OVERVIEW

The Snap Ring Joint is a highly cost-effective alternative to traditional pipe joining methods, since the stainless steel - typically cupro-nickel - used for most pipework in desalination plants, has to be TIG-welded. This is highly-skilled work and so more expensive than standard welding practices.

With the presence of seawater and the brine stream that results from the desalination process, corrosion is a major issue in desalination pipework. Since the SRJ requires no welding, the internal lining of the pipe is undisturbed, thus avoiding all the problems inherent in welded joints when corrosion occurs. This helps to curb the cost of maintenance costs, which is also easier since the SRJ is easily dismantled, facilitating pipework inspection.

By replacing conventional flanges with the SRJ, there is no need to conduct monthly bolt torsion tests since there are no bolts and it resolves the problem of weighty flanges on the roofs of evaporator units.

DESALINATION PLANTS

The integrity of electro-fusion welded joints in polyethylene (PE) pipe systems is a key issue for operators of desalination plants and poor joint performance is often a result of the low standard of workmanship applied when the joint is made.

Butt welding is a widely-used method of joining PE pipe and is currently the only option available for joining pipes which are larger than 500 mm OD. The process is costly since it involves the use of welders, bespoke installation equipment, complex pipe preparation procedures and a lengthy installation process.

While conventional PE pipe joining technologies may offer a lower initial cost, the higher failure rates make them much more expensive than the UPVC SRJ especially when the cost of intervention is factored in. Installation of the UPVC SRJ is simpler, faster and cheaper than is the case with welded joints, while its reliability in service will substantially reduce maintenance costs.

Another version of the UPVC SRJ has been developed which combines mechanical and electro-fusion jointing in one fitting. Electro-fusion of the joint is carried out once the coupling is in place, using induction heating technology and this method avoids the shortcomings that can arise from poor workmanship. The presence of a homogenous bond within the joint is designed for situations where the pipe might be subject to stretching prior to installation.

Operating Principle and Key Features

To install the connector (supplied pre-fitted with radial seals), the pipe ends are cut and prepared with the use of a conventional clamshell cutting machine. This machine, fitted with form tools, is used to machine the grooves required to locate the connector’s retaining wires in the pipe periphery.

If access is available at the pipe ends and one of the pipes can be moved longitudinally, then the SRJ connector would be installed onto one of the pipes to half its ength and the mating pipe is then pulled into the connector.

If however, the pipes cannot be pulled longitudinally, i.e. a spooled installation between two fixed ends, the connector would be completely assembled onto one of the pipes. This would leave its outer end flush with the pipe end. Then the mating pipe would be lowered into position and when the pipe ends are butted, then then the connector is centralised.

For larger OD connectors, a hydraulically-activated unit is used to position the connector on the pipe, thereby eliminating seal friction.

Alternatively, normal manual pipe handling equipment can be used. In all cases, once in position, the SRJ connector is locked in place by fitting the retaining wires. Typically, the overall length of the SRJconnector is equal to twice the pipe’s OD, so the actual access requirements are kept to a minimum, making its use ideal in tight access situations, such as the hook up phase of a project.

Benefits & Advantages

Benefits

• Cold work installation – eliminates the risk associated with Welding.
• Reduces risk of fugitive emissions

• 40/50% more compact than a comparable flange. Closer pipe runs.

• approx 3 hours per coupling with less skilled technicians.

• Time savings 18/24 hours per connection compared to welded flange.

Advantages

• Withstands high internal pressures and has equivalent mechanical strength of a weld
• Eliminates costly welding workscopes by replacing coded welders with trained operatives
• Speed of installation compared to welding workscope
• Enhances safety on-site and ATEX requirements by eliminating the risks of welding
• Does not compromise internal pipe coating, unlike welding
• Avoids the need to weld difficult materials such as CuNi, Monel and Duplex
• Potential for testing post-installation with the SRJ equipped with integrity ports
• Lightweight and compact, cutting transport costs and enabling closer pipe rack design
• Can be dismantled and reassembled

Installation Times vs. Welding

Note – Pipe preparation times for SRJ and welding considered to be equal.

SRJ vs. ANSI Flanges