Viewpoint: lifecycle lessons for choosing pumps

The process industry operates in a market that is dominated by roto-dynamic technology — particularly centrifugal pumps.

So it is not unusual for system designers and equipment specifiers to take this as their default choice when considering pumps for specific applications.

But roto-dynamic pumps have limitations in respect of the pressure they can generate and their overall operating efficiency.

There’s no doubt that if the most appropriate type of pump is selected for a specific application and duty, there will be a benefit to the overall performance and life expectancy of the pump.

Lifecycle costs

One of the essential elements in successfully identifying and selecting the best pump for a particular application has to be the analysis of lifecycle costs.

The issue of equipment lifetime operating and downtime costs has never been higher within industry, and lifecycle costs are now a major part of the specification process. Putting the purchase price ahead of performance is a common scenario, so the impetus is on the pump provider to examine lifecycle costs. They must also explain how these costs can impact on the investment to the customer.

The issue of equipment lifetime operating and downtime costs has never been higher within industry, and lifecycle costs are now a major part of the specification process

Lifecycle costs will take into account known factors such as the initial investment and subsequent spares. This is alongside the less obvious factors associated with maintenance, power consumption and efficient use of the product being handled.

When considering competing high pressure pumps, lifecycle costs analysis determines the most cost-effective option to purchase, operate, maintain and finally dispose – assuming that each pump type is equally appropriate to be implemented on technical grounds.

Operating costs

The initial cost of purchase is the smallest contributor to any lifecycle cost analysis, with estimates ranging from 5% to 15% of total lifecycle costs.

Correct sizing of the pump for the application makes sure the purchase cost is kept to a minimum.

You must then consider the costs of operation. These are probably the largest contributors coming in at between 60% and 80% of the total.

The key factor for the pump’s energy consumption is to know the pump’s mechanical efficiency. In other words: ‘how efficiently energy input for driving the motor is converted into output of liquid flow and pressure’.

Maintenance costs

The price of maintenance is usually the second highest cost affecting lifecycle costs, and can vary from between 15% and 30% – depending on pump use and service intervals.

Triplex plunger pumps are well known for their high durability, long life and low maintenance. Instances of pumps still in operation after more than 20 years are not uncommon. And, subject to recommended routine maintenance, should go on for another 20 years.

The cost of pump downtime also adds to lifecycle costs. Typical examples include unexpected breakdowns, poor performance and disruption to the equipment in which the pump is operating. These factors will impact on plant performance and can lead to significant disruption and additional costs.

Clearly, pump reliability is significant in ensuring lifecycle costs are achieved.

• Mark Austin is general manager at Cat Pumps