Marzocchi's new gear pumps: Launch of GHP and ALP pumps and motors completes product line upgrade; higher pressures, lower noise - Mobile Hydraulics

Diesel Progress North American Edition, July, 2003 by Mike Osenga

Marzocchi Pumps USA has recently announced the final step in what has been a complete redesign of its line of hydraulic gear pumps and motors.

In 2001, Marzocchi announced new models of its 0.5, 0.25 and 1P lines. Now, Marzocchi Pumps USA, the domestic operations of Marzocchi Pompe, Bologna, Italy, has redesigned the other half of its six product lines with the introduction of the ALP and GHP series pumps and the ALM and GHM hydraulic motors.

This is a major product line change for Marzocchi, a process that began in 1999 and will completely replace all of the company's hydraulic pumps and motors as of August 1. And it is evidently a process not yet complete, as Marzocchi is planning to introduce new short multiple pump models in 2004, as well as integrating valves into pump covers.

The body, cover and flange of the ALP pumps and ALM motors are aluminum, while the heavier-duty GHP pumps and GHM motors feature a cast iron cover and flange to withstand new higher operating pressures. Both series also incorporate a totally new gear and bushing design.

The GHP/GHM lines are targeted almost exclusively at the mobile off-highway markets, especially construction equipment. The ALP/ALM range is targeted at less severe off-highway uses, including rental equipment, as well as industrial applications.

According to Kirby Clot, national sales manager of Marzocchi Pumps USA, the company decided to develop two new pump and motor series to meet the specific demands of the applications for each line. The biggest changes are higher pressures -- to 4500 psi from a previous 3600 psi -- as well as a significant reduction in noise, Clot said.

The ALP line includes three pump frame sizes with displacements ranging from 1.24 to 5.31 cu.in./rev and flows from 0.61 to 38.2 gpm at 1750 rpm. Maximum speeds range from 1800 to 6000 rpm. The corresponding ALM motor line has three motor frame sizes with displacements from 0.168 to 5.31 cu.in./rev at flows of 1.21 to 38.2 gpm at 1750 rpm and maximum speeds from 3200 to 5000 rpm.

The GHP pump line has three pump frame sizes from 1.24 to 5.31 cu.in./rev with flows from 0.61 to 38.2 gpm at 1750 rpm and speeds from 3800 to 6000 rpm. The GHM motor line has three motor frame sizes with displacements from 0.168 to 5.31 cu.in./rev with flows from 1.21 to 38.2 gpm at 1750 rpm and speeds from 3800 to 5000 rpm.

One of the design goals for the new lines was maximum torque transmission. As such, the pumps feature a new design and Marzocchi developed specific production processes, including a dedicated production run-in test bench to check the mechanical efficiency of each motor.

Marzocchi SpA was founded in 1949 as a manufacturer of motorcycle and mountain bike suspensions, a business it still participates in under the Marzocchi Suspension name.

Marzocchi Pompe, began operations in Italy in 1961 and in Valencia, Calif, in 2000. It is highly vertically integrated, manufacturing all of the components used in its products with the exception of the seals. A gear pump typically consists of a gear pair supported by two bushings with Teflon-coated friction bearings, a body, a flange and a cover. The driving gear's shaft, which projects beyond the flange, is mounted on two opposite single-lip seal rings, the outer of which is a dust seal. Hydraulic power pack pumps are an exception, as they do not mount friction bearings. In their case, an integrated lip dust seal ensures the driving gear sealing.

The pump bodies, flanges and covers are made of special high-resistant aluminum alloys, Marzocchi said. The alloys are designed to sustain minimized deformation, even when subjected to high pressure, be it continuous, intermittent or peak pressure. The body is profiled by means of extrusion, whereas the flange and cover are manufactured by either die casting or gravity casting processes.

Gears are integral to the shaft and are made of special steel. Marzocchi's manufacturing process includes turning, gear cutting operations, case hardening and quench hardening. The gears are then ground and fine finished, resulting in a high degree of surface finishing. Marzocchi said proper tooth profile design and precise geometric proportions ensure low pulsation and noise levels during pump operation.

Bushings are made of special low-friction, high-resistant aluminum alloy and are manufactured from die castings. Special compensation zones on the flange and cover, which are insulated by special seals, ensure fully free axial and radial movement to the bushings, the company said. These are proportional to pump operating pressure.

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