Tips about Suction and Discharge Valves Used In Reciprocating Air Compressor.

The performance of air compressor is mostly depending upon the condition of suction and discharge valves. These valves are very important part in any reciprocating air compressor and engineering field. That’s why due care must be required. Every valve requires a periodic inspection and maintenance. Here you will find, important information about suction and discharge valves used in Chicago Pneumatic Air Compressor.

01) Dismantling of valves:-
To avoid damage to the valve and inner dowel pins, it is suggested to use a simple fixture for dismantle and assemble valves. Never tightened the valve directly in a vice and do not hammer on spanner when loosening or tightening the nut.

02) Cleaning of valves:-
Examine all the parts thoroughly after dismantled the valve. Remove the carbon formation with the help of Trichloroethylene or diesel and light scraping paper or brush. Don’t scratch the valve plate or seat while cleaning. Completely dry out the valves before installing it on compressor.

03) Inspection and Reconditioning:-
When valve plate, damper plate, spring plate shows sign of wear, it is imperative to replace these parts, even if no breakage has occurred. A maximum wear of about 10 % of the total thickness of valve plate is allowed. For highest efficiency of the valve it is important that the seat face is flat and free from any traces of wear, thus preventing valve leakage. If any damage on the seat observed, it is recommended to replace the same. Dew to presence of dowel pins, re-machining or lapping can not be carried out. It is also suggested to use a new valve plate with new valve seat.

04) Reassembly and Installation:-

A) Do the valve assembly in required sequence. (Refer diagram from instruction manual) Use fixture for proper tightening of valve nut. Check valve plate for free movement.

B) Test valves for leakage and insure it made dry after testing.

C) Suction valve equipped with unloader, the clearance between the valve plate and unloader lifter as well as the clearance between unloading piston and lifter is checked.

D) Valve cover nuts have to be tightened with specific torque by torque wrench.

E) The hollow side of the thin part in the centre of the valve plate must be placed upward facing, valve keeper.

The above information will help you to increase life of suction and discharge valve and hence the discharge pressure of the air compressor.

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How To Start New Reciprocating Air Compressor.

Below points are most essentials in air compressor engineering.
01) Be certain leveling screw in frame base has been backed off, and foundation bolts are tightened properly.

02) Clean off all accumulated dirt from exterior of compressor and electric motor.

03) Remove covers, tapes, wrapping from openings, which had been blanked and sealed.

04) Open frame top cover and check all connecting rods, bolts etc. to see that they are correctly installed and tightened. Check crankshaft end float.

05) Check and clean thoroughly the inside of the frame. Use cloth for cleaning inside. Never use cotton waste on internal parts.

06) Remove silica gel bags if placed in valve ports, do not wipe any carbon and Teflon powder from valve or cylinder. (For Non Lubricated Compressor.)

07) Fill compressor frame with correct grade of oil up to required level. (Middle of the visual screw)

08) Rotate the compressor manually, in direction of rotation and check bearing lubrication as well as free running of crankshaft.

09) Fill oil in force feed lubricator, disconnect oil line near to cylinder and rotate handle. Check oil is coming at the end of lubricating pipe. Reconnect oil line and operate pump at least 20-25 turns.

10) Check each compressor piston rod to be certain it is smooth and rust free, especially for the section where rod is passing through packing and wiper rings.

11) Check the bumping clearance as per recommended.

12) Replace frame inspection cover on the compressor.

13) Check compressor air cleaner and suction lines for dirt and clean, if required.

14) Check all electrical connections for correct tightness.

15) Check the insulation resistance with megger. If any moisture or dirt in the winding indicated, remove it immediately.

16) Remove safety devices and start motor without v-belts. Check the incoming voltage and current drawn by motor. Check electric motor for abnormal noise and vibrations.

17) When satisfied with electric motor, fit v-belts, align motor and adjust belts tension as required.

18) Check strainer/air filter before unloader and insure pressure sensing airline is clean and free from rust, dust etc.

19) Remove all suction and discharge valves and starts motor. Check oil pressure unusual noise, vibration and safety trappings.

20) Shut down compressor, check all parts for unusual heating. Install all suction and discharge valves.

21) Restart compressor and continue to run until the unit has warmed. Check various temperature and pressure gauges for proper operations.

22) If found every thing in order, put the compressor air discharge net to supply compressed air for plant utilities.

Follow all the above instructions while commissioning every new or overhauled reciprocating air compressor.

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Different Combustion Chambers Provided In Diesel Engines.

When we are going to design the combustion chamber of diesel engines the main consideration we have to keep in mind is, high compression ratio & sufficient turbulence of air. For high compression ratios overhead valve s are more preferred than side valves. Below are the some shapes of combustion chambers discussed.

01) Open or Direct Injection Chamber

For moderate & low speed engines this type of combustion chamber is most suitable. The fuel is injected directly in the combustion chamber, which is formed by a part of the piston, where it penetrates the mass of hot compressed air. The injector pressure is more than 21 kilogram per centimeter square is used. The fuel injector is placed in the center of the chamber and contains more than four orifices. Due to location of orifices the spray pattern suits the combustion chamber & does not impinge on the wall of the cylinder or piston.

This design is used by Leyland Motors Ltd has the chamber in the form of a truncated cone and the fuel injector is located near the circumference of the chamber. In some engines two injectors are located on the opposite side of the chamber. The open type of combustion chamber depends upon the primary turbulence as the main source of air movement due to which engine can start in cold condition and don't required heater plug.

02) Auxiliary Combustion Chamber

In small high-speed engines, this type of combustion chamber is mostly used. Total fuel is directly fed into an auxiliary combustion chamber where the initial combustion takes place. Due to rise in pressure the partially burnt mixture is forced at high velocity through a small orifice into the main combustion chamber where the rest of the combustion aided by secondary turbulence takes place.

As the piston descends during power stroke, the pressure difference created between the precombustion chamber and the main chamber assists in discharging the hot exhaust gases from the precombustion chamber. This type of combustion chamber has very low maintenance cost due to low injection pressure and simpler single nozzle orifice. The main combustion chamber is subjected to less pressure since the pressure shock is mainly taken by precombustion chamber. This type of combustion chamber gives clean exhaust but heat losses are higher due large surface area of two chambers.

03) Air Cell

In some designs small chamber is provided which is called as air cell. They are away from the fuel spray nozzle, which is so located that the fuel is sprayed near the narrow neck, which connects the air cell with the main combustion chamber. Piston compresses the air during compression stroke and pushes it into air cell. As the piston moves down the pressure in the cylinder falls resulting in the flow of hot air from the cell into the combustion chamber producing the secondary turbulence, which mixes the air & fuel further and completes the combustion. The air cell also requires a high compression ratio and heater plugs for starting. The heat losses are more due to large wall area.

04) Ricardo Comet Chamber

This combustion chamber is separated from the cylinder and one of the most efficient combustion chamber. In this type chamber air enters in tangential direction during compression stroke and imparts a rotary motion. The fuel is then injected into the hot compressed air and the combustion takes place. Reversal of flow takes place due to pressure rise and the hot gases are discharged into the cylinder pushing the piston up ward in working stroke. Due to higher temperature of air in the combustion chamber, fuel of low ignition quality can also be burnt satisfactorily.

05) Energy Cell

It is also called as Lanoxa chamber and works on combined principles of air cell & auxiliary combustion chamber. As fuel injector sprays the fuel, 10% of fuel passes across the combustion chamber & enters in energy cell. The combustion generally starts in the main chamber, spread to the energy cell where pressure rise considerably. Due to pressure difference between the energy cell & main combustion chamber, the hot gases from the minor cell, will sweep the fuel from the minor cell, into the combustion chamber where additional turbulence is set up to ensure complete combustion of fuel.

A restricted opening can be closed by plunger, which connects major cell with the minor cell, this effects smooth starting. Once the engine is started the restricted opening can be opened out so that the minor cell is connected with the major cell. Through a small opening, minor cell communicates with combustion chamber. Due to this small opening the hot gases are throttled and so the pressure rise in main combustion chamber is gradual. Since the fuel is sprayed direct in to the main combustion chamber where the air has highest temperature resulting in complete combustion.

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