Subsea Pipeline Repairs

7/22/2019 Subsea Pipeline Repairs

1/12

ONGC IMR Dept.

Training ReportPipeline Repair Methods

Bhavesh Parkhe

9/10/2013


2/12

Training Report

Name: - Bhavesh Parkhe

Department: - Inspection, Maintenance & Repair

Objective:-

1. To have an in-depth knowledge of the formal functional activities of IMR[Inspection maintenance and repairs]section of Off shore Logistics in

ONGC

2. To develop skills for application of theory to practical work situations.3. To test my aptitude towards this side of career.4. Self-evaluation and developing a strong resume for my future prospects.

Introduction

1. Scope & Objective of the CompanyONGC, a national E&P company of India is one of the largest oil

producers in the world.

One of the major contributors is its Western Offshore Unit which

comprises of number of oilfields

One of the major oilfields is Mumbai High located few kms away fromthe western coast of Mumbai.

IMR department is responsible for all the inspection, maintenance and

repair work in the WOU.

2. Overview of the companys workingOil and Natural gas is extracted from the fields by the offshore rigs and

after its primary processing is dispatched to the onshore units at

Uran/Hazira for further processing.

Products are separated to petroleum, paraffin wax etc.

3. Details about the WOU (Western Offshore Unit)The Mumbai High field consists of number of process complexes and

several unmanned jackets.

Oil and gas extracted is transported between the platforms as well as

onshore installations through a network of pipelines.

4.

Zones of the Rig that come under IMR


3/12

The IMR department is responsible for inspection of pipeline, riser,

structure of jacket below MSL, Splash zone members.

5. Contribution & functions of the IMR departmentFollowing are the basic (routine) functions:-The IMR department has various functions pertaining to maintenance.

BPI - Baseline Platform Inspection

SZRI Splash Zone Riser Inspection

MGR Marine Growth Removal

Routine pipeline and riser repairs

Inspection of PLEMs [Pipeline end modules].

Maintenance of SBMs.

Pipeline Repair Techniques (leakage)

Clamps

Clamps are one the most economical methods of repair.

They can be fixed around a leakage or a damaged part. The clamps can

be temporary or permanent.

There are further types featuring some variations depending on the

manufacturer.

The clamps can have pressure testing arrangement to check the seals.

In that case dual seals can be provided.Following are some of the clamp manufacturers

Oceaneering, GOV, VeeKay, Subsea

Connectors

Connectors are used to connect pipelines in subsea operations where

hyperbaric welding can prove uneconomical.

Generally, connectors are a part of sectional replacement operation.

When a section of a pipe is replaced, there might be a gap in the

replaced and existing pipeline which is inevitable.This gap is connected with the help of connectors.

Sectional Replacement

Sometimes, the region near the leakage is also found to be below the

minimum requirements.

In this case the whole defective pipe section must be replaced as a

preventive measure.

The pipe section is cut and removed. The new section is fabricated on

the vessel itself, taken to the location and is connected with help of


4/12

connector.

The pipeline as well as the riser can be repaired using the above

techniques.

Details of Repair Techniques

1. ClampsTypes of Clamps

1. Temporary ClampTemporary Clamps are used when the operational pipeline needs to

be repaired immediately and suitable clamp for the leakage is not

available.

In such cases a standard temporary clamp which is available on deck

can be installed.

It can be installed manually or with help of ROVs.

It can be used until the permanent clamp is available.

2. Structural ClampsThis type is used for permanent repair of the pipeline.

It consists of steel reinforcement collets to fix the clamp.

Dual seals are generally provided to perform seal verification tests.

The clamps can be manually or ROV installed using stud tensioners.

It also has longitudinal bolts for energising the seals.


5/12

3.

ROV installed ClampsThis type of equipment is used when the repair operation is

hazardous to human life or not enough manpower is available.

It is a relatively costlier method, hence less preferred.

The movement of the clamp is controlled from deck.

Guides are available on the ROV so that it is properly placed on the

pipe. For tightening of bolts, remotely operated tensioners can be

used.

(Based on Geometry of the clamp)

4. Patch ClampThis type of clamp can be used for

minor defects.

It consists of a patch of elastomeric

material inside a bolted clamp.


6/12

5. Pin Hole ClampThis clamp can be used in case of small pin hole leaks.

It consists of a conical seal with a pin which guides the seal on the

hole.

6. Stand Off ClampIt consists of two semi-circular sleeves which can be bolted together.

The inner side of the sleeve has seals to prevent leakage.

These are most widely used in subsea applications.

7. Enclosure type ClampWhenever leakage takes place at flange or any other component

along the pipeline it is difficult to find immediate replacement.

Thus it can be temporarily enclosed by enclosure type clamps.

They cover the entire flange, hence preventing further leakage.


7/12

2. ConnectorsTypes of Connectors

1) End Flange Connectors

It is one of the cheapest way to attach a flange to a subsea pipeline

where welding can prove to be uneconomical.It consists of collet grips or ball bearing grooves to hold it firmly over

the pipe. Double seals can be provided for pressure verification.

The flange is generally rigid. It can be swivel type depending on the

situation. It gives rotational freedom to the flange so that bolt holes

can be aligned.

2) Misalignment Flange connector

This type of connector is used when there is lateral misalignment

between the pipes to be connected.The MAF consists of a ball and socket arrangement which gives the

flange rotational degree of freedom along 2 axes. By adding a swivel

flange it will have all three degrees of rotational freedom.

Thus, the pipes can be easily connected.

It provides +/- 100

Movement.


8/12

3. Sectional Replacement

When the pipeline is subjected to extensive deterioration instead of

localised, using repair clamps would be uneconomical.

Existing flange connections can be used for removing the section of the

pipe.

If it does not exist the pipe must be cut at suitable section.

The pipe must be replaced by another pipe of same dimensions.

Welding of flanges must be done on deck.


9/12

4. Modern Non-Conventional Repair Techniques

a. Epoxy filled Repair Sleeves

Instead of using heavy clamps, a split sleeve can be used.

The annular space can be filled with epoxy grout.

This repair technique is a compromise between the conventionalclamp system and composite repair system (hence also called

hybrid).

The epoxy can fill up all the crevices uniformly.

It ensures uniform load transfer to the sleeve

Hence it can be used in case of internal metal losses.

Sleeves can be welded longitudinally or clamping bolts can be

provided.

b. Composite Materials

Composite materials are in demand in todays market due to their

simplicity and effectiveness.

They can be used for both on shore as well as in subsea applications.

They are lightweight, corrosion and abrasion resistant.

These solutions are developed by different companies which often do

not reveal the material composition.

Different companies provide different type of composite materials.

Some of the common materials are plastic polymers, glass fibers,

nylon fibers. The materials require corresponding adhesives.


10/12

Composite materials can be of two types

i. Bandageavailable on board and can be applied by staffii. Engineered applied by specific contractors

Composite Material Repair Systems

Clock Spring

Syntho Subsea LV (Metalyte Pipeworks)

Composite materials can be in the

form of wraps. Wraps are generally

of glass fiber. Adhesives are

required in this repair method.

Some composite materials can be

directly applied over the pipe

section. Generally it is a mixture of

glass fibre and a resin.


11/12

PIPEASSURE (CSIRO)

Composite Repairs (NCA Oceaneering)

Reinforcekit (3x Engineering)


12/12

X-Protect (Composol Subsea)

Syntho Glass XT (Neptune Research Inc.)

List of Manufacturers

Clamps Hydratight, Oceaneering, SubSea, QCS, ABCO subsea

Connectors Vector, Oceaneering, Hydratight

Hybrid and

Composite

GE Energy, Clock Spring, Metalyte, Neptune Research

Conclusion:-

These are some of the existing repair equipments in the market. The report

contains a summary of the things I have learnt. All of my presented objectives

were completed.

Date: 10/6/2013 Report Submitted To

Mr J.S. Kalsi (Mentor)

__________________

Documents

Subsea Pipeline Repairs