Oil & Gas

SRJ Snap Ring Joint

The weld-free Snap Ring Joint (SRJ) solves many of the problems commonly associated with welded and flanged joints in pipelines and process piping. It can be used in both new lay and established pipework, as a temporary or permanent solution.

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Sectors

Oil & Gas

  • OFFSHORE
  • ONSHORE PIPELINES & PROCESS PIPING

TOPSIDE

Keeping the weight of topside components to a minimum, welding in a hot zone environment, and the restricted space available to run pipework are all major challenges facing operators of drilling rigs, production platforms and FPSO's.

When carrying out repairs or retrofits on the pipework of topside modules, workscopes must be carried out quickly and safely, with minimal disruption to operations, production and storage capacity.

Vibration is an issue in topside modules, with refurbished pumps on FPSOs for example and it may travel considerable distances through pipework downstream. This leads to problems with bolted flange connections, where the bolts may loosen and result in leakage.

The SRJ weighs 60% less than comparable flange joints. A 4" 900# flange for use on 4" Sch. 40 pipe for example, would weigh 50 kg, whereas a 4" SRJ weighs just 16 kg. The lower weight and volume of the SRJ compared with a flange allows for smaller pipe racks.

The consequent weight and space-saving on a platform or FPSO topsides module can result in substantial cost savings. The reduced weight also means that the SRJ imparts lower inertia loads on pressure vessels. It also means less steel weight and facility volume to transport and decommission, and hence the SRJ offers a more sustainable option.

The SRJ offers the operator greater flexibility in planning maintenance work and responding to unforeseen circumstances than welded joints. By eliminating welding, there is no need to compress essential workscopes into planned maintenance shutdown periods.

When the installation is on-line, work can be carried out without the need to deploy ATEX-rated equipment and hot work permits. The SRJ is quicker to install and re-connect than other joint systems, thereby reducing offshore workforce.

ONSHORE PIPELINES & PROCESS PIPING

Conventional jointing methods - such as flanges - present a number of shortcomings when used on process piping. Welding each section of the flange to the piping and bolting them together requires lengthy installation times.

The piping may be vulnerable to internal corrosion, especially when carrying fluids with high sulphur content. Unless there is a means of applying coating after the welding process, the internal face of the piping in the HAZ, as well as the weldment itself will be unprotected.

Flanges are heavy and voluminous, leading to increased costs when transported over a long distance. They can make flowlines vulnerable to fugitive emissons, in cases when gaskets become distorted.

The SRJ is a highly cost-effective alternative to conventional mechanical coupling devices and to welded joints in many applications. While a good weld is full strength and highly ductile, there are occasions where the workmanship may prove questionable.

The SRJ provides twice the strength of the pipe and in some cases it would be possible to remove one-third of the support trestles on a typical onshore pipeline if SRJ's were used to replace welded joints. The inherent strength of the SRJ would be a major benefit in seismically active zones.

The pipe bore is much smoother with the SRJ.

Since the SRJ is much lighter than a comparable mechanical connection, transport and logistics costs are lower. On-site, fit-up times are much shorter than for a comparable mechanical connector. Above all, it eliminates the need to weld pipelines and process pipework for many applications.

Bolt-torsion tests become superfluous with the SRJ. Its use eliminates the risk of failure when pipes are exposed to vibration which can loosen the bolts of a flange, a major problem in process piping.

Operating Principle and Key Features

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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.

 

Nominal Pipe Diameter Pipe OD SRJ Diameter
4”
101.6mm
4.5”
114.3 mm
8”
203.2 mm
8.625”
219.075 mm
12”
304.8 mm
12.75”
323.85 mm

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Benefits & Advantages

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Benefits

Safety
  • Cold work installation – eliminates the risk associated with Welding.
  • Reduces risk of fugitive emissions
Size / Weight
  • 40/50% more compact than a comparable flange. Closer pipe runs.
Speed of Installation
  • approx 3 hours per coupling with less skilled technicians.
Cost Reduction
  • Time savings 18/24 hours per connection compared to welded flange.

Advantages

The SRJ offers many benefits over other pipe connection methods: –
  • 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

PROCESS
10” 900Lb
SRJ
Pipe Cutting and Preparation
=
=
Pipe Alignment
=
=
Flange alignment and welding per flange
10.1
N/A
Pre Heat
2.7
N/A
Stress relieve
5.9
N/A
XRay
1.73
N/A
Coupling Installation
N/A
3
Connecting flanges / gaskets / bolts
3.7
N/A
Total Hours
24.13
3
SRJ Saving
21.13

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

SRJ vs. ANSI Flanges

Nominal Pipe Diameter Pipe O/D
SRJ Diameter
ANSI 900 LB Dia
4"
6.4"
11.5"
8"
10.7"
15"
12"
15"
24"
Nominal Pipe Diameter Pipe O/D
SRJ Weight
ANSI 900 LB Dia
4"
35 lbs
125 lbs
8"
175 lbs
415 lbs
12"
480 lbs
767 lbs

Snap Ring Joint Limited, 9 The Esplanade, St.Helier, Jersey, JE2 3QA, UK.
tel: 44 (0) 1534 626 818
e-mail: info@srj-technologies.com
Snap Ring Joint Limited. All rights reserved