Piping

Maintenance & Inspection of Piping in Hydrocarbon Industry

Igniting Minds... Energizing Lives…Haldia Refinery

PIPING SYSTEM



PIPING TYPES

PIPING

UNDER GROUND ABOVE GROUND

INSULATED BARE


PIPING MATERIALS

CS - SR AS PER SERVICE, THICK. > 19mm

AS - POOR WELDABILITY, SR REQD.

SS - NO PRE-HEAT, SR

RUBBER LINED

CEMENT LINED

SS LINED

HDPE

PIPING MATERIALS

CARBON STEEL ALLOY STEELS STAINLESS STEELS

PIPE SCHEDULES

PIPE SCHEDULES


PIPING DESIGN/ LAYOUT

OVERALL PLOT PLAN

P&ID’s

GENERAL ARRANGEMENT DRAWINGS (GAD’s)

PIPING MATERIAL SPECIFICATION (PMS)


PLOT PLAN


PIPING & INSTRUMENT DIAGRAM


GENERAL ARRANGEMENT DRAWINGS (GAD’s)


PIPING COMPONENTS

PIPEFLANGES / VALVESEXPANSION BELLOWSFITTINGS

HALF COUPLINGSMITRE BENDSREDUCERELBOWSGASKETS


PIPING COMPONENTS

SUPPORTSGUIDE

FREE IN TWO DIRECTION

CROSS-GUIDEFREE IN ONE DIRECTION

ANCHORSNOT FREE FOR MOVEMENT

SPRING SUPPORTS


PIPING WALL THICKNESS

BARLOW’S FORMULA

t = PiD/ 2SA

tn = t + allowance(s)

t= Minimum Wall Thickness (M)Pi= Maximum Allowable Operating Pr. (MPa)

D= Outside Diameter (M)SA= Allowable Stress (MPa)

tn = Nominal Wall Thickness(M)


PIPING TEST PRESSURE

PT = 1.5P x ST/S

PT= Minimum Test Gage Pressure

P=Maximum Allowable Working Pressure

ST=Stress Value at Test Temperature

S=Stress Value at Design Temperature


PIPING FABRICATION

WELDINGSMAWGTAW

PRE/ POST-WELD HEAT TREATMENT

HOT TAPPINGBRANCH CONNECTION WITHOUT

INTERRUPTION TO THE FLOW OF FLUID

PIPE BENDING


HOT TAPPING


PIPE BENDING

GENERAL GUIDELINES



• All small bore pipings and tracer lines, size ¾” and below should be welded by TIG process for all types of joints, e.g. butt, socket, tee, etc. to ensure proper quality of welding. Use of half coupling may be considered to increase reliability of small-bore connections.

• Minimum thickness of pipe for sizes up to 1½” should be Sch.80 for CS and AS.

• Reinforcement pad shall be provided at support location.

• Steam drain points should be routed to a drain header and taken out of the unit area.

GENERAL GUIDELINES FOR PIPING


• Stiffener should be provided in small bore bleeder/ drain point connection welded to immediate upstream or downstream of safety valves.

• As far as possible, stub-in type branch connection are to be provided when branch size is less than one size than the main pipe.

• All the reinforcement pad telltale holes should be drilled and tapped properly. Gas cut holes should not be accepted.

• Wherever two phase flow in piping is expected, piping design including its support system should be checked w.r.t. most adverse conditions/ ratio of both the phases (slug flow) to avoid line vibration during operation.



• All the fittings like valves, flanges etc. in high temperature service (> = 300 0C) should also be fully insulated if they are in open area or the localized cooling can cause operational problems like coking etc.

• All SS piping should have chloride free insulation or preferably

should have SS foil wrapped between pipe and insulation.

• Branch connections for fire hydrants along the roads should be totally above grounds. Hydrant connections also should remain above ground.

• Firewater and cooling water lines emerging from underground should be wrapped coated beyond the ground level up to a length of 500mm.



• Hard surfacing with a proper slope towards open drain system is to be provided beneath the offsite pipe rack area with a clear space of 500mm from bottom of the pipe.

• Interspacing between the offsite piping on the support pedestal should be such that the lines should not touch each other even after insulation (at least 3” gap after insulation).

• Identification marks for location/ visibility of drain points of offsite piping should be provided. All drain points should be approachable and clearly visible.



• Piping insulation ends should be properly sealed to avoid water

ingress.

• Hard surfacing under the piping bay in offsite areas should be done with proper slope & drainage facility.

• Proper slope and gap should be provided in piping culverts to avoid water logging.

• In fire water lines, the hydrant tapping should not be taken from the bottom side of pipe. Tapping should be taken from the top or from side.



• Any piping circuit if idle for more than six month shall be inspected or hydrotested before taking into service

• Ensure adequate wrapping & coating and at least 0.5mtr wrapping & coating shall be visible externally at both ends on above ground portion of pipe.

• All piping route in off-site area shall be made grass & debris free.

• In Hydrocarbon service dia. 2” pipe shall be of minimum Schedule 80.

• Low point drain (LDP) shall be offset by 1 meter from the supports and shall not be embedded into soil.


PIPING FABRICATION



PIPING FABRICATION

FIT UPS


PIPING FABRICATION

BRANCH CONNECTIONS


PIPING FABRICATION

BRANCH CONNECTIONS

PIPING FABRICATION

PREHEAT TEMPERATURES

PIPING FABRICATION

POST WELD HEAT TREATMENT

PIPING FABRICATION

TYPICAL WELD DEFECTS

DEGRADATION MECHANISMS IN

PIPING SYSTEM



DETERIORATION IN PIPING SYSTEM

INTERNAL CORROSION•UNIFORM CORROSION DUE TO LOW/ HIGH pH



INTERNAL CORROSION•LOCALIZED CORROSION- IN CREVICES, BENDS ETC.



INTERNAL CORROSION•CONDENSATION/ TWO PHASE SYSTEMS



INTERNAL CORROSION•STAGNANT AREAS - IN DEAD ENDS ETC



INTERNAL CORROSION• STRESS CORROSION CRACKING



INTERNAL CORROSION• HYDROGEN ATTACK



INTERNAL CORROSION• AREAS D/STREAM OF INJECTION POINTS



INTERNAL CORROSION• IMPINGEMENT AREAS



INTERNAL CORROSION• NAPHTHENIC ACID/ POLYTHIONIC ACID CORROSION



INTERNAL CORROSION• FIRE WATER CORROSION



INTERNAL CORROSION• COOLING WATER CORROSION



EXTERNAL CORROSION• CORROSION UNDER INSULATION



EXTERNAL CORROSION• SOIL SIDE CORROSION OF UNDER-GROUND LINES



EXTERNAL CORROSION• EXTERNAL CORROSION DUE TO SOIL/ WEEDS



EXTERNAL CORROSION• ATMOSPHERIC CORROSION - SULFUROUS /

ACIDIC ENVIRONMENT



WELD CORROSION• PREFERENTIAL ATTACK ON WELD



EXTERNAL CORROSION• CORROSION AT SOIL / AIR INTERFACE



STRESS RELATED• OVERPRESSURIZATION



STRESS RELATED• VIBRATION- AS IN PUMP CONNECTED PIPING



STRESS RELATED• FAILURE OF WELD SEAM



STRESS RELATED• THERMAL STRESSES

INSPECTION OF PIPING SYSTEM



ROLE OF INSPECTION

To evaluate present physical condition of the pipeline.

To keep the concerned operating and maintenance personal fully informed about the the condition of the lines.

To determine causes of deterioration and advise suitable economical solution to the problem.

To initiate procurement action of materials.

To co-relate deterioration rate with design life for further run.


FREQUENCY OF INSPECTION

The interval between inspections depend upon :

• Degree of corrosiveness/ erosiveness of the fluid.

• Remaining corrosion allowance.

• Type of protective coating.

• Atmosphere prevailing around the piping.

• Potentially of fire /explosion in case of a leak or failure.

• Statutory requirements.

• Importance of operations.



Service External Comprehensive

Crude (sour) 3 6

LP/Natural gas 2 4

Gasoline / naphtha 2 4

ATF/ HSD/ LDO/ SKO 3 5

FO/RCO/Bitumen/ VBO 3 5

Fuel gas/ Flare gas 3 5

Lube oil 5 10

Frequency of inspection for offsite piping (hydrocarbon):



Frequency of inspection for offsite piping (Utilities): Service External Comprehensive

Fresh water 2 4

Fire water 3 (lined) / 1 (unlined) 5 (lined) / 2 (unlined)

Air / steam 3 6

Ammonia / caustic 2 4

DEA/ MEA 3 5

Furfural/ phenol 2 3

Benzene/ toluene 2 4


INSPECTION PROCEDURE

Visual Inspection: For determining leaks, misalignment, supports, vibration, external corrosion, cracks, insulation damage.

Ultrasonic Inspection: For ascertaining wall thickness, by scanning at least four spots (12 o’ clock, 3 o’ clock, 6 o’ clock and 09 o’ clock positions) on each circumferences for every 30 m of straight length and all bend locations.



Radiographic Inspection: Critical spots which cannot be inspected by UT may be radio graphed during operation to determine internal fouling, pitting, scaling etc.

Shutdown Inspection: All piping which cannot be inspected during operation has to be inspected during shutdown.



Hydrostatic Testing:

Along with all NDTs hydro test has to be carried out to evaluate strength of existing and new joints of the line in addition to establishing overall integrity of the line.

For new lines hydro test is to be done at 1.5 times design pressure.

For old lines or partially repaired or replaced line it is carried out at 1.5 times operating pressure.

Coated or insulated lines are hydro tested before coating operation.

Before using any line which has been idle for long time, hydro test is to be carried out.

Portable water is to be used for CS or AS pipes and DM water is to be used for SS pipes. Water must be drained after the test.



• In the presence of certain corrodants, corrosion rates are normally increased at areas of increased velocity and/or turbulence.

• Elbows, reducers, mixing tees, control valves, and orifices are examples of piping components where accelerated corrosion may occur because of increased velocity and/or turbulence.

• In the areas of no flow, such as dead legs, accelerated corrosion may occur.

• Such components are normally areas where an inspector would locate additional TMLs in a piping circuit.

AREAS SUSCEPTABLE TO ACCELERATED CORROSION



INSPECTION POINTS



INSPECTION POINTS


ON-LINE MONITORING OF PIPING

• pH MONITORING

• CORROSION PROBES

• CORROSION COUPONS IN WATER LINES


NDT IN PIPING SYSTEM

• ULTRASONIC THICKNESS SURVEY

• DCVG / PEARSON SERVEY

• SPARK / HARDNESS TEST OF RUBBER LINED PIPES

• RADIOGRAPHY



• DCVG SURVEYThe Direct Current Voltage Gradient (DCVG) technique is a "newer" technique for coating surveys on buried pipelines.

It has been used for not only locating but also sizing coating defects.

The technique is fundamentally based on measuring the voltage gradients in the soil above a cathodically protected pipeline.



CRACK DYE APPLIED

TRAPPED DYE ON CLEANED SURFACE

CRACK VISIBLEON APPLYINGDEVELOPER

DYE PENETRANT TESTING


DISCONTINUITY

METAL

RADIATION SOURCE

FILM


RADIOGRAPHY TESTING


Sample Films :

Lack Of

Penetration

ClusterOf

Porosity


RADIOGRAPHY TESTING


Sample Films :

TungstenInclusion

TransverseCrack


RADIOGRAPHY TESTING


Slag inclusions


RADIOGRAPHY TESTING

Lack of fusion


Suck back


RADIOGRAPHY TESTING

Root undercut


External undercut


RADIOGRAPHY TESTING

Mismatch


Poor reinforcement


RADIOGRAPHY TESTING

Excess reinforcement



LONG RANGE ULTRASONIC TESTING

This technique uses low

frequency guided ultrasonic

waves to detect a length of

piping. It locates the affected

area in terms of distance from

transducer and serves as a

screening tool to inspect large

lengths of piping especially at

difficult to access locations.







ELECTRONIC SCANNING

ELECTRONIC COMBINED WITH STEERING AND FOCUSING

PHASED ARRAY ULTRASONICS


DOCUMENTATION OF TMLs

CORROSION PREVENTION IN

PIPING SYSTEM



CORROSION PREVENTION

PAINTING

• ENAMEL, EPOXY, COAL TAR, CLORINATED RUBBER, BITUMENOUS

• HIGH TEMPERATURE PAINTS

• TEMPERATURE INDICATIVE PAINTS

• TAPE COATING



CATHODIC PROTECTIONPRINCIPLE OF CP

MOST NEGATIVE REGIONS ACTS AS ANODE

PRE-REQUISITE FOR CP COATING / WRAPPING EFFECTIVENESS

PIPE TO SOIL POTENTIAL SURVEYSOIL RESISTIVITY SURVEY

INTERFERENCE WITH FOREIGN LINES



CATHODIC PROTECTIONSACRIFICAIL ANODE TECHNIQUE



CATHODIC PROTECTIONIMPRESSED CURRENT TECHNIQUE

CAUSES OF PIPING FAILURES



PIPING FAILURES

MAJOR REASONS OF PIPING FAILURES

MATERIAL NOT SUITABLE / MATERIAL MIX-UP

5 Cr-1/2 MoCarbon steel


PIPING FAILURES


VIBRATION


PIPING FAILURES


FLOW ACCLERATED CORROSION


PIPING FAILURES


CATALYST EROSION


PIPING FAILURES


THERMAL STRESSES


PIPING FAILURES


COATING DAMAGE


PIPING FAILURES


PROBLEMS WITH LOW POINT DRAINS


PIPING FAILURESGMAJOR REASONS OF PIPING FAILURES

SEAM OPENING


PIPING FAILURES


GRASS / WEED GROWTH & SOIL CONTAMINATION


PIPING FAILURES


INTERNAL UNDER DEPOSIT / MICROBIAL CORROSION


PIPING FAILURES


CORROSION AT SUPPORT LOCATIONS


PIPING FAILURES


CORROSION UNDER INSULATION


PIPING FAILURES


IMPROPER FABRICATION


PIPING FAILURES


IMPROPER JOINT DESIGN

Standard Joint

Improper Fit Up& Welding

Poor Penetration& Under cut

Crack


Documents

Piping