Hot tapping can be a risky process without taking into consideration location, the environment or contents of the pipeline.
A thorough set-up and smooth operation is required to achieve a safe process and by following these simple guides from Wermac, you will learn the basics of the process and understand the dangers and liabilities to look out for, whether you are preparing to buy or rent a portable tapping machine.
Hot tap set-up
For a hot tap, there are three components necessary to safely drill into a pipe; the fitting, the Valve, and the hot tap machine. The fitting is attached to the pipe, usually welded.
In many cases, the fitting is a welded flange too, or a split tee with a flanged outlet. Onto this fitting, a valve is attached, and the hot tap machine is attached to the valve.
For hot taps, new Stud Bolts, gaskets and a new valve should be used when the components become part of the permanent facilities and equipment. The fitting/valve combination, is attached to the pipe, and is normally pressure tested.
The pressure test is paramount, so as to make sure that there are no structural problems with the fitting, leaks or welding issues.
The hot tap cutter, is a special type of hole saw, with a pilot bit in the middle, mounted inside of a hot tap adapter housing. The hot tap cutter is attached to a holder with the pilot bit, and is attached to the hot tap machine, so that it fits into the inside of the tapping adapter.
The tapping adapter will contain the pressure of the pipe system, while the pipe is being cut, it houses the cutter, and cutter holder, and bolts to the valve.
Hot tap operation
The hot tap is made in one continuous process, the machine is started, and the cut continues, until the cutter passes through the pipe wall, resulting in the removal of a section of pipe, known as the "coupon".
The coupon is normally retained on one or more u-wires, which are attached to the pilot bit. Once the cutter has cut through the pipe, the hot tap machine is stopped, the cutter is retracted into the hot tap adapter, and the valve is closed. Pressure is bled off from the inside of the tapping adapter, so that the hot tap machine can be removed from the line. The machine is removed from the line, and the new service is established.
Line stopping procedures
Line stopping is a similar procedure to hot tapping except these machines are intended to stop the flow of the pipe. This is usually used to replace valves, fitting and other equipment in the pipeline.
Once the hot tap has been completed, the valve is closed, then the line stop actuator is installed on the pipe. This is then used to insert a plugging head into the pipe, the most common type being a pivot head mechanism. Once the job is done, pressure is equalized, and the line stop head is removed.
The Line Stop Fitting has a specially modified flange, which includes a special plug, that allows for removal of the valve.
Warnings from the industry
As hot tapping has many risks, it is not considered a 'routine procedure' in the industry, therefore only used when there is no practical alternative.
This means all hot taps now have to be installed by a trained and experienced team noting that all special health and metallurgical concerns are dealt with and approved by senior member of the company.
Although these quick tips will give guidance on the process, its important to involve skilled members of the team and the best-suited machinery to carry out the work for your pipeline maintenance. Failure to do so may incur heavy implications such as health deterioration and company fines for any mis-management during the process.