Piston compressor, V-shaped

In a two-stage compression compressor (Figure 174.6), intake air is compressed twice: first, to a certain pressure in the cylinder of stage I, then, after passing through the cooler, under pressure enters the cylinder of stage, where it is compressed to the final pressure. As a rule, two-stage compressors create a discharge pressure of up to 12 kgf/cm2, while in the cylinders of the compressor the temperature of compressed air increases to 190 ° C or more.

Lubricating oils used for lubricating compressors have a flash point of 210-240 ° C. When this temperature is reached, the oil decomposes, releasing solid particles and gases. These gases, when mixed with air, form an explosive mixture, which may cause the compressor to explode. Therefore, to control the temperature of the compressed air after each compression stage, a cooler is installed in the compressor to cool the cylinders.

In a two-stage compressor, the same amount of air sequentially passes through the I and II compression stages. Compressor capacity 3.5 m3/min, discharge pressure 7 kgf/cm2. During operation of the compressor, air is sucked into two cylinders of stage I and compressed to a certain pressure passes through the cooler into two cylinders of stage II, where it is compressed to the final pressure.

Cast iron compressor housing with four attachment legs. Four cast iron cylinders (with ribs to increase the cooling surface) are attached to the body on studs with an in-line arrangement and a camber angle of 90 °. The crankshaft is stamped with two counterweights, rotates on two ball bearings and has a system of channels for passing lubrication. Bushing with square hole for oil pump drive is pressed into shaft end. Connecting rods of all cylinders are the same. Two thin-walled inserts filled with babbitt are installed in lower split head of connecting rod. Aluminium and cast iron pistons of stages I and II respectively are connected to upper heads of connecting rods by means of piston pins of floating type. On each piston there are four piston rings: two upper (compression) and two lower (small). Low-detachable rings have radial slots for passage of lubricant removed from cylinder mirror. Valve boxes are attached to upper flanges of cylinders of I and II stages on studs. Self-operating valves with fluoroplastic inserts. Air drawn in by compressor is cleaned in air filters connected to valve boxes of I stage. The filter element in the filters is capron packing. After compression in the cylinders of stage I, the air is cooled in intermediate coolers of the tubular type. On the valve boxes of the cylinders of the I stage there are safety valves, which are designed to maintain the specified pressure during air compression between the cylinders of the I and II stage. Refrigerators and cylinders are blown by fan installed on compressor bracket. Fan is driven by wedge belt from pulley. Inner space of compressor housing communicates with atmosphere through sapoon having check valve and filtering pack.

Lubrication supply is monitored by pressure gauge readings: oil pressure at 1450 rpm must be at least 1.8 kgf/cm2. To eliminate fluctuations of the pressure gauge arrow (due to pulsating oil supply by the pump) in the oil pipe assembly there is a hole with a diameter of 0.5 mm and a valve. The normal position of the valve is closed. Compressor lubrication combined. Oil under pressure from the oil pump through the hollow roller enters the crankshaft connecting rods and piston pins; other parts are lubricated by spraying, fan bearings - by grease. Reduction valve is installed on oil pump cover to control oil pressure. Oil is poured into compressor crankcase through hole for oil indicator or through hole for boot, oil is drained from crankcase through hole closed by plug. Oil level is checked by oil indicator at its wrapped position.