Wednesday, December 31, 2008

Recession - Crisis

What Recession ?


Action L.I.F.E. Coach

Sunday, December 28, 2008

Air Compressor Sizing

Air Compressor Sizing

3 Simple Ways on How to Select an Air Compressor

Two basic scenarios present to decide!
1. New Plant, and 2. Old Plant [to upgrade or downgrade]


1. New Plant
Step 1, Group all equipment in loading or usage categories.
If equipment is in use most or all the time into one group = 1. (100% loading)
Example: Production machinery, SMT, Conveyor etc


Another group or groups may be .6 [60% loading ], .3 [30% loading] in a day or working shift.

Step 2, Add up total usage and multiply with the usage factor, to arrive at the capacity usage.
Step 3, add about 10% to 15% of losses, due to leakage and other losses.

After listing all the air operated devices and equipments to be supplied by the air compressor, decide using charts, the pressure range and volume of air required by each and every devices and equipments.

These air compressor or compressors must maintain a minimum pressure at least equal the highest of these pressure ranges.

----- For Example:

If the highest pressure range required by any one device in a given group is 90 psi - 110 psi, a compressor or compressor must be able to supply the required volume, then the cut-in at not less than 90 psi and cut=out at 110 psi should be considered.

Exceptional:
Speed Controlled Air Compressor are used!

Then You have a rough idea of your plant compressed air requirement!

2. Existing Plant
2a. [Compressor always loading, that is cannot reach the required rated pressure]

Formula used:
P1V1 = P2V2




2b. [Compressor can off-load]

Formula used:
Air Consumption required = Vl/(u+l)





2c. Using Instruments
Energy Balance System

Friday, December 26, 2008

Positive Displacement Compressors-Screw

Rotary Twin Screw Air Compressors

Description:
Rotary, helical screw, oil-injected, positive-displacement compressors are constant volume, variable pressure machines. They are available in a range from 25 cfm to 3000 cfm at pressure up to 600 psig in single, 2-stage & 3-stage designs.


USES
The most common uses of the rotary screw compressors are engine-driven portable compressors for mining, construction, and energy exploration.

And as electric-motor driven stationary compressors for industrial and mining application.

Rotary helical screw compressors of this types are characterized by compact, low vibration, simple foundation, broad pressure and capacity ranges, and long life with minimum maintenance.

They are used for pressure or vacuum services.

Design:
The single-stage design consists of a pair of rotor meshing in a one-piece, dual-bore cylinder. The male rotor, usually 4 helical lobes, spaced 90 degrees apart. The female rotor, usually has six corresponding helical grooves, spaced 60 degrees apart.

The rotor speed ratio is inversely proportional to the lobe-groove ratio. When the male rotor rotates at 3000 rpm, the female rotor would rotate ...... ....... rpm?

The male rotor can be directly driven, belt driven or gear driven by engine or electric motor. The female rotor is driven by the male rotor without metal-to-metal contact through the thin oil film developed between the rotors. Female rotor drive is possible in some design.

The rotors inter-mesh in the dual bores of a one piece cylinder (housing, or case). The cylinder provides air passages, oil injection holes, compression chamber, and discharge ports.

Each rotor is supported by rolling element bearings located at the ends of the rotor body. The bearings at one end, usually the discharge end, take the rotor axial thrust, carry radial loads, and provide for small axial running clearances necessary.

Bearings at the opposite end are floating bearings, which allow for uneven thermal expansion of the rotors and cylinder.

For 2 and 3 stages, the individual stages are designed to be similar to the single stage as far as the rotor configuration is concerned.

2 Styles

Two styles of multi-stage compressors are in common use;

Those axially mounted, in which the second stage is driven directly from the rear of the first stage.
And side or parallel mounted, in which the stages are each mounted directly on a gear housing and are independent of each other.

Some designs remove the oil and cool the air between stages in an intercooler, while others discharge the air and oil directly into the next stage.

Multi-stages
Multi-stages are used in compressors for either to improved efficiency or for higher pressure.


Performance
The overall efficiency of the unit depends almost entirely on the achievement of proper clearance in the rotors during manufacture. The normal manufacturer's warranty allows for plus +- minus of 3% variation in performance.

Discharge temperatures are much lower than in other types of compressors. Most manufacturers supply a thermostatic oil control valve to control the minimum discharge air temperature to avoid condensation in the reservoir or oil sump.

A 2-stage, 100n psig compressor improves performance by lowering the pressure differential across the leakage paths within the rotors [Blowhole] and end plates. The altitude [sea level vs mountain top] on which the compressor is located also has an effect upon performance.

The oi-injected screw machine is capable of operating on vacuum service and produces maximum vacuum equal to that of the 2-stage, double acting reciprocating machine. The oil flow are normally reduced because of lower mass flow.

The power consumption of the rotary-screw compressor during unloaded operation is normally higher than of reciprocating types. Recent developments by some manufacturers have led to systems in with the unloaded horsepower is 15% to 25% of loaded power.

This systems are normally used with electric-motor, constant-speed drives rather than engine-drives in which the engine speed can be reduced during unload, for reducing fuel consumption.

Application of the unit as a based load compressor is also recommended to avoid any disadvantage due to unloaded power coat.

source from CAGI handbook
edited version

Thursday, December 25, 2008

Air Compressor Class



Air Compressor Classification

2 types
Dynamic
Positive-displacement

Dynamic
Ejector
Centrifugal


Positive-displacement
Reciprocating
[Double Acting & Single Acting, Single-stage, Multiple-stage, Piston, Rocking Cam, Diaphragm]
Rotary
[Single Screw, Twin Screw, Scroll, Lobe, Liquid Ring]
********************************************************

Reciprocating
Double Acting
Single Acting


Double Acting
Double Acting, Single-stage, Reciprocating Piston Type


A group of Ingersoll Rand XLE Double Acting, 2-stage, Reciprocating Piston Compressors

Single Acting
Reciprocating Single Acting Piston Type

Rocking cam
Diaphragm

Single Acting piston type

Rotary:
Rotary Single Screw
Rotary Twin Screw
Rotary Scroll

Rotary Lobe
Rotary Water Ring

Rotary Compressor Coolant

Rotary Compressor Coolant

Lubricant for Oil-Flooded Rotary Screw and Vane Air Compressors


Description:

The Rotary Compressor Coolant represents a “step-change” advance in lubricating oils specifically developed for oil flooded rotary screw and vane air compressors. They are premier quality products, highly recommended for both static and mobile plant with working temperatures up to 120 degree C.

The products are based on HVI paraffinic base oils, treated to reduce the polycyclic aromatic content, into which are blended additives to impart anti-oxidant, anti-wear, anti-corrosion, anti-foam and dispersions properties.

Extended field evaluations have demonstrated a vastly superior performance, to the extent that oil drain periods may be doubled. This effectively means an increase from the current maximum of 2000 hours to 4000 hours at a continuous maximum air discharge temperature of 100 degree C.
Combined with the extended life is a facility to keep the internal surfaces completely free from deposits whilst maintaining a steady differential pressure (dp) across the separator/coalescer. This means that premature blockage of separators/coalescers are eliminated.

MKT/JT/ABKD/104

Benefits:

Outstanding oxidation and thermal stability, which serves to extend the service life even with bulk oil temperatures up to 120 degree C.

Reduced maintenance cost resulting from the doubling of intervals between oil changes.

Excellent cleanness properties, eliminating the blockage of separators/coalescers.

Good protection against corrosion, extending the life of components in service.

Limited carry over of oil into the air stream, offering high quality process air.

Reduced risk of fire in the separator pack, due to the excellent oxidation and thermal stability of the oil.

Good anti-foam properties to suppress the tendency to foam excessively in service.

Good air release properties to minimize or avoid cavitations effects and increased compressibility.
Application:

The Rotary Compressor Coolant has been specifically developed to cater for the lubrication requirements of the complete spectrum of rotary screw and vane air compressors.

They are applicable to all types and sizes of rotary vane and screw air compressor whether oil flooded or oil injected, male or female drive, single or two stage configurations.

Although primarily designed for static industrial application, the coolant is equally applicable to the lubrication of air end in mobile plant configurations.

Oxidation Stability:

Oxidation can be considered the most important single property of oil for rotary compressors, since it is this, which primarily determines the useful life of the oil and its resistance to thickening and to the formation of carbonaceous deposits.

The excellent oxidation stability of the Rotary Compressor Coolant makes it possible to operate compressors continuously for long periods between oil changes, and at higher temperatures without the need to resort to highly price synthetic lubricants.

The IP 280 and IP 306 test results confirm the outstanding oxidation stability of the Rotary Compressor Coolant, in particular the very low ratios of sludge to TOP (total oxidation products) of 2.54% and 2.15% respectively against a permissible maximum of 40%.

Anti-foaming:

The ability of compressor oil to resist foaming is important, since malfunctioning of the compressor can occur if excessive amount of foam is allowed to form in the separator.

Tests have proved that the special additive combination in the Rotary Compressor Coolant reduces the tendency of the oil to foam in the separator.
Typical results in terms of IP 146 – the Foaming Characteristics of Lubricating Oil:

Sequence 1 10/NIL (Foaming Tendency/Foam Stability)
Sequence 2 Nil/NIL (Foaming Tendency/Foam Stability)
Sequence 3 20/NIL (Foaming Tendency/Foam Stability)

Protection Against Corrosion:

The occasional presence of water in oil-flooded compressor systems is possible, so it is important that the oil gives protection against corrosion. In addition to the associated mechanical problems, fine particles of rust dispersed in the oil will reduce the oxidation stability of the oil considerably and will also adversely affect its air release properties.

The Rotary Compressor Coolant have excellent corrosion inhibition properties and give a ‘no-rust’ result against IP 135 B – Rust Preventing Characteristics of Steam Turbine Oil in the presence of synthetic salt water.

Oil Drain Periods:
For many years, 2000 hours has been generally accepted as an extended oil drain period for rotary vane and screw air compressor maintenance schedules and service requirements.

It is recognised that operating temperature has a fundamental effect upon the rate of oil degradation through oxidation.

With our Rotary Compressor Coolant incorporating the most up to date oil technology, 4000 hours oil change may now be accepted as the norm, even when operating at a continuous maximum discharge air temperature of 100 degree C.

Internal Cleanliness:

Coupled with the long life capability is the ability to maintain excellent internal surface cleanliness in service. This is particularly relevant to the function and operation of the separator/coalescer. Design varies according to the manufacturer; nominal filtration of ½ micron is typical for this application.

Blockage of these elements with what was thought to be polymerised products of oxidation has been endemic, in some cases after only 100/200 hours of operation.

In a test using Rotary Compressor Coolant, the separator element from a Compair-Broomwade Ltd trial machine was removed and inspected after 8400 hours of intermittent operation, simulating typical in-service conditions.The metal and fibreglass element were in ‘as new’ condition, and the dp (differential pressure) across the separator was recorded at a constant 2.5 psi over the whole evaluation.
The screw element from the trail assembly was also inspected and was found to be in excellent condition.

Sealing:

The Rotary Compressor Coolant is suitable for use in conjunction with all commonly used sealing materials.

Change-over Procedure:

Changeover is relatively straightforward:
1. The original charge should be fully drained and disposed of.
2. If the oil system has shown evidence of contamination or is otherwise less than satisfactory, a flushing charge may be appropriate.
3. Assuming item (2) not to apply, the system may be filled to the correct level and run in the normal way.
4. Assuming item (2) to be necessary, the flushing charge should be introduced and run up to normal working temperature for, say, 4 hours. It should then be fully drained, preferably at 50 degree C or above and then disposed of.
5. The working charge should then be introduced to the normal working level and the machine restarted.

Health And Safety:
The Rotary Compressor coolant is unlikely to present any significant health or safety hazard when properly used in the recommended application and good standards of industrial and personal hygiene are maintained.

See separate Safety Data Sheet.

MKT/JT/ABKD/104

Air Filters maintenance

Air Filters

The 1st place that dirt get into the compressor is via the intake. To prevent dirt from getting inside is to install a appropriate size air filters.


Some typical use air compressor filter elements.

They are made of filter grade filter paper.

Filter maintenance 1
Visual inspection


Remove of filter dust trapped at cover through centrifugal flow of air inside the filter housing.


Low air pressure jet to clean air filter


Choke up air filter

Air filter need to replace.

Filtration

FILTERS

The purpose of FILTERS --- according to general definition:
Is to keep contamination transported in the air and oil out of the compressors.





Compressors together with gearboxes, fluid-power system (hydraulic & pneumatic), internal combustion engines and industrial machinery have a common problem:

"Wherever moving parts contact or mesh with one another, FRICTION results."


This friction has to be reduced. to this end, a suitable, mineral or synthetic oil, is used to provide a sliding film between the moving or rotating parts of the machines. This is only possible if the lubricating oil stay clean and remain clean. If foreign particles, even if they are microscopic in size, are transported with it.

Such particles can reach the moving or rotating parts inside the compressor in the form of sand or dust in the oil or air intake.

Whenever friction occurs, fine metallic abrasives are created, found it's way in the oil, creating even more metallic particles to get into the compressor oil or coolant.

Critical areas within the compressors are the compressor case (housing), screw rotors, seals, bearings, gears, valves etc. In addition, compression does not occur without leaving residues. If this is nor filtered out, the foreign particles acts as an abrassive mass, which can considerably accelerate wear on the moving parts.

Also, dirt particles when in excessively high concentrations though they are not as hard, can be dangerous for compressor. It can damage the compressor due to inadequate lubrication and cooling.

A well-maintained and effective oil filtration system along with good air filtering, is the best guarantee of long compressor life.
Main-flow filters and air inlet filters are usually designed for 25 micron particles filtration and 10 micron for bearings

Positive Displacement Compressors-Vane 4

Built-in Safety System

The minimum pressure valve (MPV) has a secondary purpose, that is, acting as a non-return valve when the compressor stops or off-load.

This is to prevent the line air pressure is not lost by reverse flow from the air system back to atmosphere via the compressor.

When the compressor stops, the intake valve is automatically closed, and the internal pressure within the compressor is gradually reduced or vent out to the air intake. This is achieves by mechanically, hydraulically or electrical solenoid valve.



This is to prevent hydraulic locking and possible damage when the compressor restarted.
The compressor will start with a light load and low starting current.


Safety Devices
Safety devices are install to protect the compressor against malfunction due to high air oil temperature, lack of oil, lack of cooling air or water or abnormal electrical supply.

Monitoring Devices
Monitoring devices are also installed, Certain design have more components and some with the minimum number. Signals when filters are to be cleaned or replace, Separator differential pressure, minimum & maximum pressure, oil & air end bearing temperature readings, water separator conditions, hour meter, motor conditions to indicate maintenance frequency.


Compressors with constant running control, start-stop control, manual dual control, automatic dual control, lead-lag operation for multiple compressors application.

Run-on timers for keeping the compressors running to minimize condensation during short demand periods, run-on timers to shut down compressors when there is no demand for air, are offered by various manufacturers.

They are compact, free from vibration, and with low noise levels. The air delivered is cool, clean, and free from pressure pulsation, and in some cases air receiver is not necessary. They can be mounted anywhere including immediate work areas.

Panels may be included to reduce noise level, panels for outdoor usage may also be order.

Positive Displacement Compressors-Vane 3

Operation

The lubricating-cooling system consist of oil filter, minimum pressure valve (MPV), a heat exchanger.

Thermovalve
And in some designs (usually the bigger horsepower units), temperature control (regulating) valve is used to maintain a relatively constant temperature regardless of compressor load.

Oil Circulation
The use of Compressor lubrication is very important! and cannot be denial? Especially the grade and type of lubricant use.

Oil circulation is usually provided by the pressure-differential system. Circulation in the pressure-differential system is achieved by using higher-pressure air to generate the oil flow. A preset minimum pressure valve (MPV), usually about 80 psi, allows the quick pressure build up in the oil sump before the MPV opens to discharge compressed air to the air system.

MPV
The pressure differential between the fully compressed air, and the pressure within the cell as it passes or rotates. The pressure differences thus created, caused the oil to be injected via orifices into all moving parts, including the rotor bearings located in the end covers of the stator..


In all and every cases, the compressed air pressure is relieved automatically from the discharge side of the compressor during shutdown.

Therefore, with this design and operation, there will be oil presence in the compressed air. It is not desirable to have oil in the compressed air, and it is necessary to remove the oil before it is send to the air system.

Oil Separation
Therefore; as air and oil mixture passes from the compression chamber, the oil, which is heavier, is mechanically separated by direction and velocity changes, or use of baffles, or of both, and allowed to drain back into the oil chamber or oil sump for recirculation.

Relatively clean air leaves the sump and enters the separator, where most of the remaining oil is removed by coalescence called air/oil separator/s.

The coalescence (separating media) are ceramic tubes or combination of mesh & fibre glass (Boros Silicate).

The Scavenging Line
The separated oil (residue oil) drains from the coalescing media to collection well for subsequent return via a combination of orifice and check valve to the intake side of the compressor.


Oil Carryover
The amount of oil carried over is less than 5 to 1 ppm of air measured by weight.
Air losses through the oil return (scavenging) line is controlled by an orifice.
The resulting pressure drop through the separator should be approximately 1 to 3 psig, when new. Should change or replace the separator when the pressure difference is at or more than 15 psig.

Heat Exchanger
Air-cooled or water-cooled heat exchanger are used for the oil. The air-cooled heat exchanger is of radiator type, with a cooling fan to provide air circulation. The water-cooled is shell & tube type, and need an external water circulation and cooling system.

Oil circulation at start-up
On start-up, oil bypass the heat exchanger (cooler) and circulates through the compressor and sump with cooling. This provide rapid oil supply & heating on start-up. When correct oil temperature is reached, the temperature regulator modulates the oil flow to maintain the optimum temperature.

Tuesday, December 23, 2008

Positive Displacement Compressors-Vane 2

Design

Air Compression between sliding vanes is basically a simple concepts.

Compression takes place when the volume of the spaces between the sliding vanes in a rotor is reduces as the rotor turns or rotate within an eccentric cylinder (housing).

The distinguishing features of these type of rotary sliding vane compressors is the injection of liberal quantity of oil directly into the compression chambers:
1. To seal the cells,
2. Provide lubrication,
3. Cooling,
and
4. to absorb the heat of compression


Constructions and designs varies with different manufacturers, but the principles of operation and control are similar.


The rotor has 6 to 8 longitudinal slots in which, vanes slide freely, move outward by centrifugal force against the cylinder wall of the stator.


As the rotor rotates, each vane sets pass the inlet (Suction) port to form a cell (Chamber), between it and the preceding vane sets. The air, that is trapped is compressed as volume of the cell decrease until the leading vane of the cell pass the outlet (discharge) port.

With rotation counter-clockwise, the volume between the vanes, the rotor, and the stator is increasing between the inlet port, at right, and top.

Consequently, partial vacuum is created, cause it to sucks in more fresh air from atmosphere in through the inlet port. The volume then decreases as the cell approaches the outlet post at top left, causing the air pressure to rise. Air is not leak back around the rotor, because it is sealed between the rotor and its blades, concentric bore in the stator and compressor oil.

These positive-displacement have a fixed compression ratio for any given model. Ratios up to 10:1 can be used to compressed air in a single stage.

An important factor in obtaining high efficiency is the controlled oil injection into the compression chamber.


Oil is injected for:
1. sealing each cell from its' neighbour,
2. seal between the high=pressure and partial-vacuum conditions within the cycle,
3. cool the air been compressed,
4. Lubrication.

Positive Displacement Compressors-Vane 1

Positive-displacement Compressors
Vane

Vane and Screw are classified under the main group know as Positive-displacement compressors.




According to Compressed Air and Gas Handbook:
A positive-displacement compressor is a machine in which, a quantity of air or gas occupies a space that is mechanically reduced, resulting in a corresponding increase in pressure.


It should be realised that during the last 20 over years, there has been a significant swing from reciprocating to packaged, rotary air compressors.

From Compressed Air and Gas Handbook,
The oil-injected, sliding vane rotary compressor was introduced as portable, engine-driven compressor way back in year 1950.

Actually, it was produced in Italy, way back in the year 1923 by a company now know as Pneumofore.

Shortly thereafter, it was applied as stationary industrial compressor with electric motor drive in 1956. It has since been incorporated into diesel-engine-packages. Lately, especially the smaller and more compact designs have been incorporated into the original equipment of many manufacturers.

Since, the introduction of these compressors into the industrial market, many improvements have been made, thus, providing a reliable compressor package.

The compressor is normally furnished as an engineering package, so installation is simplified.

These design minimize maintenance and is free from vibration problems, and its compact size eliminates the need for extensive foundations.

It can be water-cooled or air-cooled packages.

Motor Shaft

Main Motor Shaft Failure

Broken Main Motor Rotor Shaft of An Ingersoll Rand Model XF100.








The other section of the Broken Main Motor Rotor Shaft.


We can replace the Rotor of that shaft without purchasing new MOTOR!
It is in operation for more than a year now. This company operate 24 hours a day for 365 days.