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. 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.