In-Service Welding

Essential Maintenance

Repairs, alterations and modifications to piping systems are commonly required for maintenance or operation of most industrial units, components, and equipment. However, shutting down plant operation in whole or in part for pipe maintenance purposes is often not desirable (especially in an emergency situation). A solution to system shut-down is in-service repair procedures on live pipelines. Utilizing in-service welding for pipelines, piping and vessels requires in-depth knowledge of codes, standards and specifications coupled with hands on work experience to provide a safe and practical engineered in-service solution.

Our experience at you service

With our extensive Oil and Gas experience with almost all national and international codes and standards, our team can provide you with the expertise required to tackle in-service repairs, such as welded repairs on a pipeline and installation of split tees or repair sleeves.

A closer look at in-service welding

Primary concerns

When performing in-service welding, there are two primary concerns that need to be considered in addition to the standard welding requirements:

Hydrogen-induced cracking (Cold Cracking): This can occur when the combination of a high tensile stress, the presence of hydrogen and a susceptible microstructure are present. The higher the weld cooling rate of in-service welding (due to the flowing fluid of in-service pipe), the bigger the shrinkage and tensile stress would be expected in the HAZ.

Burn-Through: This is a main concern for welding onto in-service lines when the thickness of the pipe is less than ¼” [6.35mm], as both, detailed qualified welding procedures and skilled qualified welders are required to perform a safe and acceptable welding solution.

Types of In-Service Welding

In-service welding is typically performed as one of three joint types:

A branch connection is when a branch pipe is welded directly to the run pipe with a groove weld. This may or may not have additional reinforcement placed around the joint after the branch connection is completed.

A sleeve weld is when a sleeve is placed around the run pipe and a fillet weld is placed all around the end of the sleeve. This is commonly used for a split tee type branch, for the reinforcement of a branch type connection, or on a repair sleeve.

Direct deposition welding is when a weld bead is placed directly on the exterior of the run pipe, typically used as a localized type of repair.

A successful Welding Procedure

When qualifying an in-service weld procedure, it is typical to perform the testing requirements based on specific code requirements. In addition to this, many owner/operators have additional requirements.

The main factors for an In-Service Welding Procedure and Welder Qualification are:

The actual thickness of the repair area
Material hardenability (Carbon Equivalent)
Cooling rate due to the service condition
Working and design pressure
Other requirements (i.e. Sour Service)

The following in-service welding Standards and Specifications can be used individually or in combination:

CSA Z662 Clause 7.17
API 1104 Annex B
ASME PCC-2 Article 2.10