Designed with the benefit of more than 30 years experience in the field, Boltight has created a range of tools to meet the challenge of today’s bolt tensioning requirements.
Just watch how easy it is to install these tensioners!
Doosan Heavy Industries & Construction required a bolt tensioning solution to tighten nuclear reactor pressure vessel stud bolts. Boltight was contacted to design a hydraulic tensioning tool to achieve a predetermined bolt elongation, without exceeding the reactor head’s maximum allowable bearing stress.
The required bolt load was critically high (14,500 kN), and the space envelope was very small – the radial space available to install and operate the tensioner was particularly tight.
A tensioning system was designed to accommodate this high preload capacity within the space available. In realising these tools, Boltight engineers also incorporated a hydraulic piston retraction function into the design; to enable the equipment to be reset quickly, reducing operator fatigue. To compensate for dynamic joint behaviour, a spherical reaction nut and piston interface was integrated to accommodate any bending effects in the event of flange rotation.
Various safety mechanisms were incorporated to protect both the tools and the operators. Pressure relief valves were installed, and a floating gearbox design was engineered to avert damage should nut misalignment occur. The gearbox directly interfaced the geared nut which negated the need for a costly, heavy socket, and provided the necessary torque to rotate the nut.
Boltight were able to supply a complicated, bespoke design to exacting standards and achieved the tight delivery period set down by the client.
First published in Bolted #2 2017.
CUSTOMER: SUBSEA INNOVATION, UNITED KINGDOM
APPLICATION: OFFSHORE STRUCTURES
BOLTIGHT PRODUCTS: 14 UNITS OF M120 AND 10 UNITS OF M150 BOLT TENSIONERS
PROJECT: STRUCTURAL PIPELINE REPAIR CLAMPS FOR EPRS
Boltight solutions continue to be employed on more and more specialist applications in a multitude of markets worldwide. One example of this is Subsea Innovation, a UK-based company that serves the offshore industry. This company has been supplying subsea structures for over 25 years, and recently secured a multi-million-pound contract in Australia.
For this project, Boltight has supplied tailormade bolt tensioning equipment for structural split repair clamps. These are part of the Emergency Pipeline Repair System (EPRS) for gas pipelines off the north and northwest coasts of Australia. Boltight designed and produced two sizes of tensioner to suit M120 and M150 bolts. These tensioners are used to tighten the main bolts located around the clamp body and are activated remotely using a hydraulic control system.
The tensioners have been designed as per Subsea Innovation’s specifications, with Boltight adding its experience of supplying such solutions. The long-stroke, double-acting design means that they operate in both directions, so they can be reset without recovery to the surface. They are ideally suited for subsea use.
Boltight worked with Subsea Innovation to agree on testing and operational specifications, ensuring that the applied bolt tension is correct and that the overall EPRS system operates properly when called upon. All parts were supplied by Boltight within a strict delivery window.
The EPRS in Australia will act as a contingency if the main lines transporting gas need to be repaired.
Boltight manufactures both standard and custom built tooling for subsea applications. The subsea tensioners incorporate components that helps to save installation time, cost efficient, protects the environment and conforms to the requirements of the European Pressure Equipment Directive.
All subsea tensioners are assembled, filled with oil and have been pressure tested before dispatch. Boltight subsea tensioning tool is supported by a range of ancillary equipment such as high volume pumps, diver control valves, long length down line and hose reels.
First published in Bolted #1 2017.
Q: How does lubrication affect hydraulic tensioning and multi-jackbolt tensioning?
A: With the traditional method of tightening a nut, using a spanner, lubrication is very important, as there are a lot of surfaces moving against each other – the threads of the nut against the threads of the stud and the underside of the nut against the surface of the joint. Overcoming these frictional forces accounts for approximately 90 percent of the work (energy input) applied to generating the load in the joint.
When a hydraulic tensioning tool applies a clamping load to a joint, lubrication has no effect as it is applied directly to the stud and joint. A tension force is a linear force applied in an axial direction, so there is no rotation required to generate the load. This allows the nut to be turned down against the joint face under minimal friction.
As there is no friction to consider, there is no need to reduce the coefficient of friction using lubrication. Also, the lack of friction in the application permits much more accurate and repeatable results.
With multi-jackbolt tensioners (MJTs), the use of a lubricant on the main bolt thread does not affect the preload. It is advisable to use a very light film of lubricant with anti-seize characteristics to facilitate tensioner removal.
A more tangible effect of lubrication for MJTs is from the required lubricant use on the individual jackbolt threads, jackbolt bottoms of the tensioner, and washer face.
Proper use of lubrication is crucial to safeguarding repeatable and precise preload control in Superbolt installations. Superbolt mainly uses a graphite-based lubricant with a low friction coefficient and steady performance to achieve a positive impact on the preload. The MJTs are delivered with lubricant pre-applied to the installed jackbolts. Additional lubricant is included for application to the jackbolt bottoms. For subsequent installations, reapplication of lubricant is required to provide the intended performance.
Boltight’s Typhoon range of bolt tensioners offer a high-load, low profile solution for space-restricted applications that demand high and accurate preloads. A solution widely used within the Wind industry where such space-restricted connections are common. Additional convenience features such as a spring loaded gear drive for nut rotation and automatic piston retraction, ensure that Typhoon bolt tensioners are the ideal choice for any application demanding a powerful, portable and user-friendly bolt tensioning tool.
Boltight’s Piston Retraction system takes the hard work out of resetting bolt tensioner piston stroke. Depending on the design of the tensioner, the pump will give automatic piston retraction or assisted piston retraction.
Quick and easy, it saves operation time, reduces operator fatigue, and promotes safe and efficient working practice.
Boltight’s Xtra Load range of bolt tensioners is used extensively in the offshore oil and gas industry for bolting compact flanges.
The 1500 bar system delivers 30% more load than Boltight’s standard range in a smaller space envelope without compromising on safety, reliability and accuracy. This lightweight and innovative design was developed to suit all common sized ANSI, API and Norsok L005 compact flanges.
Watch the video demonstrating the tensioning process with Xtra Load tensioner.
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