How to select the right type of pump drive for your application

jbj Techniques Limited can make it easier for you. In this article, we will take a look at multiple power take-off units used as pump drives, and how you can select the right type of pump drive for your application. Whether you are running an industrial plant, or looking for the right power take-offs for your heavy machinery, heavy plant, mobile applications, or offshore marine machinery this guide will help you select the right pump drive for your needs.

Let’s begin with the basics. When engineering any new pumping or hydraulic system with pump drives and power take-offs, there are six basic things you must consider – before you begin creating blueprints, plans, and other project details. Here is a quick overview of each one.

1) The number and type of pumps required.
No two projects are the same. The type of pumps – and the number that you need – will vary in each and every engineering project. This depends on the performance characteristics and overall dimensions of the pumps, as well as the pipework through which the pumped medium/fluid will travel. With both of these factors understood, it should then be a simple process to select suitable pumps that will deliver enough power to meet the application demands. Failure to do so will result in sub-par performance, pumps may be stressed past their operating limits, resulting in eventual product failure.

2) Maximum torque output requirements for each pump.
After you have done the initial calculations to determine the type of pumps that you need, it is time to consider your maximum torque output requirements. You will need to make sure that this number is below the maximum value of each of your pumps, to ensure smooth and steady operation.

3) Maximum input torque.
This is where your prime mover (engine/motor operating the power take-off or PTOs) comes into play. Depending on the power and size of your prime mover, you may need to select different pumps. However, it is considered good practice to size the prime mover once the input power, as required by the hydraulic pumps, has been finalized. If you have an extremely high-powered prime mover, you will need to make sure that you have selected a heavy-duty PTO. Conversely, you must consider whether or not a heavy duty PTO is overkill if you are using a smaller prime mover, such as the engine on a truck or another piece of heavy machinery. As a rule, maximum input torque should be at least 20% below the maximum rated value for any particular clutch and PTO, and, should also take into account the type of application and the duty of the drive required. This ensures that the pump is not over-stressed, and that it will operate correctly for its intended lifespan. Failing to do so can result in damage to both the pump and the prime mover.
‍
4) Maximum input speed.
When designing a new pump system, maximum input speed should be examined to ensure that the chosen pump can accept the maximum input speed of the prime mover. For example, a smaller engine may produce less torque at a higher RPM and consequently a suitably sized pump must be chosen, so as to ensure that it can accept this high RPM power. In contrast, a larger industrial sized prime mover may have a considerable amount of torque and power, but fewer rotations per minute, which will also have an effect on the pump that you select. Whatever pump you choose, you should also make sure that the pump direction of rotation is the same rotation as the flywheel / drive shaft when the pump is viewed from its shaft end, to ensure compatibility.

5) Service factor.
Fluid pumps are often operating in high-stress, high-up time environments, particularly in industrial processing plants and other such areas. This means that a service factor should be chosen which exceeds all requirements and the duty cycle of the drive in question, to ensure that the drive remains intact and functional even in times of periodic overload. As a rule, service factors will vary dependent on the application, environment and duty cycle. A basic rule, to enable a quick selection, would be for light load and duty 1.15, medium duty 1.5 and heavy duty applications a service factor of 2 should be applied. These figures apply to straight forward pump drives, however, if the PTO has an integrated clutch then reference should be made to our clutches and gearboxes catalogue which shows a precise service factor selector. Applying a suitable factor will ensure long life and good performance from the drive train

6) Cooling.
When selecting a PTO gearbox it is important to consider the thermal characteristics of the gearbox in question.  All units will have a power limitation which will be based upon the material of the gearbox casing and the surface area of the same. The figure published within the jbj Techniques’ Pump Drive catalogue shows the maximum thermal limit when the gearbox is used under 3 different conditions, 1) a static drive, 2) a mobile application and 3) a mobile application with the gearbox fitted with a standard low flow lubricating / cooling pump. To calculate the amount of cooling required for your drive a simple formula of installed power of the drive – thermal limit of the gearbox multiplied by the inefficiency of the gearbox will show the amount of cooling that the drive will need to dissipate. i.e. a drive of 300 kW using a gearbox with a thermal limit of 100 kW multiplied by 0.03 ( 3% inefficiency within the drive) requires a cooling system to dissipate 6 kW. This rule may vary depending on application requirements and environmental situation, e.g. ambient temperatures around the area of installation are important when it comes to selecting a cooling system for a pump. If the area is quite cold – for example, in a refrigerated environment – you may not need an additional cooling system, as the ambient air will help cool the oil temperature of the pump drive. Temperatures for a gearbox should not exceed 105 degrees Celsius when using synthetic oil, or 80 degrees Celsius when using mineral oil. Failure to adhere to these guide lines may result in lower capacity for work, as well as premature pump drive failure. We have an extensive range of industrial cooling / heat exchange products available to suit a wide range of industrial and mobile agricultural / heavy plant, and marine applications.

These are six of the most important factors that should be considered when selecting a pump drive, or any kind of PTO. Failure to abide by one or more of these factors can result in a shortened equipment lifespan, or even damage to a pump or prime mover. For help choosing an appropriate PTO, this guide will help you determine factors such as Speed Limits ~ Side-Load Limits ~ Clutch Torque Limits

Beyond the six factors previously outlined, there are some other considerations that should be taken into account when selecting a gearbox or a power take-off unit of any kind – not just a pump drive. When selecting a PTO, the following things should be kept in mind.

» Type of prime mover.
A gearbox and PTO designed for use with diesel engines will not work as well with a hydraulic prime mover, for example. The type of prime mover must be considered carefully when selecting a PTO. Make sure to choose the right gearbox for a diesel, or petrol engine, or electric-powered or hydraulic motor.
‍
» Inertia of the machine to be driven.
A high-inertia machine will typically put more stress on a gearbox, due to the heavy torque loads and weight applied to the unit during each rotation. The heavier the pump or other machine is, the more robust the gearbox will have to be. Special bearings and housing designs may be required to accommodate these high loads on the input shaft. This guide is a helpful resource for analysing inertia, engine type, horsepower, and more.

» Peak torque requirements.
Care should be taken not to undersize or oversize a gearbox. Using power take-offs that are too large – or small – for a particular task will result in higher strain and efficiency losses.

» Number of clutch engagements per hour and duration of each engagement.
More durable units are required for use in applications such as heavy-duty pumping, milling, and other activities which require fast, repeated clutch engagement every hour.

» Splitter requirements.
In some cases, a single power take-off may not be the right choice for a particular application, and multiple power take-offs can be used to provide maximum efficiency, and minimize equipment redundancy. Splitter gearboxes, or multiple power take-offs, allow for a single prime mover to drive multiple pumps or other pieces of equipment. They can even be designed to accept inputs from multiple prime movers, and output to a single application, creating a dual drive input.

» Splitter design.
Splitter gearbox selection is defined by all of the above statements but care should also be taken to ensure that the unit has a suitable distance between output centre lines to ensure space for pump oil feed connections. It should also be noted that by selecting a speed increasing ratio within the splitter may allow for the selection of smaller capacity pumps that will still ensure that the flow capacities of the drive are met. Due to potential overhung loads exerted upon the gearbox input mounting flange, it may be necessary to fit stirrup mounts to the sides of the gearbox, see jbj Techniques’ Pump Drive catalogue for details. When selecting either a single pump drive or a multiple power take-off, each of these factors must be considered. Failing to choose the right unit will lead to poor performance and an inefficient design, so ensure that you do your due diligence, and refer to all available resources, such as this selection guide from jbj Techniques Limited. By doing so, you can ensure that you choose the right unit for your particular needs.

Wondering if a single pump drive or a splitter gearbox (multiple power take-off) is right for your needs? It can be quite difficult to select the right pump drive for your needs. Here is a quick overview of the pros and cons of both single gearboxes and splitters.

» Versatile and flexible.
While splitter gearboxes are usually used to provide power from one prime mover to multiple drive units, they can also be used to unite the power provided by two different prime movers, and drive it into a single pump or other machine.

» Allow multiple pumps or other devices to be driven with one prime mover.
Splitter gearboxes allow for multiple pumps to be driven by a single prime mover with a high enough capacity. This includes gear pumps, vane pumps, screw pumps, and more. Of course, their usefulness is not only limited to pumps – they can drive a variety of other devices, such as water pumps, generators or connected with output drive shafts.

» Typically more expensive.
As you may expect, it’s more expensive to purchase a two, three or four-way power take-off than it is to purchase a single output PTO gearbox.

» More mechanically complex.
Though only a single prime mover is required to drive multiple pumps, the PTO itself is more mechanically complex, and great care must be taken to choose the proper unit.

» Simplified design.
A single pump drive has a more simple design, as it is not designed to output power to more than one device. In some cases, this can also mean superior performance when driving a single pump, though this depends on the particulars of the application.

» Comparatively inexpensive.
Lower mechanical complexity means a lower overall cost of the unit, which can be a benefit in lower-budget projects.

» Can’t be used to unite multiple prime movers.
This is one of the biggest drawbacks of a single pump drive. Being able to use one pump drive to accept power from multiple prime movers is very useful when designing and implementing projects.

» Not ideal for parallel pumping.
Parallel pumping is gaining acceptance in the world of hydraulics and plant design. It allows for less stress on each individual pump, and faster delivery of fluids via smaller pipes. Compared to multiple power take-offs, single pump drives are not ideal for parallel pumping.

Both single and multiple power take-offs have their own ideal applications – and it’s up to you to decide which one may be right for your product, due to their unique advantages and disadvantages. However, jbj Techniques have the expertise to assist you and are happy to help!

jbj Techniques Limited has available for you a tremendous variety of single and multiple power take-offs and gearboxes – each of which can be used as a pump drive for many different tasks.  Whether you need a single or multiple pump drive for use in a mobile application, through to large heavy plant vehicles, or you’re designing a new piping and liquid flow system for an industrial manufacturing plant, you can find the right jbj Techniques Limited product for your needs. So take another look at this guide now, and think about how you can choose the proper pump drives for your next project. Don't forget, you are not alone, jbj Techniques Limited are here to help! If you have more questions about selecting the drive unit that’s right for you, you can always contact jbj Techniques by sending an email to info@jbj.co.uk, or contact them by telephone at +44 (0)1737 767493.