In Industry both the maintenance departments 'Electrical & Mechanical' work Hand In Hand. Both the departments discuss troubleshoot if they have doubt in their minds.

As we are from Electrical Department, doesn't mean that we don't need to learn about mechanical part. It is beneficial for us when we have something extra As famous quote "The more we know; the better we become !"

In today's modern era, pneumatic system & hydraulic system play a very important role. Maximum part of these systems is mechanical But these systems are so powerful & reliable. Infact, maximum machines are running with these two systems.

That's why it is important; we should know about hydraulics & pneumatic systems.
We can't explain the full mechanical part but at least we will explain that mechanical part which is important from Electrical point of view.

'Hydraulics & pneumatics' Both the systems are branch of Engineering which uses the power of fluid flow. In hydraulics, hydraulic oil is used as fluid on the other hand in pneumatic system, compressed gas or compressed air is being used.

In this post, we are going to discuss the pneumatic type solenoid actuated Directional control valve. We will discuss it's technical specifications, configuration & working.

Solenoid actuated Pneumatic Directional control valve by JANATICS PNEUMATIC

Before proceeding to directional control valve we should know about the pneumatic cylinder first.

Pneumatic cylinders

These cylinders are used to obtain the linear shaft movement. These cylinders have piston in it which is being fitted on a piston rod. At both the outer end of cylinder, Pipe connector(socket) is provided for air connections.

Piston & joints contains rubber seal so that no air leakage takes place.

Pneumatic cylinder

Rubber seal inside the pneumatic cylinder

When we apply rated air pressure from base pipe connector(socket), the air pressure pushes the piston outward.

Similar the case when we apply pressure on another connector(socket) of cylinder it pushes the piston Inward.

By controlling the pressure on both the end connectors(socket), we can control the linear piston movement As shown in image below:

Air Cylinder piston movement due to compressed Air.

NOTE:

In whole process of movement, one big thing needs to be understand that Whenever we apply air pressure from one of the side, The free air is always present on another side of piston which do not allow piston to move freely until this free air allowed to pass easily.

We concluded that to move the piston we need 2 things:

1. Rated air pressure at one of the air connector(socket).

2. At that same time, another air connector(socket) should be blockade free so that free air passes out easily.

Directional control valves performs Both the above said tasks.

Directional Control Valve

Directional Control Valve As name suggests, It is the device that control the 'ENTERY & EXIT' of compressed air. These valves have multiple holes in it; In which some holes are Air Inlet-Outlet while some are air exhaust.

Directional Control Valves by JANATICS PNEUMATIC

There are many types of DCVs which operates with different methods & these methods known as Actuation.

• Valves which are physically operated by hand known as Manual actuation valve.
Manual Actuation Valve by JANATICS PNEUMATIC

• Some valves are operated through air pressure known as Pneumatic actuation valve.

• Valves which are operated through solenoid coil are known as solenoid actuation valve.

Solenoid Actuated Pneumatic Directional control valve

In automation system, DCVs based on Solenoid actuation have been used. These DCVs operates through an Electrical solenoid coil while solenoid coil energizes with power supply.

Solenoid actuated Pneumatic Directional control valve by JANATICS PNEUMATIC

These solenoids are available in both AC & DC voltages.

AC(50/60Hz)_ 24,48,110,230

DC________12,24,48,110

These DCV's are categorized with two numbers. For example- 2/2, 3/2, 4/2, 5/2, 5/3.

The first number represents Holes present in valve & the second number represents the states of the valve.

2/2 valve:

This valve has 2 Holes. 1one hole for air Inlet & another hole for air outlet. This valve has 2 states 'Open & Close'.

5/3 valve:

This valve has total five holes. 1 hole for air inlet, 2 holes for outlet & 2 holes for Exhaust. This valve has 3 states in which 2 states for 2 outlet holes while 1 state is neutral state like closed valve.

There are many types of valve like 2/2, 3/2, 4/2,5/2 & 5/3. Every single valve has same working mechanism with little changes in them. We can't explain all type of valve in single post so we have taken one valve for explanation that is JANATICS PNEUMATIC 5/2 Valve.

MODEL: DS255SS61

TYPE: 5/2

WORKING PRESSURE: 2-10Bar

PILOT PRESSURE: 2-4Bar

AMBIENT TEMPERATURE: 5°C to 60°C

AIR FLOW: 1200lts/min

MATERIAL OF CONSTRUCTION: Aluminum, Nitrile, Stainless Steel, Brass, Acetal

DUTY CYCLE: Continuous

CLASS OF INSULATION: Class F

COIL PROTECTION: IP65

Configuration of the valve

This valve has 5 holes In which one is inlet, two outlets & two exhausts. Solenoid coil's voltage is 230VAC.

Parts of Solenoid actuated 5/2 DCV

DCV's main part is aluminum block which contains multiple holes in it. These holes are arranged in special symmetry which are provided for 'ENTERY & EXIT' of air. Solenoid coil is tightened on a hollow metallic shaft. For coil connection power plug is provided as shown in image above.

Aluminum block of Solenoid DCV

Generally, DCV's are spool designed, A metallic spool carrying multiple rubber seals moves inside the cylindrical hole of aluminum block. Although these rubber seals on spool are also arranged in special symmetry.

Solenoid DCV spool type

The movement of spool inside cylindrical hole makes the ports of aluminum block 'Open & Close'.

Apart from Inlet-Outlet holes, Pilot hole is also being provided. (This pilot hole; we will explain later)

LIFTER KNOB

For the manual actuation of DCV; A LIFTER KNOB has been provided.

LIFTER knob on solenoid DCV for manual actuation

To actuate the valve for just a moment; press the knob.
To actuate the valve permanently; press the knob & rotate in clockwise direction. To deactivate the valve, move the lifter knob in anticlockwise direction.

Pneumatic Silencer

Both the Exhaust ports of DCV are tightened with pneumatic Silencer; As name suggests, pneumatic silencer reduces the noise produced by exhaust ports.

Pneumatic Silencer fitted on Exhaust port

Mounting Holes

These DCV's can be mount on any type of surfaces with the help of multiple mounting holes. AS shown in figure below:

Multiple mounting holes on DCV

Working of Solenoid DCV

Before proceeding to the working of DCV, We need to see schematic diagram printed on aluminum block first.

Schematic Diagram 5/2 DCV

As printed in diagram, Port 1 is inlet which is placed in between exhaust ports (5&3)along with 2&4 are outlet ports.

This valve has two states, Both the sides are equipped with solenoid coils. When left side coil energizes STATE1 actuated while right side coil actuates STATE2.

According to STATE1 Diagram when Left side coil energizes, 1(INLET) gets connected to 4(OUTLET) along with 2(OUTLET) gets connected to 3(EXHAUST).

Entire Inlet pressure get available at PORT4 & PORT2 work as a exhaust which allows free air present in cylinder to pass.

According to STATE2 Diagram when right side coil energizes, 1(INLET) gets connected to 2(OUTLET) along with 4(OUTLET) gets connected to 5(EXHAUST).

Entire Inlet pressure get available at PORT2 & PORT4 work as a exhaust which allows to pass the free air present in the cylinder.

The outlet ports 4&2 exchanging their function; at a time one of the port work as pressure port & another one work as a exhaust. This all opening & closing of ports are happening because of spool movement whenever one of the solenoid coil energizes.

Now, we need to see configuration image again to understand the working completely.

Parts of Solenoid actuated DCV by JANATICS PNEUMATIC

We have seen DCV's all the parts & schematic diagram printed on aluminum block. By considering all the described details of DCV it becomes easy & simple to understand the working.

"Actually, This solenoid doesn't control the spool movement directly Instead it controls the pilot pressure which further moves the plastic piston after that plastic piston moves the spool.

This all spring wrap metallic pin, plastic block, plastic piston are aligned linearly placed on both the sides of aluminum block & Spool is present inside the aluminum block."

PILOT HOLE

Air pressure is always available in pilot hole because it is directly connected to INLET port. Both the sides of aluminum block contains pilot hole As shown in image below:

•Pilot hole in solenoid DCV
•Air flows from image 1 to 4

One side of plastic block contains metal pin & another side contains plastic piston

Inside the plastic block of DCV

At Normal state, metal pin presses the pilot hole of plastic block behind the plastic piston. When solenoid coil get energizes, a spring wrap metal pin moves in opposite direction to aluminum block or towards the solenoid.

At this stage, metal pin opens the pilot hole along-with; After that Pressure become available behind the plastic piston through the holes behind plastic piston which results pressure moves the plastic piston & At last this plastic piston moves the metallic spool.

This all process is happening in one side of aluminum block.

Metal pin contains rubber seal JANATICS PNEUMATIC

The metal pin again retain its normal position with the help of spring fitted across it; when solenoid de-energizes. Whereas, plastic piston remains in forward position that's why spool continue maintains its position even after solenoid de-energizes.

NOW, when another side of solenoid energizes. The whole process; metal pin movement, pilot hole opening, piston movement remains the same as explained above which results spool now moves in opposite direction. While spool moving in opposite direction; spool itself pushes the opposite side plastic piston back.

The free air present at the back of piston moves through metal pin cut outs through hollow metallic shaft & at last exit through the Nut holes.