On a basic level, hot tapping is an installation procedure that connects pipelines whilst they remain in service. It is implemented when repairs to pipelines are required, due to damage or corrosion, or if the operator has decides to add branches to modify their current network.
Complex and risky procedure
The nature of the procedure, which includes undertaking work whilst a pipeline is still live, means that there are strict rules around when and how hot tapping can be carried out. Hot tapping should not be considered, for example, as a routine procedure – only when there is no other practical alternative. To put this into context further, the API (American Petroleum Institute) have launched several safe hot tapping guides assisting engineers in their hot tapping practices.
Their reports even include internal review processes to force that hot tapping should always be a last resort. A seven step safety checklist for engineers can be read on our blog here.
What is required?
Hot taps have the ability to tie into a pressurised system by drilling or cutting into the pipeline. To complete the process, engineers require a tapping machine along with the cutter and housing, tap fittings such as reinforced branch or split tees, and an isolation valve such as a gate or ball valve.
Sometimes mechanical fittings may be used for mounting taps on pipelines, but these must meet a strict criteria that are designed to fit the dimensions and operating pressure of the pipeline. They must also meet design, fabrication, welding and NDT standards to ensure maximum safety and efficiency.
How does it work?
The hot tapping procedure is one continuous process which cuts through the pipe wall and ends in a section of the pipe detaching in the shape that hot tap has made. This is known in the industry as the coupon. The coupon is commonly retained by u-wires which are attached to the tapping machines themselves. This retention strategy ensures for a clean procedure, however it is not 100% guaranteed that the coupon can be saved in every procedure.
Once the cutter has completed the coupon, the tapping machine is stopped, cutter retracted into the adapter and the valve is then closed again. The adapter, which requires the pressure to be bled from the system, can then be removed with the machine from the line so that the new service/further maintenance can be resumed.
What machines should you use?
With industry-leading and patented hot tapping features such as a close cutting helical gear drive, rotary pressure seals and four fixed feeds for differing pipeline conditions – it is easy to see why Mirage are the preferred suppliers to global operators for their portable performance machines.
Mirage have split their tapping range into two different ranges, for those who are required to complete a low pressure or high pressure application. Here’s a look at just two of the machines on offer from Mirage:
Low pressure machines
The MHT range with a working pressure capacity of 1480 p.s.i. and a cutting range from Ø 3” to 60” can be used to make connections and shutdown pipelines across a broad range of applications, either on the surface or subsea. It has also been designed for ease of use with 1 speed fixed feed gearbox, a measuring rod, and either a pneumatic or hydraulic front of machine mounted helical geared drive.
Find out more about the low pressure hot tapping range, and all the technical specifications by reading our Buyer’s Guide here.
High pressure machines
The CHT range, with a working pressure capacity maximum of 5,000 p.s.i, can hot tap from Ø3” to 60”-and is specifically designed for all pipeline intervention and wellhead maintenance. For ultimate accuracy, the range features a drive as close to the cut as possible, variable auto feed to match differing cutting conditions and a geared mechanical depth display.
More technical specifications, and images of the machines insitu, can be seen in our Hot Tapping Machine Buyer’s guide available to download here.