As Australasia’s infrastructure ages, maintenance engineers face challenges in replacing original and sometimes crude slip joints supporting thousands of aqueducts and elevated pipelines.
The problem with such joints – which prevent pipelines buckling or cracking as they repeatedly heat and cool over many seasons – is that many older types of grease bearings have exceeded their lifespan, corroded, lost their flexibility and bound rigid.
"Some of the older bearings supporting industrial and municipal pipelines were little more than a sandwich of metal plates with an axle grease filling, which have corroded and deteriorated over time. Now they are still carrying the same heavy point loads, but not offering much protection at all to vital contents, including water, slurries, oil, gas and chemicals. It is a headache to get the old bearings out and find a way to replace them with cost-efficient and maintenance-free alternatives," says David Booty, Manager, slip joint and bearing manufacturer Hercules Engineering.
Hercules Engineering (a division of Cut to Size Plastics) is offering a solution to new and replacement bearing installations through its range of Herculon Type D Bearings (HLD/SG, HLD/FF and HLD/FX), which are widely proven on applications ranging from steel and concrete beam engineering structures through to materials handling and processing facilities including pipelines and aqueducts.
Herculon HLD Bearings are part of a comprehensive range of Hercules composite slip joints and structural bearings incorporating high performance combinations of engineered thermoplastics and stainless steel facing surfaces that don’t break down in the way that earlier types of bearings deteriorate.
"These are a long-term solution, which are engineered to minimise downtime and maintenance by accommodating the vertical and horizontal stresses imposed by expansion, contraction and varying loads," says Booty.
They can be engineered for simplified retrofitting, as they were in an aqueduct project where Hercules Engineering partnered with the client by fabricating and locating a dummy bearing first to facilitate the precise installation succession of Herculon D bearings without any interruption to the flow through the pipeline. This installation – which involved ten 10-ton bearings in addition to the dummy positioning bearing – was typical of a project involving replacement of bearings in difficult, remote or inaccessible elevated pipelines.
"We were working high above a rocky river bed, so we wanted a bearing type and an installation method that maximised safety, minimised installation time and gave a long service life without the need for ongoing maintenance." said Booty. The old dry bearings were cut out on site and replaced with the new sliding bearings bolted to the supporting piers and to a saddle supporting the aqueduct pipeline as it expanded and contracted on a daily basis. A special feature of the new bearings was the use of grade 316 stainless steel in combination with materials that would obviate any electrolytic reaction between dissimilar metals, which could impair bearing function.
"Engineering for low maintenance is essential whether you are involved in municipal water and waste water work, or working on elevated section of pipelines serving remote resources and industrial projects where you can’t afford to have pipelines out of commission or needing frequent maintenance," said Booty.
Benefits of HLD Bearings, compared with more sophisticated and expensive heavy alternatives such as pot bearings and roller bearings, include lower initial cost, easier installation and no maintenance for periods of 30 years or more. HLD bearings are very suitable for a wide range of aqueduct, elevated pipeline, bridge, materials handling and process equipment structures up to 60 tons per bearing.
Herculon type D sliding bearings – incorporating polymers proven globally for outstanding durability without lubrication or maintenance – were developed to fulfil the need for low-friction bearings on corbels and columns where continuous slip joints were not appropriate.