Modern jointing technology for Polybutene-1 piping systems, whether the jointing is pre-fabricated in the workshop, or carried out on the building site, provides easier, safer and more cost-effective installation.
There are four possibilities for joining pipes made from Polybutene-1 with fittings. These are compression, socket fusion, and electrofusion fittings, and push-fit plumbing systems.
Mechanical compression fittings are designed with plastic characteristics in mind. By separating the sealing and clamping areas of the fitting, a tension-free, durable and leak-proof connection between pipe and fitting can be achieved without the use of an elastomeric seal. Due to the creep behaviour as well as the flexural strength and heat resistance of Polybutene-1, the connection can be subjected to temperature and pressure stress immediately after installation is completed.
The socket fusion method for connecting pipes and fittings is suitable only for off-site pre-fabrication, in a workshop environment, of sub-assemblies such as basement manifolds and riser pipe systems. To achieve consistently acceptable welds, it is important that the temperatures of welding and the procedures for bringing the pipe and fitting components together to produce the weld are precisely controlled. This can only be achieved when the required equipment is operated under workshop conditions. The light weight of Polybutene-1 means that pre-fabricated sub-assemblies are easily transported to the site, and installed quickly and efficiently.
Off-site pre-fabrication can be an added advantage on busy building sites where efficient scheduling of the various sequences of construction is key to meeting project deadlines.
The butt fusion method for connecting pipes and fittings is mainly applied for larger pipe sizes. Butt fusion fittings are available up to OD 225 mm. To achieve consistently acceptable welds, it is important that the temperatures of welding and the procedures for bringing the pipe and fitting components together to produce the weld are precisely controlled, in line with the instructions of the pipe system manufacturers.
Electrofusion fittings have a moulded-in wire heating coil and plug connector. The coil lies just below the surface of the area to be welded to the pipe. Once the pipe is in position, an electrically operated fusion device is connected to the fitting via the plug. This fusion device automatically measures the resistance in the heating coil to determine the type and dimension of the fitting. An appropriate current is then passed through the heating coil for a precise time to provide optimum welding temperature conditions. When the weld is complete, the device produces a signal which indicates the pipe and fitting can then be disconnected.
This system is extremely reliable and produces consistently good high performance welds. The fusion device is small enough to operate on site in confined spaces - all that is required is a source of electricity. For larger pipe sizes, electrofusion is often used to produce pre-fabricated assemblies in a workshop environment.
Push Fit Plumbing Systems
Push fit plumbing systems are quick to install, without the need for tools, glues or heat. They may be used on plastics pipe or copper tube, provided the manufacturers instructions are followed.
All push fit fittings comprise of four basic elements:
1. Fitting body, in which all the components are housed, together
with a cap (which may or may not be removable) to hold the
components in the fitting
2. A sealing mechanism, usually either an 'O' ring or ring seal
3. An integral gripping mechanism which permanently grips the
pipe firmly in position.
4. A support sleeve which fits into the end of the pipe to prevent
deformation when the pipe is inserted into the fitting.
Although push fit fittings are very simple to use, there are certain steps which must be taken to ensure that an effective joint is made:
1. Pipes carry depth insertion marks at intervals along the pipe.
The pipe should be cut square at a depth insertion mark, using
a purpose-designed cutter. The end should be free of swarf.
2. The support sleeve should be inserted into the pipe end
3. The pipe should be pushed firmly into the fitting until the next
depth insertion mark reaches the end of the cap
4. The pipe should be tugged back, to ensure that the gripping
mechanism has engaged on the pipe.
In all cases the manufacturer's specific installation instructions should be followed when installing push fit fittings.