STATS has successfully completed a challenging hot tap and line stop isolation on a 33bar operating system, allowing for the safe replacement of two 6" Slam Shut valves while maintaining uninterrupted gas supply at Beeston Above Ground Installation (AGI) near Nottingham.
As a result, valve replacement was required. The client selected STATS' hot tap installed BISEP technology to provide leak-tight double block and bleed isolation, ensuring maximum safety. The BISEP features an integrated bypass which allows production to be maintained even after the isolation is installed and avoids disruption to the gas supply.
The challenge presented in this project was the configuration of the inlet header, where the valves needing replacement also served as the stream inlet isolation valves. The next upstream valve would have isolated both streams which was not a viable option due to the site being sole-fed.
To overcome this, a pre-existing flange was used to install a plug valve, enabling the introduction of a secondary supply of filtered and heated gas to the streams. Tie-ins were required for each stream and due to limited space on the spools, the decision was made to weld a split tee fitting downstream of each failed slam shut valve. These fittings provided a hot tap point on each stream, enabling the installation of a dual seal BISEP at each valve location.
The bypass pipework was fabricated to link the BISEP's together and connect to the newly installed inlet valve, enabling 100% flow of filtered and heated gas to each stream. The outlet valves were then reconfigured to act as slam shuts (lineguards). This approach ensured full resilience of this critical Pressure Reduction Station during the isolation of the inlet header and the replacement of the slam shuts.