How to prevent hydraulic oil overheating

Overheating is the second most common issue that occurs in hydraulic systems, behind leakages. Overheating of hydraulic systems is caused by inefficiencies which have resulted in loss of input power being converted to heat. To achieve stable fluid temperature, a hydraulic system’s capacity to dissipate heat must exceed its heat load. Overheating can be avoided by a reduction in hydraulic oil heat load and/or increasing heat dissipation.

Why reduce oil temperature?

Hydraulic fluid temperatures above 82°C (180°F) is likely to lead to oil degradation and cause damage to hydraulic seal compounds. While the operation of any hydraulic system at temperatures above 82°C should be avoided, fluid temperature is too high when viscosity falls below the optimum value for the hydraulic system’s components. This can occur well below 82°C, depending on the fluid’s viscosity grade (weight). To achieve a stable oil temperature, the hydraulic system must be able to dissipate heat faster than it is built up.

Heat dissipation

Heat dissipation occurs in the hydraulic reservoir. Regularly check there are no obstructions to the air flow into the reservoir and that fluid levels are correct.

Heat exchangers

Similarly to the reservoir checks, ensure the core of heat exchangers are not obstructed. Heat exchangers rely on flow-rate, hydraulic oil temperature and coolant in order to disperse heat suitably. It is vital that faulty cooling circuits are replaced. Infra-red thermometers are a reliable way to measure the performance and oil flow rate of heat exchangers.

Oil pressure and leakage

Reduction in system pressure or oil leakage will cause increased heat generation. It is critical that the cause of the leaking is identified and then rectified appropriately. If a relief valve is underneath or positioned too closely to the pressure setting of a pressure-compensator in a closed-centre circuit, it may lead to increased heat generation and the system pressure cannot reach the pressure compensator setting. Subsequently, the component will continue to move oil thorough the system, passing over the relief valve, which produces heat.

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Grain ship-loader replacement electro-hydraulic control system

Thanks to the working relationship spanning many years, Rotec were invited to quote for the replacement of the hydraulic power unit and controls of the grain/feed products ship loader travelling gantry system. The client was faced with reliability and obsolescence issues with the original equipment dating back to the 1980s. It is the only plant capable of this function at the port and is in use constantly.

The ship loader hydraulic functions consist of a dual pumping system and associated hydraulic equipment built into an up-cycled twenty-foot shipping container. The container sits on the machine approximately 20 metres above dock level, which presented some unique access issues.

 Based on the original system design, Rotec designed and manufactured a complete self-contained hydraulic system and associated dedicated electrical control panels which control vertical and horizontal movements of the grain conveyors and loading chute to align over the vessel’s holds as required.

The container was specially modified to accept and fit the hydraulic system. This included full sound and fireproofing, internal full bunding and bespoke flooring and ventilation integration. The hydraulic system consists of a primary pump system driven by a 100KW 3300VAC electric motor and proportionally controlled variable displacement pump with a completely redundant secondary backup system in case of partial or total power loss. This 400VAC backup system is supplied from an external generator and is used to recover the chute off a vessel during a power loss when necessary. The main pump systems are supported by cooling and filtration systems and associated electrical control and monitoring equipment which in turn all interface and interlock to the main ship loader external control system.

21The project initially began in 2017, but project was temporarily halted by Brexit and later on, the outbreak of COVID-19. However, following a major fire one evening whilst in use on a vessel which completely destroyed the old containerised system, surrounding cabling and pipework, the project objectives and target completion date was rapidly brought forward to minimize the client’s downtime.

Due to our very flexible approach and ability to respond to an everchanging priorities list, Rotec was able to pick up and resume the build process quickly and managed to complete and factory test the unit ready for site delivery and install by the end of May. Our on-site engineers in the meantime stripped out and replaced large quantities of fire damaged external fixed stainless and special alloy tubing and replaced all external flexible hoses on the machine. The container unit and system were craned into place, pipework connections completed then flushed thoroughly. The system has now finished its commissioning and setting to work process, on time and on budget, and is ready to serve the port for this vital service for at least another 30 years minimum. The client is completely satisfied with the product and service received by him by our team of design, manufacturing, and field service personnel.

 

Propeller Press

A customer who we have a longstanding relationship with requested a propeller press    re-fit for us ein the marine industry.

The customer supplied the framework, into which we incorporated a new valve block, fabricated a weld on bracket for gauge and a pressure relief valve and fit custom made hydraulic hoses as per technical drawings supplied by Rotec.

This bespoke piece of kit is going to Indonesia for use with straightening propeller shafts, to check propeller shafts are true.

Contact us today to see if we can assist you with your fluid power project: sales@rotec.net or 01823 348 900

Date: 8/10/19

Author: Sarka Humpolcova

 

Warship Power Units & Reservoir

After 4 months work replacing hydraulic pipework on a warship, Rotec’s engineers needed to flush the pipes to meet the required cleanliness standards. Due to a change in conditions on board the decision was made to design and build modular bespoke power units and a standalone reservoir.

Rotec have a long history working with the defence industry and specialise in bespoke design and manufacture of hydraulic power units for marine applications, amongst others.

Our team designed and built the power units using 55Kw electric motors close coupled to Berarma Vane pumps and included a flowmeter and a pressure gauge. The Berarma pumps are pressure compensated with variable flow rates. This gives the operators the flexibility to tailor flows and pressures thus ensuring turbulent flow conditions are met to maximise the cleaning action.

Electrical control panels are mounted direct to the trollies to allow ease of use

The power units are fitted with castoring braked wheels for easy manoeuvrability in tight spaces. The Rotec team also designed and manufactured a standalone reservoir, suitable for multiple applications and high volume (fluid) displacement, enabling maximum flexibility as design changes can be incorporated or removed as desired. The system includes pressure return filters which help remove any contaminants from the existing system, ensuring the pipes comply with client specified level of cleanliness.

Rotec delivered to the tight deadline, with just 1 week turnover.

Date: 26/09/2019

Author: Sarka Humpolcova

 

Case Study: Waxing Machine

This unique piece of equipment was recently designed and built at our Taunton depot. The unusual request came as a result of one of our existing existing customers, a well-known candle manufacturer, recommending Rotec to their supplier – a company specialising in the manufacture of candle wicks.

Rotec previously undertook a variety of repairs and control system projects for the candle maker and had also supported the wicks manufacturer’s machinery. Following a successful PLC re-programming project, we were asked to manufacture a waxing machine. Using old conceptual designs left by the previous manufacturer, Rotec produced an up-to-date design, new CAD drawings and a modern control system. Our team of talented engineers then successfully completed the build.

The machine is designed to impregnate and coat a continuous length of wick cord with wax and re-spool onto a new drum. The process involves a multi-pass immersion process through a molten wax reservoir followed by periods of cooling and hardening. The wax is maintained at a constant temperature, indirectly heated by hot water in a vessel located below the wax reservoir. A plc is used to control wax temperature, main drive motor speed and spooling control of the finished product. The machine is now complete and will be installed at the customer’s premises within the next couple of weeks. The machine is capable of producing sufficient finish waxed wick for up to half a million wicks a day, depending on the length of the wick required.

Rotec and the customer are already in discussions about the next project, the design and manufacture of a wicking machine designed to cut the wicks to the desired size and insert the sustainer (the small metal disc sitting at the bottom) ready to be inserted into a candle.

 

Date: 08/04/2019

Author: Sarka Humpolcova

 

Case Study: Beam trawler gets a dose of planned maintenance

Rotec recently completed a thorough service on a beam trawler, as a part of a traditional annual service on one of three local boats.

In addition to remedying the regular list of faults & based on previous experience Rotec suggested expanding the normal work list to include Planned Maintenance work. Typically this would include stripping and checking pumps, motors & valves in addition to addressing any outstanding leaks.

By carrying out Planned Maintenance tasks unexpected breakdowns of hydraulic and pneumatic components can be avoided. This was in a bid to remedy some recurring issues with steering and winching systems.

Rotec serviced the main winching system, removing and overhauling 3 hydraulic pumps, hydraulic motor & gearbox. On inspecting the drive shaft found a worn splined coupling, if this had failed thein it would have stopped the crew from retrieving their nets.

Other work included replacing a large selection of hoses, draining and inspecting the oil tank, supplying and fitting filters and a spare gear box.

 

 The engineers then stripped and repaired the pneumatic engine controls, completing a tricky job due to the controls being obsolete.

All hydraulic and pneumatic issues have been successfully rectified to customer satisfaction. This gives the skipper and his crew the confidence to go back to sea for another year.