Pipelines are recommended to be inspected at regular intervals based on the expected corrosion mechanisms within the system. Due to the design of some systems, conventional ILI may not be considered possible. Alternative options, such as bi-directional ILI or crawler inspection can be used in this instance though these typically require additional engineering to overcome the operational complexities.
The client operates a crude oil pipeline which ties into a main export pipeline via a tee. There are no permanent pigging facilities, however a temporary launcher is available, and a subsea receiver could be installed to enable conventional ILI. Conventional ILI cannot therefore be carried out without modification to the system, hence the client wanted to assess the suitability of alternative pigging options.
Due to Jee’s previous successful projects with the operator and expertise within pigging, the client approached Jee to review suitability of alternative pigging options and perform subsequent pigging assurance activities for the chosen technology to minimise risk during the operation.
For the first phase of the project, Jee chaired a workshop with the client to review the available inspection options, focusing on Bi-Di and crawler, to determine the most suitable inspection technology for the system. As a result of the workshop, it was decided that a crawler tool was the optimum solution and would be utilised for the inspection.
Jee therefore assured the crawler tool design to ensure suitability with the pipeline geometry and expected operating conditions during the inspection. As a tethered crawler tool was to be utilised, pull-back trials were carried out by the vendor, and witnessed by Jee, to assess the maximum permissible pull-back force after each bend within the system to ensure the proposed limits are not exceeded if an issue occurred and the tool was unable to drive back itself during the inspection.
Jee then used these measured pull-back forces to derive pull-back limit curves to be used to aid decision gates beyond certain features, reducing the risk of the winch limit being exceeded, should it be required in the event of propulsion failure.
With Jee’s support, the client was able to successfully inspect the required section of the pipeline and recover the crawler tool without issue.
For more information, visit www.jee.co.uk/pigging
To contact our Head of Pigging, Sean Tucker, email sean.tucker@jee.co.uk, or call +44 (0)1732 371 371.
Jee Ltd
