![]() However, the lower part is lubricated by the pumped liquid. As previously stated, the upper part of the mechanical seal is lubricated by the oil in the endplate chamber. It has both a stationary face and a rotating face. This seal uses an inner and outer seal arrangement. Some companies use a Type 21 mechanical seal as its standard submersible motor seal. The mechanical seal keeps moisture out of the motor. It also lubricates the upper part of the mechanical seal. ![]() The oil acts as a barrier to trap moisture and provide sufficient time for shut down if water enters the motor. The drive endplate has a special design that includes a chamber filled with oil. Also, a moisture monitoring probe is used to detect moisture entering the chamber. An oil filled chamber and a mechanical seal serve this function. Since the motors are designed to run continuously while submerged in water or effluent, they include features to keep water out. The drive end of submersible motors is a critical part of the design. This cable should never be used to lift the motor. Standard lengths vary from 25 to 30 feet, but other lengths are available upon request. Typically, two separate cables exit the cable cap epoxy potting compound a four conductor power cable and a five conductor control cable. An epoxy filled, non-wicking cable cap assembly protects the motor from moisture that could enter through the opposite drive end of the motor. Machined fits have grooves with O-rings to prevent water ingress to the motor. Submersible motors use cast iron frames that are precision machined for tight fits between the parts. Explosion-proof motors are UL (Underwriters Laboratories) listed and CSA (Canadian Standards Association) certified for Division 1, Class 1, Groups C and D with a 1.0 Service Factor and T2A temperature code. ![]() These locations require an explosion-proof motor design. An example of a hazardous location is a sewage application where flammable gases might be present. Submersible designs are available for hazardous and nonhazardous locations. Most motors come standard with 316 stainless steel hardware and 416 stainless steel shaft material. The motors have cast iron frames and end plates. Submersible motors are rugged and corrosion resistant, making them suitable for demanding applications. (Article images courtesy of Baldor Electric Company.) Many submerged motors rely on the effluent to stay cool and run continuously while submerged. This allows the motor to dissipate heat while running continuously in a dry pit application that only experiences flooding under unusual conditions, such as heavy rains or a backup in the system. These motors can also be designed for continuous operation in dry pit applications by de-rating a larger horsepower motor frame. These standard designs are also rated to run in air for 15 minutes when conditions require it. Wet pit motors use the effluent for cooling and are designed to run continuously while submerged. These are totally enclosed, non-ventilated (TENV) motors. Municipal and industrial wastewater markets use submersible motors for both wet and dry pit applications. While end users ultimately decide which motor best fits their need, this article explains how the designs differ and provides information that will help end users make informed decisions. Motor manufacturers routinely answer questions about the differences between submersible and immersible motors and the applications best served by each design.
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