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Tuesday, July 21, 2009

Portable Air Compressors, Industrial Air Compressors, 12 Volt Air Compressors, Screw Compressors

Portable Air Compressors, Industrial Air Compressors, 12 Volt Air Compressors, Screw Compressors

Compressors

Machine that raises the pressure of a gas, vapor or a mixture of gases and vapors. The pressure of the fluid is increased by reducing the specific volume of it during its passage through the compressor. Compared with turbo blowers and centrifugal fans or axial flow, in terms of output pressure, the compressors are generally classified as high-pressure machines, while fans and blowers are considered low pressure.

The compressors are used to increase pressure for a variety of gases and vapors for a multitude of applications. A common case is the air compressor which supplies air at high pressure for transport, paint gun, tire inflation, cleaning, pneumatic tools and drills. Another is the refrigeration compressor, used to compress the gas from the vaporizer. Other applications include chemical processes, conducting gases, gas turbines and construction.

CLASSIFICATION OF COMPRESSORS

When classified according to the indication constructive compressors are subdivided into the piston and rotor and vane in centrifugal and axial. It is possible the division of the compressors into groups according to the kind of gas that is moved, the type of transmission and the destination of the compressor.

Alternative or Compressor Piston

Compressors operating with alternative adiabatic principle by which gas is introduced into the cylinder by the inlet valve, is retained and compressed into the cylinder and out of the valve, against the discharge pressure. These compressors are seldom used as individual units, unless the process requires intermittent operation. For example, if a catalyst to regenerate every two or three months or has a reserve supply of another source, this would allow time to repair or replace the valves or piston rings, if necessary. The compressors are alternative parts in contact, like the rings of the pistons with the cylinder walls!, Springs and valve plates or disks that are attached to their seats and between the gasket and rod. All these parties are subject to wear by friction.

Alternative compressors can be lubricated or non lubricated type. If the permitting process, it is preferable to have a compressor lubricated, because the pieces will last longer. Be careful not to over-lubrication, because the charring of oil in the valves and overheating can cause adhesions. Moreover, the discharge tube saturated with oil is a risk of fire power! Therefore should be placed downstream of a separator to remove oil. The biggest problems in compressors with lubricated cylinders are dirt and moisture, thus destroying the film of oil inside the cylinder.

The best way to prevent grime is to use temporary suction strainers to have a clean system to boot. Moisture and condensable reaching the suction of the compressor can be avoided by an efficient separator placed as close as possible to the compressor. If you were to compress a wet gas, will have to be in shirts or steam preheating inlet gas, downstream of the separator.

In the compressors without lubrication, the dirt is usually the most serious problem, and there are other problems that can cause the gas itself. For example, a completely dry gas can cause severe wear on the rings, in which case you should consult with the manufacturer, because it constantly get new test data. In non-lubricated compressors, piston rings and wear are often made with materials filled tefion, bronze, glass and coal, as gas is compressed. Polishing cylinder 12 pi (rms.) tends to prolong the duration of the Rings. The gasket is susceptible to wear the same ring of the piston.

Gasket for leaks should be sent to a burner system or return them to the suction. Lubricated compressors may require separate tubes to lubricate the gasket, although in small diameter cylinders may not be required. The Teflon packing without lubrication typically need water cooling because its thermal conductivity is very low. If gas is handled at temperatures below IOIF, the manufacturer must calculate the amount of gas by preheating internal recirculation. This means you need a slightly larger cylinder to move the same mass flow.

The compressors must be alternative, preferably low engine speed, direct link, especially if they are more than 300 HP; generally constant speed. The speed control is achieved through valve unloaders, and these must be of the cutting plate of the type of valve or unloader with stopper or plug. The surge that lifted the entire valve seat can create sealing problems. The discharge may be automatic or manual. The steps are normal discharge 0-100%, 0-50-100% or-25-60-75-100% and intermediate steps are available boxes or bottles of dead space clearance, but should not be used these boxes if polymerization may occur unless proper precautions are taken.

Alternative piston compressors are classified:


Depending on the compression phase

Single or simple fact, when the piston performs a single stage of compression (the compression action of the running one side of the piston).

Biphasic, dual-purpose or when the piston performs reciprocating double compression (the compression action is performed on both sides of the piston).

According to the stages of compression are classified as:

Stage compressor when the compressor performs the compression process in a single step.

Multi-stage compressor when the compression process is performed in more than one stage such a stage of low pressure and high pressure stage.

According to the arrangement of cylinders are classified as:

Vertical-Horizontal

Alternative compressors ranging from very small up to about 3000 PCMS. Equipment processes, typically are not used much larger sizes and are preferred centrifuge. If there is high pressure and a rather low cost, you need the alternative. The number of stages or cylinders must be chosen with respect to the discharge temperature, size available for the cylinders and the load on the compressor body or rod.

Rather small sizes, up to about 100 HP, can take simple action-cylinder, air cooling, and can allow the oil vapors in the tank (sump) is mixed with air or compressed gas. These rates are desirable only in special designs modified.

Rates for small processes, and a cylinder 25 or 200 HP, have water cooling, double-acting piston, which allows separate glands leak can be controlled and non-lubricated ¡, in which the lubricant does not touch the air or compressed gas. Are used for air tools or in applications for small gas processing. The larger compressors for air or gas are two or more cylinders. In almost all installations, the cylinders are arranged in horizontal series, so that two or more stages of compression. The number of stages of compression depends largely on the temperature rise at a time, usually limited to about 250'F, the load on the body or rod that can handle and, occasionally, of Increase in total pressure at a time, for design ¡¡compressor valves, which tend to be less than 1,000 psi.

The ratio or total compression ratio is determined to have a rough idea of the number of stages. If the ratio is very high, between 3.0 and 3.5 for a single stage, then the square root of the total is equal to the phase relationship for the two phases, the cubic root in three stages, etc.. Interstages pressures and the actual stage will be modified by after taking into account pressure drops in interenfriadores, inter-stage pipeline, separators and pulsation dampers, if used.

Piston compressors compress gases and vapors in a cylinder through a piston and linear movements are used to drive pneumatic tools (6 to 7 kg/cm2), ammonia refrigeration (up to 12 kg/cm2), supply gas at a distance (up to 40 kg/cm2), liquefaction of air (up to 200 kg/cm2), compressed air locomotives (up 225kg/cm2) and synthesis and hydrogenation under pressure (up to 1000 kg/cm2).

Rotary compressor or centrifuge

Driving centrifugal compressors and compressed gas through paddlewheel.

The fans are low-pressure centrifugal compressors with a paddlewheel low speed (10 to 500 mm water column; special types up to 1000 mm). The machines are rotary blowers centrifugal compressors high tangential velocity (120 to 300 m / sec.) And a pressure step of p2/p1 = 1.1 to 1.7. Mounting up to 12 or 13 series rotors can be achieved in a box a final pressure of '12kg/cm2, compressing air cooled repeatedly.

Sliding vane compressors

This type of compressor basically consists of a cylindrical cavity within which is located in an eccentric rotor with deep grooves, a rectangular pallets slide freely within the slots so that the rotor rotates the centrifugal force pushes against the blades cylinder wall. The entering gas is trapped in spaces formed by the pallets and the wall of the cylindrical cavity is compressed by reducing the volume of these spaces during rotation.

Liquid piston compressors

The rotary piston compressor fluid is a machine with multiple rotor blades spinning in a box that is not round. The box is filled in part of water and as the rotor turns, bring the liquid with the paddles in a series of bags. As the liquid, alternately leaves and re-bag between the pallets (twice per revolution). As the liquid comes out of the bag pallet full of air. When the liquid returns to the bag, the air is compressed.

Compresores lobe (Roots)


They are known as dual-rotor compressors or dual impeller those working coupled with two rotors, mounted on axes parallel to a single stage of compression. A machine of this type is widely compressor lobes couple known as "Roots" of enlargement on the feeder! Diese engines or gas blowers with moderate pressure. Rotors, usually two or three lobes are connected by external gear. The gas entering the blower is trapped between the lobes and housing, with the movement of the rotors of the machine, where sale, could not return because of the close game between the lobes that move on the inside.

Screw Compressors

The parallel compression rotors can also occur in the axial direction with the use of spiral lobes in the manner of a screw without end. Connecting two rotors of this type, a convex and concave, and making them rotate in opposite directions is achieved by moving the gas, the two parallel axes, between the lobes and the housing.

Successive revolutions of the lobes gradually reduce the volume of trapped gas and therefore its pressure, compressed gas thus is forced axially by the rotation of the helical lobes until 1st download.

Principle of operation - Flow

The rotary compressor belonging to the class of volumetric machines, for its principle of operation is similar to the rotary pumps. The most widespread are the rotary compressor plate; recently found cornpresores helical apply.

By turning the rotor, excéntricarnente located in the body, the plates are enclosed spaces, which move the gas from the cavity to the suction cavity drive. This makes the compression of gas. Such a scheme of the compressor, having good balance of mass in motion, would communicate to the high frequency of rotor rotation and rnaquina connect directly with the electric motor.

Running the compressor plate shows a large amount of heat due to the pressure over the body of the compressor 1.5 is made with water cooling.

Compressors plates can be used to collect gases and vapors in the spaces with less than atmospheric pressure. In such cases the compressor is a vacuum pump. The vacuum created by vacuum pump plate reaches el95%.

The flow of the compressor plate geornétricas depends on their size and frequency of rotation. If one considers that the plates are the radial gas volume trapped between two of these where f is the maximum of the cross section between the plates, 1 the length of the plate.

The principal working parts of the compressor are visinfmes (thyme) of special profile, the provision of reciprocal screws is strictly fixed by the wheels are in gear, fitted on the trees. The strike in the gear sprockets synchronized in these is smaller than the thyme, so the mechanical friction in the past were excluded. The screw holes is the distribution of the closure, so the power transmitted by the wheels of synchronized sprockets is not large, therefore, little wear. This is very important because of the need to retain sufficient strikes in the couple of screws.

Flow regulation

Of the equation to determine the flow of the compressor rotor is that the flow is let's provide the frequency of rotation of the shaft of the compressor. It follows the regulatory process for changing Q n.

The compressor plate is joined to the electric motors in most cases directly, and the frequency of rotation of these are 1540, 960, 735 rpm. To regulate the flow in this case it is necessary tie between the trees! Engine and a compressor vareador speed.

The frequency of rotation of the screw compressors is very high, reached in the case of gas turbine drive, 15,000 rpm The major manufacturing screw compressors normally operate at a frequency of rotation of 3000 rpm.

For both types of rotary compressors used in the procedures for regulating the flow choked in the hope, the transfer of compressed gas in the suction pipe and stopping at regular intervals.

Structure of Compressors

Compressors are manufactured plates for flow rates up 5OOm3 \ rnin and two-stage compression with intermediate cooling to create pressure 1.5Mpa.

The main elements of this structure are: rotor, body, lids, cooler and trees. The body and the lids of the compressor are cooled by water. The building blocks have certain particularities. To reduce energy losses of the mechanical friction of the ends of the plates against the body are placed in two rings rotate freely download it in the body. The outer surface of these is' send lubrication. By turning the ends of the rotor plates are supported on the discharge ring and slide in part by the interior surface thereof; download ring simultaneously in the rotating body.

In order to reduce the frictional forces the plates into the slots are placed but not radically diverted to proceed in the direction of rotation. The angle of deviation is 7 to 10 degrees. In this case the direction of the force acting on the plates on each side of the body and the rings download closer to the direction of movement of the plate in the slot and the force of friction decreases.

To reduce the leakage of gas through the axial strikes, in the hub of the rotor ring is placed on springs empacaduras tight against the surface of the lids.

On the exit side of the tree through the cover, has placed a seal gland with spring tensioning devices.

Dead Space

Cylinders of the compressors are always manufactured with dead space that is necessary to avoid the blow of the plunger against the lid to get to this extreme position.

The volume of dead space is usually seen in proportions or percentages of the workload of the cylinder and is called relative volume of dead space:

A = Vm / vtr

In the single modern compressors in the case where the valves are in the stage of cylinders A = 0.025 0.06

Distribution and Control

The bodies of the closure of entry and exit of the gas in the cylinder valves are generally automatic plate steel and frosted on both sides for 2 to 3 mm thick, commonly with a ring-shaped and spring-loaded pressure for safety closure.

The race of the valve (usually 2 to 4 mm, number of revolutions for 1 to 1.5 mm) is limited by a cap screwed to the valve seat. They arranged to one side of the cylinder or the butt of it, are easy to assemble and disassemble. So that the valves are maintained better and cause little loss of load must exceed 30 m / sec. And with pressures above 100 kg/cm2 only 15 m / sec. Material for valve plates highly fatigued, low alloy steel.

Compressor installations with power working in general irregular and need, therefore, a regulation. Customary systems of regulation:

Start-Stop. For small installations with electric drive. As the accumulator air automatically connect and disconnect the engine and cooling water. The tank should have sufficient capacity to perform not more than 8 to 10 switches per hour.

Adjust the speed in the drive piston machines. With constant number of revolutions:

Regulation by motion in vacuum. The pressure regulator weight or spring loaded to connect to the compressor running on empty in the accumulator exceeds the adjusted and connects back to full burden on the low pressure 10%. The mark is verified by vacuum suction tube closing or keeping open the suction valve using a decompressor.

Regulatory step. The power is reduced gradually to 75%, 50%, 25% and void spaces for insertion of harmful fixed up and a vacuum of different sides of the piston effect of multiple steps.

Gradual adjustment of spending (not staggered). In general is keeping open during an adjustable time (more or less) the intake valves during the compression runs through decompressors powered by gas or oil pressure or by springs.

If the compressor is regulated by a number of steps only the first step, ie it decreases the extent of their use, leaving it nothing but the ratio of pressure and increase their use, leaving it nothing but the ratio of pressure and increases in the latter, the ratio remained almost constant pressure and increases in the latter, the ratio remained almost constant pressure in all the intermediate steps.

To start download the compressor as completely as possible.

Keeping open the valve normally aspirated. Compressors are great for this special duct bypass. In the small machines that aspire to the plunger, the vacuum is made up by closing the suction duct, opening at the same time a by-pass which provides communication between the sides of the drive and ambition.

Grease

For the lubrication of piston compressors are used the same methods as for steam engines, except the high standards of lubricating oils due to the high heat radiated by the cylinders of steam.

For the lubrication of cylinders, as steam engines are used piston plunger pumps required for operation of the transmission.

Even with high gas pressures to obtain low viscosity oils. A viscous oil requires an unnecessarily large power and makes the valves have a greater tendency to stick and tear. For very high pressures are used, however, sometimes viscous oils to improve the tightness, but the gas temperature is lower. If possible use the oil for lubrication of the cylinder and transmission, since it facilitates the recovery and re-employment of the oil. Oils for cylinders with 7 to 28 degrees Engler oils are also good for the transmission.

Driving oil in steam engines. The oil consumption of the compressor is only the third of which is indicated for the steam engines.

To save valuable oil cylinders, machines that compress gases with additions of oil soluble (benzene, bensol, naphthalene and sulfur dioxide) are derived with emulations of oil in water. Please introduce yourself here oil presses are available are suitable.

ANCILLARY FACILITIES

Gas coolers (to cool the gas after each step)

With low pressures used preferably tubular beam of the cooler, the gas flowing outside the tubes and the water inside them, or with elements of the cooler tube fins.

In tubular beam coolers are gas changes direction through a maze walls in order to speed the gas is desirable for good heat transfer. In the refrigerator there is no maze of elements, thus resulting in fewer losses. Other advantages of the cooler elements: space occupied by the fin tubes, which can provide large buffer space and condensing on the cooler box, ease of cleaning and ease of disassembly of the refrigerators.

For gases with many impurities, which get dirty quickly fin tubes are used, although the heat transfer is less efficient, cooler tubular beam (c) with flow of gas through the inside of the pipes and water by the countercurrent outside. These coolers are very susceptible to external corrosion by water in the immediate entry of gas.

Pressures are used for large refrigerator coil (e), in whose interior circulating gas, submerged in a water tank or the cooler tubes double (d) coaxial gas flowing through the tube interior, and water, in counterflow, the space between the two tubes.

Data on size and weight of the tubular beam and table 3.

It seeks to achieve a cooling of gases to about 5 to 10 ° above the temperature of inlet cooling water.

GAS COOLERS

Spending compressor suction m3/min

The amount of heat Q [kcal / h] eliminated in each step is obtained about the power of the step Ni [HP] and the amount of water vapor condensed in the cooler GW (Kg) by the formula

Q = 632 Ni + 600 Gw.

Of Q and the temperature rise allowed in the cooling water is obtained the required quantity of the latter. The outlet water temperature should not exceed 40 ° to prevent the formation of fouling. Velocity of water 1.5 to 2 m / sec., 5 gas velocity of 15 m / sec.

A resistance to the passage of heat 1 / k for clean surfaces must be added the inevitable dirt 0.0005 0.001 M2H ° / kcal per side in contact with water or gas, or more if working under unfavorable conditions.

Dust filters

Accumulator air pressure. Compensates for the pulse compressor and also, as its name suggests, acts as an accumulator. Its capacity will be comfortable to avoid excessive work of the regulator and get a good effect of the water separator and oil.

Volume of the accumulator to be spending the compressor.

Batteries air regulated as pressure vessels, wear safety valve, pressure gauge with flange check, and at its lowest point, drain devices.

The gauge will carry a sign indicating the maximum pressure. Adjust the safety valve fully guaranteed. Batteries of 800 mm in diameter and larger lead manhole oval to facilitate the internal inspection.

Service

Instructions to refrain service compressor and machine-operated. In general:

Getting Started

Check the oil level in the crankcase the heads of the rods and the crankshaft counterweights should not dive, the suction pipes and the drive gear pump must be filled with oil). If necessary, clean the filter. Load the grease nipples of the cylinder pressure and, by observing the glass peepholes, rotate them by hand occasionally. Check freedom of work and pressure regulator to connect the compressor running on empty. Open cooling water and wait for exit. Open the gates of the keys or suction tubes and drive. To launch the drive machine (usually be achieved the maximum number of revolutions after about 10 seconds). Charge the compressor slowly. Adjust the cooling water so that its output reaches a temperature below 40 ° (danger of fouling).

In launching the first machine-operated, check the direction of rotation, then turn upside down if not work the gear pump or the pressure lubrication system. After major repair will be given by hand several turns the machine to ensure that the pistons move and the transmission smoothly.

Operation

Monitor the level and oil pressure and the loading and operation of grease nipples for the cylinder pressure, temperature and gas pressure and the cooling water circuit. Auscultate regularly occurs if the machine blows or abnormal noise in the valves. Check often bearings, sliding surfaces and the piston rod itself heated than usual. Playing with the hand the suction pipes of the gas glands (if those are hot, glands are poorly adjusted, small leaks are fixed with a heavy oil). At intervals of half an hour will be given out to oil and water accumulated in coolers. Once a day, at least be removed from the water tank of air. Every hour, read and write in the daily machinery of the working pressure, the temperature of the gas, oil and cooling water and other service data. The grease nipples are always filled with new oil, checking occasionally oil consumption and rectifying regulation.
Portable Air Compressors, Industrial Air Compressors, 12 Volt Air Compressors, Screw CompressorsSocialTwist Tell-a-Friend

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