Submersible motors are most often used with ROVs and AUVs, although they can be used for various other items. Our submersible motors are very compact, safe, and lightweight. However, our motors are still very powerful.

Besides the most efficient thrusters in the world, Innerspace manufactures streamlined, lightweight, efficient hydraulic & electric submersible motors with tapered stainless steel shafts for direct propeller attachment.  No separate adapter shaft, bearings, and compensated chamber are necessary.

When it comes to creating an environment that is maximized to avoid trouble, choosing to install a submersible motor is one of the best practices you can adopt. These motors can provide a reliable and efficient means of powering a pump. You don’t want to have trouble with the power to your pump when you need that pump to be operating – as that usually means there are other priority areas you need to address.

Making sure your submersible motor lasts

One of the common mistakes made is not to review and plan for an operation environment that promotes a long life with your submersible motor. It doesn’t take much to keep the motor happy. It needs to be placed in a suitable operating environment. What makes that suitability is what you have to pay attention to when placing the motor. A suitable operating environment is going to allow for a protected and uninterrupted supply of electricity to the motor, there will be adequate water flow to promote cooling going over the motor, and you also have to make sure that your pump load is sized to match the motor capacity.

How power cycling will affect life span of components

While you’re submersible motor may be made out of long lasting parts, the core components that allow for control of the motor, such as:

  • pressure switches
  • starters
  • relays
  • capacitors

are going to have a shorter lifespan than the mechanical working parts. The influencing factors on their lifespan come right from the power cycling the motor will experience. This cycling can include the number of starts between maintenance points, and the speed of the cycles. Too rapid a cycle can also affect the mechanical parts of the motor, like the spline and bearings, which can damage easily if the motor load causes overheating.

Managing thrust and torque for Submersible Motors

The installation of the motor must be done to exact specifications of bolt and mount torque in order to prevent the thrust and torque of the motor under load from wearing out the bearings and loosening connections. Depending on the motor you choose, it may have different mounting requirements. Most require a stable bolt mount that can absorb the shock of the starting thrust, and then manage short runs of upward thrusts. The torque of the motor does communicate through the body and puts additional wear on the mounts. Always check the integrity of the mounts during your maintenance cycles.

The basics of cooling management

One of the most important things to understand about the design of a submersible motor is that it is not meant to be exposed to the air. It can run for about 15 minutes in a dry environment, but the cooling design of these motors is entirely based upon the external. The motor is dependent on water running over the body to allow for dissipation of heat through the liquid body. When exposed to air, it will become overheated and damage as air cannot dissipate heat as well as liquid. This is why one component of a prime operating environment requires the motor to be able to remain submerged at all times.

Knowing your hazard

The onus is on the installer to know whether or not there is an explosion risk in the operating environment the submersible pump will be placed. It is common to find flammable gases, liquids and combustible dust in water and waste-water applications. Depending on the National Electrical Code (NEC) and National Fire Protection Association (NFPA) 70 regulations, your motor may have to have a Division 1, Class 1, or Group D certification. A good reference to consult to determine what your operating environment needs is the Standard for Fire Protection in Waste Water Treatment and Collection Facilities. The NFPA 820 will specify the definitions and classifications of areas, as well as what needs to be in place.

What are the best submersible motors made of?

Cast iron is the only choice for the body construction of a submersible motor. Not only can it withstand abuse to prevent internal components from being damaged, but cast iron can be machined precisely. This means better seal integrity from the beginning. The integrity of the seal is essential to keeping water out of the motor.

The external power leads also have to be maximized to resist water. For this, it is best to use a non-wicking cable cap with a butt splice that is filled with epoxy to form the sealing rubber grommet. As these motors are submerged, power has to be completely sealed against the water or the water, and the motor, can become electrified.

Monitor conditions with regular maintenance and inspections

The best way to prolong the life of your submersible motor is to monitor its condition using regular maintenance points and inspections. The most important areas to monitor are the seals. Seals that fail can let water into the motor, this will dilute the oil used to cool the motor and can lead to faults in the control electronics. You also want to inspect the built in alarm functions. The alarm is what allows the motor to shut down when probes and sensors detect a problem.

Your submersible motor is built to withstand a lot of stress, but it will only last as long as your regular maintenance and inspections allow it too. Create a prime operating environment, and then follow through with regular inspections to make sure that motor is always ready to power the pump when you need it most.

Being of superior hydrodynamic design, our thruster/motor assemblies produce 90% reverse thrust.