Piping Installation, Welding & Fabrication Method Statement

TABLE OF CONTENTS

1. PURPOSE
2. SCOPE
3. REFERENCES
4. DEFINITIONS
5. RESOURCES
6. RESPONSIBILITIES
7. SEQUNCE OF WORKS
8. QA/QC REQUIREMENTS
9. HSE REQUIMENTS
10. EMERANCY CONTACTS

Purpose:

The purpose of this methodology is to provide a systematic control and direction for the activity for the installation of piping at a construction site.

This method statement provides the expectation to execute work in safe, eco-friendly manner and in compliance to the project HSE and Quality requirements.

Scope:

Installation will be comprised of welding of field joints and the assembly of completed pipe spools which were prefabricated at external workshop.

References: 

• Contracts Specification and Documents
• Shop and Field Fabrication of Piping
• Technical specification for piping system
• HSE Manual
• Process piping manual
• Specification for welding and inspection of shop and field fabricated carbon steel process and utility.
• Project Quality Plan
• AWS D1.1 – Structural welding code
• DEP 34.28.00.31A -Structural steel works

Definitions: 

• Client     –
• QHSE    –  Quality, Health, Safety & Environment
• QCI        –  Quality Control Inspector
• ITP         – Inspection and Test Plan
• WPS       – Welding Procedure Specification – A Welding Procedure Specification, or WPS, is a formal written document describing standard welding procedures.
• NDT       – Non Destructive Testing is a testing and analysis technique used by industry to evaluate the properties of a material, component, structure or system for characteristic differences or welding defects and discontinuities without causing damage to the original part.
• PWHT   – Post weld heat treatment (PWHT) is a controlled process in which a material that has been welded is reheated to a temperature below its lower critical transformation temperature, and then it is held at that temperature for a specified amount of time.

Resources:

• Welding machine
• Grinding machine
• Preheating torches with propane gas cylinders
• Holding ovens/baking ovens
• PWHT equipment
• Hiab, Crane, trailer
• Cutting tools
• Generator

Responsibilities:

Welding contractor shall arrange all the resources deemed necessary for carrying out the works related to the steel piping installations.

In addition to the above contractor will also ensure that adequate safety precautions are put in place in order to carry out the pipe welding job in a safe manner.

Construction Manager:

The Construction Manager is responsible in executing the works as per client procedures and approved method statement.

Supervisor/ Foreman:

• Ensure that welding equipment, baking oven, quiver are in good condition.
• Ensure welding is done as per the approved WPS and approved for construction drawings and in line with HSE requirements.
• Ensure that weld maps / spool drawings are available.
• Coordinate with QC personnel to study the cause of any reported weld defects and arrange to take corrective and preventive action.
• Adhere to the HSE requirements.
• Make sure the compliance with PTW requirements.

QC Inspector:

• Carry out the inspection as per the Inspection and test plan.
• Approving/ rejecting the item based on inspection.
• Submitting the quality records to the client and getting their approval.
• Responsible to keep records of all inspection related activities & Material traceability.
• Adhere to the QHSE requirements.

HSE Officer:

• Advise the construction crew on HSE aspects and ensure their safety.
• Arrange through Job performer for tool box talk covering risk assessment in language understandable by workers.
• Cross checking certified material devices and equipment’s are used.
• Do weekly, monthly HSE audit.
• Ensure appropriate safety measures are taken as per the risk assessment and controlled documents.
• Ensure that all staff adhere to the HSE plan and HSE requirements.

Sequence of Works for Piping Installation

PTW Issuance: A Hot Work permit will be issued to carry out the works, along with the permit to work crane certificate, approved method statement, risk assessment, and approved drawings shall also be attached.

Safety Setup

Arrange the required safety signs, barricades and other related safety precautions highlighted in the risk assessment and permit prior to commencing the works.

The works shall only commence after the job performer has checked and ensured that all safety precautions and safety requirements are in place.

Ensure employees understand the hazards and control measures related to the critical activities, i.e. lifting, welding.

Ensure personnel stay away from lifting zone and do not enter under the suspended loads.

Qualified First Aider must be on site and identified by a sticker on his helmet.

Display Emergency Contact number on site.

Site Works Field Joints

Prefabricated pipe spools shall be carefully loaded and transported to site.

The transported spools will be tied down with ample support to prevent any damage.

Spools will be tied down using nylon straps/belts.

Under no circumstances will the pipes be tied down using chains or cables to prevent any scratches or damage.

Upon receiving the pipes at site, they shall be offloaded and placed either in position on the pipe supports or placed on the ground on top of wooden supports.

All flanged ends or open ends will remain sealed to prevent any sand or debris from entering.

Lifting of the pipe spools shall be done by using either a HIAB or Crane.

Third Party certified slings and riggers shall be used during the lifting operations.

All lifting tools and tackles shall be color coded based on the current color code.

Once the spools are lifted into position, the fabricator/pipe fitter shall ensure that proper alignment is achieved, lengths of spools are correct as per the piping layout and isometric sheet prior to either bolting the spools together or welding any field joints.

Welding and grinding of field joints shall be carried out inside a closed habitat made of fire retardant material.

Any live facilities will be covered with the fire retardant blanket as an additional precaution.

Welding shall be done as per the approved procedure, specification and approved for construction drawings.

Approved welders for the specific WPS shall be used for welding.

Welded surfaces shall be clean and free from grease, oil, paint or other foreign material which are detrimental to welding.

When the weather does not permit satisfactory workmanship welding shall not be done, on site in windy condition the pipe ends shall be closed to prevent through draughts during welding. Suitable covering using tarpaulin (fire retardant) shall be provided.

Welding shall not be done when the weld surface is wet or when the area is exposed to rain and strong windy conditions.

Preheating to be done properly during cold weather.

Site Works – Welding of Pipe Supports

As required some structural steel pipe supports are to be welded to the base plates inserted into the precast foundations.

Other pipe supports are to be welded to the existing pipe support structural steel racks.

Locations to be welded will be covered as required with a fire proof tarpaulin.

The base plate or support shall be cleaned by grinding to remove any surface debris, or paint.

Support will then be placed in position, aligned, and tack welded.

Once tack welding is completed, the alignment will be rechecked and final welding will be carried out.

Welding shall be done based on the approved welding procedure for structural steel.

Site Works Valve Installation

Wherever valves are to be installed, the installation/orientation of valve handles and flow direction shall be according to the piping layout.

All valves to be installed will be cross checked to ensure that the proper valves are installed in the proper location.

Valves shall be installed in the closed position except for ball valves and plug valves.

New gaskets will be installed between the valve flange and pipe flange.

Final tightening of all nuts shall be done once proper alignment is achieved.

Bolting of flanges will be done in a cross pattern.

All bolts, gaskets and valves shall be properly stored to avoid contamination with the environment.

Valve ends will be sealed until installation and gaskets and bolts shall be kept clean of any debris such as sand.

Scaffolding

Scaffolding if required shall be erected by qualified personnel in a safe and suitable manner.

Scaffolding above 2 m in height shall be inspected by a scaffolding inspector and a scaff-tag shall be signed and provided on the scaffolding near the ladder.

No one shall use the scaffolding without the scaff-tag being approved.

Scaffolding material to be used shall be in good conditions, brass hammer shall be used to assemble and tighten the scaffolding locks.

QA/QC Requirements

Weld Identification

Each weld shall be uniquely identified with the joint number and welder number.

After completing the weld the welder shall mark the joint no: & welder no: near the weld using paint or indelible crayon.

After welding each spool the line no, spool no etc. shall be marked / tagged on the spool and stocked over wooden sleepers or other suitable material above ground.

Non Destructive Testing: Non destructive testing shall be done as per the approved procedure using approved sub contractor.

Alignment Circumferential Welds

Butt weld alignment shall satisfy the requirement of ANSI B 31.3 and conditions stated below.

Internal misalignment of pipe work shall not exceed 1.6 mm in order to facilitate welding of the root pass.

When a GTAW process is to be used maximum misalignment shall not exceed 0.8 mm.

If there is excess misalignment tapering of the internal diameter of the thicker member to a taper of 1:4 shall be done.

Ensure minimum wall thickness is maintained.

If misalignment up to 3.2 mm exists, internal grinding or machining may be conducted to improve root alignment, provided the taper does not exceed 1 in 4 maximum and the minimum required wall thickness is maintained.

External or internal clamps shall be used not only for misalignment correction but also for alignment in general. Misalignment correction using heavy hammering or heating of the pipe shall not be done.

Weld Separation

Circumferential welds (Girth welds):

Distance between weld shall be measured between the adjacent edges of the cap passes.

Circumferential butt welds (Girth welds) shall be separated by maximum possible distance.

However between fittings, short pipe lengths may be required. In this case, butt welds shall not be within 75 mm of adjacent girth weld for nominal pipe sizes of 75 mm and above.

For pipe sizes less than 75mm nominal, girth weld shall not be within the greater of 4 times the wall thickness or one pipe diameter of adjacent girth welds.

Girth welds closer than the above limit shall require approval of the client and may require PWHT solely at the discretion of the company.

Branch / Nozzle / attachment welds.

Branch / nozzle and other pressure attachment welds shall have minimum 3” distance to adjacent pressure welds.

Non pressure containing attachment welds shall be separated by 2” from adjacent pressure containing welds.

Longitudinal seams of adjacent pipes shall be separated by at least 4”.

Repairing the Welding Joints

Any defects which require repair shall be entirely removed to sound metal.

Metal shall be removed 1” on both side of the defect without substantial removal of the Base metal.

By grinding, the metal shall be removed and the groove shall be smooth without any undercut.

Visual examination and magnetic/dye penetrant test shall be done on the grove.

If repairs are done after hydro test / PWHT, the same will be repeated after repair.

Welding repair shall be done only twice.

After second repair if the weld is not acceptable the weld shall be removed, re beveled and re welded.

Same NDT technique & acceptance criteria for the original weld shall be done after repair welding.

Proper cutting disc shall be used. Grinding disc shall not be used for cutting purposes.

HSE Requirements

Risk Rating

Risk Rating is Medium: Job will have to be closely supervised by Job Performer, Safety officer and Supervisor.

HSE Requirements

Basic PPE, such as coverall, helmet, safety shoes, gloves, goggles and face mask (during windy days).

Appropriate approved PTW and certificate shall be obtained prior to commencing the job.

Standby vehicle will be present for emergency purposes.

Daily toolbox talks to be conducted.

Approved and valid fire extinguishers (dry powder) shall be available.

Sufficient cold drinking water to be available at all times.

Third party certificates of all riggers and cranes shall be available at site.

Proper color coding of all lifting tools, tackles shall be done

Emergency Contacts

The following shall be the contact persons in case of any emergency.

• Project Manager
• Safety Officer
• Rescue Service