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Various industries depend on natural gas for their energy need, while residential areas rely on gas for heating. However, gas distribution networks need maintenance, and increasing consumption levels require additional infrastructure.
Industries and residential areas need a steady supply of gas. Maintaining and building gas lines can be challenging without cutting the gas supply to the users, but it’s not impossible. There are methods of installing new gas lines without stopping distribution. In this article, we will take an in-depth look at those methods.
Hot Tap Applications
In short, the hot tap is the application of taking a new branch from a live steel pipe gas line. A live gas line is a part of the distribution network with active gas flow.
Hot tap application needs specialized tools for safety reasons. Sparkless grinders and special drill ends are used to prevent combustion. To see our collection of sparkless tools click here.
At first, the underground gas line needs to be exposed by careful excavation. Excavators can be used to dig the top layer of dirt, but as the excavator gets closer to the gas line, it is better to use hand tools to prevent damage.
Once the gas line is exposed, a licensed technician uses a sparkless grinder to sand off the protective layer of polyethylene from the steel pipe. The technician grinds off the protective layer to expose bare steel for drilling and welding.
After the exposure of the bare steel surface, the technician places the sparkless drill on top of the gas line, making sure that the drill is braced and leveled.
Before drilling, the technicians performing the application wear full-body fire protection gear, and the work area is covered with fire-stopping blankets. Fire extinguishers or preferably a fire truck with a team of firefighters must be ready around the work area. Any unauthorized personnel must be cleared from the area while the technicians working outside of the trench needs to stay at least 5 meters away from the gas line. In a steel gas line, the operating pressure is around 19 bars. That means, in case of ignition, the flames will shoot up into the air. Anyone who stands up around the trench is at risk. This is why standing away from the trench is extremely important.
Once all the precautions are in place, the drilling process begins. The drilling is performed under low revs and with an adequate amount of lubricants. The drill has a valve attached to it, when the drill goes inside the pipeline, the welding point of the valve is in full contact with the steel surface. After the drilling is complete, a welder welds the valve onto the pipe. The surface temperature of the pipe must be kept in check to prevent combustion. The welder uses coolants in between welding sessions to prevent overheating.
After the welding of the valve, the drilling bit is taken off and the valve gets shut immediately. This allows for the new branch to be welded at the sealed end of the valve. After the branch welding is completed an NDT (nondestructive testing) specialist inspects the quality of the welding with x-ray photography. After the NDT inspection, if the new branch is installed correctly the pipe gets isolated with a protective layer of polyethylene sheet. If the welding point has cracks that could cause leaks, the welder does repair work. The welding of gas lines cannot be repaired more than once therefore if the repair work doesn’t get approved by the NDT inspector, the sealed-off section of the valve gets cut and a new branch welding process starts.
Post Hot Tap Applications
When the hot tap work is complete, the construction teams take over by padding the gas line with thin sand, compressing the protective layer, and then closing off the trench. It’s usually a good idea to get GPS readings to record the exact coordinates of the hot tap point for future periodic check-ups and inspections.
Advantages and Disadvantages of Hot Tap
Hot taps biggest advantage is allowing the installation of new lines without cutting off the gas supply. The process is expensive and risky however, the benefit of continuous gas flow during new installations makes the hot tap a useful tool for engineers to use.
Fire and explosion hazards are the biggest risks of the process. However, the technicians who are licensed to practice the technique go under intensive training. Correct use of safety precautions is crucial to ensure safe applications.
Final Words
Industries and residencies rely on a continuous flow of energy. This could prove to be difficult for engineers to plan maintenance and new installations. Methods which allow engineers to work on energy lines without cutting off the energy supply are extremely important. The hot tap is one of those useful tools which allows the installment of new branches on live gas lines. However, due to the risks of the process it needs to be performed by trained professionals under extreme safety precautions.
