Online pipework replacement cuts shutdown costs

Edited by the Engineeringtalk editorial team Jan 6, 2005

Innovative engineering and pipeline intervention expertise enabled Furmanite to avoid an expensive shutdown for Huntsman European Petrochemicals at the North Tees site on Teesside.

Innovative engineering and pipeline intervention expertise enabled Furmanite to avoid an expensive shutdown for Huntsman European Petrochemicals at the North Tees site on Teesside, representing massive savings for the chemical giant.

The achievement involved providing an online solution that enabled Huntsman to replace pipework and associated valves on top of a 5000t ethylene vessel while the vessel remained full.

The Furmanite solution successfully avoided the need to offload the ethylene into storage vessels, or run it down and cease production while the necessary work was carried out, either of which would have been at significant cost.

The pipework on top of the 30m-high 60m-diameter tank (which contained ethylene at some -100C), consisted of a "candelabra" manifold a single nozzle at the top of the tank, branching into three outlets, each with a safety valve to vent away ethylene if pressurised.

The problem had arisen when it was discovered that the weight of this manifold (with its design placing the full load on a single nozzle) was over-stressing the top of the carbon steel tank, and could have led to problems of fatigue, and ultimately fracturing.

Huntsman needed to replace the manifold with a new, lighter-design unit, which meant having to remove and replace the safety valves, and test and recertify them for insurance purposes.

Furmanite was called in for its pipeline intervention expertise and innovative engineering design skills (including the design of bespoke machines) to solve the problem by enabling this work to be undertaken with minimal disruption maximising asset uptime.

Furmanite's novel approach to the problem involved the use of an inflatable double-plug to isolate the inlet line while the necessary work was carried out.

The first stage was to fit a saddle to the manifold, to hot tap into the pipework and gain entry into the vessel.

This achieved, the hot tapping machine was then replaced with a purpose-designed and built machine which released the two inflatable plugs (still deflated) on a multi-service semi-rigid umbilical into the pipework.

Once in place, the plugs were inflated, via the umbilical, with nitrogen, and the interspace between the two used to monitor the pressure also via the umbilical.

The flange was then broken with the nitrogen-filled stoppers in position, and the manifold and associated valves removed and replaced with the new lighter design.

Finally, with the new manifold and valves in place, the plugs were deflated and removed through a withdrawal assembly, in a highly controlled process.

"This is typical of our ability to understand the customer's requirement and engineer a solution that involves no or minimal disruption to operation, helping to avoid considerable expense", Furmanite Business Manager Martin Wilson pointed out.

"Extensive trials were undertaken in our Kendal workshops to ensure that the process would work as planned, during which we replicated the pipework assembly and site conditions, and tested the inflating of the plugs, disconnecting of the umbilical, and monitoring of the interspace".

"The trials were witnessed by Huntsman too".

Commenting on the project, Senior Mechanical Engineer Norman Stewart of Huntsman European Petrochemicals said: "The ability to approach the problem with an open mind and engineer a solution that avoided having to empty the vessel was a valuable benefit in terms of minimising time, cost and disruption".

"With there being major consequences if things went wrong on the day then the prior testing of the equipment and job method at the Furmanite workshop was absolutely critical in demonstrating that this was a safe and high integrity operation".

"This is now a proven method and will be considered for other similar applications".

Huntsman European Petrochemicals' North Tees site is home to its Aromatics business, with facilities including a major aromatics manufacturing complex and ethylene liquefaction facilities.