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Construction Details

SEECO MNM operators are designed for maintenance-free operation in severe operating and environmental conditions. Operator components and systems are rugged, reliable and of the most contemporary design available for their intended function.

Modular Design

The overall design (figure 1) is highly modular and the interior cabinet lay-out is spacious and well organized. Access to all systems and components is available through the front door, eliminating the need for removable side panels. The modular design makes extensive use of separate sub-systems (assemblies) and molex-style connectors (figure 2); each sub-system is initially assembled and tested external to the operator. In final assembly each sub-system or component is secured to a sheet metal chasis or interior cabinet wall. Electrical sub-systems are then connected to the control circuitry through molex-style connectors making final assembly essentially "plug and play." A rigorous final unit assembly test of all operator functions involves over 40 separate tests.


The powertrain is electro-mechanical (non-hydraulic) and utilizes a powerful 3/4 horsepower permanent magnet motor, heavy-duty worm gear mechanism and advanced solid state motor control circuitry. The full rated torque and speed are available throughout the entire range of operation.


The motor (figure 2) is high torque, starting and running, at minimum ANSI and NEMA voltages with the full rated torque available at nominal voltage. All bearings are permanently lubricated and sealed and require no maintenance. The motor has a standard NEMA face mount, which allows the motor to be easily changed out without the use of heat or pullers to remove gears or coupling halves.

Motor rotation (direction) can be easily changed in the field by reversing the two wires exiting the motor using the supplied molex-style connectors. A torque relief knob is also provided, which allows the torque on the switch control pipe to be relieved for ease of coupling and de-coupling. The torque relief knob can also be used for fine adjustment of the auxiliary (limit) switches.

Worm Gear Mechanism

The gear mechanism (figure 3) is a heavy duty, industrial worm gear reducer with totally enclosed gearing. The entire gear is factory submersed in grease to eliminate corrosion and requires no further field maintenance by customer personnel. The use of a worm gear prohibits the gear mechanism from being back driven from the output shaft eliminating the need for continuous braking. The gear housing is provided with a separate gear reducer output shaft seal and cabinet output shaft seal that prevents contamination of the interior of the gearbox.


To prevent over-travel of the motor beyond the open and close limit switch positions, dynamic braking is utilized to control motor rotation. When the output shaft of the worm gear mechanism reaches the open or closed limit switch position, a relay is energized and the motor is shorted; braking is simple, precise and immediate without hesitation or delay. Also, the inherently self-locking nature of the worm gear mechanism makes continuous braking unnecessary and eliminates the need for solenoid actuated brake components or other mechanical devices, which can fail or require periodic maintenance and adjustment.

Auxiliary (Limit) Switches

The operator is provided with ten auxiliary switches (figure 4), which follow the output shaft of the worm gear mechanism; two are reserved as motor control limit switches and the remaining eight are for customer use. Each limit switch is a form "c" contact and can be easily changed from NO to NC by repositioning shunts. The use of shunts makes field change quick and simple, eliminating the need for traditional wires and ring terminals. The cams are independently adjustable using setscrews.

For customers who require indication of switch position independent of the position of the worm gear output shaft, SEECO has two different optional mechanisms available. One mechanism is the traditional canister-style auxiliary switch (barrel switch), which is available in increments of two up to a maximum of fourteen switches. The second mechanism is a newer, more contemporary concept that utilizes limit switches in conjunction with the coupling mechanism to provide absolute indication of coupling status (coupled or de-coupled) as well as overhead switch position.

Operator Control Panel

The operator control panel (figure 5) is provided with open (green) and close (red) push buttons for local operation, switch open and switch closed indication lights and a local/remote switch with position status indication (dry contact). The control panel is colored yellow for easy identification by customer personnel .

Power Distribution Panel

The Power Distribution Panel (figure 6) includes a 15 amp GFI receptacle, motor over- current breaker, heater breaker, an AC present indication light, loss of AC status indication (dry contact), MOV surge protection and RF filters. A DC knife switch is provided as standard equipment in conjunction with the Power Distribution Panel. The panel is also colored yellow for ready identification. Optional features include an AC knife switch, a two pole AC breaker and a two pole DC breaker.

Temperature Control System

An advanced temperature control system (figure 7) is provided as standard equipment. The system includes a 120 VAC, 350 watt strip heater with re-circulating fan, thermocouple, protective sheet metal enclosure, programmable control and data logger. Control of the fan and heater is based on two user definable set point values. When the lower set point value is exceeded the heating element is activated and the fan will distribute the heated air throughout the operator enclosure. When the upper set point value is exceeded the fan alone is activated and air is circulated through the enclosure to cool the cabinet interior. The set point values can be changed through

Windows Hyper Terminal and the customerís laptop using the RS232 comm port provided. The data logger captures the interior cabinet high (max) and low (min) temperature, by day, for a rolling 30 day period. The daily max and min values can be displayed through the same Windows Hyper Terminal feature as the set point values.


The enclosure (figure 8) is completely maintenance-free and weatherproof. It includes a formed water channel (drip trough) around the door lip, entrance overhang and fully gasketed door to provide protection against windblown dust, rain and hose directed water. Other features include a removable door with lift-off hinges, a pneumatic door holdback, heavy-duty stainless steel three point latch with padlockable handle, a screened louvre with removable dust filter of washable nylon, a door activated convenience light, remote door open status indication (dry contact) and a 10" X 7" removable conduit plate located on the cabinet bottom. The standard enclosure is aluminum but a stainless steel enclosure can also be provided.

Mounting Brackets

Galvanized steel mounting brackets are designed and fabricated for each specific mounting structure (by order and location) or to a customerís standard structure. No modification to the structure is required, which reduces installation time and cost.

Swing Handle

An expandable telescoping swing handle (figure 9) is provided for manual operation of the overhead switch and is inserted into a socket above the coupling mechanism. The swing handle is stored within the enclosure utilizing a pivoting socket and latching mechanism. The latching mechanism (figure 5) incorporates an auxiliary contact (limit switch) that provides remote status indication of the presence, or absence, of the handle. As a safety feature for field personnel, removal of the handle from the latching mechanism disables the remote operation of the motor operator through the terminal blocks. Remote operation is restored when the handle is returned to the latching mechanism.

Coupling Mechanism

The coupling mechanism (figure 10) is located external to the enclosure, which allows manual operation of the overhead switch without entering the enclosure. The coupling mechanism is factory set and requires no field adjustment other than to pierce the set screws of the pipe coupler. The mechanism assembly consists of three components: an upper, center and lower coupling section. The lower coupling section is permanently tied to the worm gear output shaft and turns with the shaft. The upper coupling section is cross bolted to the operating pipe. The center coupling section slids freely up and down between the upper and lower sections to couple and de-couple the overhead switch to the motor operator.

The coupling mechanism is designed to be foolproof, as it can only be coupled in the one true correct position. This is accomplished by the machining of one dog ear different from the others in the mating coupling components. The mechanism is designed for a single padlock to be used in any sequence of actions. Locking stops are provided for padlocking the switch open or closed in the de-coupled position.

Pipe Coupling

A heavy-duty, thick-wall pipe coupling (figure 11) is provided as standard equipment. The pipe coupling is physically located immediately above the handle socket and can be provided for any diameter of control pipe as required by the overhead group operated switch. An optional universal joint can be provided, at additional cost, where the off-set dimension or angle of the control pipe cannot be accommodated by a straight pipe coupler.

Terminal Blocks

Six hundred volt rated, high barrier terminal blocks with white marking strips are standard. All customer connections are made to one side of the terminal blocks. Optional sliding link terminal blocks can also provided at additional cost when specified.

AC Power Supply

For applications where 48 or 125 VDC is not available, an integral 24 VDC power supply can be provided (requires customer supplied 120 VAC). The 24 VDC power supply is housed within the main operator enclosure and consists of the following system components:

Gelled electrolyte batteries - Two 12 volt, 33 amp hour batteries.

"Smart" charger - heavy-duty battery charger (figure 12), 130 watt, with 120 VAC input and 24 VDC constant voltage output. Provides three stage charging: bulk charge, over charge, and float charge. Charger has short circuit protected outputs and is temperature compensated. Also includes LED charge status indicators.

Advanced battery management system (LAB Tester) - unit (figure 13) has built-in loss of AC voltage alarm, low voltage DC alarm, battery load test function, battery check test function and DC knife switch position indication. Load and check tests are based on user defined time intervals which can be modified through Windows HyperTerminal. Unit provides automatic scheduled testing of batteries, with local LED and remote (dry contact) indications of battery status and condition. See SEECO LAB24 catalog section for a more detailed description of features and functionality.

Solar Power Supply

For remote applications where 120 VAC is not available, or practical, an economical and highly reliable solar power supply (figure 14) can be provided. The solar power supply includes the solar modules (panels), mounting brackets, inter-wire kit, charge controller, batteries and the advanced battery management system (LAB Tester). The solar power supply is sized for the specific geographical location and the current draw (load requirements) of the associated equipment, including RTU, radio, etc.

As the solar power supply is a DC only system it will not include AC-specific functions such as loss of AC alarm, the heater and re-circulating fan, GFI receptacle and interior cabinet light. For northern latitudes where extreme low temperatures are a concern, an optional insulated enclosure can be provided at additional cost.

More Information

For additional information on SEECO motor operators, please view the following pages:




Type MNM1 Operator




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