Autonomous Maintenance. Pneumatics training module for operators

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Basic Pneumatic – Introduction

Introduction Overview:

Pneumatics is all about using compressed air “to make something happen”.

The word Pneu is Greek meaning wind, breath or air. Pneumatic equipment refers to those items that use or are driven by air. Air has no definite shape or volume it takes on the shape and expands to fill it’s vessel regardless of its size.

Think of blowing up a balloon !!!

Compressed air is simply the air we breathe squeezed into a small space under pressure.  You might remember that air under pressure possesses potential energy which can be released to do useful work.

A pneumatic system consists of a group of pneumatic components together so that a signal (compressed air) is passed through the system to make something happen at the output.

Understanding pneumatics is really very simple.  All you have to do is learn how a few basic components work. There are two main groups.

Pneumatic systems are found throughout any food plant and other manufacturing facilities.

Compressed air is also used to drive many types of instruments and hand tools.

In this unit you will learn the basic components of a pneumatic system, as well as how to safely work with pneumatic systems.

Always treat compressed air systems with respect ! A jet of compressed air directed onto the body may introduce air into the blood stream, could produce blindness or other eye injuries if directed to the face. Always wear safety glasses and gloves!

Always follow the proper LOTO procedures.

Objectives:

The information, activities, and practice provided during this unit will enable you to:

  1. Describe the hazards and safety precautions for a pneumatic system.
  2. Describe the function of the components of the pneumatic system.
  3. Identify the basic components of a pneumatic system.

Air Pressure Source System:

The picture below is a picture of one of our compressor units that produces compressed air needed to operate the equipment within the factory. The compressor room has the storage tanks that are required to maintain the volume of compressed air for the factory.

Compressed air contains impurities and a great deal of attention must be paid to those that are in suspension as they may cause failures in the pneumatic controls (water, dust, rust, etc…).

Air Filter, Pressure Regulator and Oiler

Air Filter:

An Air Filter makes sure the air being used is free of contamination. The filter prevents foreign objects such as water or dirt from entering into the valve or cylinder causing damage.

Pressure Regulator:

These are used to set the pressure that is required to run our machines.

Lubricator:

The lubricator’s purpose is to provide a mist of lubricating oil to the air driven device being used.  The lubricator consists of a reservoir filled with oil, a flow adjusting knob, and a sight glass which indicates the rate of oil flow. Not all systems have an oiler.

Regulator

A regulator is a device that controls the maximum supply pressure to a compressed air user. Regulation of pressure is necessary. Inspection: Ensure that the pressure is steady and that the adjusting knob is functional.

 

Basic Pneumatic – Pressure Gauge

Pressure gauges indicate operating pressure of a system in PSI (Pounds Per Square Inch).

Gauges come in many different sizes, styles and pressure ranges.

Inspection: Ensure that the operating pressure is reading in the green demarcated area. If not, the air pressure is incorrect for the sub system.

Lubricators

The pneumatic elements (cylinders, valves, etc.) have mobile parts that need lubrication. So that they are sufficiently and continually lubricated, a certain quantity of oil is added to the compressed air by means of a lubricator.

The lubricator has the task of supplying the pneumatic elements with lubrication. Advantages of lubrication:

  • Notable decrease in wear;
  • Decrease in losses through friction;
  • Corrosion protection;
  • Inspection: Ensure that the lubricator has the proper oil level.

Inspection:

Filters are a must to keep systems operating at their potential.

Carefully drain any foreign material and/or moisture out of the trap bowl.

Ensure the filter is not plugged by checking the downstream pressure is correct while the equipment is running.

Basic Pneumatic – Care and Maintenance

Mounted properly – Pneumatics are hard on themselves and may come loose from the mounting.  Make sure all lines are secured and fasteners are tight.

Air Leaks – Listen for any air leaks and report them immediately to your maintenance department.

Air Gauges – Many pneumatic systems are designed to maintain 100 psi with some pneumatic systems rated at 175 to 200 psi.  Make sure air gauges are at the appropriate pressure level.  If not, report them immediately to your Mechanic. Adjust the gauge to the appropriate visual control setting. Air Gauges come in a variety of sizes, colors, pressure ranges, and styles. This is determined by where you want to use it and the operating pressure.

Pipe, Fittings and Shut-off Valves:

Pipes come in many sizes, shapes, and types. Piping is made of steel, plastic, and rubber depending on  the application.

Fittings also come in many different types.Some require a nut with an insert to hold the fitting and pipe together, while others press into each other.This also depends on what it its being used for and where it is being used.

Shut-off Valves are used to turn the air pressure off to a system. They come in a variety of types and sizes. The most commonly used are called Dump Valves, Ball Valves and Gate Valves.

Basic Pneumatic – Introduction

Solenoid Valve

Directional Control Valves are just as their name implies. They control the direction that the air goes by channeling it to different ports. They are often used to control air cylinders. Like cylinders they come in a variety of sizes and shapes. The valves have specific applications depending on their design.

Flow Control Valve

Flow Control Valves are used to control the speed at which an air cylinder moves when air is applied to it.

The valve can be adjusted by turning a knob. It controls the air in one direction and allows it to flow with no restriction the other or opposite direction. Proper adjustment of these controls will extend the life of the cylinder by controlling its speed.

Air Cylinders

Air Cylinders are the part of a pneumatic system that performs a task, such as moving a part of a machine, lifts or lowers, or even as little as applying pressure to hold something in place.

Basic Pneumatic – Valves

There are many types of valves in a compressed air system. Each has its own special purpose:

Ball valves are usually for on/off applications.

Flow Control Valves are for controlling the flow of air. And the speed of the cylinder or device it is attached to.

Dump valves are shut off valves that also bleed off any residual air pressure these are used for safety shut off valves.

Exhaust Mufflers are for the purpose of noise reduction.

 

 

Basic Pneumatic – Solenoid

Solenoid valves are commonly used in the plant and use an electromagnet to move the internal piston from one position to another which in turns causes the air cylinder to move in different directions. In a single solenoid valve the piston moves in one direction when power is applied to the solenoid and in the other direction by an internal spring. Double solenoid valves move the piston in the direction that power is being applied the solenoid. It will remain in this position until the other solenoid is activated.

Single solenoid 2 position valve

Double solenoid 2 position valve

Basic Pneumatic – Cylinders

Air Cylinders:

Air Cylinders are the part of a pneumatic system that performs a task, such as moving a part of a machine, lifts or lowers, or even as little as applying pressure to hold something in place.

Single acting cylinder

Double acting cylinder

Basic Components of a Pneumatic Valves:

Valves control the switching and routing of air in a pneumatic system. Valves not only have to control the flow of the compressed air, they also have to control the flow of the exhaust to the atmosphere.  There are two main types of valves used in pneumatic switching circuits:  2/3 valve and 2/5 valves.

Air Cylinders:

They come in a variety

of sizes and shapes and are made by

numerous companies. It is important to

understand the basic principle of an

air cylinder.

Basic Components of a Pneumatic Cylinder:

Cylinders convert the energy in the compressed air into straight motion (forward and backward or up and down).  The air enters the cylinder and pushes a piston from one end of the cylinder to the other.

Basic Components of a Pneumatic Cylinder:

Single Acting Cylinders:

A single acting cylinder has only one air connection, while a double acting has two.

With a single acting cylinder, the piston is pushed outwards by the pressure of the air.  When the air supply is removed and the air inside the cylinder is allowed to escape (we call this the exhaust), the piston moves back to its rest position using a compressed spring.

Double Acting Cylinders:

The double acting cylinder has two air connections.  When compressed air is sent to one side and the other side is allowed to exhaust, the piston is pushed to one end of the cylinder.  When air is then sent to the other side and the first side is allowed to exhaust, the piston is pushed back. This type of cylinder is more powerful on the return stroke than the single acting cylinder.

Basic Pneumatic – Safety

System Hazards:

The pneumatic system can pose two potential safety hazards:

*  Pinch Points

*  Stored Energy

Both can potentially cause bodily and equipment harm.  The Pneumatic system is composed of both moving and non-moving components. Particularly, where there are air cylinders (moving parts).  Pinch points are one of the primary safety concerns.  For example:  If your hand or any other part of your body gets caught between the shaft of an air cylinder and another  piece of equipment, injury could result. Therefore, the importance of following LOTO procedures is essential!

In regards to non-moving components of the pneumatic system, stored energy becomes a primary concern.  When air is under pressure, there is the possibility of the air being released unexpectedly potentially causing bodily harm or damage to equipment.  For example:stored energy can also cause the cylinder to move in the opposite direction once air pressure is released.

Air Leaks:

If the system experiences a sudden loss of pressure or there is a hissing noise, there is a leak somewhere in the system.  The leak could indicate a fractured pipe or broken hose.  If the pipe/hose ruptures or blows apart, personnel and equipment could be in danger.

Never attempt to find a leak by running a hand over the piping without the proper PPE.Due to high pressure, the compressed air could enter the hand through the skin causing a serious injury.

Never tighten air line fittings while they are under pressure. Isolate the air line and bleed off the air pressure, before making any repairs.

Swollen areas on air lines are an indication of wear and could burst. They must be repaired or replaced immediately.

As compressed air is produced, oil and moisture are mixed with the air.  When the compressed air leaves the compressor, the oil and water mixture may be in the form of a fine mist.  The oil contained in the mist is flammable.  A spark or open flame can ignite the air and oil moisture.  In the event of a leak in the system near the compressor, keep all open flames and sparks away. There are separators and a dryer to remove the oil and moisture from the air before it leaves the mechanical room.

There is always electrical wiring around the components of a pneumatic system.  Ensure that any loose or bare wiring is F – Tagged immediately .

Broken or Damaged  wiring could create a spark that could ignite the oil and air mixture.

Basic Pneumatic – Vibrators

Pneumatic vibrators use compressed air to force a metal ball to spin in a circle at very high speeds. This creates vibration, which can help components feed down the line in certain applications.

Inspection: To avoid waste, set the air flow at the lowest rate that still does the job.

Vacuum System

Vacuum Systems have many uses, to open shippers in the cases packers, pull down cartons and transfer pouches from the gripper chain etc.

Here are some examples of some vacuum pumps that are used in food manufacturing factory.

Some Vacuum Systems used in the factory are what is known as Vacuum Generators or Venturi  Systems.

The Vacuum System consist of an air source or air supply, a filter to clean the air going into the system, a pressure control valve or regulator to control the amount of air pressure, piping and fittings, direction control valve or solenoid valve which allows air to travel through the vacuum valve, and the vacuum valve. There is no oiler in this type of system. There is an added filter in  this system in the vacuum or suction line. Trash particles and debris must be kept out of the vacuum generator. At the end of the line is the Vacuum Cups (Suction Cups). The Vacuum Cups are what does the work. They come in all different sizes and shapes and are made from many types of materials.

Vacuum Generators generally operate off of low air pressure which is used to produce the vacuum. The size and type of generator will determine how much air is needed and the amount of hold it has. The air comes into one side of the valve and exits out the other side. In the middle is where the vacuum is generated. This is produced by air passing through chambers within the valve. This type of vacuum generator is expensive to operate because of the compressed air used. Vacuum pumps are a lower cost method of generating vacuum.

Vacuum Filters

Care and Maintenance

Just like the Pneumatic System, it’s important to make sure there are no leaks in a Vacuum System. It is necessary to check lines for hole, make sure the vacuum cups don’t have holes in them and are not torn or worn which can result in vacuum loss. The filters need to be kept clean so the vacuum or suction is not reduced. That’s why the pick off filters and Brenton are so important to ensure reliability.

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