Pump study reveals life cycle cost differences

The results of a detailed comparative study of pump life cycle costs were revealed recently when its author spoke at a press conference organised by Wanner International

The results of a detailed comparative study of pump life cycle costs (LCC) were revealed recently when its author, Dr- Ing Friedrich-Wilhelm Hennecke, spoke at a press conference organised by Wanner International.

Using data provided by leading manufacturers, he compared 5 different types of pump commonly used in processing plants - centrifugal, side-channel, peristaltic, membrane piston and Hydra-Cell - over a range of flow capacities and pressure levels.

Results showed significant differences in LCC between types, with the Hydra-Cell emerging as 'the most economic over the considered range'.

Dr Hennecke, former pump chief at BASF, was co-editor of the landmark 'Guide to Pump Life Cycle Costs' published jointly in 2001 by Europump and the Hydraulic Institute in the USA.

Retiring from BASF in 2002, he remains a member of the Pump Working Group of the VCI (Association of the Chemical Industry) and the Pump Standards Committee in Germany (DIN) and active as moderator of joint international seminars for pump users and manufacturers.

These activities confirm his view that pump Life Cycle Costs are increasingly important as a factor in decisions about plant design and purchase.

Life Cycle Cost is the measure of the true cost of a pump - from purchase to scrapping.

It includes energy consumption and the costs of repair and routine maintenance, as well as the original purchase outlay.

For his comparative study, Dr Hennecke approached prominent manufacturers of each type of pump, requesting each company to select its most appropriate model for given operating requirements in 3 flow capacities.

Also, to supply data on routine maintenance needs, expected time between repairs, costs of spare parts and labour.

The scope of the investigation covered flow rates of 1.4, 4.2 and 8.4m3/hr and pressures of 5, 10, 50, 75 and 100 bar.

In practice, not all the pump types are suited to operation in all circumstances.

Limiting factors include pressure, temperature, solid content, hazardous fluids and pump pulsation.

Dr Hennecke's research into LCC was very detailed.

Comparing the 5 types of pump at various pressure levels, some interesting findings emerged.

For low flows and low pressures, LCC for Hydra-Cell, centrifugal and side-channel pumps were similar.

The peristaltic pump (lowest initial cost) had high repair costs.

The membrane piston pump, though energy efficient, had easily the highest initial cost and was expensive to repair.

Where higher flow was combined with low pressure, the centrifugal pump had the lowest LCC.

For pressures above 10 bar, irrespective of flow rate, only positive displacement pumps were considered suitable - ruling out centrifugal, side channel and peristaltic types.

The figures showed that for these higher pressure applications the LCC of the Hydra-Cell pump was substantially lower in each case than that of its only real alternative - the membrane piston pump.

Dr Hennecke's general conclusions.

In terms of LCC, the Hydra-Cell, whose efficiency at high pressure is around 85%, is the most economic pump overall in the considered range and it can pump abrasive, viscous, corrosive and fluids with particles.

The LCC of the side-channel pump is comparable, within its pressure range, but the pump can only handle clean fluids.

Centrifugal pumps 'are for low pressures and high flow rates'.

The LCC of the peristaltic pump is increased by its high consumption of replacement tubes.

Membrane piston pumps are very efficient, but their investment cost and the cost of spare parts and labour when changing membranes is extremely high.

The Life Cycle Cost of this type of pump can be up to 3 times higher than that of the Hydra-Cell.

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