January/February 2018

HYDRAULICS 24 HYDRAULICS & PNEUMATICS January/February 2018 www.hpmag.co.uk Doosan has introduced its new DL420CVT-5 Stage IV compliant wheel loader, the first model in the Doosan wheel loader range to be equipped with a Continuously Variable Transmission (CVT). A CVT transmission comprises a hydraulic motor combined with a hydraulic pump that provides a smooth and continuous speed variation. The CVT design combines the benefits of a mechanical transmission and a hydrostatic transmission in the same machine. It allows the DL420CVT-5 to automatically transition from hydrostatic power at low speed to the mechanical system to operate at higher speeds. By combining the two types of transmission, the new CVT technology ensures high loads can be carried at low engine speeds with high dynamics for an optimum wheel loader operating cycle. The DL420CVT-5 therefore provides an increase in machine performance for operators working in digging, loading and lifting applications. Up to 15% additional fuel savings The complete driving range, forwards and in reverse, is controlled by the CVT system. Low engine speeds ensure a high efficiency and the highest driving comfort irrespective of the traction speed. The power splitting continuously variable technology facilitates moving off softly and hydraulically. Furthermore, with the CVT, a fuel saving of up to 15% is said to be achievable. Load-sensing hydraulic pumps All new generation Doosan wheel loaders have a load sensing hydraulic pumping system, whereby the variable axial piston pump generates the flow upon demand in the amount necessary to perform the work. www.doosan.com/en Fuel-efficient Doosan DL420CVT-5-wheel loader Settima screw pump distributor, Applied Pumps Ltd., recently demonstrated its ability to solve difficult fluid handling applications by using two completely different pump technologies on the same system. The application was for coolant handling on a large, bespoke matching centre. These machine tools are expensive and run at very high speeds generating enormous heat at their cutting surfaces. This particular design included a deep boring function and required a reliable supply of high pressure fluid to cool and lubricate its cutting tools while also flushing away swarf particles away from the immediate cutting area. The coolant was a viscous synthetic oil and the machine used a complete system complete with several high-volume sumps and a custom-built filtration system. Applied pump selected two pumps for the system. Return pump Coolant, once supplied under pressure to the immediate cutting area, hot gushed away and ran back to a collection sump under gravity. From here, it then had to be re-fed back through a cooling and filtration system to a main holding tank ready to be used again. Applied Pumps supplied a Victor ‘S’ series, cast-iron, self- priming centrifugal pump for this purpose. Victor self-priming pumps have an open, non-clogging impeller that can handle heavily aerated fluids. The pump also has a special abrasion-resistant type shaft seal with an auto-lubrication cartridge. Also, and very importantly, all of the pump’s internal wearing parts are replaceable. Duty: 400 Litre/min at 12m differential head. Supply: Victor S50 G31T fitted with a 3ph 2.2kW 2-pole motor. Coolant feed pump After cooling and filtering, the returned oil was held in a holding sump ready for use again. The requirement then was for a pump to deliver a high volume of pressurised coolant to the cutting area, which had to be completely reliable and constant. Applied pumps selected a Settima triple screw pump for this part of the system. The pump chosen was cast-iron with hardened screws and a special hard- faced shaft seal. The fluid at this point had been filtered but nevertheless it was decided to play safe with a robust pump design. Triple screw pumps are excellent for supplying a smooth, high volume flow of high pressure fluid, and being positive displacement pumps their volumetric output is proportional to their shaft speed. This was important as the machine tool had several operating points; meaning any pump had to be of variable speed. Duty-1: 225 Litre/min at 25 barG. Duty-2: 1,125 Litre/min at 7 barG. Supply: Settima GR110 SMT16B-2300L G HA TMK 22U31 fitted with 3ph 22kW 4- pole motor fitted with PTCs for use with a VFD. Supplier integrity and equipment quality was essential for the customer. The cutting forces generated by large modern machine tools are high and failure of the coolant supply, even for a short period, would be catastrophic. www.appliedpumps.co.uk Two pump technologies make the cut for machine tool application