STATS Group isolated a pressurised 254 mm LPG pipeline, using its BISEP™, for the first time in Australia.
The isolation was required to allow a launcher valve to be safely replaced while the system remained live and at an operating pressure of 41 bar at a natural gas plant in Victoria.
STATS utilised its hot tap installed ANSI Class 600 BISEP which provides a fail-safe, fully proven double block and bleed (DBB) isolation.
The BISEP was deployed through a welded split tee fitting, without the need for additional hot taps to bleed or vent.
The isolation is provided by a spherical dual seal plug, deployed from a pressure competent launcher through a slab valve and rotated towards the pressure threat.
The spherical head houses twin compression seals and provides a facility to bleed the seal (void) annulus providing a zero-energy zone between the fully proved seals.
The annulus bleed port is initially used to test each seal at 100 per cent of the isolated pressure; it is then used to constantly monitor the isolation during the intervention work.
The elastomeric seals are activated by a hydraulic cylinder inside the plug, which compresses the seals. The radial expansion then pushes the seals out against the pipe bore.
Venting the pressure downstream of the plug causes a piston effect on the plugging head, which acts to further energise the seals providing leak-tight isolation, even in corroded or pitted pipework.
The differential pressure loading is such that a minimal differential pressure across the plug will enhance the hydraulic actuation and maintain both seals even with no hydraulic pressure present.
This feature is called self-energisation and makes the isolation fail-safe with dual redundancy in activation, providing the specified minimum differential pressure is maintained.
After performing validation tests on the BISEP, technicians confirmed successful double block isolation and an isolation certificate was issued.Nitrogen was then flushed through the BISEP launcher to purge the system and create safe worksite conditions to allow removal of the launcher valve.
Once the new valve had been fitted, nitrogen was again used to perform a joint re-instatement leak test of the valve against the back of the set BISEP.
After a successful leak test of the reinstated valve and the pipeline pressure was equalised, the BISEP was then unset and recovered into its launcher.
The slab valve was then closed, allowing the BISEP launcher to be depressurised and removed.
The hot tap machine was then reinstalled to allow a completion plug to be deployed and set into the flange of the welded fitting.
With the completion plug set and tested, the hot tap machine and slab valve were removed from the pipeline and a blind flange was installed onto the welded fitting.
STATS supplied personnel and equipment, including split tee fittings, hot tapping machine, DBB slab valve, BISEP and completion plugs.
All hot tapping and line isolation work was carried out by STATS technicians.
Upon client request a system integration test was conducted at the facility prior to BISEP deployment onsite.
“This project marks a significant milestone for STATS. This is the first time that our BISEP has been deployed in Australia and we are encouraged by the level of interest shown in the region to adopt this game-changing technology,” said STATS Regional Sales Manager for South East Asia Gareth Campbell.
“The BISEP offers significant safety advantages over traditional line stop technology. The hydraulically activated dual seals provide leak-tight isolation of live, pressurised pipelines.
“By using the BISEP operators can make significant savings by performing maintenance or repair work without the need for a shutdown.
“The single-entry point of the BISEP reduces costs and operational timescales by providing a verified double block and bleed isolation through a single intervention point, without the need for additional hot tapped bleed ports.”
STATS Group has invested more than £3 million (US$3.86 million) in developing a range of hot tapping machines.
The SureTap™ propriety range comprises four models with cutting capacities ranging in size from 76.2 mm to 1,219.2 mm to provide safe and reliable hot tapping operations on a range of pipeline materials and mediums up to 153 bar (ANSI Class 900).
For more information visit the STATS Group website.
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