CAE team solves pump geometry problem

Over the years, March Manufacturing has relied on specialty compounder RTP Company to provide materials for its nonmetallic, magnetic drive pumps.

Over the years, March Manufacturing has relied on specialty compounder RTP Company to provide materials for its nonmetallic, magnetic drive pumps.

When developing its new 335 Magnetic Induction pump, March selected an RTP 100 Series glass-reinforced polypropylene compound for the housing sections.

Confident in its choice of material, March sought the same degree of security for the pump design.

In order to increase prototype accuracy and to meet an ambitious "to market" schedule, March sought the assistance of RTP Company's computer aided engineering (CAE) team who performed design reviews including mould flow and finite element analyses (FEA).

The housings constituted a truly "deflection critical" application because they are subject to applied pressures of 0.55MPa while in use and the clearance tolerance is tight - about 0.76mm.

The FEA determined that, when exposed to maximum operating head pressure, there would, indeed, be interference with the pumps' internal moving parts.

March and RTP Company engineers discussed remedies, including changes in gusset geometry and limiting unsupported areas.

Further analysis indicated that recommended alterations would cut deflection to 0.20mm vertically and a scant 0.04mm on the radial axis.

These movements are well within tolerances and were calculated at 1.5 times normal operating pressure, allowing for a generous safety margin.

March engineer Mike Wasserman notes that empirical evidence is the ultimate proof, but the early CAE involvement "allowed adjustments to be made in the computer room, rather than in the tool room".

He continued: "The monetary savings are significant, but eliminating unforeseen delays was even more valuable".

According to Robert Sherman, RTP Company's CAE Manager, the technology's capabilities are often used for basic purposes, such as troubleshooting.

Properly used, CAE can eliminate the need to incorrectly assume isotropic behaviour and other nonvariable properties.

Wassermann summed up the value of the CAE assistance when he stated: "These capabilities allowed us to build this mould compromise strength and stiffness for processability, but we did need to balance them".

He continued: "This is where the FEA and flow analyses really worked together and helped us to provide accurate timing and performance estimates to both our marketing people and to our customers.

We put our product on the market with no material changes, no mould changes, and no scheduling changes".

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