Filter modifications guarantee reliability of hoist gearboxes

A major steel plant was concerned about the reliability of gearboxes on their 500 ton hot metal cranes and although the plant had no major problems with gearbox failures they were concerned with the results of oil sample analysis from an independent company. The sample results showed an alarmingly high level of contamination which was attributed to both wear debris from the gear-box itself and dust from the environment of the working area.

This contamination if not removed could eventually lead to catastrophic failure of the gearbox leading to huge repair costs and inevitable loss of production. To overhaul a gearbox would cost in excess of £250K, with a new replacement coming in at £450K. The cost of downtime due to critical nature of crane operations would run into tens of thousands of pounds and could lead to a knock on effect further down the line with loss of steel for processing.

John Morfield engineers conducted a gear-box audit and proposed installing a filtration system into the lubrication circuit using a Pall SRT UR699CF48AT40HB9 (22) micron to replace the original duplex filter unit fitted with 120 mesh filter baskets This was accepted and installed by John Morfield Ltd in Feb 2008. Oil samples were taken before & after fitment, these showed a visual clean up, a further sample taken 10 days later showed a vast improvement. Again independent oil samples support the results and these samples will continue to be taken as part of a planned maintenance regime.

In addition to the lube filter Pall air breathers were installed to help control the ingression of dust from the process. The second crane of the seven on site has now been fitted with the new filtration system and the customer intends to carry out the same modification to the remaining five gearboxes as part of a continuous plant improvement system. This filter system and oil monitoring now gives the customer the confidence that the gearbox lubrication will operate in a clean condition and should in time reduce the maintenance and overhaul intervals

As a result of the audit John Morfield also identified improvements that could be made to the process used for the gearbox filling system .Due to the working height of the cranes any oil change or flushing of the gearboxes was a major logistical problem. The original system involved the maintenance operators hauling oil drums up to the gearbox and manually filling the system. Working closely with the customer John Morfield designed and installed a bespoke sealed oil filling system to the cranes with the advantages of reduced dirt ingression during filling, elimination of manual handling thereby reducing health and safety concerns and metered oil usage which could identify any increased oil usage due to leakages.