A pair of 8” cooling water lines needed to be rerouted in order to facilitate furnace modifications. The reroute needed to be completed without a loss of the water supply to the furnace otherwise a costly shutdown would be required. Additional challenges were that the system operated at over 150 psi. The field fabricated pipe was oval. The oval pipe geometry made the insertion of either a pivoting head or a folding head linestop impossible. The flow rate was over 5 feet per second, so a freeze was also out of the question.
RJ Stacey working with engineers from our supplier had custom hot tap insertable bladders designed and manufactured that could perform an effective linestop at 150psi on the oval pipe and satisfy the safety requirements of all parties. The bladders were 8 layers thick alternating between Kevlar fabric of the same design as bulletproof vests, and high strength EPDM. The resulting design had a 2.0 safety factor on pressure and temperature, they were still bundled small enough to go into the pipeline through a hot tap and had an abrasion resistance that would prevent scale, etc. from puncturing them during service. We were also told they were bulletproof, which everyone got a grin from.
Once the method of isolation issue was solved the rest of the job was straight forward. First, we welded on fittings and placed the valves. Pairs upstream and downstream on both supply and return sides of the 8” pipe. Next, we hot tapped all 8 of the valves. Once the valves were all live the piping contractor ran the new rerouted pipeline and put it into service. Finally, we inserted the hot tap insertable bladders into the other taps isolating the original segment of pipe. Residual pressure was bled down and the segment between the bladders was cut and capped. At the end of the project, the bladders were indexed back out of the pipe, completion plugs were set and blind flanges put on the fittings used for the bladder insertion.
The entire project was completed with zero interruption of cooling water supply to the furnace. The resulting reroute allowed the plant to install efficiency upgrades without having to take a costly forced outage.