Namur solenoid valve

Namur solenoid valve for powering pneumatic actuator

Pneumatic actuator

Namur type solenoid valve

Namur type solenoid valve can be connected directly on the pneumatic actuator body without any instrument fiiting & tubing attached to it.

If the coil is energized it will create magnetic force the plunger will be pulled by the magnetic force the air will coming into the pilot chamber it will push the piston forward the spools will move forward it will

arrange a certain opening for the air to come into or out of the pneumatic actuator

If the coil is DE-energized the magnetic force is gone the plunger will re-seated back & close the incoming air inlet the spools will move backward to the initial position it will arrange a certain closing for

the air that come into or out of the pneumatic actuator

How it works

Switch “CLOSED”Switch “OPEN”

Double acting pneumatic uses5/2‐way solenoid valve

Air supply Air supply

Switch “CLOSE”

Switch “OPEN”

Namur type solenoid valve

Single acting pneumatic actuator uses:3/2‐way solenoid valve

Air supply

Switch “CLOSE”

Switch “OPEN”

Air supply

Namur type solenoid valve

Namur type solenoid valve

Namur type solenoid valve

• A Namur solenoid valve can be used to power double acting pneumatic actuator by installing a 5/2-way interface place in between the solenoid valve & actuator body

• A Namur solenoid valve can be used to power single acting pneumatic actuator by installing a 3/2-way interface plate in between the solenoid valve & actuator body

• The 5/2-way interface plate & 3/2-way interface plate are supplied together with the Namur solenoid valve

Switch‐box

Switch-box for pneumatic actuatorSwitch box

Usually a quarter turn valve such as ball or butterfly valve that are coupled with a pneumatic actuator they need an additional switch-box

Inside a switch-box there are:• Local indication of opening or closing of the quarter turn valve• Switches such as limit switches or proximity switches inside it• CAM (mechanism to actuate the switches)• Terminal block/Terminal strip for the wiring (for power supply

wires, Solenoid valve’s wires & Switches wires)

Upper limit switchLower limit switch

Limit switch (Basic switch or Micro switch)

• When the switch’s actuator has NOT been pushed by the cam inside the switch-box NO electricity will flow out from the switch

• When the switch’s actuator has been pushed by the cam inside the switch-box electricity will flow out from the switch

• When the switch’s actuator has NOT been pushed by the cam inside the switch-box electricity will flow out from the switch

• When the switch’s actuator has been pushed by the cam inside the switch-box NO electricity will flow out from the switch

Switch-box for pneumatic actuator

There are 2 number of CAM inside a switch-box housing (top CAM & bottom CAM)• When the quarter turn valve is in closed position the top CAM pushes the top switch

actuator then the electricity will come from the top switch into an indication lamp inside the control panel

• When the quarter turn valve is in closed position the bottom CAM has not pushed the bottom switch actuator No electricity comes out of the bottom switch

Neutral

Live

Neutral

Live

Switch-box for pneumatic actuator

There are 2 number of CAM inside a switch-box housing (top CAM & bottom CAM)• When the quarter turn valve is in open position The top CAM has not pushed the top switch

actuator No electricity comes out of the top switch • When the quarter turn valve is in open position the bottom CAM pushes the bottom switch

actuator then the electricity will come from the bottom switch into an indication lamp inside the control panel

Neutral

Live

Neutral

Live

Switch-box with proximity switch

For switch-box that are using proximity switches there are 2 type of proximity switch:• PNP or NPN proximity switch • Namur type proximity switch

This type of proximity switch is identified as Eex ia intrinsically safe approved

When a proximity switch detects a target metal (the target metal is installed on a CAM inside the switch-box) that is detected inside the proximity switch detection range the proximity switch will send a certain signal output

The metal detection

point

NPN & PNP proximity switch (3-wires)

• In a NPN sinking circuit proximity switch Eg. A DC indicating lamp will get power from the (+) brown color cable and the black color cable out of the switch

• In a PNP sourcing circuit proximity switch Eg. A DC indicating lamp will get power from the (-) blue color cable and the black color cable out of the switch

Namur proximity switch (2-wires)• Namur proximity switch (intrinsically safe) can be installed in a hazardous area EXCEPT the

electricity power has to pass a safety barrier first (safety barrier is a module to limit the electricity power to a safe power to be used by the electrical component/equipment installed in hazardous area)

• How Namur proximity switch works:- If metal target is detected switch output signal is between 1 to 2 mA- If metal target is not detected switch output signal is 4 mA

At site (hazardous area)In-engineering room

(safe area)

Alarmoutput

Safety barrier

amplifier

Namur ProximitySwitches

What is intrinsically safe

Hazardous area Safe area

Safety Barrier

Safety barrier module such as IS-card will limit the power going into the safe area to power Transmitters, Valve’s positioner, Solenoid valve, Switches (including proximity

switch) etc. The benefit of intrinsically safe products The products are not so expensive as

compared with products with explosion proof housing (Eex G)

IS card

Intrinsically safe equipment is defined as "equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration." (ISA-RP12.6) This is achieved by limiting the amount of power available to the electrical equipment in the hazardous area to a level below that which will ignite the gases.

In order to have a fire or explosion, fuel, oxygen and a source of ignition must be present. An intrinsically safe system assumes the fuel and oxygen is present in the atmosphere, but the system is designed so the electrical energy or thermal energy of a particular instrument loop can never be great enough to cause ignition

Traditionally, protection from explosion in hazardous environments has been accomplished by either using EXPLOSION PROOF apparatus which can contain an explosion inside an enclosure, or PRESSURIZATION or purging which isolates the explosive gas from the electrical equipment.

Intrinsically safe apparatus cannot replace these methods in all applications, but where possible can provide significant cost savings in installation and maintenance of the equipment in a Hazardous area. The basic design of an intrinsic safety barrier uses Zener Diodes to limit voltage, resistors to limit current and a fuse

What is intrinsically safe

What is intrinsically safeA Hazardous Area may contain flammable gasses or vapours, combustible dusts, or ignitable fibres.There are different systems used in Europe or the United States to classify the type of hazard and whether the Hazard is always present or only present in an emergency condition such as a spill or failure of venting equipment. In most cases the equipment is designed for the worst case, which would be to assume the explosive atmosphere is always present and the electrical or thermal energy is the lowest required to cause a fire or explosion.

What is intrinsically safeMost applications require a signal to be sent out of or into the hazardous area. The equipment mounted in the hazardous area must first be approved for use in an intrinsically safe system. The barriers designed to protect the system must be mounted outside of the hazardous area in an area designated as Non-hazardous or Safe in which the hazard is not and will not be present.

Equipment which has been designed for and is available for use in hazardous areas with intrinsically safe barriers includes:• 4-20 mA dc Two Wire Transmitters• Thermocouples• Rtds• Strain Gages• Pressure, Flow, & Level Switches• I/P Converters• Solenoid Valves• Proximity Switches• Infrared Temperature Sensors• Potentiometers• LED Indicating Lights• Magnetic Pickup Flowmeters• Etc