ESR Technology          

 

                               ACoReS

         GUIDELINES FOR THE USE OF COMPOSITE REPAIRS

 

For further information/enquiries please contact Richard.Lee@esrtechnology.com

1.        ACORES.. 2

2.        STANDARDS.. 3

3.        ALLOWABLE DEFECT TYPES.. 4

4.        APPLICATIONS.. 4

5.        CHEMICAL COMPATIBILITY.. 5

6.        APPLICATION ENVELOPE.. 6

7.        QUALIFICATION DATA.. 6

8.        DESIGN.. 7

9.        INSTALLATION.. 8

 


1.         ACORES

ESR Technology established ACORES as a trade association (Association of COmposite REpair Suppliers) to:

o    Promote competency & compliance within the industry.

o    Be a forum for current generic technical issues.

o    Provide a focus for coordinating industrial requirements relating to composite repairs.

ACORES verification audits have been performed with a number of composite repair suppliers in the past but has been dormant for a few years. We are consulting with selected oil and gas asset owners/ operators to enquire if this should now be revived in light of the recently updated ISO24817 and ASME PCC-2 composite repair standards. All accredited members of ACORES are independently audited, at regular intervals (2 yearly), to ensure their continued compliance to the International Standards. Each supplier will be able to provide a compliance certificate indicating the audit date and level of competence, including defect and component types that the supplier can repair.

The ACORES audit process covers the following issues with regard to qualification, design, installer training and installation practices:

Design Considerations and Methodology

·         Provide evidence of Datasheets.

·         Types of Defects repaired.

·         Loading Geometry.

·         Design Calculations.

·         Risk Assessment.  

Qualification Data

·         Repair Laminates.

·         Substrate interface.

·         For Defect Type A and/or B.

·         Performance Tests.

Method Statements

·         Risk assessment / Work Conditions (Owner Supplied).

·         Installer training / Qualification.

·         Design Information.

·         Plant Operating Conditions.

·         Repair Design – Materials.

Health & Safety

·         MSDS Sheets.

·         National Safety Regulations.

·         Details of Personnel Protective Equipment.

·         Hazards.  

Quality Assurance

·         Documentation.

·         Design Records.

·         Evidence of Cure.

·         Materials.

·         Batch Numbers.

·         Hydro-test Results.

·         Independent Inspection Data.

Training Records

·         Installer Qualification.

·         Training Records.

·         Certificates.

·         Validity.

Job Records

·         Repair System Details.

·         Repair Reference Numbers.

·         Tg & Indenter (Barcol / Shore) Data.

Other Comments  

·         Service Inspection Intervals.

·         Repair Condition.

·         Other Relevant Details.

·         Examples of Recent Projects.

 

2.         STANDARDS

The most relevant, applicable standard for composite repair systems is ISO 24817 (ASME PCC-2 in USA) – Composite repairs for piping. The scope of both ISO 24817 and ASME PCC-2 covers the following components;

 

·         Pipelines.

·         Pipework including straights, elbows, tees, flanges, reducers, valve bodies.

·         Tanks and vessels including nozzles and attachments.

 

The content of ISO 24817 includes details on;

 

·         Qualification requirements; tests suppliers are required to perform to conform to the standard.

·         Design details; how to design a repair.

·         Installation guidance; what are the critical issues, e.g. surface preparation and applicator training requirements.

·         Monitoring guidance; how to inspect the repair system.

 

No other reference standard or guideline is required to complete the composite repair application.

There are also two ASME composite repair standards;

 

·         ASME PCC-2 – Article 4.1: Non-metallic composite repair systems for pipelines and pipework: High risk applications.

 

·         ASME PCC-2 – Article 4.2: Non-metallic composite repair systems for pipelines and pipework: Low risk applications.

 

The scope of these ASME PCC-2 standards includes pipelines and pipework but not tanks and vessels. The content of the composite repair standards mentioned is comparable and not contradictory. These standards cover pressure containment applications including pipelines, pipework and vessels also including risers. However, there is no current standard that covers structural strengthening of primary (or secondary) members. For this application of composite repairs, each application must be treated on its own merit and designed specifically for the intended application.

 

 

3.         ALLOWABLE DEFECT TYPES

The types of defects that are covered by ISO 24817 include;

·         External corrosion, e.g. general wall loss, where the defect is or is not through wall. In this case the application of a repair system will usually arrest further deterioration - Defect type A

·         External damage such as dents, gouges and fretting e.g. at supports - Defect type A

·         Internal corrosion or erosion, e.g. general wall loss or pitting corrosion, where the defect is or is not through wall. In this case corrosion and/or erosion may continue after application of a repair system and therefore the design of the repair system should take this into account, i.e. the defect may continue to grow and become through wall (if not already through wall) - Defect type B

 

In the above description of the types of defects, growth can be in either or both the axial and hoop direction.

Crack like defects are not covered by ISO 24817, although if it can be demonstrated in the defect assessment procedure that the crack will not grow then a composite repair can be applied to strengthen the defect affected region. Also, composite repairs may be applied to surface breaking cracks where the intention is to prevent leakage. This application will in most cases be short term as the repair will not prevent either further crack formation or crack growth. In general the repair of crack like defects using composites will not stop crack growth. However, composite repairs may be used as a short term solution until an alternative repair or replacement option is available.

Leaking defects cannot be directly repaired. The leak needs to be stopped before the appropriate surface preparation procedure for the repair system can be applied.

ISO 24817 does not define what is an acceptable defect to repair, but assumes that a decision has been made to repair a given defect, under the relevant code, using a composite repair. The decision of what constitutes an acceptable defect for repair is beyond the remit of ISO 24817.

 

4.         APPLICATIONS

ISO 24817 defines the range of potential applications in terms of Classes. Simply, these Classes can be considered as a simplified risk assessment grouping in terms of application. Table 1 lists the definition of Class with example applications. Class 1 refers to low risk applications, with higher Class numbers referring to higher risk applications.

The class of repair (from Table 1) will determine the detail of the design method to be carried out, design margin or safety factor, together with the requirements for supporting documentation.

In general all substrates (i.e. pipe or piping materials) can be repaired. To qualify the repair system for each substrate material in question, the appropriate qualification tests (as defined in ISO 24817, Section 8.2) must be performed.

 

In general, composite repair systems can be applied to the following applications;

 

·         Above ground and buried pipelines.

·         Piping.

·         Tanks and vessels.

·         Splash zones.

·         Jetties.

 

 

Repair Class

 

Typical Service

Pressure

Temperature

Class 1

Low specification duties, e.g. static head, drains Cooling medium, sea (service) water, non-leaking utility hydrocarbons

< 10 bar g

-200 to 400 C

Class 2

Fire water/deluge systems

< 20 bar g

-200 to 1000 C

Class 3

Produced water and hydrocarbons, flammable fluids, gas systems.

Class 3 also covers operating conditions more onerous than described.

Qualified  upper limit

-500 C to qualified upper limit

Table 1: Repair Classes

 

Repair systems can be applied to the following substrates;

 

·         Carbon steel.

·         Cast iron.

·         316 stainless steel.

·         Duplex.

·         Super Duplex.

·         6 Moly.

·         Titanium.

·         Cunifer.

·         FRP – Fibre reinforced plastic (e.g. glass reinforced epoxy, vinyl ester or polyester) pipe. In general composite repairs can be applied to FRP where the P is a thermo-setting resin but cannot be applied to thermoplastic systems, e.g. Polyethylene or Polypropylene.

 

Simple decision guidance rules are presented in Appendix 1 to help decide if a composite repair is feasible for the intended application. These rules should be used as a guide only. There will be situations where a generic guide such as this is not appropriate but the aim is to provide some initial guidance as to whether a repair using a composite solution is practical. 

 

5.         CHEMICAL COMPATIBILITY

The following service fluids are considered acceptable for the application of composite repair systems;

 

·         water, sea-water.

·         produced hydrocarbons, both liquids, gas and gas condensate including alkanes and cyclo-alkanes.

·         utility fluids including diesel, air.

To assess the chemical compatibility of a repair system to either the internal or external environment the following approach is adopted by ISO 24817; qualification tests (Section 8.2) demonstrate that the repair system is compatible with aqueous environments at the qualification test temperature and aqueous environments are relatively aggressive towards thermoset resins. In general, thermoset resins (e.g. epoxies, vinyl esters) are compatible with a wide range of environments but in environments which are strongly acidic (pH<3.5), strongly alkaline (pH>11) or contain a strong, polar solvent (e.g. methanol, toluene) in concentration greater than 25%, then guidance on compatibility should be confirmed with the repair supplier. Resistance to UV degradation and weathering is not a concern for repair systems as all commercial resin systems have UV stabilisers added.

 

6.         APPLICATION ENVELOPE

The application envelope of a specific composite repair system can be defined in terms of an upper pressure and temperature limit and also a lower temperature limit.

 

Upper Pressure Limit of a Qualified Repair System

The upper pressure of a repair system is a function of the type of defect under consideration and the thickness of the repair laminate. A specific pressure cannot be defined until these application parameters are given.

Upper Temperature Limit of a Qualified Repair System

The upper service temperature of a repair system is a function of the glass transition temperature (Tg), or heat distortion temperature (HDT) of the resin system. The following table summarises the maximum temperature limits.

 

Temperature measurement

Defect type B

Defect type A

Tg

Tg –30oC

Tg –20oC

HDT

HDT-20oC

HDT-15oC

Table 2: Upper Service Temperature Limit

 

Lower Temperature Limit of a Qualified Repair System

There is no material limitation on the lower service temperature limit of a composite repair. From ambient temperatures down to -450C both the modulus and strength remain approximately constant. However, the thermal expansion (contraction) mismatch between the composite repair and the substrate places a mechanical limit on the lower temperature of application. Typically this value of lower temperature performance ranges from -50 to -1000C, depending on the repair material and substrate. At temperatures lower than -450C a detailed design calculation must be performed to demonstrate that the strains developed within the repair laminate (both axial and circumferential) through thermal mismatch are less than the design allowables.

7.         QUALIFICATION DATA

The purpose of qualification of a repair system is to demonstrate that the repair system is appropriate for the intended application and also to provide the relevant mechanical data for the design of the repair. The qualification data for the repair system should be contained within the technical specification of the repair system supplier. This specification should not only contain the data but should also state the test method used to obtain that data.

 

The required qualification test data as defined by ISO 24817 is:

 

 

Material Property

Test method

Mechanical properties

Young’s modulus

Poisson’s ratio

Shear modulus

Thermal expansion coefficient

Glass transition temperature of resin or heat distortion temperature of resin

Barcol or Shore hardness

ISO 527 or ASTM D3039

ISO 527 or ASTM D3039

ASTM D5379

ISO 11359 or ASTM D696


ISO 11357-2 or ISO 75, ASTM D6604, ASTM E1640, ASTM E831, ASTM E2092


BS EN 59 or ISO 868 or ASTM D2583

Adhesion strength

Lap shear

BS EN 1465 or ASTM D3165

Optional performance data

Long term strength

 

ISO 24817 Annex E,
ASME PCC-2 Annex 5

Defect type A only

Short-term pipe spool survival test

ISO 24817 Annex C,
ASME PCC-2 Annex 3

Defect type A and B

Energy release rate test


Impact test

ISO 24817 Annex D,
ASME PCC-2 Annex 4

ISO 24817 Annex F,
ASME PCC-2 Annex 6

Table 3: Repair system qualification test requirements

Appendix 3 presents a summary diagram on repair supplier selection for the range of defect types and service conditions considered in ISO 24817.

 

8.         DESIGN

The design process of a composite repair system answers the following questions;

·         Is the composite repair system strong enough to carry the applied loads in both axial and hoop directions? (termed the strength calculation)

·         Will the repair laminate remain bonded to the surface, for through wall defects (defect type B) only, for the design life of the repair? (termed the strength of bond calculation)

·         Is the extent of the repair laminate sufficient to ensure load transfer between repair and substrate? (termed the axial extent calculation)

All these questions require answering for any repair application. The outputs of the design calculation for the repair system are:

·         Thickness of the repair laminate (often expressed in terms of the number of wraps)

·         Total axial repair length (it is assumed the repair covers the full circumference of the substrate)

The repair design should follow ISO 24817. The input for the design calculation requires a definition of all possible loads, both short-term and long-term that could act on the repair. These loads include hoop, axial, bending, torsion and shear. The design rules convert these applied loads into equivalent axial and hoop applied loads and it these two equivalent loads that are used in the repair laminate strength calculation.

8.1            REPAIR LIFETIME

The lifetime of a composite repair system is often termed permanent or temporary. These two definitions have been removed due to the vagueness of their definition. Instead repair lifetime should be specified as part of the design input information that is provided to the repair supplier. Within ISO 24817 a minimum default lifetime of 2 years is specified.

8.2            DESIGN TEMPERATURE

The influence of design temperature is accounted for the in design calculation. Repair suppliers perform their qualification tests at a set test temperature. If the design temperature is greater than the qualification test temperature, but less than the maximum temperature limits (as defined in Table 2 above), then temperature de-rating factors are provided within ISO 24817.

8.3            AXIAL EXTENT OF REPAIR

The overlap length (axial extent) of the repair is defined as the axial length of the repair from the edge of the defect to the edge of the repair. The minimum required overlap length is a function of the defect type. Formulas are provided ISO 24817 for determining this axial length. It is always recommended to taper the repair especially when axial loads are present. The (axial) taper length is additional to the overlap length and should be at least 5 times the repair thickness.

8.4            Piping components, tanks and vessels

The previous discussion has implicitly assumed that the substrate is a straight pipe section. The repair design procedure for other components (e.g. bends, tees, nozzles etc.) is a comparative approach based on an equivalent straight pipe component. This procedure is comparable to other piping system design procedures. The design procedure is first to calculate the thickness of the repair for an equivalent straight pipe section followed by a further calculation of a multiplicative factor, called the repair thickness increase factor, which accounts for the stress intensification due to the geometry of the component. The design repair thickness for the component is given by the product of the repair thickness increase factor times the repair thickness for the equivalent straight pipe section. ISO 24817 (Section 5) presents repair thickness increase factors for each component listed.

8.5            Repair data design sheet

Appendix 3 presents a data sheet which the asset owner should complete to enable the repair supplier to perform the design of the repair. It is important that as much information as possible is provided to the repair supplier to enable an accurate repair design to be performed.

 

9.         INSTALLATION

The application of a composite repair system requires either;

·         the combination of a fibrous reinforcement and a thermosetting polymer matrix that is subsequently subject to a chemical curing process or

·         the adhesion of a pre-engineered roll

This implies that the load carrying material is formed or cured as or immediately after the repair is applied. The final properties of the repair are significantly influenced by the method of application, the details of the lay-up, the form of reinforcement used and the curing of the resin or adhesive. These points emphasise the need for installation procedures to be fully controlled, to ensure that the repair achieved on site is the same from a technical point of view as that previously qualified by the repair system supplier. Appendix 4 contains an installation check list which contains guidance on how to ensure that a repair system has been correctly installed.

 

9.1            INSTALLER QUALIFICATION

Personnel involved in the installation of composite repairs should be appropriately trained and be qualified in the repair method to be undertaken. The minimum training and knowledge requirements of both installers and supervisors are detailed in ISO 24817. This should include the handling of composite materials, surface preparation, lay-up techniques, quality control procedures, and health and safety issues. It is important that the training given provides sufficient technical background to allow personnel to obtain a good understanding as to why key operations such as surface preparation, material handling and lay-up technique are so important. It should also be noted that using trained installers and supervisors is an essential element of a successful repair. Training in one repair option does not necessarily qualify personnel for alternative methods.

Installers should be the subject of a continuing review of competency with a log book kept of experience in the application of repairs. ISO 24817 defines a minimum of 10 composite repairs in one year as a sufficient number of repair applications to demonstrate continued competency. This is important as the levels of competence and experience achieved by an individual installer should also be considered in the context of repair activities. For example, working in confined spaces or applying material around complicated geometries can pose additional difficulties that should be taken in to account.

Supervisors should be trained in the relevant technique and ideally should have had a period during which they were engaged in the application of repairs. Supervisors should also be the subject of a continuing review of competency, as defined in ISO 24817.

 

9.2            INSTALLATION GUIDANCE

The repair system supplier should provide full installation instructions. The guidance given in the following sections is intended to complement that given by the repair system supplier and to emphasise the key operations necessary for a successful repair. 

Full instructions for each repair system application should be included in the repair method statement.

 

Surface Preparation

Surface preparation is the single most important operation in the achievement of a successful repair.

The surface preparation should extend over the whole surface onto which the composite repair is to be applied, i.e. the total axial extent of the repair.

 

Laminate Lay-up

The details of the lay-up procedure vary according to the repair system to be used and these should be fully specified by the repair system supplier.

 

Cure

The cure of a repair laminate is strongly influenced by temperature and the correct mixing of resin constituents prior to application. It is important that the prevailing temperature conditions are considered when, for example, resin catalyst levels are being assessed. On no account, however, should the limits set by repair system supplier be exceeded without recourse to further information. It should be noted that for curing in extreme ambient conditions there may be special resin formulations that may be required.

 

Key Hold Points

The key hold points to be observed during repair installation are given below:

 

Hold Point

Checked by

Method statement

Installer

Risk assessment

Supervisor

Materials preparation – reinforcement, resin

Installer

Surface preparation – inspection, mechanical test

Supervisor

Filler profile

Installer

Stage check on reinforcement

Installer

Tests on repair laminate – cure, thickness, dimensions, external inspection

Supervisor

(Hydro) Pressure Test (if required by the Technical Authority)

Inspection Authority

Table 4: Key Hold Points During Installation

 

APPENDIX 1 - REPAIR DECISION GUIDANCE

 

Defect type

Pressure

Diameter

(units bar.mm)

Maximum pressure (bar)

Maximum temperature (0C)

Environment

(in contact with repair)

Comments

External

<20,000

200

250

Water, air, soil with 4<pH<11

Generally lifetime of repair can be up to 20 years

Internal and/or through wall

<15,000

100

150

Hydrocarbon, gas, water with 4<pH<11

Repair will not halt degradation process so any an indication of the degradation rate is required for the intended lifetime of the repair. The repair must be designed with the defect size estimated at end of life.

Structural strengthening

N/A

Max. strain in composite 0.0025

250

Water, air, soil with 4<pH<11

 

 

The above limits should be seen solely as a guide. Not all repair systems supplied can meet these limits, so caution is required in interpretation.

 

For higher temperatures, greater than 400C, care should be taken that the environment does not limit the application and lifetime of the repair. If in doubt about the compatibility of the environment with the repair laminate, contact the repair supplier.


APPENDIX 2 - REPAIR SUPPLIER SELECTION GUIDE

 

 

 

APPENDIX 3 - REPAIR DESIGN DATA SHEET

 

This Appendix provides an example of a design data sheet. This data sheet should form the basis of the scope of work provided by the client to the repair system supplier and be used in the preparation of the design of the repair. One sheet should be completed for each repair. In practice it may not be possible to define all the input data sheet values, e.g. all the loads acting on a piping system. In this case it is recommended to first discuss with the repair system supplier about any specific parameter and its relevance; a compromise should be reached on the actual value of this parameter to be used in the design.

 

Customer Details

 

Contact

 

Company

 

Address

 

 

 

 

 

 

 

Postcode

 

Country

 

Telephone

 

Fax

 

E-mail

 

Job Reference

 

 

Pipe Details

 

Installation

 

Location

 

Quantity

 

Pipe Identification

 

Pipe Reference

 

Pipe Specification

 

Material / Grade

 

External Diameter (mm)

 

Wall Thickness (mm)

 

Medium

 

Design Temperature (0C)

Minimum

 

Maximum

 

Operating Temperature (0C)

Minimum

 

Maximum

 

Pipe Coating (existing)

 

Existing repair on pipe for leak sealing

 

 

Risk Assessment

Repair Class

 

Repair Lifetime (years)

 

Other Data

 

 

 

 

Loading

Operating

Design

Test

Comments

Pressure Rating (bar)

 

 

 

 

Axial Load (kN)

 

 

 

 

Bending Moment (Nm)

 

 

 

 

Shear Load (kN)

 

 

 

 

Torsion (Nm)

 

 

 

 

Other loads (N)

 

 

 

 

Notes: Any original design calculations and piping isometrics should be appended to this datasheet. Loads should be defined as either sustained or occasional in the comments column

 

Details of Defect Area

Attach drawings of pipe system, inspection reports, digital photographs etc where available.  Indicate any access restrictions and proximity to other equipment.

 

 

 

 

 

Repair Specification

 

Type of Defect

 

Nature of Defect

 

Current Size

Area (mm2)

 

Depth (mm)

 

Projected Size

Area (mm2)

 

Depth (mm)

 

Cause

Corrosion

 

Erosion

 

Effect

External

 

Internal

 

 

Perforated

 

MAWP (bar)

 

 

Anticipated Conditions during Implementation of Repair

Pipe Temperature (0C)

Minimum

 

Maximum

 

Ambient Temperature (0C)

Minimum

 

Maximum

 

Pipe pressure (bar)

 

Pipe contents

 

Humidity (%)

 

External Environment

 

Constraints

 

 

Facilities to be Provided by Client / Installation (surface prep. etc.)

 

 

 

Other Information

 

 

 

Note: This should include any remarks on previous repairs, fire protection requirements, etc


APPENDIX 4 - INSTALLATION CHECKLIST

 

Hold Point

Comment

Method statement

This document should contain the details of the repair, the installation procedure, installer qualifications. It should also indicate required facilities on site, e.g. enclosures etc.

Materials preparation – reinforcement, resin

Check to ensure sufficient reinforcement and resin available for the repair

Check that appropriate volumes of resin and hardener are available

Surface preparation –

         inspection, mechanical test

Check that the surface preparation procedure has been performed according to the installation procedure. Procedure could include mechanical abrasion e.g. grit blasting and chemical cleaning. Ensure correct sequence of cleaning and abrasion.

Surface profile (mechanical) should be measured by profile pad.

Filler profile

Check that filler has been applied according to installation procedure and smoothed to the correct profile

Reinforcement application

Check that the appropriate number of layers or wraps have been applied

Check that the appropriate layer orientation is applied

Check that the correct axial extent of repair has been applied

Check that the taper geometry is applied

Curing of repair

Check that the correct time for cure has elapsed before re-starting the system through hardness measurement.

If post curing is required, then check that the heating blanket is set to the correct temperature.

External inspection 

Check that there are no visible defects