Pump Ordering Guide
The most important piece of advice when sourcing a pump is to make sure you are buying the right pump. This is obvious right? However a pump may be suitable for an application, but if the installation is pushing the performance capabilities of the selected model, not only will it be operating less efficiently but the lifespan may be reduced.
With a vast range of pump types, material options and performance specifications, sourcing a pump requires experienced technical knowledge. Some procurers know exactly the pump they want, some know the performance requirements and others may solely know the application for which they need a pump. When you are unsure of exactly the pump you require, Castle Pumps understand that you need to be able to rely on an experienced supplier who can take the information you have and specify a solution that precisely meets the requirements.
This guide aims to talk through the information typically required to ensure that a technical solution can be specified that matches your individual application and performance requirements.
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The application that the pump will be used for will determine the pump type, material and impellers required. The more detail that the application can be described in, the better informed the decision will be as to selected material, design features as well as the rpm of motor. For example, a pump that is designed to run 24/7 will typically run slower, have additional bearings and need to be easier to maintain in situ than a pump that is required to operate less frequently.
Full disclosure of the liquid is needed to ensure its chemical compatibility with the pump wetted parts, including the casing, impeller, wear rings and any elastomers fitted. The fluid will therefore have a direct influence over the materials selected. Typically, cast iron is used for fresh water and bronze/aluminium for seawater; however pumps can also be supplied in stainless steel and duplex stainless steel.
The viscosity and temperature may also be required to determine the power absorbed by the pump, as well as any impellers required to provide the specified duty. The viscosity of Heavy Fuel Oil (HFO) for example can vary greatly with temperature, which in turn impacts upon the pump requirements. For example with a viscosity of 20cSt, if a flow rate of 98M³H is required at 2.5 bar, a 12Kw motor is required. With the same flow rate requirements, a viscosity of 1500cSt will require a motor of 28KW.
Typically measured in L/min or M³H although other units are acceptable.
Usually measured in bar or M.
For centrifugal pumps, at certain pressures a multistage pump may be required and depending on the pressure the pump may need to be manufactured in a different material. If the pump is a positive displacement type, relief valves would need setting to the correct pressure.
Voltage and frequency
The voltage and frequency have a direct influence over the pump chosen, as at 60hz there is a 20% increase in flow and pressure over the same pump in 50hz. Often vessels may be operating on single or three phase and it is important this information is made clear at the outset.
If there are any specific dimensions or existing pipework requirements for a particular installation, this will also help determine the pumping solution most suitable. For example, if space is an issue a vertical pump may be more suitable than a horizontal orientated option. If an existing pump needs replacing, the replacement may need to be specific dimensions to fit within the pipework. Some manufactures construct models to match existing pump and pipework specifications, and DIN 24255 pumps are also available that can be interchanged with other DIN 24255 pumps.
Certification such as a witness performance test is another important part of satisfying class requirements.
There are other technical considerations which should be given during the procurement process. There are various low maintenance options of pumps that may be desirable depending on the liquid being pumped and the individual servicing requirements.
- Spacer coupling
A spacer coupling can be fitted to vertical pumps to ensure that the inner parts such as impellers, seals, and wear rings can be replaced without having to remove the motor.
- Back pull out design
A back pull out design enables the motor to be removed without disconnecting the pump from the pipework.
- Magnetic coupling
Magnetic couplings remove the need for a mechanical seal as being driven by a magnet means that the pump head is seal-less. This eliminates the chance of leakage and reduces service intervals.
- Priming pump
In situations where a short priming time is required, or where it is not possible to keep the suction flooded with the use on a non-return valve, pumps can be fitted with a priming pump.
Manometers and vacuometers are a valuable addition to any pump. They measure the difference between the inlet and discharge pressure to check the pump is working as per the curve.
- Control panel
Fitting a control panel with an hour meter confirms how long the pump has been in operation, therefore helping to determine service intervals such as bearing greasing and inspection.
- Performance related energy costs
It is reported that energy output works out at approximately 45% of a pump’s total cost of ownership. The use of frequency converters to control the speed of the motor based on actual requirements of the pump can help to significantly reduce energy consumption.
- Replacing pumps
Pumps can be manufactured to a variety of specifications including wetted part material choices, mechanical seal, motor size, frequency, rpm and any additional accessories. The serial number is therefore essential to guarantee an exact replacement is supplied, as the model number alone may not indicate the unique pump specification. The serial number is usually indicated below the pump model on the name plate and on some pumps also engraved on the discharge flange.