FAQ: HOW MUCH TORQUE DOES AN ACCUSTALTIC PUMP REQUIRE?

Before we start, a few quick facts about torque:

What is torque? Torque is the leverage that a motor can put on a shaft, to produce rotary motion. it it typically expressed as inch-pounds (english) or kilogram force-centimeters (metric). We will use english here. A converter is found at the bottom of this page.

If you know the torque, and the speed, you can determine the required horsepower for any application by the following equation:

Torque(inch-pounds) * Speed (rpms)/63025 = Horsepower.

Before you choose a motor:

If you purchase a complete motor and pump combination from Ledebuhr Industries, you can rest assured that your combination will not only be be reviewed and approved for suitability, but also test run if possible before shipment. You do not need to continue further here, unless for your own curiosity.

If you intend to purchase a bare pump or a pump/gearbox combination:

If you prefer to buy a pump and finish it with your own motor, we're happy to assist you. There are two options:

• Bare Pump: for direct mounting a hydraulic motor or shaft-coupling to another motor or gearbox.
• Pump/gearbox combination: a direct mounted gearbox with 56C faced input gives you the ability to simply add your motor of choice.
  • Various ratios from 5:1 to 20:1 allow the use of smaller motors
  • Create different fixed speed pump outputs. See Fixed & Variable Electric Options for more detail

Torque and horsepower:

Accu-Staltic metering pumps are constant torque applications, with a momentary breakaway torque requirement that can be up to 100% higher than the running torque. Constant torque means that after the pump starts rolling, doubling the speed of the pump will also double the horsepower required. A motor should be chosen to provide both the required breakaway torque (typically called the stall torque) and maximum horsepower required at peak speed. When in doubt, oversize the motor if possible. Electric motors only draw the energy they need, so you wont be wasting energy, and the extra size will pay dividends in longer life and cooler operation.

Matching the proper motor to the pump is important so that you always have adequate torque to start and run the pump without damaging the motor.

Why a Gearbox?

If you are going to use an electric or airmotor, the output torque tends to be too low to drive an Accustaltic Pump. By using gear reduction, the torque can be amplified and the speed reduced into the operating range of the pump, typically 20-450 rpms.

For example, A 10:1 gearbox theoretically gives a 10x increase in output torque, and slows the pump to 1/10th of the motor speed. This can typically allow the safe use of a .75 to 2 HP motor to drive the pump. Refer to your motor specification.

There's one big exception that you need to be aware of and take account for: most gearboxes in this size range (including ours) are about 60% efficient. That means 40% of the torque that goes into the gearbox, stays in the gearbox (actually, it leaves as heat, not output torque). So you will need to make sure that you size your motor so that 60% of the motor's output torque is sufficient to do the job.

Example pump operating torques:

The following torque values are for pumps outfitted with new, unused PROTHANE II tube, manufactured by Randolph-Austin Company. This is the highest tensile strength tube we use,  giving the highest possible input torque requirements. Once the tube is “broken in”, the torque drops alot. See notes following this table.

These numbers are all representative of pumping water with no suction lift and open flow- no backpressure.  For high lift and high output pressure applications, use the torque increase factor in the right-hand column below.

Very high viscosity or high density fluids (such as if you were pumping mercury) will increase the input torque. If you want to know how this will affect the torque, you'll need to buy one and pump your own mercury.

Torque requirements, using 1/2" ID, 1/8" wall Prothane Tubing (Inch-Pounds):

Why so much torque?

Remember, unlike other peristaltic pumps that have small motors and only 1 channel, the Accustaltic motor may be turning up to 12 channels at once, and you can't escape the laws of physics- 12 channels is 12X as much work. However, when you divide it out, it's not so different than most other peristaltic pumps: when using a 2 HP motor, on a 12 channel pump, that is only 1/6 Hp per channel.

Notes:

*For each 1 bar (14.7 PSI) of backpressure, with ½” ID 1/8" wall Prothane tubing,  add 3.3 inch-pounds per channel (40 inch-pounds/bar for 12 channel, 27 inch pounds/bar for 8-channel)

We can evaluate other tube elastomer and size combinations upon request. For example, 1/2" ID, 1/8" wall NORPRENE A-60-G, another common tube, requires approximately 50% of the published values above.

Smaller ID tubes will also require substantially less torque.

1 inch-pound = 1.15 kilogram (force) centimeter (kgf*cm)
1 Bar= 14.7 PSI

Torque units converter: convert our charts to your units