Intro to ROTEX Solenoids, Valve Actuators and Limit Switches

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Introduction of ROTEX Controls product line of solenoid valves, Infinity ECV line of rack and pinion actuators, DRS and DRV scotch yoke actuators, and HYV hydraulic actuators and limits switches.

ROTEX offers a range of Solenoid Valves and Air Operated Valves used for handling almost any fluid with various of temperature, pressure or vacuum for use in Control and Automation applications.

ROTEX limit switches are designed to last and meet your required service conditions. Both the weather proof and explosion proof switches feature an aluminum die cast enclosure that is powder coated for superior corrosion resistance resulting in a weather proof enclosure to IP67. Stainless steel enclosures are available, also confirming to IP67.

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NEMA (National Electrical Manufacturers Association) Classifications for Limit Switches

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Choose the right Limit Switch enclosure

Limit switch enclosures carry classifications for tightness and protection from external environments. The National Electrical Manufacturers Association (NEMA) maintains these classifications.

Here is a listing of the most typical NEMA classifications for limit switches. The definition below are from the NEMA site and the entire document can be seen here.


Type 4 Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (falling dirt and windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); and that will be undamaged by the external formation of ice on the enclosure.

Type 4X Enclosures constructed for either indoor or outdoor use to provide a degree of protection to personnel against access to hazardous parts; to provide a degree of protection of the equipment inside the enclosure against ingress of solid foreign objects (windblown dust); to provide a degree of protection with respect to harmful effects on the equipment due to the ingress of water (rain, sleet, snow, splashing water, and hose directed water); that provides an additional level of protection against corrosion; and that will be undamaged by the external formation of ice on the enclosure.

Type 7 Enclosures constructed for indoor use in hazardous (classified) locations classified as Class I, Division 1, Groups A, B, C, or D as defined in NFPA 70.

Type 9 Enclosures constructed for indoor use in hazardous (classified) locations classified as Class II, Division 1, Groups E, F, or G as defined in NFPA 70.

In Hazardous Locations, when completely and properly installed and maintained, Type 7 enclosures are designed to contain an internal explosion without causing an external hazard. Type 9 enclosures are designed to prevent the ignition of combustible dust. 

You should always consult with an application engineer before choosing the limit switch enclosure for your application.

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Industrial Valve Limit Switches

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In industrial valve terms, a limit switch is a device containing one or more magnetic or electrical switches, operated by the rotational or linear movement of the valve actuator. They are used to show the open or closed position of an industrial valve, or as safety interlocks to protect man or machine. The enclosure is usually classified in NEMA (National Electrical Manufacturers Association) Standards, such as NEMA 4, NEMA 4X or NEMA 7 (explosion resistant).

Internal Mechanical Limit Switch

The internal switches can be electromechanical or magnetic. Electromechanical switches respond to a mechanical cam on a shaft to change state (make or break electrical contacts). Magnetic switches use a magnetic field to change state in a reed switch, or  to sense a disruption in the magnetic field, or through capacitance.

Internal Magnetic Limit Switch

Along with an electrical signal, visual indication is an important part of a limit switch. Most switch come standard with a "dome" or "beacon" displaying "open" or "closed" or positions anywhere in between.

When applying limit switches on industrial valve application one should consider the following:

1. Environment - is the limit switch in an area where there may be dust, spray-down, rain, corrosive gasses, combustible gases, or require sanitary conditions. Choosing the correct NEMA classification is critical.
2. The electrical rating of the signal being transmitted. AC or DC? High voltage or low?
3. Operation Frequency and Cycle life - will the switch only open/close occasionally, or will it cycle every few seconds? Mechanical switches have inherently shorter cycle lives than do proximity or magnetic switches. Choose the best switch considering load and cycle life.
4. Visual indication - do you need to see the valve status from a distance? 
5. Auxiliary outputs - besides opening of closing the primary signal, are their other signals you must send by using additional switches in the housing. 

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