Hot tapping sounds like magic. A pipe stays full and under pressure the whole time, yet a hole gets drilled straight into it without a drop escaping. It is not magic, though. It is a set of carefully designed tools working together, each one doing a specific job.
We have already covered how hot tapping a pipe works step by step elsewhere on the site. This post is different. Rather than walking through the whole process again, we are going to open up the kit bag and look at the actual hot tapping equipment involved: the saddle, the valve, the machine and the cutter, and explain what each part does.
The kit, in one sentence
A hot tapping job needs four main pieces of equipment, all bolted or welded together in a line on the outside of the pipe. First comes a saddle, then a hot tap valve, then a tapping machine, and inside that machine sits the pilot drill and cutter that actually make the hole. Once all of it is fitted, the pipe can be drilled into without ever being switched off or drained.
The tapping saddle: the first thing fitted
The tapping saddle is the starting point for the whole job. It is a curved metal fitting shaped to match the outside of the pipe, and it is welded or mechanically clamped on so that it forms a solid, leak-tight base. Nothing gets drilled through the pipe until the saddle is properly fixed and tested.
Once the saddle is in place, it gives the rest of the equipment somewhere secure to attach to. Everything that follows, including the valve and the machine, is built on top of this one solid connection point.
The hot tap valve: the gatekeeper
Next comes the hot tap valve, bolted straight onto the saddle. Think of it as a gate that can be opened or closed on command. While the hole is being cut, the valve stays fully open so the tapping machine can reach the pipe. Once the cutting is finished, the valve is closed before anything is removed.
This is the part of the equipment that keeps the job safe. Closing the valve seals the new connection off from the tapping machine, so the cutter and the metal disc it has just cut out, known as the coupon, can be taken away without any loss of pressure or liquid from the live pipe underneath.
The tapping machine, pilot drill and cutter
The tapping machine sits on top of the valve and houses the tools that do the actual cutting. Inside it are two important parts working together.
The pilot drill goes first. It is a thin, sharp drill bit that pierces the pipe wall and holds everything steady, a bit like the small point in the middle of a compass that stops it sliding around while you draw a circle. With the pilot drill in place, the main cutter, a hollow tube with sharp teeth around the rim, follows behind it and cuts a clean, round hole through the pipe wall.
As the cutter breaks through, it does not just make a hole. It also removes a neat disc of pipe wall, the coupon mentioned earlier, and holds onto it so that no loose metal is left floating around inside the pipe. The whole cutting stage happens while the machine, valve and saddle stay sealed, so the fluid inside the pipe never escapes.
How the equipment keeps everything sealed
The reason none of this leaks comes down to the way each piece of equipment is designed to seal against the last one. The saddle seals against the pipe, the valve seals against the saddle, and the tapping machine seals against the valve. Every joint uses gaskets, seals or welds rated for the pressure and fluid involved, so the whole chain stays airtight or watertight from start to finish.
This layered approach is what makes under pressure drilling equipment different from an ordinary drill. A normal drill has nothing stopping the contents of a pipe from spraying out the moment it breaks through. Hot tapping equipment is built with sealing at every stage, so the fluid stays exactly where it should be the entire time. For a closer look at how this sealing works in practice, our guide to understanding under pressure drilling covers it in more depth.
Why the pipe wall thickness matters for the equipment
The equipment cannot just be bolted onto any pipe and used without a second thought. The thickness of the pipe wall has a direct effect on which saddle, valve and cutter size are suitable for the job. A wall that is too thin for the equipment being used could weaken under pressure, while equipment that is not matched properly to the pipe can struggle to cut a clean hole or seal correctly.
This is why engineers always check the pipe wall thickness before choosing equipment for a job, rather than after. You can read more about the specific figures involved in our guide to the minimum pipe wall thickness needed for hot tapping to go ahead safely.
Hot tapping equipment at a glance
| Equipment | What it does |
|---|---|
| Tapping saddle | Fixed onto the outside of the pipe first, giving a solid, sealed base for everything else |
| Hot tap valve | Opens to let the cutter through, then closes to seal the pipe off once the hole is cut |
| Tapping machine | Bolts onto the valve and houses the pilot drill and cutter that do the actual work |
| Pilot drill | Pierces the pipe wall first and keeps the cutter steady and centred |
| Cutter | Cuts a clean, round hole through the pipe wall and removes the coupon in one piece |
Equipment that is built and maintained to a standard
None of this equipment is something you could put together in a shed. Because it is classed as pressure equipment, it has to be designed, tested and maintained to recognised safety standards, and checked regularly by a competent person. The Health and Safety Executive sets out these requirements clearly in its guidance on the Pressure Systems Safety Regulations 2000, which explains why equipment like this needs a written scheme of examination before it is ever used on a live pipe.
This is also why the team using the equipment matters just as much as the equipment itself. If you are hiring in a specialist for a job, our guide on the certifications to look for in a hot tapping contractor is a useful next read.
Seeing the equipment in action
Reading about hot tapping equipment is one thing. Seeing what it can actually achieve on a real project is another. Our case studies show examples of this kit being used on live pipework across a range of sectors.
If you have a project that might need hot tapping and want to know more about the equipment and approach we would use, our hot tapping service page has the full details, or you can get in touch with our team directly, and we will be happy to talk it through.
