FEATURE PUMPS, VALVES & ACTUATORS A BALANCING ACT
While a low pump purchase price may appear attractive, with 80% of the TCO coming from its running costs, keeping these lower over the pump’s lifetime will provide a greater return on investment in the long run, says Lesley Eaton from SEEPEX
P
umps are critical to a range of industries, and the number of different
pump types on the market means choosing one can seem like a daunting task. In today’s squeezed economy, maximising productivity is essential if companies are to remain competitive – and correct pump selection is key to this. Productivity is measured by the ratio of
output per unit of input. Many companies see it as a balancing act – how can they increase their output without increasing their costs? It is closely linked to efficiency, ensuring that every piece of equipment and every part of the process is optimised, delivering greater value for money to the operator. The most important criteria when
specifying a pump is to ensure it is fit for purpose. To do this, it is important to understand the product to be pumped, and the process involved. Is the product in question liquid or semi-solid? Is it viscous? Will it need to be transferred over a long distance, or pumped to height, for example to storage vessels and silos? Other important information includes,
for example, does the product contain solid particles? Also bear in mind the length of the discharge pipework and the configuration regarding bends and lifts.
TOTAL COST OF OWNERSHIP (TCO) After thoroughly researching the options available, it may transpire that more than one pump design is fit for purpose. While a number of pumps may be able to do the job, in order to ensure optimum productivity, operators must then consider the total cost of ownership (TCO). Although some operators can be swayed by the initial purchase price, this can be a false economy. The lifecycle cost of a progressive cavity (PC) pump, for example, is typically 10% capital purchase cost, 10% maintenance/spare parts, and 80% energy costs (based on £0.10p per kW/hr over a 20-year period, using WIMES calculations). With such a high percentage of a pump’s
TCO coming from its running costs, selecting a pump which is energy efficient is key to enhancing productivity. Unlike piston, diaphragm and peristaltic pumps, PC pumps produce low pulsation flow and
8 SEPTEMBER 2018 | PROCESS & CONTROL
require smaller drives and motors for the same duty. And unlike air-operated pumps, they run on a direct energy source, without the conversion of electricity to compressed air. This all helps to reduce the energy required to run the pump. Some of the more intelligent pumping solutions on the market, such as SEEPEX’s Smart Conveying Technology (SCT), can deliver greater energy savings. By optimising the clamp between the rotor and stator, and using a variable speed drive, the SCT pump can be up to 20% more energy efficient than traditional PC pump designs. As maintenance and spare parts are
responsible for 10% of the TCO of a pump, finding a solution that is easy to monitor and maintain is also important. The SCT range can improve whole life costs due to the ease of replacing parts and clearing blockages. The fact that these pumps can be remotely monitored also makes it easier to anticipate problems, enabling predictive maintenance. In addition, the use of variable frequency drives (VFD) means that speed can also be controlled. This is important because as the pump performance drops over time, its speed will increase to maintain flow; once this is identified, the SCT pump can be quickly adjusted to regain its original capacity, keeping efficiency high and providing more time to plan for maintenance. The use of level controls with VFD to speed and slow pumps, and the regular, laminar flow created also helps to deliver a higher quality, more uniform pumped product. This reduces the wear rate of the pump, extending its service life. Another cost consideration for operators
is whether a pump will require the purchasing of ancillary equipment. Many traditional pump designs require pulsation dampeners and check valves, all of which come at a cost, and are liable to blockages as solid particles can get caught behind the valves. In contrast, due to their constant, virtually pulse-free action PC pumps do not require dampeners, and the interference fit between rotor and stator negates the need for check valves, saving operators money and reducing downtime. In addition, high-pulsation pumps increase the pressure rating of the
By optimising the clamp between the rotor and stator, and using a variable speed drive, the SCT pump can be up to 20% more energy efficient than traditional PC pump designs.
downstream pipework, which means rising costs in terms of pipework and associated valves. PC pumps have a low pulsation action which generates a lower pressure on discharge, and reduces costs. As well as controlling TCO, operators can
Lesley Eaton, business development and marketing manager, SEEPEX, says ‘whatever solution you choose, make sure to take into account its energy efficiency, maintenance requirements and the costs of any ancillary equipment before signing on the dotted line. Put simply, specifying the wrong pump could decrease your productivity – choosing the right pump will almost certainly increase it’
also reduce their initial purchase price by talking to their supplier about the different options available. For example, could a smaller, smarter pump do the same job as a larger, more expensive solution? Is it worth integrating a boundary layer injection system to reduce pipework friction losses further downstream? Could labour costs be cut by specifying a pump with excellent suction lift capabilities, such as a PC pump which can lift liquids from the base of settlement tanks? A responsible pump supplier will work with an operator to specify the most cost effective solution for their needs.
PRODUCTIVITY IN PRACTICE Anglian Water uses an advanced heating, pasteurisation and hydrolysis (HPH) process prior to anaerobic digestion, which requires thickened sludge at a dry solids (ds) content of 4-8% to be pumped through heat exchangers. However, at Basildon WwTW, the original lobe pumps had a lower than expected flow rate and were unable to feed the heat exchanger efficiently. The pumps also required full maintenance interventions every three months and complete overhauls of the heat exchanger when blockages occurred. SEEPEX supplied Anglian Water with a
PC pump, which could deliver up to 72m3
/hr through the heat exchanger to
the digesters, even when faced with a variable sludge ds% input. The result was a well-mixed, less variable sludge for digestion and an increase of up to 100% in the volatile fatty acids (VFA). As VFA are an indicator of final gas yields, the SEEPEX pumps have improved energy production. In the 12 months since the pumps have
been installed, they have required no service interventions and caused no heat exchanger problems.
SEEPEX
www.seepex.com
/ PROCESS&CONTROL
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