Mumbai
2019
At HPCL’s Mahul refinery, a 4-inch gas exhaust line carrying hazardous and toxic exhaust gases was experiencing recurring leakage around a welded section. Continuous vibration and thermal expansion had contributed to cracking and micro-leakage, making conventional welded repairs a recurring maintenance challenge.
Cenergy Offshore provided a safer alternative using PYPLOK® cold-swaging technology. The damaged pipe section was replaced with a mechanically swaged connection, eliminating the need for welding, flames or sparks while significantly reducing the repair window. The completed connection was verified leak-free, restoring the line with improved reliability and reduced operational risk.
The 4-inch gas exhaust line operates in a demanding refinery environment, exposed to thermal expansion and continuous vibration. The line carries hazardous and toxic exhaust gases, including unburnt hydrocarbons and carbon monoxide, making even small leaks a serious safety concern.
Previous repairs using conventional welding had experienced recurring problems, including:
Heat-affected zones and repeated thermal loading contributed to cracking and micro-leakage around welded joints.
Continuous mechanical vibration from upstream equipment created additional fatigue stresses around the welded sections.
Repairing the line through conventional welding required extensive isolation, gas-freeing procedures and strict hot-work controls.
Limited working space around the pipe rack made it difficult to consistently achieve high-quality full-penetration welds.
The challenge was therefore not simply to replace a damaged pipe section, but to find a repair method that could provide a reliable, leak-free connection without introducing another welded joint.
To overcome the limitations of conventional welding, the affected pipe section was reconstructed using a Pyplok® non-welded piping system.
The system uses a specially designed mechanical fitting and a portable hydraulic tool to create a permanent connection through controlled cold swaging. The process requires no welding, flames, sparks or threaded connections.
This made it particularly suitable for a critical gas service where hot-work restrictions and leakage prevention were major considerations.
1. Pipe Preparation
The compromised welded section was removed using cold-cutting equipment. The pipe ends were deburred and prepared to provide a suitable surface for the mechanical seals.
2. Fitting Installation
The Pyplok® fitting was positioned over the prepared pipe ends and checked using the specified insertion-depth markings.
3. Hydraulic Cold Swaging
A portable hydraulic tool was positioned around the fitting and used to apply controlled radial force, permanently compressing the fitting onto the pipe.
4. Joint Verification
A Go/No-Go gauge was used immediately after swaging to verify that the connection had achieved the required compression profile.
The repair was carried out through a controlled four-phase installation process.
The damaged 4-inch welded section was identified and removed using cold-cutting pipe cutters. The pipe ends were then deburred and the external surfaces prepared for the sealing system.
Insertion-depth markings were applied to ensure that the Pyplok® fitting was correctly positioned over both pipe ends before compression.
The hydraulic swaging tool was positioned over the fitting and actuated to create the permanent mechanical connection. The swaging operation itself was completed in less than one minute.
A physical Go/No-Go ring gauge was passed over the completed fitting to verify the final swaged profile and confirm that the connection had been properly compressed.
The project demonstrated how non-welded mechanical joining technology can provide a practical alternative to conventional welding for critical refinery utility piping.
By replacing repeatedly failing welded connections with precision-engineered Pyplok® fittings, the repair addressed the immediate leakage problem while also reducing the safety and operational challenges associated with hot-work repairs.
The successful intervention improved joint reliability, workforce safety and equipment availability, providing HPCL with an alternative approach for future high-risk gas exhaust and vent-line modifications.
When conventional welding is restricted or repeatedly fails in critical piping applications, non-welded mechanical joining can provide a faster and safer route to restoration.
At HPCL Mahul, the application of Pyplok® cold-swaging technology transformed the repair approach—from repeatedly repairing a vulnerable welded joint to creating a permanent mechanical connection designed for the operating environment.
The result was a leak-free repair with reduced downtime and without the need for hot-work welding.
4" Schedule 40 carbon steel gas exhaust line
Pyplok® cold-swaging technology
100% leak-free seal verified after installation
More than 65% reduction in the repair window
Cold installation without welding, flames or sparks
Completed without safety incidents
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