Fittings are the point where an industrial tank stops being a vessel and starts being part of a system. Get them right and the tank connects cleanly to pipework, valves, sensors, overflows and fire couplings. Get them wrong and you have a leak path, or a connection that fails the first time the ground moves.
Promax offers three types of fitting for our industrial tanks, each with its own advantages and disadvantages depending on your needs. Here is what each one is, what it suits, and where it runs out of road.
What a Tank Fitting Has to Do
A fitting has to do two things at once. It has to make a sealed connection between the tank wall and the pipework, and it has to keep making that connection under the conditions the site puts on it. Ground can shift. Pressure in the line can change. Pipework is often fixed to something rigid while the tank is not. The fitting sits between those two conditions, which is why the choice matters well beyond the joint itself. On an industrial tank the same wall may carry a large inlet, an overflow, a sensor and a fire service connection, and each of those has a different size, a different pressure and a different consequence if it fails.
Stub Spigot and Backing Ring
This is the most secure and robust type of fitting, which is why we call it the "Belt and Braces" of fittings. It consists of a stub spigot, a piece of PE pipe welded into the sidewall of the tank, and a metal backing ring attached to that spigot with bolts. The backing ring provides a strong and stable connection between the tank and the pipework, and allows for some flexibility and movement in case of ground shifts or pressure changes. That tolerance is the point of it. This type of fitting is ideal for large-diameter pipes and high-pressure applications, where you need a reliable and leak-proof connection. It is also the most expensive of the three, and it requires an expansion joint that absorbs shocks and vibrations and protects the tank warranty.
PE Pipe
This is a more cost-effective and simple type of fitting: a piece of raw PE pipe welded into the sidewall of the tank. It connects to the pipework with a compression shear band coupler, either a PlumbQwik or a Gibault, which clamps around the pipe and seals it. It suits overflows and small inlet pipes, where the pressure and flow are not too high, and it is easy to access and replace if needed. The trade-off is resilience. A PE pipe fitting is not as secure or resilient as a stub spigot and backing ring, and it may leak or fail if the pipe is too large or the ground moves too much. We recommend using it only for pipes up to 225 mm in diameter.
BSP Spigot Adaptor
The cheapest and simplest of the three: a threaded spigot adaptor welded into the sidewall of the tank. It can be male or female depending on the type of thread you need. It suits small fittings such as sensors, valves or intakes, where a threaded connection is what the component expects, and it is easy to install and remove if needed. The limits are worth knowing before you specify it. The size range runs from 32 mm to 110 mm, it may not be compatible with some types of pipework or components, and it is not very strong or flexible, so it may crack or leak under stress. Use it where the connection is small and the load is low, not as a substitute for a heavier fitting.
Matching the Fitting to the Pipe Size
Size narrows the field quickly, so it is a useful first pass. A BSP spigot adaptor covers 32 mm to 110 mm, which means anything outside that range rules it out immediately. A PE pipe fitting is recommended up to 225 mm in diameter, which covers most overflows and small inlets. Above that, or wherever the pressure is high, the stub spigot and backing ring is the fitting designed for the job. Working through the connections on the tank in size order sorts them fast: the small threaded ones, the mid-range welded ones, and the large or high-pressure ones that need the backing ring and its expansion joint.
How to Choose the Best Fitting for Your Project
Size is not the only factor. The type of fitting you need also depends on:
- The size and type of the pipework and components you are connecting to the tank
- The pressure and flow of the water or liquid in the tank and the pipework
- The location and environment of the tank and the pipework, such as the soil conditions, temperature and seismic activity
- The budget and specifications of your project
These factors pull against each other. The cheapest fitting is rarely the most tolerant of movement, and the most tolerant is rarely the cheapest. On a site where the ground moves, or where seismic activity is a design consideration, paying for a fitting that accommodates movement is usually the cheaper decision measured over the life of the tank.
Getting the Specification Right
To choose the best type of fitting for your project, we recommend you consult an expert, such as our team at Promax, who have extensive knowledge and experience in industrial tank fittings. We work with engineers, consultants and contractors to make sure your tank system meets the standards your project calls for, and we can provide drawings, plans and quotes for both the tank and the fittings, plus advice on the best options and practices. Do this at design stage rather than at installation. Fitting positions, sizes and types are cheap to change on a drawing and expensive to change on a welded tank. If your project needs something outside the standard range, our custom tank service covers that.
The Tanks Behind the Fittings
A fitting only works as well as the tank it is welded into. Promax industrial tanks are made from high-quality polyethylene, which is strong, durable, corrosion-resistant and UV-stabilised, and they are certified to AS/NZS 4766, which covers design, manufacture and testing. Polyethylene does not corrode, and all three fittings described above are welded into the sidewall, so the connection is continuous with the tank wall rather than a separate part clamped onto it. The range runs to a variety of sizes, shapes and colours. If you are specifying storage for an industrial site, our industrial sector page sets out the wider range.
For advice on the right fitting for a specific project, get in touch with our team.