Swivel joints present one of the most challenging seals within a fluid transfer application – especially when the media needs to migrate across different transfer lines. These mechanisms connect two objects, where one rotates away from the other in a horizontal plane, vertical or both.
Examples include jumper assemblies and loading/unloading arms, both commonly found in the petroleum and oil and gas industries but equally in grain feed loading and unloading systems.
Swivel joints are often used as a reliable alternative to flexible hoses. Within the heart of the joint is a seal, which plays a pivotal role in ensuring leak-free operation. Various designs and materials are used to make this happen – the right type and combination depend on the application.
The sealing capability of whatever medium is used is key for leak-free operation and a smooth, safe industrial process.
Whatever the pipework is transporting, be it chemicals, oil products, gas or food grains, the integrity of the swivel joint seals must be able to withstand excessive force and – very often – a harsh environment. These stresses can be asserted internally, externally or through a combination of the two. Some of the typical contributory pressures come from:
- Temperature extremes, both outside and inside the transfer units
- High operating pressure
- Abrasive media
- Velocity of the media
- Friction level and wear
Sealing solutions for swivel joints come in various designs, with cantilever spring designs being widely used. However, Chesterton would like to introduce a relatively new kid on the block – that of the spring energised seal.
The Case for Spring Energised Seals
A spring energised seal is designed to be used within critical applications and extreme operating conditions. When a standard seal (either elastomer or polyurethane-based) can’t effectively perform within the required operating limits, this is the exact situation where the uniquely designed spring energised seal can revolutionise the quality of the seal.
Such is the efficiency of a spring energised seal, upgrading – even where standard seals meet minimum standards – can dramatically increase reliability and MTBR.
The reasons spring energised seals are so effective is because:
- Of a unique rigid design: They’re made from engineered plastics and fluoroplastic compounds that provide a rigid construction with outstanding physical and technical characteristics.
- Through consistent load: This is achieved by springs throughout the whole unit to create a leak-free seal between the hardware and the jacket.
- Creates additional sealing forces: They use the system pressure to increase the load. In turn, this increases the spring force.
Spring energised seals can be used in multiple applications – oscillating, reciprocating and rotary – making them suitable for both static and dynamic industrial equipment. Depending on the requirements, bespoke designed seals might be necessary to maximise performance. Chesterton is one of the few companies that offer this.
Many industries are already benefitting from the advantages afforded by spring energised seals. Success stories can be found in upstream and downstream oil and gas, chemical processing, the energy sector, military, transportation, automotive, medical, aerospace and more.
Typical applications where the use of spring energised seals are particularly advantageous include:
- Transfer systems: couplings and swivel joints
- Subsea: valves, manifolds, flowmeters, pumps, hydraulic couplings
- Exploration: tools and wellheads
- Floating production: turret swivels
- Offshore platforms: pumps and compressors.
When to Consider a Spring Energised Sealing Option
The sealing solution is so additionally effective thanks to a design that uses the force of the medium travelling through the pipes. As this increases, so does the integrity of the seal. In addition, the tension that’s applied to the seal also compensates for other external influences, such as moderate equipment deformities, misalignment, thermal expansion/contraction and any manufacturing tolerances.
More about this can be found in the blog article, Understanding Spring Energised Seals.
Deciding whether to stick with standard seals or to upgrade to spring energised differs depending on the situation. Some considerations that would suggest that the technology could be extremely effective are:
- Higher or lower operating and ambient temperatures
- Higher moving speeds of the medium
- Higher operating pressures
- Abrasive media
- High levels of friction and wear
- A harsh environment
This article was featured in Infrastructure Magazine.
