Module 5 Pipeline repairs.pdf

(1)

Pipeline Operations and Integrity

Management

Module 5 Pipeline Repairs Module 5 Pipeline Repairs

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2 2

Outline

Where are w

e?

Pipeline Operations Pipeline Operations Pipeline Maintenance Pipeline Maintenance

Pipeline Integrity management Pipeline Integrity management

Inspection and Assessment Methods Inspection and Assessment Methods Pipeline repairs

Pipeline repairs

Emergency Response Planning Emergency Response Planning

(4)

Pipeline repair topics

•

• Safety considerations

Safety considerations

•

• Types of defects to repair

Types of defects to repair

•

• Pipeline repair methods

Pipeline repair methods

•

(5)

REPAIR: Rule 1… Safety First!

• Safety is always our first consideration.

– Pressure reductions, excavation safety,

trench safety, welding safety, pipe movement safety, fire prevention, emergency procedures, etc., are our primary concerns.

– Pressure reductions alone may not be

sufficient to demonstrate safety prior to working on a pipeline.

• Some pipelines may have ‘locked-in’

stresses; for example, from ground movement (onshore) or a buckle (offshore).

• These locked-in stresses need to

considered prior to work on the line

.

Use recognised, proven procedures, and qualified personnel, and make use of relevant standards e.g. API RP 2200.

(6)

REPAIR: Rule 2… Caution

• Some wise words on repair*:

– ‘Do no harm!’

• A bad repair can make matters worse.

• Repairs need careful engineering, at least as much as a new construction.

• Do not act in haste.

– A repair is often not a good time to try something new.

• There is less experience with a new procedure, compared to tried and tested designs. Surprises may occur with uncertainty and incompletely planned engineering.

(7)

REPAIR: Rule 3… For life!

❖ Remember*… a good repair approach/philosophy is:

❖ Replace ‘like-for-like’.

❖ Apply a ‘temporary’ repair, until replacement can be carried out.

❖ Apply a ‘permanent’ repair, only where replacement is not practical.

(8)

Pipeline Repairs

• The concept of repairing a pipe presumes that an

injurious defect is present.

• The purpose of a repair is to restore the full

serviceability of the pipe permanently, although

temporary repairs may sometimes be necessary.

• Safety before, during, and after the repair operation

is the first priority.

(9)

How Repair Situations Arise

▪ A leak is discovered

▪ Excavator reports or is observed

hitting the pipe

▪ An anomaly identified by in-line

inspection is confirmed in the field

▪ Excavation for another purpose reveals

a repairable condition

(10)

Terminology

▪ Anomaly – A condition or possible imperfection

that appears to be different from normal pipe

▪ Flaw – A confirmed imperfection that is not

injurious to the pipe

▪ Defect – A confirmed imperfection that is

injurious to the pipe

▪ Discovery – Occurs when enough is known to

(11)

Terminology

•

Leak – A defect that permits the pipe

contents to escape but that does not

render the pipe inoperable

•

Rupture – A sudden, unstable, and

rapid propagation of a crack or opening

emanating from a defect

(12)

Terminology

▪ Maximum Operating Pressure, MOP – The

maximum level of steady-state pressure

permitted by the pipeline-design criteria, the

federal regulations, or the company’s

operating procedure, whichever is less.

▪ Discovery Pressure – the pressure level

existing at the location of the anomaly at the

time it is discovered or reported.

(13)

Terminology

• Historical Pressure – A pressure level that is known to have

existed at the location of the anomaly after the anomaly was

present in its current state.

• For a gas pipeline, no pressure level may be considered a

historical level if it occurred more than 1 year (365 days)

prior to the discovery of the anomaly.

• For a liquid pipeline, no pressure level may be considered a

historical level if it occurred more than 60 days prior to the

discovery of the anomaly.

• A previous hydrostatic test pressure can be used as a

historical pressure level if it meets the time requirements.

• Repair Pressure – The pressure level at the location of the

anomaly to be repaired at the time the repair is carried out.

(14)

(15)

Safety Issues

• Pressure reduction

• Excavation safety

• Trench safety

(16)

Safety is the first

consideration

▪ A defect could be on the verge of failure

▪ Lowering the pressure may be necessary

▪ Prevent excavation damage to the pipe

▪ Observe trench safety requirements

▪ Observe fire-prevention standards

▪ Use qualified maintenance personnel

▪ Use qualified repair procedures

▪ Observe live-line welding requirements

(17)

Factors to Consider

▪ Pipe Material: Diameter, thickness, grade, seam

type, chemistry, toughness

▪ Operating Characteristics: Maximum operating

pressure, type of product, flow rate

▪ Location: Terrain, accessibility, proximity to

population

▪ Special Circumstances: Leaking or not, brittle pipe,

high built-in stress, couplings or acetylene welds

(18)

Pressure Reduction

•

A pressure reduction is considered

appropriate where

uncertainty

exists

that an anomaly is safe at the operating

pressure. This is particularly true at the

time of excavation, as a matter of

(19)

PRESSURE REDUCTIONS: Why reduce

pressure?

• We need to reduce pressure to a safe level before repair, due to:

– LEAKING PRODUCT. If pipe is ruptured or the defect is leaking, we need to make the pipe and surrounding safe.

– REPAIR: We may need to plan future pressure

reductions depending on type of repair/rehabilitation.

• Some composite repairs require pressure

reductions of 50%.

Images from Clock Spring Literature www.clocksprong.com

(20)

PRESSURE REDUCTIONS: Why reduce

pressure?

• We need to reduce pressure to a safe level before repair, due to:

– LEAKING PRODUCT.

– REPAIR.

– RECOATING: Recoating may require removal of pipe from trench, and pressure may be

required to be reduced to zero.

In situ coating com pleted

1 9

(21)

PRESSURE REDUCTIONS:

Operational Experience

Minor releases are sometimes recorded during excavation (e.g. during grit blasting the pipeline), but casualties are very rare.

However, there are recorded failures of pipelines during

excavation of known defects, and these failures have resulted in fatalities*.

Because of this risk, companies do reduce pressure.

(22)

PRESSURE REDUCTIONS: Why reduce

pressure for non-leaking defects?

Pressure reduction is needed in a damaged pipe because:

Pipeline damage can fail when held

at constant pressure (‘time dependent effects’)*.

Pipeline pressure is never constant, and can increase above the MOP, e.g.

due to overpressures (‘operational effects’).

Load

(23)

PRESSURE REDUCTIONS: Examples of Pressure

Reductions

ALL DAMAGE

SEVERE DAMAGE

If the defect is very severe (e.g. very long (with a risk of rupture), or very deep

(>80%wt), or a crack)

’80%’* _{- For pipe wall defects,}

lower operating pressure to 80% of that at which defect was

discovered/inflicted, until defect has been assessed. For structural

defects (e.g. buckling) structural assessments will be needed.

’30% SMYS’ _{- The pipeline}

pressure should be reduced to the lower of 80% of the

pressure at which the defect was inflicted/discovered, or a hoop stress level of 30%

SMYS

Pressure should be controlled. Overpressures not allowed.

We have two types of guidance for pressure reductions that relate to the ‘severity’ of damage:

(24)

Pressure Reduction Policy

Reduce pressure when:

▪ A defect is discovered unexpectedly, unless

it is obviously a superficial flaw

▪ An ILI anomaly is categorized as

“Immediate Repair Condition”

▪ When excavating other ILI anomaly

categories and uncertainty exists as to its

nature or severity

(25)

Pressure Reduction Policy

Reduce pressure level to:

▪ The calculated safe operating

pressure for the anomaly, or

▪ 80% of recent maximum pressure

level

(26)

API RP 2200

▪ Personnel

▪

Qualified oversight (supervisor, team leader)

▪

Repair personnel should not only be trained but briefed about issues specific to a particular repair

▪

Careful planning is essential

▪ Training and equipment

▪

Lockout/tagout procedures

▪

Confined space

▪

Worker’s right-to-know

▪

Personal protective equipment

▪

Fire prevention and protection

▪

Emergency response training

(27)

API RP 2200

Job Planning details

•

Applicable laws and regulations

•

Permits

•

Adjacent utilities

•

One-Call

•

Traffic control

•

Limit public access

•

Shut-down procedures

•

Safety-related condition

•

Drain-down/purging

•

Tools and equipment

•

Brief personnel

•

Material safety data sheet

•

Maintain communication regarding pressure and flow

•

Shut-down procedures

•

Leak/rupture spill/flammability hazard

•

Combustible gas indicator

•

Toxicity testing

•

Check confined space (trench) for oxygen

•

Safe trenching practices

•

Support and secure pipe

•

Confirm wall thickness with UT

•

Turn off, lock, tag rectifiers

•

Electrically bond separation points

•

Cold cut unless area made safe

•

Monitor atmosphere

(28)

Pop Quiz

True or false?

• An anomaly is injurious to the pipe______

• A flaw in the pipe requires a repair______

• A pressure reduction during the repair

process is recommended______

• A pressure reduction of 10% may be

appropriate______

(29)

(30)

Types of defects

• Corrosion (internal, external)

• Stress-corrosion cracking

• Long seam defects

• Girth weld defects

• Dents and mechanical damage

• Metallurgical features

• Construction damage

(31)

(32)

Internal corrosion

Microbe-induced

corrosion

(33)

Selective corrosion on

girth welds

(34)

Stress-corrosion

cracking (SCC)

(35)

Lamination affected by hydrogen blister and cracking

(36)

ERW Pipe Defects

Cold Bond

(LF only)

Hook Cracks (LF

or HF ERW)

(37)

DSAW Pipe Defects

Hot Cracks

Offset

Beads

Shipment

Fatigue

(38)

Typical

(39)

Typical mechanical damage

Note creases in pipe wall (left);

cracking, and crushed

microstructure (below).

(40)

NDE of mechanical damage

Probably a waste of time on gouges in as-found

condition. No gouges should be left in pipe operating at

high stress levels in untreated condition. Grind damage

out first, then do NDE.

(41)

Typical damage from

poor padding during

construction

(42)

Puncture caused by sharp

rock under pipe

SCC in rock dent

(43)

Damage from seismic

survey shot adjacent to

pipe. Discovered by ILI.

(44)

(45)

Dresser coupling construction

(46)

Buckles caused during construction

Ripples

in field

bend

Onshore

line

(47)

Buckles due to

(48)

(49)

Slag Inclusions

Incomplete

Penetration (IP)

Hollow Bead (Porosity)

Some Common

Welding Defects

(50)

Some Common Welding Defects

Hydrogen-Induced Cracking

(HIC), High-Low, and

(51)

(52)

Selection factors

• Codes, standards, regulations

• Company policies

• Effectiveness in situation

• Impact on service

• Feasibility and availability

• Cost and convenience

(53)

Types of Repair

• Pipe replacement

• Surface grinding

• Steel sleeves

• Reinforcement

• Pressure containment

• Compression type

• Grout-filled

• Expanded

• Nonmetallic

• Mechanical

• Hot tap and fitting

(54)

WELDED SLEEVE REPAIR*

❖ The ‘welded sleeve’ is a very popular repair method.

❖ It is used as a permanent repair method for many types of

damage.

❖ It involves welding* together two ‘half shells’ around the damaged

pipeline, to form a ‘sleeve’.

(55)

Type A and Type B Sleeves

• Defect filled with hardenable material

• Steel half shells closely fitted around the defect area

• Joined by longitudinal welds

• Ends not welded (Type A) or welded (Type B)

• Type B sleeves designed to be pressure containing

(56)

Sleeve

WELDED SLEEVE REPAIR

❖ The welded sleeve involves welding* together two ‘half shells’

around the damaged pipeline, to form a ‘sleeve’.

❖ See API RP 1107 and API STD 1104 for guidance on their

application.

Half shell Half shell

(57)

Non-pressure containing sleeves:

• side seams groove or fillet welds

• end gaps sealed to keep out water

(58)

Pressure-containing:

• side seam must use groove butt welds

• welding procedures for end fillets must be

suitable for pipe metallurgy and cooling rates

(59)

How reinforcing sleeves work

▪ Reinforcing sleeves take up negligible hoop stress (15%). They

restore strength of pipe by restraining bulging at defect.

(60)

WELDED SLEEVE: Effectiveness

Research at AGA showed these sleeves (‘Type B’ – see later) can strengthen damaged pipe up to a failure stress of 100% SMYS.

(61)

WELDED SLEEVE: Principles of

operation

Most welded sleeves increase the failure pressure of a damaged pipe by:

‘stress sharing’ between the sleeve and the damage pipe; and,

restraint of pipe ‘bulging’.

(62)

WELDED SLEEVE: Principles of

operation (1)

STRESS SHARING: If the welded sleeve fits around the pipeline perfectly, there is ‘stress sharing’ – the stress in the carrier pipe is reduced.

If this sleeve is of a similar thickness to the carrier pipe, and applied at a pressure of P_r, and the pipeline pressure is then increased to P_o, the sleeve shares the increases in stress from P_o to P_r.

Thicker sleeves take higher stresses. Any carelessness in fitting will result in poor stress sharing.

REPAIR SHELL DEFECT 1. LOAD IS TRANSFERRED 2. DEFECT IS RESTRAINED

(63)

WELDED SLEEVE: Principles of

operation (2)

RESTRAINT OF BULGING :The sleeves stop a defect from ‘bulging’ in the ductile line pipe.

Defects in pressurised pipe bulge outwards prior to failure.

If this bulging is prevented or restricted, the failure is prevented.

REPAIR SHELL PIPELINE DEFECT 1. LOAD IS TRANSFERRED 2. DEFECT IS RESTRAINED

(64)

Methods for

achieving tight

fit-up between

(65)

Use of filler materials

▪ Effectiveness of repair is improved by close

fit-up, fill of annular spaces, and pressure

(66)

Use of filler materials

Hardenable filler materials

• Polyester epoxy (e.g. auto body filler or

purpose made resins)

• Work time affected by mix, temperatures

• Apply sleeve prior to cure and squeeze out

excess filler, or

• Allow to harden first then shape the contour

by grinding

(67)

• A Type B sleeve needs to be a ‘close fit’, so grind off weld

reinforcements at DSAW welds and girth welds.

•

Filling the annulus with hardenable materials is good

practice (removes any corrosive environment, helps

‘close fit’, and prevents internal pressure within the

annulus)***.

TYPE B SLEEVE*: Close fit and fill

***’Repair of Pressure Equipment and Piping’, ASME PCC-2-2006. January, 2007, and ASME B31.8 Section 851.42.

(68)

Comments About Sleeves

▪ For Type A, sleeve wall and grade need not match

carrier pipe or meet Barlow equation to be effective.

▪ For Type B, sleeve integrity relies on seam weld quality.

▪ Type B sleeves thicker than the pipe should be edge

tapered to the wall thickness

▪ Tapping thru sleeve and pipe removes hoop stress from

pipe. Not recommended where not absolutely

necessary (taps vulnerable to damage, sleeve becomes

pressure component).

(69)

Edge treatment on sleeves

▪ Unlike the fillet welds on socket welding fittings or

flange hubs, the fillet weld on the end of a repair

sleeve is not structural, even if it is intended to

contain pressure.

▪ In order to avoid excessive stress concentration,

the fillet weld should be no larger than 1.0t, rather

than 1.4t.

▪ If the sleeve is heavier than the pipe, it should be

tapered to nominally 1.0t.

▪ Any gap on fit-up should be added to the fillet leg

dimension.

(70)

Poor fit-up and lack of penetration in seam weld adversely affects reliability of pressure-containing sleeves.

Repair sleeve seam consisting of cap welded over bar stock

(71)

Other sleeve configurations

Dresser 110 – For

repair of girth welds

Dresser 220 – For

repair of couplings

(72)

(73)

(74)

•

No in-service welding

•

Annular space accommodates deformations

Epoxy

grout-filled shell

repair sleeve

(75)

Compression repair sleeve

▪ Concept involves heating the sleeve at the

time of installation

▪ Clamp in place and weld side bar

▪ Involves no welding to the pipeline

▪ Thermal contraction upon cooling creates an

interference fit with the pipeline

▪ This relieves hoop stress in the pipe due to

internal pressure

(76)

(77)

Compression repair sleeve

Installation quality verified by measuring amount of shrinkage after cooling

(78)

(79)

Special enclosures for

leaking flanges

(80)

Mechanical clamps

• Versatile

• Involves no welding (though some can be

welded to make permanent seal)

• Can accommodate out-of-round pipe

• Usually considered “temporary”

• Large sizes are expensive

(81)

Grinding out mechanical damage in

dents

▪ Metal loss caused by gouging is worse than

metal loss caused by corrosion due to surface

damage, cracks, indentation

▪ Mechanical damage can be converted to

ordinary metal loss by removing the

damaged metal

▪ Demonstrated by testing and service

experience

(82)

Effectiveness of grind

repair -- test data

Restoration of

pressure capacity

(83)

Grinding out mechanical damage in

dents

Grind out gouge to smooth contour, to max depth of

40% of wall over limited to length as follows:

Ref: CSA Z662 and “Repair of Pipeline Dents Containing Minor Scratches” J.F. Kiefner and C.R. Alexander, PRCI L51788, 3/18/99

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(84)

Damage repaired

by grinding

Inspection by PT and UT

verified removal of any

cracks and adequate

(85)

Nonmetallic composite wrap repair

▪ Polymer matrix reinforced by oriented

strand or woven fabric

▪ May be preformed to shape or hand

laid-up wet

▪ Chemically bonded to pipe and between

layers, cured in place

(86)

Composite Repairs

• Wide range of products now

available

• Composite sleeves are typically

cured offsite, then attached to

the pipe with adhesives; other

composite repairs are cured on

site.

• Most work by keeping a defect

from bulging. So, the defect

needs to be filled with

hardenable material.

• Can carry some (not a lot) hoop

stresses depending on

installation procedure.

(87)

Composite wrap repairs

1. Apply Filler

_{2. Apply}

Adhesive

3. Wrap

5. Coat and

Backfill

Clockspring® composite wrap repair

(88)

COMPOSITE REINFORCEMENT

SLEEVES

• Fibreglass re-inforced composite material wrapped around the pipe can restore pipeline strength in the hoop direction.

• Composites can have 10x the

strength of a steel, and 25% of the weight and can have wide-ranging applications**.

• They follow the contour of the pipe/damage.

• They are light and easy to handle.

(89)

COMPOSITE REINFORCEMENT

SLEEVES

• All composite repair systems on pipelines employ*:

• some type of fibre system that

provides strength and stiffness (typically glass or carbon fibres);

• a resin matrix used to transfer load

between fibres; and in the case of

‘layered’ systems;

• an adhesive that is used to bond

(90)

COMPOSITE SLEEVES: Caution

• Composite strength tensile strength) and stiffness (elastic modulus) can diminish with time.

– The materials must be tested for long

term properties.

• No ‘hot’ work needed on line:

– but adhesive used has a limited

working time;

– and repair may need several hours of

curing, before the pipeline can be backfilled.

Image from Wrapmaster Literature

Video courtesy of Craig Hall, GE-PII

(91)

COMPOSITE SLEEVES: Caution

• There are now many types of composite sleeve.

– Use recognised methods**:

• What is the effect of pressure at

time of installation?

• Effect of cyclic pressures?

• Effect of surface preparation? • Repair of mechanical damage? • Etc.

Images from Clock Spring Literature www.clocksprong.com

(92)

• Care should be exercised:

– they are not specifically designed to resist bending or axial

stresses;

– some wraps do not alter MFL indications, so cannot be detected

by pigs;

– technicians need to be trained to apply the repairs.

(93)

TD Williamson

Black-Diamond® CF

composite wrap

repair

(94)

WrapMaster PermaWrap® composite wrap repair

(95)

Armor Plate® composite wrap repair

(96)

Permabond®

polyurethane

sealant-filled encapsulation

system for leaking

couplings

(97)

(98)

• Composite wrap concept extensively tested

• Lightweight and does not corrode

• In-service welding not required

• Requires marking to show up on ILI or

thorough records of installations

(99)

▪ Effectiveness is a function of stiffness, not

strength. Most products are effective, but not

all demonstrate equal performance.

▪ Suitable for ordinary non-leaking corrosion or

other flaws that have been converted by

grinding to blunt metal loss free of cracks.

(100)

▪

▪ Low modulus of composite is incapable of

Low modulus of composite is incapable of

limiting strains in the steel pipe.

▪

▪ Not suitable for:

Not suitable for:

▪

▪ mechanical damage untreated by grinding

mechanical damage untreated by grinding

▪

▪ LF-ERW seam defects

LF-ERW seam defects

▪

▪ selective corrosion

selective corrosion

▪

▪ str

strain-sensitive defects or

ain-sensitive defects or any situation involving

any situation involving

brittle material behavior

Composite wrap repairs

(101)

Hot tapping

•

• Hot tap may be used to remove a defect

Hot tap may be used to remove a defect

smaller than the tap

•

• Full-size sto

Full-size stopple may be

pple may be used to isolate

used to isolate

pipeline section for replacing pipe without

interruption of service

(102)

(Shown: Standard Valve used when (Shown: Standard Valve used when tapping to install lateral lines. tapping to install lateral lines.

SANDWICH® Valve SANDWICH® Valve Option allows Option allows temporary plugging temporary plugging operation.) operation.) 1. A fitting is 1. A fitting is permanently secured permanently secured 3. A TDW

3. A TDW Tapping MachineTapping Machine is is installed on the fitting, and installed on the fitting, and the valve is opened. After the valve is opened. After pilot drill penetrates, the pilot drill penetrates, the tapping machine fills with tapping machine fills with product, and air is purged product, and air is purged from the housing. The tap is from the housing. The tap is make through the line and the make through the line and the coupon is retained

coupon is retained..

4. The valve is closed, 4. The valve is closed, and the tapping

and the tapping

machine is removed. A machine is removed. A branch connection is branch connection is added, and the valve is added, and the valve is opened. The new

opened. The new connection is ready to connection is ready to put into service. This put into service. This field-proven TDW field-proven TDW

Hot tapping

(103)

Hot tapping

1. The four fittings are

permanently secured to the line.

2. Temporary SANDWICH®

Valves are installed on the fittings, and taps are made through the valves.

3. Two STOPPLE® Plugging

Machines are installed. Product is diverted through the temporary bypass. The isolated section is purged. Modifi cations are made to the isolated pipe section. The new section is purged and equalized, and the plugging heads are retracted.

4. The temporary bypass is

removed. LOCK -O-RING® Plugs are installed in the STOPPLE® Fittings with a tapping machine. All

equipment is then removed and blind flanges are installed on the fittings to

(104)

(105)

(106)

(107)

PIPE SECTION REPLACEMENT

• Severe damage may need to be cut out the pipe and replaced by ‘pre-tested’ sections. • This will require:

• Isolation of flow and pressure, depressurisation and purging of section to be

replaced.

• Hot-tap, Stopple and Bypass to bypass flow if the pipeline must continue to be in

operation, perhaps at a reduced pressure.

Replace Remove

(108)

Cut out

•• If line can If line can be shut be shut down, depressurizedown, depressurized, and d, and evacuatevacuated, a ed, a relativrelatively simpleely simple repair

repair

•• If the line cannot If the line cannot be shut down, depressurized, and evacuated, a muchbe shut down, depressurized, and evacuated, a much more complicated repair:

more complicated repair:

–

– Requires stopple fittings (a Requires stopple fittings (a way to stop the flow in the pipe) way to stop the flow in the pipe) on bothon both sides of the section to be replaced

sides of the section to be replaced

–

– After stopples are activated, section After stopples are activated, section with defectwith defect is depressed, removed, and replaced

is depressed, removed, and replaced

•• Bypass piping can be connected to stoppleBypass piping can be connected to stopple and used to maintain flow.

and used to maintain flow.

(109)

We can bypass damaged pipe, and maintain flow by constructing a ‘hot tap, We can bypass damaged pipe, and maintain flow by constructing a ‘hot tap,

stopple, and bypass’. stopple, and bypass’.

HOT T

HOT TAP: cutting into a live pipeline using a AP: cutting into a live pipeline using a special tee, welded or clamped to special tee, welded or clamped to the pipthe pip STOPPLE*: insertion of a temporary plug into the

STOPPLE*: insertion of a temporary plug into the line, through a hot-tap tee, to line, through a hot-tap tee, to isolatisolat BYPASS: attachme

BYPASS: attachment of bypass nt of bypass pipe to a pair pipe to a pair of hot-tap tees to provide a of hot-tap tees to provide a flowflow bypass aroundthe isolated section.

(110)

Freeze plugging

▪

FreezFreeze plugging e plugging is used is used to isolateto isolate a pipe segment containing a

a pipe segment containing a liquid without draining down liquid without draining down entire line

entire line

▪

LN2 is circulated within a jacketLN2 is circulated within a jacket around the pipe

around the pipe

▪

Temperatures are monitored toTemperatures are monitored to assure freezing of liquid

assure freezing of liquid

▪

Plug is locked in place by Plug is locked in place by thermalthermal contraction of the pipe

contraction of the pipe

▪

Pipe to be Pipe to be frozfrozen should been should be subjected to NDE

subjected to NDE

▪

(111)

In-Service Welding

Production welding procedures are

inappropriate for welding on a line in service

if the line contains a flowing gas or a flowing

or quiescent liquid. Such conditions cause

high weld cooling rates, which,

when

combined with

susceptible base metal

chemistry

and

the presence of hydrogen in

the welding environment, may lead to

underbead or hydrogen-induced cracking

(HIC) in the heat-affected zone.

(112)

In-Service Welding

Weld cracking is avoided by one or more of the

following:

▪ minimizing hydrogen in the welding

atmosphere by use of low-H electrodes

(E7018) or process (FCAW or GMAW)

▪ welding procedures that provide sufficient

heat input for the pipe material chemistry

and effective cooling rate

(113)

In-Service Welding

• Maintenance welding procedures are

developed by weld procedure testing,

computer thermal analysis, or measurement

of heat-sink capacity and cooling rates.

• Maintenance welding procedures and

welders are qualified in accordance with

Appendix B in the 19th Edition of API 1104

(supercedes API RP-1107).

(114)

WELD METAL DEPOSITION*

We can grind smooth part wall defects in a pipe wall, and fill the area with weld metal.

(115)

WELD METAL DEPOSITION*

It is a simple and direct application of additional wall thickness, but always use an approved procedure that is applicable to your line/product/defect.We also need to reduce pressure prior to this type of repair.

(116)

WELD METAL DEPOSITION:

Advantages

• Gas Research Institute (USA) say weld deposition is feasible to 900 psi

for minimum 0.125” wall thickness pipe. API 1160 limits this to >0.181”

(4.5mm).

• Can be useful where sleeves are not possible - at fittings and bends - or

where access is difficult.

• Fatigue and fracture tests at Edison Welding Institute (USA) have shown

good properties.

(117)

WELD METAL DEPOSITION:

Concerns

•

Defect assessment can usually show it is not needed.

•

Possible blow-out or penetration of pipe:

–

penetration depends on wall thickness, weld heat input and

removal of heat by flow of fluid inside pipe.

• The pipe’s static and fatigue strength must be restored, and

significant defects must not be introduced (including hydrogen

cracking in the heat affected zone).

•

The repair can be difficult to QA, and can show as small pits in an

(118)

In-Service Welding

Recommended maintenance procedure

qualification test arrangement

Pipe coupon

inclined at 45

degrees with

fresh water flow.

Simulated repair

sleeve clamped

in place prior to

welding.

(119)

In-Service Welding

▪ Welding on a line containing quiescent gas may not

require a special welding procedure. However, if

there is flow or if the sections are thick (e.g., a large

hot-tap), use of low-H is strongly encouraged,

particularly if CE is high.

▪ Preheat is unlikely to be effective where cooling

rates are controlled by product in the line.

▪ If line is under pressure and t < 0.25 inch, use of

low-H electrodes and limits on heat input to avoid

burn-through are strongly encouraged.

(120)

In-Service Welding

▪ Assurance that cracking has been avoided is

strengthened by NDE using UT and/or MPT of

the weld, allowing 48 to 72 hours for delayed

cracking effects.

▪ Alternatively, set aside procedure test

coupon for 48 hours and check for cracking

before destructive tests to establish a

crack-proof welding procedure

–

no delay in field

needed.

(121)

Weld metal deposition repair

▪ Codes allow repair of corroded areas by

filling them with weld metal.

▪ Refer to “Guidelines for Weld

Deposition Repair on Pipelines” by Bill

Bruce, EWI, February 24, 1998, A.G.A.

Cat. No. L51782 for further information.

▪ Useful for small areas that cannot be

sleeved, such as bends, elbows, tees.

(122)

Weld metal deposition repair

Direct deposition repair

welding procedure

qualification test

arrangement

(123)

Pop Quiz

True or false?

• A reinforcement sleeve is ineffective for internal

corrosion_____

• Composite wrap repair is not permanent_____

• Composite wrap repairs cannot be detected by ILI____

• Steel sleeves must match the pipe grade_____

• In-service welds should be made using low-hydrogen

welding____

• The reason for using low-H welding is to avoid cracking____

• Steel sleeves should be tapered to the pipe thickness at their

edges____

(124)

CODES, STANDARDS &

REGULATIONS

(125)

Applicable documents

Gas Pipelines

▪ 49 CFR 192

▪ ASME B31.8

▪ ASME B31.8-S

▪ CSA Z662

▪ PRCI Pipeline Repair

Manual

▪ Company SOPs

Liquid Pipelines

▪ 49 CFR 195

▪ ASME B31.4

▪ API 1160

▪ CSA Z662

▪ PRCI Pipeline Repair

Manual

(126)

Repair of Corrosion

Repair Method ASME B31.4 ASME B31.8 CSA Z662 Cut out Yes, as complete cylinder

Grind out No

Reinforcement sleeve (Type A)

Yes, if not leaking and not selective on ERW seam

Yes, if not leaking Pressure-containing

sleeve (Type B) Yes

Compression sleeve Included as A or B See as A or B Yes

Composite wrap

Yes, if not leaking and d/t<0.80 and not selective on ERW seam

No Yes, if not leaking and d/t<0.80

Mechanical clamp Yes Yes No

(127)

Repair of cracks

Grind out Yes, g/t<0.40 Yes, per corrosion limit Reinforcement

sleeve (Type A)

Yes, after grind out

and g/t<0.40 Yes Yes, after grind out Pressure-containing

sleeve (Type B) Yes

Compression sleeve Included as A or B See A or B Yes, after grind out Composite wrap Yes, after grind out

and g/t<0.40 No Yes, after grind out

Mechanical clamp Yes No

Hot tap or fitting Yes No Yes

(128)

Repair of Mechanical Damage

Grind out Yes, g/t<0.125, d/D<0.06 g/t<0.10 any L g/t<0.40 limited L d/D<0.04 Yes Reinforcement sleeve (Type A)

Only after removal by grinding and with filler

Only with filler Only after removal by grinding

Pressure-containing

sleeve (Type B) Yes

Compression sleeve Included as A or B See A or B Yes

Composite wrap

Only after removal by grinding and with filler

Only if of proven design

Only after removal by grinding and not in a dent

(129)

Anomalies PRIMARY REPAIR STRATEGIES (1) Weld Metal Deposition (2) Type ‘A’ Sleeve Type ‘B’ Sleeve Composite Reinforcement Hot Tap External Metal Loss <80% w.t.

Pipe Seam Yes Yes Yes Yes No Girth Weld Yes Yes Yes Yes No Pipe Body Yes Yes Yes Yes Yes Bend Yes Yes (3) Yes (3) Yes (4) Yes Internal

Metal Loss <80% w.t.

Pipe Seam No No Yes No No Girth Weld No No Yes No No Pipe Body No No Yes No Yes Bend No No (3) Yes (3) No Yes External

Metal Loss >80% w.t.

Pipe Seam Yes No(8) Yes No(8) No Girth Weld Yes No(8) Yes No(8) No Pipe Body Yes No(8) Yes No(8) Yes Bend Yes No (8) Yes (3) No(8) Yes Internal

Metal Loss >80% w.t.

Pipe Seam No No Yes No No Girth Weld No No Yes No No Pipe Body No No Yes No Yes