 Section 3.3.1 – Changed Preferences to Considerations and added Note “NOTE: In-Service Leak Testing on it’s own should only considered when all other options are not Technically feasible”

19 Figure 1 – Changed wording Step 18

22 Section 3.4 Step 16 para 2 “If this is not possible, due to either the size of system under test or the availability of N2 at site then an approved 3rd party company will be contracted.”

22 Section 3.4 Step 18 changed wording “N2 leak testing activities will be carried out by a 3rd party contractor controlled by Operations personnel under the PTW system.”

Added “NOTE: Sensitive Leak Testing shall be used where High H2S is present in the production streams. Details of Sensitive Leak Testing can be referenced from SP-2051 Specification for Flushing, Pressure Testing, Pickling and Sensitive Leak Testing of Mechanical Equipment and Piping.”


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Addendum 2 – Changes at Revision 4.0

Page Description of Change

8 Removed Section 1.5 – Structure of the Document not needed

8/9 Moved Roles and Responsibilities to Section 2 – All following sections moved up one number i.e. 2 to 3 etc.

8/9 Moved Abbreviations to Appendix 3

24 Added Section 5.1 – Draining of Vessels and Pipework

10 Section 3.2 – Draining of Vessels and Pipework to Open Pits added

18/19 Section 4.2 – Definitions added

Operating, Maximum Operating and Design Pressure Definitions.

19 Section 4.3 changed following statements

“Minimum In-service Reinstatement pressure is Maximum Operating Pressure as defined in 4.2 above”

“It is a deviation from this Procedure, if In-service Leak testing is proposed or carried out to Operating Pressure as defined in 4.2 above.“

19 Section 4.3.1 changed

3. “Gross Leak Check (circa 2 - 10 bar), followed by In-service Leak Test to Maximum Operating Pressure.

Removed 4

24 Section 4.6 para 3 changed to read “The In-service Reinstatement test must be carried out to the ‘Maximum Operating’ pressure. The process medium must be introduced slowly. The pressure shall be increased in stages of not more than 20% of the maximum pressure obtainable or 10 bars (g), whichever is the greater, up to 80% of the maximum pressure obtainable and thereafter in 10% or 10 bar (g) stages.”

26 Added Section 5.1 – Draining and Flushing to Open Pits

Added Appendix 3 and 4


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Interim Amendment March 2011 (Revision 4.1)Page 7 Section 1.1 – Added “IMPORTANT: 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.

Page 14 Section 3.3.2 – Changed sub-heading to “Gas Freeing”. This is to avoid confusion with purging operations after the work is completed.

Page 18 Section 4.3 – Changed 3rd & 4th paras to read “In-service Leak Testing may be utilised only if achieving the Standard is ‘Not Practicable’ and has been Risk Assessed as acceptable.

Minimum In-service Reinstatement pressure is Maximum Operating Pressure as defined in 4.2 above and shall be used for ‘Low Risk’ scenarios where 5 or less flanges have been disturbed”.

Page 18 Section 4.3.1 – Added para “The PDO Standard is Sensitive Leak Testing for Sour Service and Nitrogen for Sweet Service. Option 3 below shall only be considered if Options 1 & 2 are ‘Not Practicable’, the affected flanges are 5 or less and a Risk Assessment has been conducted. Refer to Section 4.4 for more detail”. Removed “NOTE: In-Service Leak Testing on its own should only considered when all other options are not Technically feasible.”

Page 19 Section 4.4 – Section amended to reflect changes made in Sections 4.3 and 4.3.1.

Page 24 Section 4.8 –“Reinstatement Testing of Multistage Compressors” removed.

Page 24 Section 4.8 – “Reinstatement Testing of Relief Valves Connected to the Flare or Relief Headers” added

Purpose for changes / additions – Strengthening the requirement for achieving the Reinstatement Test Standards and assisting Operations where meeting the Standards are not achievable i.e. Flare and Relief Systems.


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