Sauer-Danfoss Expands Open Circuit Pump Family

Diesel Progress North American Edition, April, 2001 by Mike Osenga

Series 45 adds K and L axial piston pumps; off-highway equipment, plus fan drives and steering systems, seen as applications

Sauer-Danfoss Inc. has expanded its series 45 open circuit hydraulic pump family with the addition of four new displacements. New to the Sauer-Danfoss line are the K and L axial piston pumps, with four models -- the L25C, L30D, K38C and K45D -- rounding out the line.

The new sizes are the second expansion of the series 45 in recent years. Last year, Sauer-Danfoss, added the H75D and the G90C displacements to compliment the H57B and G74B pumps released in the late 1990s 990s for coverage from 3.5 to 5.5 cu.in./rev. Now comes the addition of the K and L pumps that expands the series 45 into displacements from 1.5 to 2.5 cu.in./rev.

The new K and L pumps are targeted at a variety of mobile uses. Sauer-Danfoss' Lyle Bretz, product manager-piston products, said target applications include agricultural equipment such as tractors sprayers and combines, as well as construction and material handling equipment such as loaders, mini--excavators, skid--steer loaders and aerial lift platforms. Bretz said the new variable displacement piston pumps could also be used in hydraulic fan drives and steering systems.

Built at Sauer-Danfoss' Ames, Iowa, facility, the K38C and K45D pumps began production in February while the L25C and L30D pumps will begin production in April. At this time, Ames is the sole manufacturing source for the new pumps, with Sauer-Danfoss considering other global manufacturing options as use of the new pumps expands.

The K and L pumps will make their public debut at the Bauma show in Germany, though prototypes and some production units have been installed in equipment before the show.

The two L pumps, the L25C and L30D, have displacements of 1.5 and 1.83 cu.in./rev respectively with a rated speed of 3050 rpm and continuous pressure of 3770 psi (L25C) and 3045 psi (L30D). Maximum pressure is 5075 and 4350 psi respectively while maximum speed is 3600 rpm.

The K pumps include the K38C with a displacement of 2.3 cu.in./rev and the K45D, with a displacement 2.75 cu.in./rev. Continuous pressure is again 3770 and 3045 psi respectively, with the same maximum pressure as the L pumps. Rated speed for the K pump is 2650 rpm.

Control options include a pressure compensator, as well as pressure compensation and load sensing. The controls can be located on either side of the endcap.

Bretz said Sauer-Danfoss made use of the Quality Function Deployment (QFD) methodology at the beginning of the program to understand and prioritize customer needs. "We knew the base pump had to be competitive for performance and noise, but the QFD process identified low cost and high reliability as key to customer acceptance," he said.

The result, Bretz said, are compact, high power density pumps, designed for quiet operation. To eliminate potential leak paths, the K and L pumps use O-ring seals, not gaskets.

Bretz said what is unique about the series 45 pump line is that Sauer-Danfoss avoided scaling in unwanted features and inherent cost across the entire product line. Each pump displacement is optimized with the required option package, performance and cost for the target markets identified.

In developing the new pumps, SauerDanfoss also made extensive use of computational fluid dynamics (CFD) to optimize the speed capability and reduce potential cavitation of the pump. The company also used a 3-D printing machine that allowed the design team to rapidly transform 3-D CAD models into plastic parts and assemblies for visual feedback from customers as well as the design and manufacturing teams. Design for manufacturing (DFM) and design for assembly (DFA) were given high priority by co-locating team members for the duration of the program.

Other design features of the new pumps include the use of a single servo-offset swashplate that lowers cost, yet meets the required control response. All of the model-specific options like rotation, control location and system port configuration are located in the pump endcap. The servo is also designed in the endcap to reduce overall cost, resulting in a simple housing design as system pressure is located only in the endcap.

The pump housing itself uses the cradle style swashplate with no trunnion covers, combined with a stiffer housing to reduce noise. The housing is common for both the K and L pumps to minimize part count, which helps overall product cost.

Installation critical dimensions include a shaft centerline to clean side housing width of 62 mm and, an overall length, with axial ports, of 203 mm. Options include either axial or radial ports, where both inlet and outlet use O-ring boss ports per ISO 6149 or SAE 1926 or split flange style ports. The case drains and the control's load sense port can be either configured with English or metric O-ring boss threads.

Auxiliary flanges are standard SAE A or B with full, through-torque capability, for radial ported end caps. Internal, nonadjustable maximum displacement limiters are optional. The front flange is an SAE B flange with either 13- or 15-tooth spline or 1 in. taper input shafts available. Allowable radial and axial shaft loads for each model are 270 lb. and 225 lb., and 337 lb. and 270 lb. for the L and K pumps, respectively.