COMPRESSOR BASICS

TYPES OF COMPRESSORS POSITIVE DISPLACEMENT COMPRESSOR CENTRIFUGAL COMPRESSOR

POSITIVE DISPLACEMENT COMPRESSOR PD COMPRSSOR WORK BY TRAPPING A CERTAIN AMOUNT OF GAS AND FORCING IT INTO A SMALLER VOLUME A COMMON TYPE OF PD COMPR. IS RECIPROCATING COMPRESSOR. TWO OF THE MAIN PARTS OF RECIPROCATING COMP. ARE CYLINDER AND A PISTON

GAS ENTERS THE CYLINDER AND IS TRAPPED INSIDE THE CYLINDER GAS ENTERS THE CYLINDER AND IS TRAPPED INSIDE THE CYLINDER. THE GAS IS THEN FORCED INTO A SMALLER SPACE BY THE ACTION OF THE PISTON. FORCING THE GAS IN SMALLER SPACE INCREASES THE PRESSURE, THE COMPRESSED GAS IS THEN DISCHARGED.

CENTRIFUGAL COMPRESSOR IT USES A DEVICE CALLED IMPELLER TO SPIN THE GAS AROUND THE ACTION OF THE IMPELLER ACCELERATE OR INCREASES THE SPEED OF THE GAS FLOW. IT GIVES THE GAS ENERGY. AS THE GAS FLOWS OUT IT SPEED OUT AND SLOW DOWN AND ITS ENERGY IS CONVERTED INTO PRESSURE

SHARING CHARACTERSTICS COMPRSSORS ARE RATED FOR DISCHARGE PRESSUR AND FLOW RATE ALL COMPRESSORS REQUIRE SOME FORM OF DRIVE MECHANISM ELECTRIC MOTORS ARE COMMONLY USED DRIVES.

COMPRESSOR HAZARD MOVING PARTS HOT SURFACE NOICY LEAKS FROM THE GAS SYSTEM FLAMMABLE EXPLOSIVE GASES (SPARK PRODUCING EQUIPMENT SHOULD NEVER BE USED)

ACCESSORIES LUBRICATION COOLING FILTERING

LUBRICATION SYSTEM MAIN FUNCTION IS TO REDUCE FRICTION BETWEEN THE MOVING PARTS LUBRICATION HELPS COOLING THE COMPRESSOR MOVING PARTS AND HELP PREVENT THE LEAKING GAS OUT OF COMPRESSOR.

DESCRIPTION OIL FROM THE COMPRESSOR FLOWS INTO THE OIL PUMP.THE OIL IS THEN PUMPED THROUGH FILTER WHICH REMOVES ANY SOLID PARTICLE FROM THE OIL. OIL FLOWS THROUGH THE HEAT EXCHANGER WHERE IT IS COOLED FROM HEAT EXCHANGER MOST OF THE OIL FLOWS DIRECTLY TO COMPRESSOR LUBRICATION.

REST OF THE OIL GOES TO OILER. OILER SUPPLIES A SMALL AMOUNT OF OIL TO THE COMPRESSOR CYLINDER THE OIL LUBRICTES THE PISTON RINGS AND HELPS SEAL THE SPACE BETWEEN THE CYLINDER WALL AND THE RING.

COOLING WHEN A GAS IS COMPRESSED HEAT IS PRODUCED THIS HEAT CAN CAUSE TWO PROBLEM 1. EXCESS HEAT CAN BREAK DOWN OIL CAUSING IT TO BE LOOSE ITS LUBRICATING CHARECTORSTIC 2. GASED EXPAND WHEN THEY ARE HEATED SINCE COMPRESSOR IS DESINGED TO COMPRESS GASES THE EFFECT CREATE ADDITIONAL FORCE WHICH COMPRESSOR MUST OVERCOME.

HEAT REMOVAL AIR COOLING AND WATER COOLING ARE TWO TECHNIQUES 1. AN AIR COOLED COMPRESSOR EASILY IDENTIFIED BY MEAL FINS ON ITS CASING THE FINS PROVIDE INCREASED SURFACE AREA.

2. ANOTHER WAY TO REMOVE THE EXCESS HEAT IS TO COOL THE GAS AFTER THE COMPRESSION IS COMPLETE, THE DEVICE THAT DOES THIS IS AN AFTERCOOLER OR INTERCOOLER DEPENDING UPON ITS LOCATION THESE EXCHANGERS ARE CLASSIFIED AS INTERCOOLER OF AFTER COOLER.

INSTRUMENTATION AND CONTROL THE PROPER OPERATION OF COMP. DEPENDS UPON INSTRUMENTAITON AND CONTROL DEVICES THESE DEVICES ALLOWS THE COMPRESSOR TO BE STARTED AND STOPPED. THEY PROVIDE INFORMATION ABOUT THE COMPRESSOR OPERATING CONDITIONS

THEY MAINTAIN THE VALUES OF PROCESS VARIABLES THEY KEEP THE COMPRESSOR OPERATION STABLE THEY CAN SHUT DOWN THE COMPRESSOR IF UNSAFE CONDTITON OCCURED CONTROL PANEL MAY HAVE CONTROL TO REGULATE THE SPEED

CONTROL PANEL ME ALSO CONTAIN ALARMS THAT LET THE PERSONNEL KNOW WHEN ABNORMAL AND POTENTIAL DAMAGING CONDITION EXISTS PRESSURE CONTROLLER CONTROLS THE DISCHARGE PRESSUR AND IF IT DEVIATES CONTROLLER MANUPULATE THE INLET FLOW

SURGE CONTROL FOR A GIVEN DISCHARGE PRESSURE A COMPRESSOR HAS A CERTAIN MINIMUM FLOW RATE. BELOW THIS FLOW RATE THE COMPRESSOR BECOME UNSTABLE. A DECREASE IN FLOW BELOW THE MINIMUM FLOW CAN CAUSE A SERIES OF MOMENTARY REVERSAL OF FLOW THROUGH THE COMPRESSOR. THIS SITUATIION IS CALLED SURGE

SURGING RESULTS IN VIOLENT FLUCTUATIONS IN DISCHARGE PRESSURE. WHEN AN ELECTRIC MOTOR IS USED AS DRIVER SURGING CAN CAUSE EXTREME VARIANTION IN MOTOR CURRENT. SYMPTOMS OF SURGING ARE LOW GAS FLOW, EXCESSIVE VIBRATION AND BANGING SOUND INSIDE COMPRESSOR

TO PREVENT THE SURGING THE FLOW RATE OF THE GAS THRU THE COMPRESSOR MUST BE KEPT ABOVE THE MINIMUM STABLE FLOW RATE OR SURGE POINT WHEN THE DEMAND IS LOW FLOW RATE IS MAINTAINED BY RECIRCULATING THE PORTION FROM DISCHARGE TO BACK TO COMPRESSOR.

START UP PREPARING THE COMPRESSOR FOR STARTUP WARMING UP THE COMPRESSOR STARTING THE GAS FLOW THRU COMPRESSOR

COMPRESSORS GAS SUPPLY IS AVAILABLE, CONTROLS ARE SET IN POSITIONS. VALVE LINE UP MEANS ALL THE VALVE ARE PROPERLY SET. START THE COMPRESSOR AUXILARIES AND MAKE SURE THEY ARE OPERATING PROPERLY. OPERATOR MUST CHECK THE COMPRESSOR AND MAKE SURE THAT NO ABNORMAL CONDITION EXISTS.

IF THE COMPRESSOR HANDLES THE FLAMMABLE GAS IT MUST BE PURGE WITH AN INERT GAS LIKE NITORGEN. ONCE PURGED IT CAN BE STARTED AND KEPT IN WARMING UP. ONCE THE COMPRESSOR AND ITS PARTS RUNS FOR A WHILE AT A LOW SPEED THE COMPRSSOR CAN BE BROUGHT UP TO NORMAL SPEED. THIS INVOLVES THE INCREASE OF SPEED AT CERTAIN RATE CALLED RAMP RATE

CRITICAL SPEED – FOR CETRUFUGAL COMPRSSOR CERTAIN ROTATIONAL SPEED CAUSE SEVERE VIBRATION, IT IS CALLED CRITICAL SPEED. IT IS DUE TO PHYSICAL CHARECTORSTIC OF MOVING PARTS OF COMPRESSOR. WHEN A CRITICAL SPEED IS REACHED THE RAMP SPEED IS USUALLY INCREADED TO PASS THROUGH THE CRITICAL SPEED.

OPERATION ONCE STARTED COMPRESSOR SHOULD BE CHECKED ROUTINELY. WHILE CHECKING A COMPRSSOR OPERATOR MUST KEEP IN MIND THAT IT OPERATES AT VERY HIGH SPEED. AN IMPORTANT PART OF CHECKING A COMPRSSOR IS TO LISTEN TO THE ABNORMAL SOUND.

IT IS IMPORTANT TO CHECK THE COMPRESSOR BEARING FOR EXCESSIVE VIBRATION AND OVERHEATING IT INDICATE PROBABLE BEARING FAILURE. COMPRESSOR AUXILIARY CHECK IS IMPORTANT DURING OPERATION OF COMP. LIKE OIL LEVEL IS IN NORMAL RANGE,OIL IS CLEAR AND NOT MILKY. OIL PRESSURE IS IMPORTANT PARAMETER TO CHECK, INIDCATE MALFUNCTION OF OIL PUMP OR OIL LEAK IN SYSTEM.

OIL PARAMETER IS CRITICAL PARAMETER, HIGHER THAN NORMAL OIL PRESSURE INDICATES THE CLOGGING OF SOME PART IN OIL LUBRICATION SYSTEM. G