Marzocchi Hi-Low Pumps
Very special double stage pumps with unloading valves. HL pumps are ideal for applications requiring a quick approach and/or return of the actuator at low loads (defined by the sum of the flows of the first and second stage) and slow motion of the actuator at high loads (defined by the first stage). Compared to traditional pumps, HL ones require a less powerful motor. HL pumps are available for groups 1, 1P, and 2. All displacement combinations for the two stages, flanges and shafts are available for a very flexible configuration of the pump.
Please strictly follow assembly and use indications given for top performance and longer life of Marzocchi products. Some general considerations should be made on the hydraulic system, in which the pump must be fitted. Special attention shall be devoted to hydraulic system design and assembly, especially to intake, delivery and return pipes and position of system parts (valves, filters, tanks, heat exchangers and accumulators). Proper safety devices and reliable instruments to avoid fluid turbulence, especially in return pipe to the tank, and prevent air, water or foreign bodies from entering into the system are of major importance. It is also very important to equip the hydraulic system with a proper filtering unit.
|Marzocchi Group HL|
|First stage smaller displacement High pressure||From 1.1 to 8.3 cm3/rev - P1= up to 250 bar|
|Second stage bigger displacement Low pressure||From 3.7 to 35.2 cm3/rev - (pressure set by unloading valve)|
|Unloading valve||Standard setting from 30 to 50 bar, special settings on request|
|RPM range||From 1000 rpm to 3500 rpm|
|Ports||Common inlet. Common outlet. Side ports code FG, FA, D|
|Flange and shafts||According to the HL pump type|
Marzocchi Group HL products include: 1PHL, 1HL, 2HL.
Basic Marzocchi Design Information
External gear pumps are the most popular pumps used in modern hydraulic systems. They feature versatility, strength and long useful life. Their simple construction ensures limited purchase costs and servicing.
Thanks to these basic concepts, together with ever-improving product design and features, research -based on many years of experience - accuracy in material selection, production process followed in great detail and tests on mass-produced parts, our gear pumps have reached top quality standards.For this reason, our products can work under heavy operating conditions and transmit high hydraulic power. Furthermore, Marzocchi pumps feature good hydraulic, mechanical and volumetric efficiency, low noise level and, last but not least, compact dimensions and low weight/power ratio.
A gear pump usually consists of a gear pair supported by two aluminum bushes for groups 0.25, 0.5 and 1P, or bushes with plain bearings coated with antifriction material for groups 1, 2, 3 and 4, a body, a securing flange and a cover. Shaft of the driving gear projecting beyond the flange mounts a twin-lip seal ring (the inner lip being a seal, the outer lip being a dust seal) for groups 0.25, 0.5 and 1P, or two opposed single-lip seal rings (the outer being a dust seal) for groups 1, 2, 3 and 4.
Pump body, flange and cover are made of special hi-resistant aluminum alloys for minimized deformation even when subject to high pressure, be it continuous or intermittent or peak pressure. The body is profiled by means of extrusion, whereas flange and cover are obtained by means of die-casting (even gravity die-casting for some models).
Gears are made of special steel. Their manufacturing process includes case-hardening and quench hardening. Then gears are ground and fine finished so to have a high degree of surface finishing. Proper tooth profile design and geometric proportions ensure low pulsation levels and low noise levels during pump operation. Bushes are made of special low-friction and hi-resistant aluminum alloy and manufactured from die-casting.
Special compensation zones onto flange and cover, insulated by special seals with anti-extrusion rings, allow fully free axial and radial movement to the bushes, which is proportional to pump operating pressure. In this way, internal dripping is dramatically reduced, thus ensuring very good pump performance (both in terms of volume and in general) and proper lubrication of pump moving parts.