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28

Set Double Block

and Monitor Tool

at location

BY THE

NUMBERS

Offshore pipeline maintenance typically falls into one of four categories:

valve replacement, tie-in, riser repair, or heavy lift protection.

During these types of maintenance, operators rely on non-intrusive inline

isolation methods to protect their people, achieve compliance, and mitigate

reductions to production. The most common isolation is the DNV-certified

double block and monitor method, as seen here.

DNV-Certified Double Block

and Monitor Isolation Method

1

2

3

4

5

HIGH

LINE PRESSURE

ANNULUS PRESSURE

Monitoring and

Tracking Module

Plug

Module #1

DNV Recommended Practice for Pipeline

Subsea Repair Criteria (DNV-RP-F113/3):

. Each barrier must be able to retain full line pressure

. Independent locking system

. Seal must be independently tested

. Ability to monitor line integrity

. Seals must be independent

from each other

Through the use

of independently operated isolation

barriers and continuous monitoring,

the system allows high-pressure

pipeline operators to carry out remedial

pipeline work in a safe, controlled, and

monitored environment.