Power Generation

SRJ Snap Ring Joint

The Snap Ring Joint (SRJ) is a highly cost-effective alternative to conventional mechanical coupling devices and to welded joints in many applications. It offers lower costs in each phase of the life cycle.

srj

Power Generation

INDUSTRY SECTORS
Sectors

Power Generation

  • OVERVIEW
  • POWER STATIONS

OVERVIEW

The challenge for designers is to ensure that the integrity of pipelines and process pipework is maintained through the anticipated service life. Implicit in this approach is the need to take a whole life cost/benefit view at the earliest phase of design and development.

Essential maintenance and integrity management activities must be carried out with minimal disruption to operations, and any means of reducing the cost of modifications, upgrades, retrofits, spares and replacement kit to limit OPEX will be keenly sought. The SRJ can make a tangible contribution to this effort.

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, a key issue in power generation. When the installation is on-line, work can be carried out without the need to deploy ATEX-rated equipment and hot work permits.

POWER STATIONS

Two major challenges face operators of power stations: the need to maximise plant availability and the difficulty of welding in a hot zone environment.

The SRJ provides all the strength and integrity of a welded joint, but is also non-permanent, facilitating subsequent works and maintenance. The elimination of welding brings significant benefits, with coded welders being replaced by trained fitters who prepare and machine the pipes on site, install the sleeve, place the joint in position and install the wire.

The SRJ uses far less material than a normal flanged joint, with a 4" standard 600 # RF flange weighing 32 kg, compared to the equivalent SRJ fitting which weighs just 16 kg, easing the kinetic handling issues. It is simple to dismantle and install, and does not suffer from the problem specific to the reconnection of flanged joints, whereby the sealing surfaces may have been compromised.

It also resolves the problems caused by vibration, whereby flange bolts become loose and can result in joint failure. Bolt torsion tests must be conducted on a monthly basis to monitor the integrity of the joint. Vibration also creates a problem in that welded flanges are not resonance tested, because of the joining method.

During its time in service, any power station pipe connection must endure extreme loading conditions and the SRJ is currently undergoing a rigorous battery of tests to ensure fitness-for-purpose. Designed to be used both as a temporary and a permanent joint, the SRJ is likely to be subjected to multiple assembling and dismantling operations during its lifetime and maintains a leak proof seal after repeated dismantling and assembly.

Operating Principle and Key Features

srj

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

srj

Benefits & Advantages

srj

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