Renewable Oil Services Limited are the UK’s largest supplier of oil products and oil exchange services to the wind turbine industry covering both the onshore and offshore wind markets
The company, formally known as Peter Lonsdorfer UK Limited, have been carrying out gearbox and hydraulic oil exchanges on wind turbines across the UK and Ireland with the use of their specialised oil pump trucks for over 10 years now and back in 2013 they were the first company worldwide to carry out a vessel mounted combined gear and hydraulic oil exchange on an offshore wind turbine using their own specially designed and manufactured vessel mounted pumping system.
Specialised trucks and offshore units are fully bunded units and have an in-house developed oil heating and filtration system which allows the company to pre-filter and heat the new gear oil products to between 40⁰c and 55⁰c allowing them to pump the viscous 320ct new gear oil products up 180 metre hoses to the nacelle and into the gearbox.
With truck or vessel in place at the base of the turbine they start with winching hoses up to the nacelle and from there they connect the waste oil hose and pumping system to the gearbox drain point or points and drain the full system of the old oil.
The next step, depending on the contamination level and oil sample results of the gearbox oil, will determine the level of system flushing required.
- Level 1 – a basic oil exchange with no flushing required where a routine oil exchange is taking place with no or minimal contaminates currently found within the oil sample
- Level 2 – an oil exchange with single flush if low to moderate levels of contaminates are found in the oil sample. For this a pre-defined system volume quantity of oil is used and the quantity will vary depending on the turbine and gearbox type – the new oil is pumped up to the gearbox via a closed system.
The reason for carrying this out in a closed system is so that you do not have to open the gearbox lid as this is one of the main points of contaminates being introduced into the gearbox itself.
To achieve this closed system they use specialised fittings to connect to the gearbox keeping the gearbox lid sealed and contaminate free – the oil enters the gearbox at between 40⁰c to 50⁰c to allow the operation of any internal system thermostats to open fully allowing the flow of oil to pass through all of the gearbox auxiliary systems freely (oil coolers, filter blocks, etc).
The oil is then circulated and flushed through the gearbox and ancillary systems with the use of the gearboxes own internal or external gear oil pump for a set time period – once complete the flush oil is then drained from the gearbox via the sump drain point as before
- Level 3 – an oil exchange with double flush. This is carried out if moderate to high levels of contaminates are found in the oil sample or if a change of product type was taking place. The procedure for this would be exactly the same as the Level 2 only carried out in its entirety twice as two full flushes
- Level 4 – an oil exchange with full invasive system flushing. This is where extremely high levels of contaminates or sludge is found in the oil sample. If this is the case it may be required for a high viscosity gear oil detergent to be put into the gearbox several days prior to the oil exchange taking place to break down any heavy sludge or contaminate build up within the gearbox and associated systems.
The procedure would require some gearbox pipework disassembly then a full individual component system flushing of coolers, filter blocks and all associated pipework to ensure all contaminates are removed from each of the individual parts of the system. Recommendation would be to replace the inline filter during this flushing procedure to capture additional contaminates during the flushing.
Opening of the gearbox lid will also be required to carry out internal gearbox rinsing of the surfaces with pressurised hot oil to ensure any build-up of sludge in the gearbox casing surfaces. Webbings and ledges are rinsed down into the sump for removal and pumped out via the drain point as before.
Once this is completed the systems are reassembled and lid placed back onto the gearbox in preparation for full closed system flushing as the Level 2 flush to ensure all residuals and any introduced contaminates, having the systems and lid open, are fully flushed out
Once the gearbox has been emptied, along with any flushing requirements, the filters are replaced with new units and then the gearbox and associated systems are refilled with new clean oil to the specified levels. This is carried out via a pump and hose system filling the gearbox using a closed system to ensure the new oil pumped directly into the gearbox is contaminate free.
The procedures and principles for the gear oil exchange are also applicable for the wind turbine hydraulic systems. This is also carried out in a closed loop system with various options of flushing depending on the contamination level of the oil.
Glycol coolant exchanges
Also in the case of glycol coolant exchanges a similar principle is adopted using in-house specialist pumps and hoses which are used to drain the glycol system. Systems are then refilled using a specialist glycol pump unit to progressively fill the systems taking care not to create bubbles in the new glycol minimising the risk of system airlocks.
Renewable Oil Services Limited