If a hot tapping machine is on your procurement list and you’d like a reminder of the key considerations, this article provides guidance to help you choose the right machine.
What are the minimum and maximum pipe diameters you want to tap into on your projects? Many sizes of hot tapping machine are available, such as the HTM150XL which is manually but has the option of a powered drive. This product is used on pipe diameters from as little as ½” up to 6” and incorporating a manual drive and feed. At the other end of the spectrum are machines capable of making cuts with diameters as large as 60”. If you are on-site services company looking to get involved in a wide range of projects, you may want to look at the wider picture and choose more than one machine to extend your capabilities.
This is another fundamental consideration. Hot tapping machines are available to handle the many different pressures used across the oil and gas, petrochemicals, power generation and utilities industries. There are many machines for “low to medium” pressures up to 1480 psi and some specialist machines such as the LPHT3-12 for low pressures up to 285psi. For high pressure pipelines, you can choose various machines from the CHT and VHT range capable of withstanding up to 5000 psi.
The spindle travel, often referred to as ‘boring bar travel’ or ‘stroke’, generally increases in relation to the cutter diameter. Smaller machines in the Mirage range start at around 30” travel, with the largest being as much as 180”. When choosing your machine you should check that the spindle has enough travel (stroke) to complete the cut.
Many machines can operate continuously at temperatures up to 177°C. For intermittent use the temperature range is wider, for example from -9°C up to 371°C.
So, you’ve found a machine that will fit to the required flange diameter, but how much space do you need around the job? If you are positioning the machine in the horizontal orientation, you’ll need to be sure there’s plenty of space for any supporting equipment. If, however, the machine is to be used vertically do you need a machine with an integral ladder and platform, or will you build a scaffolding platform around the job?
Hydraulic Power Pack
In most situations, if you need a hot tapping machine you’ll need access to a hydraulic power unit. These are normally diesel driven and are available in a range of outputs. You will need to know the flow rate needed for the specific hot tapping machine you specify for the job.
Pneumatic Feed Option
Machines are also available with pneumatic motors for both the feed and drive operations. The CHT and VHT machines can be supplied up to the 1675 spec and MHT machines up to 12-36 spec.
Valve Hot Tapping
If you need to carry out a hot tapping operation into a seized valve, a purpose-built valve hot tapping machine is recommended. The VHT range incorporate a long spindle travel and (available from Mirage from 38” up to 160”). The spindle is also a smaller diameter (a (1” to 3”) to allow for clearance inside Christmas tree valve assemblies.
If you are working on a subsea project, there are various machines available which are used with an ROV. One example is the CHT1000 SSW Subsea Hot Tapping Machine.
What else do you need?
As well as the usual spare parts, the range of hot tapping accessories to consider include; flange adaptors, cutters, pilot drills and hole saws. If you don’t already have one, chances are you will need a line stop actuator to temporarily isolate a section of the pipeline.
Gears and feed type
Consider whether you want a machine with a manual or automatic feed. CHT and VHT machines have an automatic variable feed rate which can be adjusted to suit the individual cut size and pipe material between 0.001” and 0.020” per revolution. As standard, these machines can also be manually fed by the operator. MHT machines have a fixed feed rate of 0.003” per rev. On all machines the cutter speed can also be controlled to suit the cutter diameter and pipe material.
What happens if a problem arises? Will you get the necessary support from the machine manufacturer? Does the manufacturer have dedicated representatives covering your region? And how will you get hold of spares and accessories?
What are the lead times from receipt of order? Most hot tapping machines are normally not custom built and are held in the stock, often at various locations throughout the world.
Find out more by downloading the Hot Tapping Machine Buyer’s Guide, or if you prefer to discuss your options please click here to get in touch.