Limit Switch Box- A Complete Guide

For 20 years, Instruthinkhas been among the famous manufacturer and suppliers of different instruments delivering in UK and around the globe. It includes valves, flowmeters, transmitters, and a limit switch box.  Instruthinkhas a complete range of limit switch boxes that you can fit on the pneumatic actuator to receive positive feedback and provide positioning that indicates the installation of the valve. The limit switch box by Instruthinkis available in different shapes and sizes that include the safety area boxes and approve by the ATEX for hazardous applications. The most famous limit switch box is mounting the Namur and the position indicator. it is suitable for the safety areas and the entry-level limit switch box.

Following are the answers to the questions about the limit switch box:

What is a limit switch box?

The limit switch box is the electromagnetic device that operates through the physical forces applying to an object. It has an actuator that gets connected to an electrical switch. The limit switch box helps detect or sense the object’s presence or keeping monitoring and tells whether the movement of the particular object exceeds automatically. The proper use of the limit switch box is to define the limit as the name shows through the object travels before being stopped. It is the point where you can engage the switch for controlling the limit of travel. The limit switch box is the replacement of proximity sensors in many applications.

What are the series of limit switch boxes?

SF series:  The design of this series of limit switch boxes is for hazardous areas. The SF series of limit switch box facilitate with the electrical and visual positioning feedback through automotive valves. The series of this limit switch box is available in die-cast aluminum with various lids, but the material for the closing remains the same. The whole device is entirely metallic by the covering of transparent polycarbonate. The solution of limit switch box is applicable in food, beverage, chemical, and petroleum industries.

Features of SF series of limit switch boxes:

• Twin designs of the shaft are available. The beam divides into two parts; every part gets fit and seals inside the body and the insulation.
• Availability of two entries of the cable
• This type of limit switch box improves the resistance towards corrosion by having powder coating of the polyester on the housings of aluminum
• The wiring is accessible by the terminal board of the PCB
• The captive bolts are present for screwing the lid
• You can use the SF series limit switch box in the artic application

APL-2n limit switch: 

• The enclosure is weatherproof and follows the standard of IP67/NEMA4&4X
• the design is compact and solid
• it is easy to mount the bracket
• the placing of the bolt is on the visual position indicator
• There are two entries of the cable

APL-3n limit switch:

• the design is flexible and different options are available
• 3-4 extra switches
• 8-16 points of terminal strips
• NAMUR standard stainless steel shaft and bracket

APL-4n limit switch:

• The enclosure is weatherproof and waterproof
• There is durability in the designing of this limit switch
• Different options for the buttons are available
• Captive cover bolts
• Terminal strips

 

APL-5n limit switch:

• The holder of the shaft is already in the built-in the cover
• It is easy to place the visual position indicator
• Availability of different designs for the visual indicator to put on the threading joint kind of cover
• The entries of the cable: 2x ¾ as standard
• Captive covering of the bolts and spring loading covering the bolts
• The housing of Stainless steel (316) as an option.

What are the specifications of the limit switch box series 5A?

Classifications of the area	· Class I: division 1 and groups A, B, C, D & T6 · Class II: division 1, groups E, F, G & T85 C
Enclosure ratings	IP66/67, NEMA 4/4X, UL50E Salt Spray
Options of switch	Mechanical: SPDT Switch, SPDT (Low Power) Proximity: PNP, NPN, 140V 2-Wire, 250V 2-Wire, Reed Switch NAMUR Intrinsically Safe
Mounting	F05 pattern ISO5211, VDI/VDE 3845 Compliant (NAMUR)
Certifications	Standard: cULus, CE Optional: ATEX, IECEx
Protocols for communications	None
Visual display	High visibility indicator
Quantities of switch	2
Range of the temperature	-25 degrees Celsius to 65 degrees Celsius

What are the features and benefits of the limit switch box series 5A? 

Enclosure:  The compact is weatherproof VSM and low profile along with the certification of the NEMA type 4, 4X, and IP66/67. The polyester powder’s die-cast aluminum cover and coating prevent corrosion, water, any effect, and resistance from ultraviolet.

1. Hight visibility of the position indicator: The visual opening and closing of the indication is the dome style indicator that affects the resistance.  Removing the dome and rotating it to 90 degrees helps invert the closing and open the visual output. It is not necessary to remove the cover and expose the inner wiring of the VSM to change the position of the indication.

1. Stube shaft secondary seal: It assures that the area of the indicator is separate from the internals of the VSM. It gives a secondary seal to avoid the ingress of the water is a dome or its sealing compromise because of adverse conditions of the site.

1. Captive Cover bolts: The cover gets attach to the base through the captive stainless-steel bolts. Its placing is on the outer area of the sealing.

1. Protective washers: The washers are transparent, non-metallic, and resistant to corrosion are helpful in coating whenever the cover bolts get tight.

1. O-ring seal for water tightening enclosure: The placement of the O-ring seal is between the cover and base for providing the weatherproof seal. It helps to protect from corrosion internally.

1. Sensor cams: The designing of the splining cam permits easy and correct settings of activating the switch without using any tool.

1. Limit switches variety of switch options and configurations for meeting the requirements of connectivity.

1. Terminals: The marking of the terminal blocks is positioning towards the user to provide accessibility.

1. Conduit entries: The availability of the conduit entries in either imperial or metric threads

1. Grounding: coding in green color and easy accessibility to the grounding of the bolt.

What are the types of limit switch boxes? 

1. Limit switch box for pneumatic actuator: The SK series limit switch box has multiple functions. Firstly, it provides the panoramic visual indication towards the value position, and secondly, it gives electrical feedback from the two micro-switches. The strip of the terminal and the entry points of the twin conduit permits the solenoid valve and micro-switches wiring up by the single multi-core cable.

 2. Brackets suitable for limit switch box:  The bracket of stainless steel gets fixed in the interface of Namur for positioning and mounting the limit switch box. Both sizes are available 80 mm and 130mm for mounting and heights of Namur interface.

3. Multi Size Namur Bracket 30mm to 40mm Powder Coated Carbon Steel: The multi-size bracket is for fitting in the interface of Namur for positing and mounting the limit switch box. Both the suits of 80mm – 130 mm for mounting the Namur interface and adjusting the height from 30mm – 40mm.

4. 316 SS Limit Switch Box for Pneumatic Actuator IECEx: This limit switch box is for hazardous areas. Designing is for mounting on the top of the pneumatic actuators to deliver positive feedback. There are four adjusting SPDT mechanical switches (two are for opening and two are for closing) wiring into the terminal block. Also, it is the termination point for the solenoid valve for using the single multiple cables. Then the wiring of the solenoid is by the second conduit entry. The sight of the dome is coded with color for clarifying the position of the valve instantly. The yellow one is for opening, and the red is for closing.

5. Hazardous Area Limit Switch Box for Pneumatic Actuator IECEx: It is similar to the 316 SS limit switch box for pneumatic actuator IECEx and available in stainless steel upon request.

6. Multi Size Namur Bracket 40mm to 52.5mm Powder Coated Carbon Steel:  The suits for both 80mm – 130mm of Namur interface for mounting and adjusting the height from 40mm – 52.5 mm.

7. Sight Dome to suit the SK100 limit switch box: The spare sight dome fits the SK-100 series limit switch box. 

8. Topworx Limit Switch Box Microswitch: Topworx TVA-M2WYNCM limit switch box has 2 m Single Pole Double Throw (SPDT) limit switches. It consists of a visual indicator and two M20 conduit entries. Namur has compatibility with the 304 Stainless Steel shaft.

What are the advantages and limitations of the limit switch box? 

Advantages of limit switch box: 

• The design of the limit switch box is primarily straightforward
• The limit switch box works well in almost every industrial processes
• The accuracy and repeatability are high in the limit switch box 
• The power consumption is low in the limit switch box
• The limit switch box has the capability for switching to the high-inductance loads
• The limit switch box can also switch to the multiple loads
• The installation process of the limit switch box is easy
• The limit switch box is a reliable device
• You can use a limit switch box to switch to the current’s higher level directly without any need and use relay control at the secondary level.

Limitations of limit switch box: 

• The limit switch box is dependent on the mechanical action. So, the limit switch box is helpful in the equipment that works at low speed.
• There are contact sensors in the limit switch box, which means that the limit switch box needs to physically contact the target for the operation.
• The nature of mechanical design in a limit switch box means that devices might wear and tear with the period. So eventually, it would help if you replaced it.

How does the limit switch box work? 

The limit switch box is helpful in industrial applications. It is an electromagnetic device with a mechanical actuator whose linkage is with a series of electrical contacts. When the object gets in touch physically with the actuator, the movement of the plunger of the actuator results in the limit switch box either closing (for opening the circuit) or opening (for closing the course) their electrical connectivity. Thus, the limit switch box requires mechanical movement of the actuator’s plunger for controlling and changing the state of the electrical form. The devices similar to the limit switch box, such as inductive and capacitive proximity sensors, deliver the same results without being in contact with the object. Mainly, the limit switch box works mechanically and has heavy-duty connections. In addition, it has the capability of switching to higher currents.

What is the importance of the limit switch box? 

The limit switch box is an economical method for creating the link between the physical and electrical domains. In the manufacturing process, the role of the limit switch box is significant because the structure of the limit switch box is simple and available at a low cost. The limit switch box is helpful in three essential purposes, which are as follows:

• Detecting and counting the product: when the product pushes against the limit switch box, the signal is sent to the control system. With the help of PLC ladder logic, the user can easily count the number of items going through the limit switch box and display the counter for the operator.

• Safety of the personnel: the limit switch box helps detect the opening of the guard for protection that stops and energizes the machine again. If the guard opens during the operation, the machine stops working, and If the guard opens when the machine stops, the limit switch box stops the engine from starting. In these cases, the limit switch box protects the operator from damage.
• Safety of the machine: the limit switch box helps protect the machinery from any damage unintentionally. There are components in the limit switch box that are wearing out over time, and components (like shafts and gears) might get damaged if any failure occurs.

What is the purpose of using a limit switch box? 

Whenever you are motorizing the rolling up of the door and want to stop it when the door opens entirely automatically, for the above situation, you need to mount the limit switch box for the above or similar position to it. The adjustable arm mounting along the roller connects with the limit switch box at the pivot point. When the door reaches its highest point, the tab present on the door press the roller and makes it rotate. The activation of the limit switch box is through the rotation of the arm and shuts off the motor. There are different ways to actuate the limit switch box. For example, instead of the rotating arm, you can use the plunger or button.

How does the limit switch box work in the quarterly turning of the valves?

The limit switch box helps detect the valve’s position manually and pneumatically operate the valves’ quarterly turning for processing the plants automatically. This signaling is receiving by the visual indication and transmission towards the controlling system of the plant. With the standard interface, you can fit the position indicator on the quarter-turn valves, such as the butterfly valve/ball valve. Along with the addition of the micro limit switches, the limit switch box is available in 2-wires or 3-wires proximity switches. It has a protection class and is helpful for explosion type of areas. In addition, the limit switch box helps in assuring the reliability of the safety functionalities. The 3D optical positioning indicator is also available as an option along with the number of electrical connectivity. There are varieties of electrical position indicators for quarter turning of the valves and the addition of limit switch box, which enables the quarter-turn value to integrate and control the automation of the plants.

How to check the working of the limit switch box? 

The ohmmeter or digital multi-meter helps in determining the working of the limit switch box. Disconnect the limit switch box from the system and connect the ohmmeter on every terminal. If the limit switch box usually opens, keep the resistance at a higher level. If the limit switch box closes typically, keep the resistance to zero or close it. Fasten the limit switch box into the active position and keep measuring the resistance. Check the occurrence of the opposition for determining the working of the limit switch box.

What are the components of the limit switch box? 

The limit switch box has an actuator and the operating head, body of the limit switch box, and a range of electrical terminals. It is helpful for the connection with the switch towards the controlling of the electrical circuit. The operating head needs to be in contact with the target. The actuator translates the operation for closing and opening the limit switch box. The body of the switch consists of the mechanism whose state is controlling by the actuator. The electrical terminals connect with the switch contacts and enable the wires to join the button by the terminal screws.

Industrial applications need control switches in automatic processes that get activated depending on the involvement of the performance of the machines. For the repetition of the methods, the accuracy rate of the limit switch box has to be reliable and deliver a fast response rate. During the installation and maintenance of the limit switch box, some characteristics are significant for the mechanical performance of the machinery. It includes operating force, method of mounting, and rate of stroke. Match the rating of the limit switch in the limit switch box with the load of the mechanical system to control and avoid any failure in the industrial application.

Final thoughts: 

The limit switch box is an instrument that helps detect the valve’s state in the automatic controlling system. It is helpful for output to open or close the position of the valve as the switch signal and to receive from the remote controller. In addition, you can use the limit switch box as an essential valve for interlocking the protection and indication of the alarm in the automatic control system.

Instruthinkis a professional manufacturer and supplier of limit switch boxes in UK. We have dedicated the production and sales of limit switch boxes according to the specifications of the industries. As a result, the limit switch box by Instruthinkis of high quality and available at economical rates.

Please place your order now through our official website. Most customers demand a limit switch box for the pneumatic actuator, positioners, and other products. This series of limit switch boxes are top-rated, and Instruthinkis selling it around the world.  You can contact our technical team regarding any query about the limit switch box.

For quick quotations, an online form is also available on the website of Instruthink. Contact through WhatsApp and Skype is also available. So please place your order of little switch box now and get it to deliver for your application with 7 working days.