The scope of this project is to assess the suitability of the Microstop system to support partial replacement of network risers where pipework is found to be in satisfactory condition, further to risk assessment. This includes technical appraisal as well as field trialling of the appropriate equipment.

During the initial review of the Microstop system, it was determined that further tests in addition to those originally specified were needed to satisfy the technical and safety requirements as the manufacturer was unable to provide sufficient evidence of the product’s suitability. SGN therefore asked the project supplier MACAW to provide a series of tests to support the approval process and prove the equipment was fit for field trial. The additional tests include:

• An application test, to demonstrate the product satisfies the required functional performance and to allow a first-hand assessment of how the process works for their application. Further qualification tests may be defined as a result.
• A test to assess if the saddle could leak due to over tightening of the bolts. Considering the design, it is expected to be unlikely that the saddle could be deformed sufficiently to cause a leak by over tightening the bolts.
• Tests to demonstrate the force required to twist the mechanical saddle around the pipe. Torsional loads may occur during installation (i.e. from the weight of connections) or through third party interference. The proposed gasket to be used with the Microstop system is applied to 180 degrees of the pipe surface, therefore must be tested for adequate performance in the event of torsional movement.

Initially 2 years were allowed to assess the suitability of the Microstop system to support partial replacement of network risers where pipe work is found to be in satisfactory condition. However, further tests were required to satisfy the technical and safety requirements, as well as provide evidence for the field trial approval process. A suite of tests were then devised and carried out. This resulted in the previous scope of the project being changed. The original end date (September 2015) was extended by a year, with an additional cost of £72,800 being added to the project budget.

Unfortunately, there has been further testing issues in the last year with regards to the clamp fitting and the gasket system. Leakage paths were identified on various seals which required design modifications and retesting to enable the pressure testing to be successfully completed. These changes have inevitably resulted in a further delay to the project while the supplier identified satisfactory alternatives and the new samples were manufactured.

As a result, we are requesting that the project duration is extended by a further 9 months (until June 2017). There is no additional cost involved in the most recent project change.

The changes are beneficial as the additional testing programme will determine whether the system meets the necessary standard to be used on the GB Gas Network and allow completion of the objectives and success criteria as planned with no change to the expected benefits.

Benefits

The success criteria for this project are to:

• A review of the manufacturer’s specification, and their suitability to the GB gas industry
• Completion of extensive field trials to test the equipment in a variety of different scenarios
• A report containing the findings of the field trial
• Improve speed of operation and reduction in customer interruption
• Resolve aesthetic issues with other live transfer techniques
• Maintain gas supplies whilst replacing below ground riser section
• Reduce the amount of materials required to carry out riser replacement.

If successful, Microstop will support partial replacement of network risers where pipework is found to be in satisfactory condition, further to risk assessment.