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The Right Motor Type Enclosure For A Water Treatment Plant

Posted by Anthony DeLoach, President on Sep 7, 2017 1:32:19 PM

Different types of electric pumps, blowers, compressors,

and even material conveying equipment utilized to operate a water treatment process facility whether it is municipal, industrial, aquaculture, or a pisciculture facility.  All of these applications share a common requirement which is the need to have an electric motor provide the torque and energy necessary to operate the equipment and perform the required function. 

7 motors enclosure styles

One of the most common questions asked or considered during the design phase of the water treatment process is what type of motor enclosure should be selected.  There are 7 

types of motor enclosures that are available and defined by NEMA standards MG1-1.25 through MG 1.27.  The final decision should be driven by the all of demands that the application will have placed upon it.

The selection of the type of motor enclosure can be a difficult choice. 

If the application is for a process like Reverse Osmosis, Degasification, or Decarbonation, it is important to consider the efficiency of the motor and what the motor will be exposed to during its operating life cycle.    We will briefly review each of the 7 different types that NEMA defines for motor enclosure types. 

ODP Motor-1The ODP (open drip proof) is one of the most common types of enclosures. 

The enclosure is open and vented at the back end of the motor and allows air to circulate in and around the motor windings carrying off heat.  The ODP motor is designed to prevent liquid from entering the motor at a 15-degree angle based on the vertical alignment.  ODP motors are normally utilized at water treatment facilities or aquaculture facilities where they will not be exposed to corrosive conditions such as HVAC systems.


TEFC Motor-1TEFC (Totally Enclosed Fan Cooled) describes a totally enclosed motor housing,

that has an external fan located at the back of the motor and during operation it directs air forward across the motor housing. The motor housing will have a ribbed structure that is a type of heat sink to help dissipate the heat.  TEFC motors are the most common type of motor in municipal water and Industrial water treatment and all Degasification and Decarbonation treatment systems are equipped with TEFC motors.  In addition, all Odor Control Scrubbers are equipped with TEFC motors to avoid corrosive gases entering the motor and damaging the windings. 

TENV Motor-2A TENV (Totally Enclosed Non Ventilated) is a type of motor that is also enclosed with no opening but has no external fan or ribs on the motor enclosure housing. 

These motors are not normally utilized in Industrial Water applications, odor control, or decarbonation, due to the need for continuous duty and the ability to dissipate heat.

TEAO Motor-1The next motor enclosure type is a TEAO (Totally EnclosedAirOver) motor that is considered to be dust tight

and is selected for blower duty services where shaft-mounted fans are required or even belt-driven fans.  The motor must be mounted in a position that the blower or fan that it is driving provides the required air across the motor to cool the windings.  These types of motors are normally found in HVAC systems or indoor blower clean air applications.


TEWD Motor-1

A TEWD (Totally Enclosed Wash Down) motor is a motor that is enclosed

and is specially designed to withstand high pressure from wash-down applications or increased high humidity or other types of wet environmental applications.  The TEWD motor can be found in extreme wet environments and chemical exposure environments.  It is not designed for hazardous locations and has no rating for hazardous exposure. The type of motor can be utilized in CATION, ANION, Degasification, Decarbonation, and Odor Control/ Air Emission type systems.  It is also suitable for Reverse Osmosis and Aquaculture of Pisciculture processes because of its ability to withstand harsh, wet, humid, and corrosive exposure.

EXPL Motor-1The EXPL (Explosion Proof Totally Enclosed) is a motor that is totally enclosed

and is engineered and built to withstand an explosion of a specified gas or vapor inside the motor casing.  The types of motors are typically designed and selected for very specific hazardous applications where the surrounding atmospheres contain gases known to be combustible. All explosion-proof motors are strictly designed, manufactured, and tested under the strict rules and requirements of the Underwriters Laboratories (U.L) guidelines. It is very common to see EXPL-type motors in industrial water treatment systems on Decarbonation, Degasification, and Odor Control applications and all types of pumping systems.

HAZ Motor-1The last type of motor enclosure option is a HAZ (Hazardous Location) motor enclosure

and it is classified by the type of environment present and the specific chemical or material that is creating the hazardous condition and any possible exposure to the environment including the maximum safe temperature level for the specific substance or chemical. These types of motors and their selection fall under the NEC code (NFPA-70) and they are defined by different classes I, II, III, and within each class there are different Groups such as A, B, C, D, E, F, and G.   Again these types of the motor enclosure are commonly seen on applications in industrial and municipal water treatment for Filtration, Decarbonation, Degasification, Aeration, and Odor Control.  Likewise, a HAZ motor enclosure can b utilized in Aquaculture and Pisciculture applications based on the corrosive nature of the water. 

Motor Nidec-Table-2

Improperly selecting the type of motor enclosure can result in motor failure from overheating, corrosion, abrasion or

in worse case scenarios create a serious safety hazard if the correct motor enclosure is not selected for a hazardous condition. 

If the water treatment process involves degasification there is a possibility that harmful and corrosive gases may be released such as Hydrogen Sulfide (H2S) that can cause extreme corrosive actions on electronic equipment and motors if the motors are ODP (Open Drip Proof) the life expectancy on an ODP motor will be very short.

DeLoach Industries, Inc reviews both the application and location and all variable

before selecting the correct motor enclosure for your pumps or blowers on any of our Degasification, Decarbonation, Filtration, or Odor Control Systems.  Always consider all factors during a water treatment design and you will want to think about not only the size of the HP needed or the correct voltage, but also where will the motor be located. Even if the electrical motor is enclosed inside a blower housing that is located where corrosive gases such as hydrogen sulfide (H2S) may be present, then utilizing an ODP motor will allow the internal winding of the motor to be exposed to corrosive gases. In that scenario, the selection of a TEFC (totally enclosed fan-cooled) motor would be a better choice.  And keep in mind the duty cycle of the motor for its application.  The main components of the motor are sealed and will not be as susceptible to corrosion. This is a common mistake that can be made with induced draft aerators or decarbonators. 

The motor is often overlooked, due to its location inside the blower housing. The blower pulls air up and through the blower, while the motor gets direct exposure to harmful and often corrosive gases. The performance of the motor does not vary when selecting either an ODP or TEFC-type motor and each will perform its respective work duty based on the HP rating. Please remember that a TEFC motor is not by classification a “vapor proof” or spark proof type motor, so it will not qualify for Class I or Div II locations. For more information or to learn more contact the professionals at DeLoach Industries Inc. at (941) 371-4995.


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Topics: water treatment, water distribution system, advanced treatment solutions, About DeLoach Industries, water plant, motors, pumps, municipal water systems

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