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Pneumatics
Being the driving force behind most factory, manufacturing, mining machinery, heavy vehicles and equipment, pneumatics are a vital part of our industry today. The field of pneumatics is vast and knowledge is constantly requested in the workings and troubleshooting thereof.
464 Questions
They are powered by compressed air, supplied via an air-hose under high pressure from an electric or petrol engined compressor.
Examples of pneumatic systems?
Simplest example I can think of is possibly an automatic door, where the pneumatics are pushed along, operating the valve which opens the door. Where a pilot makes it return to its original position.
Pneumatic pressure is the pressure exerted by a pressurized gas.Compressed air is commonly used for this purpose.Vehicle tires are inflated with compressed air or nitrogen.Placing a pressure gauge on the valve will read a number on the dial, say 28 or 32.Which means the pneumatic pressure exerted by the gas inside the tire is 28/32 psi.
How do you decide when to use pneumatic or hydraulic power?
when high power transmission is involved then hydraulics is the best option this because there are hydraulic fluid available to suit the various pressure levels. liquids have almost zero compressibility.
in pneumatic system air is the working fluid, too high pressure could compress the air to such an extent to liquify it causing the tubes to crystallize and burst it. air is highly compressible and hence power loss should also be accounted for the compressed air so only low power systems possible here eg: pneumatic door openers .
Is a crane a pneumatic or hydrolic system and why?
Older type cranes used pneumatics for the operation of the crane's control systems. The actual movement of the crane's working components are usually operated by hydraulic cylinders or winch systems. The winch systems used to be powered by mechanical friction mechanisms but are typically powered by hydraulic motors today. Typically, pneumatics are never used to power the crane's load bearing functions
Why we don't use high pressure in pneumatics?
one reason air is much harder to control the heat and air has a lot of water in it and a hydraulic system dose not need water in the hydraulic oil. There is no way at the high pressure that a hydraulic system has to work at,it would not be possible to control the heat.
How are pneumatics better than hydraulics?
Poster below is correct. Air systems typically have a tank that is the analog of a hydraulic reservoir.[ebolton]
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Actually there is need for air reservoir in industrial pneumatics systems.
Hydraulics can handle more powerful aplications than pneumatics for the same overall dimensions, or can be more compact for the same power.
What are the Advantages and disadvantages of electro-pneumatics?
ADVANTAGES OF PNEUMATICS.
1. Simplicity of Design And Control
The control machines are easy to design. i.e they can be manufactured using standard cylinders & other components. Controlling mechanism simply contains two ON-OFF states, so its easy to implement and understand.
Also these components have versatile usage, they can be used in many situations. Pneumatics are easy to install and have useful mechanical movements. For an instance Straight-line movements can be obtained without further adjustments, such as levers, cams...etc
2.Reliability
pneumatic control mechanism is well known for its long lasting operation life time. In fact they need very little maintenance but operates continuously with high reliability.
Air /gas used as the working fluid is less likely to damage the equipments since gas are good in absorption of shock, and excessive forces, but hydraulics react directly transferring the stress to mechanical parts.
3.Safe to use
Pneumatic controls have high safety profile due to many reasons. Air used in these are fire proof, and less vulnerable to explosions and electric hazards. These are adoptable in extreme weather conditions, and we can rely on their continuous operation. This is because compressed air can stay in good condition in high temperature fluctuations, unlike hydraulic s ystems that tend freeze or boil in these situations.
Even a leak occur there is less chance of getting fire. Also there is no toxicity in air used, so we can expect no harm to living beans. Since pneumatics are sound in safety, very less precautions need to be taken.
4.Storage
Compressed Gas can be stored easily, and once compressed, above a certain threshold level they can be operate with out further need of compressing. This feature allows the use of machines when electrical power is lost.
5. Clean
Since working fluid is purified air, there is no messy waste produce at the end of the day. A little leak will not make the surrounding shady. Also, since ir is used no risk of toxic hazards t o machines or humans. Industries like pharmaceutical, food..etc tend prefer pneumatics for their cleanness.
6. Easily transported
Air is easily obtainable from atmosphere and can be used with little purification. Air can be pumped to long distances in pipelines, so can control pneumatic equipments for long distances. This makes central controlling possible. These also requires no return line, so easy to manage and cost effective.
7. Light in weight
Air is very light compared with other fluids, which are very heavy. They don't need high power to transfer.
8.Cost Effective
This is a very economical controlling mechanism. The Pneumatics require low maintenance cost, since wear of equipments are very less. These operates at low pressure , so equipments can be produced for low cost using cheap materials. In contrast hydraulic controlling systems require high pressure, so need tough materials, which comes in high prices.
9 high speed working medium
Compressed air controllers are able to achieve high work speeds, the flow rate may go up to 20 m/s, while hydraulics is restricted around 5m/s.
10.safe operation in Overloads
The shock absorbent properties of air make overloading safe. Under excessive forces air can compress easily avoiding damage to equipments.
11 Variable pressure
Pneumatic systems can work in various pressures, this also alow the speed control.
DISADVANTAGES OF PNEUMATICS.
1. Air is largely compressible, which may be good for some reasons, but the major draw back is the inefficiency in accurate positioning and speed controlling. These often need to be tuned to work correct and sound. Since Compressible,not possible to achieve uniform and constant piston speeds.
2.Unable to work with heavy loads (commonly used working pressure of 7 bar, the require output force is economical only up to about 20 KN to 30 KN ) Unlike hydraulics or electrical system these cant be used for heavily loaded operation.
3. Air used needs to be purified, air containing moisture may lead to corrosion of the equipments.
What advantage does galvanised pipe have over black mild steel?
Great material for oil lines /natural gas /steam / hydronics / condensate /chilled water piping /air
What is the history of pneumatic systems?
Joseph Bramah patented the hydraulic press in 1795.[1] While working at Bramah's shop, Henry Maudslay suggested a cup leather packing.[2] Because it produced superior results, the hydraulic press eventually displaced the steam hammer from metal forging.[3]
To supply small scale power that was impractical for individual steam engines, central station hydraulic systems were developed. Hydraulic power was used to operate cranes and other machinery in British ports and elsewhere in Europe. The largest hydraulic system was in London. Hydraulic power was used extensively in Bessemer steel production. Hydraulic power was also used for elevators, to operate canal locks and rotating sections of bridges.[1][3] Some of these systems remained in use well into the twentieth century.
Harry Franklin Vickers was called the "Father of Industrial Hydraulics" by ASME.
What Specifics dangers when working with pneumatic system?
The main danger is the pent up power of compressed air. If the tie rods on an air cylinder fail the end would fly off at some terrific speed whereas with an hydraulic cylinder as soon as the end came off the pressure would be gone even though it was much higher to start with.
What are some examples of pneumatic devices?
Yes there is. Pneumatic valve springs. They are metal bellows that have air in them. Their use is in replacing metal wire springs in a high-speed combustion engine. An example would be formula one engines.
What is difference between vacuum pump and centrifugal pump?
A compressor is a piece of equipment that compresses gas either to transfer to a specific location or for a certain process requirement. Compressor are manufactured depending on application and can be class into two basic types; positive-displacement and centrifugal.
Integrally geared centrifugal compressors can operate at many times higher speeds than reciprocating compressors. The higher speeds ultimately result in smaller package sizes, requiring a smaller footprint as compared to a reciprocating compressor. The operating speed of a reciprocating compressor is very slow due to mechanical and dynamic limitations. Furthermore, the lower speed of reciprocating compressor lends itself to larger compressor size, heavier weight, and larger plot plan size. Whereas the centrifugal compressor with higher operating speeds results in smaller overall compressor package sizes such as smaller gearing, bearings, seals, lubrication system, and foundation. Smaller packages ultimately lend themselves to saving in lower overall installations as well as lower capital and spare parts costs.
Higher reliability is fully attainable with centrifugal compressors. The rotating aerodynamic components (impellers) have no physical contact with the stationary parts (inlet shroud). On the contrary, the reciprocating compressor moving components such as the piston and valves are physically in contact with the cylinder and other stationary components during operation. The physical contact causes wear and tear of both moving and stationary components, which requires constant maintenance. However, a centrifugal compressor operates for many years with continuous service without overhaul maintenance, resulting in less power plant down time. This eliminates loss of product, provides more profit, lowers risk, and results in lower maintenance cost. Overhaul periods are more predictable by analyzing characteristic efficiency and vibration trends. A typical centrifugal compressor overhaul inspection period is more than 7 years as compared to less than 2 years for most reciprocating compressors.
In addition to the economical advantages of implementing a centrifugal compressor over a reciprocating compressor, many technical advantages are also evident. The centrifugal compressor discharge pressure can be regulated to less than 0.5% per second. The well-regulated compressor discharge pressure provides very steady supply of fuel to the gas turbine. This is an advantage since it does not cause additional burden to the turbine controls. On the other hand, a reciprocating compressor at best can provide 2% or more of pulsating pressure. Unsteady supply of fuel may cause hardship on the turbine control system. A reciprocating compressor would require an impractically over-sized pulsation bottle to minimize supply pressure pulsation to the level as steady as a centrifugal compressor.
Considering there is no physical contact between the centrifugal compressor aerodynamic components, the need for lubrication within the compression components is not required; thus it will not add oil or other contaminants to the process gas. However, a reciprocating compressor requires oil lubricant for the piston rings. This oil eventually ends up in the process gas or it has to be separated to protect the gas turbine. Due to physical contact between the piston rings and the cylinder, the wear of the rings and packing causes particle contamination of the fuel gas. Hence, this contamination could cause premature wear on the turbine blades and other turbine fuel gas passages
A pneumatic actuator converts energy (in the form of compressed air, typically) into motion. The motion can be rotary or linear, depending on the type of actuator. Some types of pneumatic actuators include: * Tie rod cylinders * Rotary actuators * Grippers * Rodless actuators with magnetic linkage or rotary cyclinders * Rodless actuators with mechanical linkage * Pneumatic artificial muscles * Speciality actuators that combine rotary and linear motion--frequently used for clamping operations * Vacuum generators A Pneumatic actuator mainly consists of a piston, a cylinder, and valves or ports. The piston is covered by a diaphragm, or seal, which keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphragm downard, moving the piston underneath, which in turn moves the valve stem, which is linked to the internal parts of the actuator. Pneumatic actuators may only have one spot for a signal input, top or bottom, depending on action required. Valves require little pressure to operate and usually double or triple the input force. The larger the size of the piston, the larger the output pressure can be. Having a larger piston can also be good if air supply is low, allowing the same forces with less input. These pressures are large enough to crush object in the pipe. On 100 kPa input, you could lift a small car (upwards 1,000 lbs) easily, and this is only a basic, small pneumatic valve. However, the resulting forces required of the stem would be too great and cause the valve stem to fail. This pressure is transferred to the valve stem, which is hooked up to either the valve plug (see plug valve), butterfly valve etc. Larger forces are required in high pressure or high flow pipelines to allow the valve to overcome these forces, and allow it to move the valves moving parts to control the material flowing inside. Valves input pressure is the "control signal." This can come from a variety of measuring devices, and each different pressure is a different set point for a valve. A typical standard signal is 20-100 kPa. For example, a valve could be controlling the pressure in a vessel which has a constant out-flow, and a varied in-flow (varied by the actuator and valve). A pressure transmitter will monitor the pressure in the vessel and transmit a signal from 20-100 kPa. 20 kPa means there is no pressure, 100 kPa means there is full range pressure (can be varied by the transmiters calibration points). As the pressure rises in the vessel, the output of the transmitter rises, this increase in pressure is sent to the valve, which causes the valve to stroke downard, and start closing the valve, decreasing flow into the vessel, reducing the pressure in the vessel as excess pressure is evacuated through the out flow. This is called a direct acting process. http://en.wikipedia.org/wiki/Pneumatic_actuator
When to choose pneumatic or electric actuators?
pneumatics are used only in low power applications
hydraulics are used in medium to high power applications.
Difference between electrical and mechanical energy?
Light travels exclusively through space or along optical fibres by the mechanism of electromagnetic propagation. Electrical energy can also do that, in which case it is called microwave radiation or radio waves, but it can also be carried on wires.
How do you calculate hp from amps?
1 HP is 746 watts in principle. The power is in watts, and the power is the volts times the amps. For an AC motor the power is the volts times the amps times the power factor times a factor that depends on the power-conversion efficiency of the motor.
Why a gap is left between two pieces of rails in the railway line?
These days that's no longer always the case. It used to be because as the rail warmed up in the sun it got longer, so gaps was left for the rail to have something to expand into. w/o the gapsor with too small gaps it happened that the rail broke loose from the sleepers and caused the train to derail. To day many railroads are using concrete sleepers, which are strong enough to keep the rails in place w/o any gaps.
A hose is a hollow tube designed to carry fluids from one location to another. Hoses are also sometimes called pipes (the word pipe usually refers to a rigid tube, whereas a hose is usually a flexible one), or more generally tubing. The shape of a hose is usually cylindrical (having a circular cross section).
What is Pneumatic double acting cylinder?
- single acting: actively driven by hydraulic fluid pressure in only one direction, passively returned in the other direction by another force (e.g. springs, gravity)
- double acting: actively driven hydraulic fluid pressure in both directions
What are the properties of hydraulics and pneumatics?
One similarity is that they both use fluids. Both gasses and liquids are fluids. the two are also compressible.
Pneumatic vs hydraulics which is cheaper?
As systems, neither one is better than the other. There is no "Better", only "More suitable for a specific purpose." Car tyres are Pneumatic... they're full of air. Air is compressible, which is why it's used. If you filled your car tyres with Hydraulic fluid (which is incompressible) you would not only increase the weight of the tyres dramatically (and hence increase the relative tread-wear), but also make them hard, decreasing their ability to absorb shock. This would defeat many objects in the design of car tyres! The rams on a digger or crane, however, are Hydraulic. They need to be filled with something that is not compressible in order to fulfill their function. If you were to fill the rams on a digger with air the arm would bounce up & down like a yo-yo! Also, at the pressures required by these systems, air would quickly leak from the seals, no matter how tight they were. Hydraulic fluid, being far more viscous than air, however, does not leak under the same conditions. As a rule, Pneumatic systems are employed where a certain amount of "play" or "give" is required, or where the loss of fluid would be undesirable (Air power-tools for example) Hydraulic systems are used when extremely great pressure is needed in order to move something. Hydraulic systems are also easier to control & regulate due to their ability to retain pressure indefinitely. There are many uses for both Hydraulic and Pneumatic systems but because both types have specific roles, there is no saying that one system is better than the other.
