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MHT machines and the hot tapping process

MHT12-42-hot-tapping-machine-build

The MHT range of hot tapping machines is a tried and tested series of products used for medium pressure pipeline projects. In this article we give you an insight into the products, their features and benefits, along with applications and benefits. But first let’s cover the fundamentals of hot tapping.

A pipeline shutdown, whether it’s for oil & gas, petrochemicals, water or power generation, has the potential to cause major disruption to businesses large and small, and also to consumers at home. Essential work may need to be carried out when a new junction or valve is to be added, or when a section of pipe needs to be replaced.

So how can a pipeline be maintained without the need to shut off the supply?

The answer is to carry out a hot tapping operation. This allows a temporary bypass to be created to divert the pipeline product, which then allows the necessary work to take place.

The process is done using hot tapping and line stopping equipment. The hot tapping machine makes the cut into the pipeline and the line stopping machine ‘plugs’ the pipeline - stopping the flow to the area requiring maintenance. 

To illustrate, the chart below shows the maximum pressures allowed for different classes of carbon steel flanges. As you might expect, as the temperature increases the maximum permitted pressure is reduced.

What are the risks?

If anything goes wrong, the consequences for people in the vicinity, to property and to the environment can be significant. The liquid or gas running through the pipeline may be incredibly toxic, under high pressure and at a very high temperature.

So whoever is carrying out the work needs complete confidence that all equipment they use is robust enough to enable the job to be completed safely. This doesn’t just apply to the hot tapping and line stopping machines, but also applies to any accessories used, such as flange adapters, spools and cutters. When a large machine is used in the vertical orientation, a machine with an integral ladder and platform can be specified.

Industries using hot tapping equipment

Hot tapping is carried out in almost any industry that has product flowing under any pressure within a pipeline. Industries and applications include oil and gas flow lines, national oil companies who own plant and pipelines, petrochemical plants, steam and water lines in power generation. Oil and gas, petrochemicals, power generation and utilities.

Pressures

The graphic below shows hot tapping types arranged by pressure.

hot-tapping-pressure-comparison

The pressures involved in a hot tapping project can be low pressure: less than 500 psi (pounds per square inch), medium pressure (500 to 1480 psi) or high pressure (above 1480 psi).
Just to put the above figures into perspective, a properly inflated car tyre will usually be around 30 psi. So you can see why manufacturers carry out important and demanding pressure tests before products are released for sale or hire.

MHT Hot Tapping Machines

mht12-42-hot-tapping-machine

Above: MHT12-42 Hot Tapping Machine

The letter ‘M’ in each machine’s MHT prefix identifies the product as suitable for medium pressures. Medium is classed as between 500 psi and 1480 psi. This means that MHT machines are ideal for oil & natural gas pipelines - used for transmission and pipe runs at process plants. ‘Medium pressure’ covers approximately 80% of all hot tapping activity, and is up to Class 600#, 1480 psi.

Features and Benefits

MHT machines include a hydraulic drive motor, but the smallest (the MHT3-12) can be specified with a pneumatic motor.

The rotating bar within the machine (sometimes known as the boring bar) incorporates industry standard connections, making it compatible with standard flange adapters, pilot drills and cutters.

Different hot tapping machine sizes are available, with the smallest, the MHT3-12 capable of tapping hole diameters as small as 3”, and the largest, (the MHT24-60) creating holes up 60” diameter.

The travel of the bar varies and as you would expect, is greater in the larger machines.

Here's a round-up of MHT hot tapping machine features

  • Drive is situated close to the cutter
  • Helical geared drive
  • A range of machines covering diameters from 3 to 60”
  • Boring bar (stroke) from 42” to 180”
  • 1 speed feed gearbox
  • Cutter holders included
  • Industry standard connection flanges
  • Interchangeable seal cartridge
  • Fast traverse available on MHT8-24 and larger.

hot-tapping-machine-comparison-mht

Considerations when selecting a hot tapping machine

Understanding your requirements before you reach out to a hot tapping machine manufacturer will set you well on your way to making the right decision. Below we’ve listed some key considerations but if you prefer to talk through your requirements we welcome your enquiry by using the form on this contact page. 

  • What pressure?
  • What temperature?
  • What hole size required?
  • What pipe material?
  • Connection diameter required?
  • What is the product within the pipe?
  • Orientation of the machine – horizontal, vertical, upside down?
  •  Is access difficult?
  •  Is a ladder unit required?
  • Power source?
  • Accessories/flange adaptors, spools required

Download The Hot Tapping and Line Stopping Buyers Guide

Visit our website to download a buyer’s guide for your chosen machine type or if you would like to speak to our technical team about our products you can get in touch below

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