PRZOOM - /newswire/ -
Lambourn, Berkshire, United Kingdom, 2010/02/03 - As a company specialising in the design and manufacture of hydraulic nuts and bolt tensioning equipment, Tentec used their considerable expertise in this industry and was chosen as the exclusive supplier of these TR530 thread nuts.
With one of the largest engineering workshops in Western Europe and a history going back over 170 years it’s unsurprising that when a world leader in the invention, production and supply of the high-nickel, high-performance alloys was looking for a company to refurbish its 1750 Tonne ‘Bliss’ forging press, they turned to a major global press refurbishment company. Both companies have long and established reputations within the metals industry and after having been in almost constant use for several decades, the press was in need of a major overhaul to return it to optimum working condition and to deal with increasing 24/7 production demands.
The remit was to restore the press back to its original design criteria, with additional improvements to the alignment, geometry, preloads and capacity. Several engineering studies, including 3-D modelling and Finite Element Analysis, supported by site inspection visits, were carried out in order to identify the scope of refurbishment and upgrade. The press refurbishment company’s engineers then created a plan to accomplish the press refurbishment within a two-week downtime. As well as the machining in the European workshop, other components were needed to complete the refurbishment. Included in the list were a number of very large hydraulic nuts that had to be specifically designed to suit the 530mm columns manufactured by the press refurbishment company.
Having worked with UK engineering company Tentec before, the press refurbishment engineers asked Tentec to quote for the supply of a set of unique hydraulic nuts designed and manufactured specifically to fit the 530mm tie bar on this large forging press. As a company specialising in the design and manufacture of hydraulic nuts and bolt tensioning equipment, Tentec used their considerable expertise in this industry and was chosen as the exclusive supplier of these TR530 thread nuts.
The hydraulic nuts were designed and manufactured to meet the exacting specifications. Special tooling was required to manufacture these high load nuts and a bespoke “V” form MJ530 x 20 pitch thread was developed to enable accurate and secure attachment.
Prior to the use of hydraulic nuts it was common practice to use a thermal expansion technique to pre-stress large diameter press columns and this technique is still used today.
Thermal expansion involves inserting a heating element down a pre-drilled hole in the top of the column allowing the column to thermally expand. The load retention nut (not a hydraulic nut) is then rotated down by a predetermined amount. When the column cools it then wants to contract to its original length but is prevented by the fact the nut has been rotated down against the frame of the press, hence a pre-load is induced into the column. This is a very time consuming technique and due to the high temperatures involved that can lead to a molecular change in the column material the required pre-load is not always achieved. There is also a potential fire risk.
By replacing the load retention nuts with hydraulic nuts the problems outlined above are eliminated. The use of hydraulic nuts allows the columns to be pre-stressed quickly and to a high degree of accuracy. Speed of operation is important particularly if the columns have to be de-tensioned for a non-scheduled maintenance shutdown.
When delivered to the press refurbishment company, a Tentec engineer was present to ensure the test fitting went smoothly. It turned out there was no need. The nuts fitted perfectly first time, once again, demonstrating the professionalism and expertise of both companies.
The press was returned to production after commissioning, which saw the introduction of further refinements to guard against the intense thermal effects that the press has to endure during almost continual operation. The press recondition was the first phase in a multi-million pound upgrade for the alloy manufacturer, which will ultimately see a new rail-bound manipulator and a new pump and control system. The high performance alloy manufacturer has seen a vast quality improvement to the forgings produced resulting from the accurate alignment of the press.