Introduction

In January 2009 the technical department of iNPIPE PRODUCTS™ was approached by National Grid regarding an urgent problem that had developed at their Partington LNG storage plant, Manchester.

 

Client Requirements

Ice covered valve requiring replacement

 

A class 150 control valve, situated on a 12” Sch 10 stainless steel insulated flow line to one of their main storage tanks, had developed a leak and required replacement in a live situation.

iNPIPE PRODUCTS™ was requested to review the problem and revert with suggested solutions based upon their extensive experience and proven isolation technologies and products.
The request from National Grid included a stipulation that safety was of paramount performance given the fact that the LNG storage tank, which was 42m high and 82m in diameter, with a capacity of over 221,892 cubic metres of LNG maintained at -161˚ Celsius, hence the formation of ice one the leaking valve.

iNPIPE PRODUCTS™ has supplied similar technical isolation solutions to a range of worldwide operating companies in the past, including BJ Services (Canada) and the Oil and Pipelines Agency which manages the UK Government Pipelines and Storage system on behalf of the Ministry of Defence.

 

iNPIPE PRODUCTS™ Solution

Valve location in relation to the LNG storage tank

 

Following an internal review of the information provided by the client and a site survey being conducted by iNPIPE PRODUCTS™ the technical solution was provided to National Grid. The concept approved by the client consisted of an MP pipe plug, incorporated into a purposely manufactured stuffing box, which would be connected to the faulty valve flange. The isolation tool would then be inserted through the valve to a pre-determined position, beyond the valve, and then energised to provide isolation of the line. This isolation within the flow pipe will then allow for the removal of the old, leaking valve and replacement with a new one, following any necessary repair to the pipe flange face. The proposed solution was designed, manufactured and underwent full factory approval testing (FAT) at the purpose-built company production facilities in North Yorkshire within 8 weeks. The conceptual design was fully tested, with all testing being Client witnessed, before installation on site by the iNPIPE PRODUCTS™ team.

 

Project Execution

Following the necessary site preparations, including the erection of scaffolding and sheeting to provide a safe and weather tight working environment, the valve change out took place under the control and project management of iNPIPE PRODUCTS™ personnel together with ancillary sub-contracting companies.

iNPIPE PRODUCTS™ plugging system innovation. Granted Patent number GB2470997

Note the flange mounted stuffing box

 

The actual valve change out began on 16th June 2009 when the ‘plugging system’, including stuffing box, isolation tool and ancillary connections, was connected to the open faced flange of the existing faulty valve. As a precautionary measure and to ensure full control whilst the work was on-going the gas pressure and pipeline temperature was monitored constantly. Heaters were installed on to the pipeline to ensure that the temperature of the pipeline was maintained at ambient temperature. Once National Grid engineers were satisfied that the gas pressure and pipeline temperature were stable and under control then iNPIPE PRODUCTS™ technicians were able to open the valve and insert the isolation plug through the valve to the pre-determined position located beyond the valve and previously agreed with the client. Following further temperature and gas checks the Posi-seal℗ isolation sealing tyres were inflated and the seal made. An inner cavity pressure was then created, using nitrogen gas to provide a further check, and to ensure that the seal, using the MP isolation plug, had been effectively formed.

 

 End view of iNPIPE PRODUCTS™ plugging system
Granted Patent number GB2470997
Note the stuffing box in foreground with the valve behind

 

Following the successful installation of the plugging system and creation of the safe working barrier, the stuffing box was removed with the isolation plug remaining within the pipeline and providing the isolation within the pipe.

National Grid engineers and their nominated contractors were then able to remove the leaking valve and allow iNPIPE PRODUCTS™ and their contractors to re-machine the gasket face of the pipe flange before National Grid contractors fitted the new valve on to the newly machined flange face.

 

End view of the isolation plug within the pipe

Note: the quick release connections on the isolation plug used for inflation of the Posi-seal℗ polyurethane inflatable tyres.

Individual Posi-seal℗ tyres are individually inflated and deflated to ensure additional safety by design.
Once the new valve had been fitted to the pipe flange the stuffing box was reconnected to the isolation plug and the new valve. With the re-introduction of the gas pressurized to 1.7 bar g the new gasket, valve and flange modification assembly underwent a low pressure test accordingly. Before the inner cavity was depressurised stringent safety checks were carried out before deflating the Posi-seal℗ tyres. A temporary problem was identified with the furthermost tyre which had frozen due to the exceptionally low temperatures experienced during the pipeline isolation. In order to resolve this, additional induction heaters were positioned around the pipe to thaw the frozen tyre prior to deflation. The MP isolation plug was then successfully retracted through the newly installed valve and back into the stuffing box which was then disconnected. Finally the National Grid contractors fitted a blind flange to the valve flange to conduct the final proving test.

 

Project Timescale

Despite slight unforeseen problems, such as one of the Posi-seals℗ becoming frozen, the work scope was successfully completed on time, to budget and to the complete satisfaction of the Client, National Grid.

 

Client Satisfaction

Following successful completion of the project the Client Operations Engineer for National Grid, Mr Ian Briggs, confirmed their complete satisfaction “the operation was a great success, with the whole team having full confidence in iNPIPE PRODUCTS™ equipment.”

 

iNPIPE PRODUCTS™ is an internationally recognised leader in the design and manufacture of pipeline pigging products, including foam pigs, cup pigs, bi-directional cleaning / gauging pigs, pig handling equipment, pig signalers, engineered solutions for pipeline isolation and joint testing, launching & receiving systems as well as bespoke pigging solutions based on specific client project requirements.