Answer / engineer muhammad masoom shafi

Surging is a momentary back flow through the compressor from
the discharge to the suction.This can occur when the mass
flow of gas to the compressor falls below a critical level
with a high pressure difference across the m/c.when there is
not enough gas to replace that being pushed
Forward,discharge gas will flow backwards through the
compressor towards the suction side this back flow will tend
to decrease the speed of rotation while the speed controller
will try to maintain the correct speed.the gas flowing
backward provides more volume to the suction side and the
compressor picks up and begins to push gas forward again.the
m/c speed will tend to increase and the governor will again
try to maintain the correct,set speed.all of this take place
very quickly,the forward and backward gas flow together with
the speed control action cause rapid fluctuation in the flow
and pressure in the system.this surging condition is similar
to an aircraft'stall'condition,or pump cavitation.

Answer / hader

Surge happended when the flow start to reverse in direction
from the last compressor stage to the previouse stages, due
to low quantity of fluid entering the inlet, it avodied by
anti surge valve which take flow from the exit and
discharge it to the inlet to keep enough quantity in the
inlet.

Answer / ahmed

Dirty intercoolers—Increased air temperature reduces air
density into the compression stage, resulting in reduced
stage pressure ratio and reduced rise to surge.
Dirty inlet filter—Reduces the pressure into the first
stage, resulting in a lower natural surge point. A lower
natural surge point reduces the throttle range.
Hot coolant—Increased air temperature reduces air density
into the compression stage, resulting in reduced stage
pressure ratio and reduced rise to surge.
Hot inlet air—Increased air temperature to the first stage
reduces air density into that stage, resulting in reduced
stage pressure ratio. Since pressure is multiplied as air
moves through a multistage compressor, the first stage has
the most dramatic effect on rise to surge.
Driver input speed—Ability for a centrifugal compressor
stage to make pressure decreases as the square of the stage
speed. A reduction in driver input speed dramatically
affects the total machine pressure ratio and the rise to surge.

Answer / s

Surge is a flow instability that results in a global
collapse of flow through the compressor.
Compressors do not continue to operate or flow once surge
has occurred. Surge should be avoided.
Surge is not the rough operation, vibration, pulsation, or
noise that develops at low flow conditions.


Surging is a momentary reversal of flow.When the pressure in
the centrifugal comp. increases,the mass flow rate
decreases.There is a limit up to which the pressure can be
increased,then after the flow becomes instable and momentary
reversal of flow take place,vibrations are produced and
mechanical damage occurs.

Answer / mohmmmed

Surging is a momentary back flow through the compressor from
the discharge to the suction.This can occur when the mass
flow of gas to the compressor falls below a critical level
with a high pressure difference across the m/c.when there is
not enough gas to replace that being pushed

Answer / zahid akhtar

Centrifugal compressor surge is seen as a very dangerous and detrimental phenomenon in compressed air systems, dangerous because it causes the compressor to vibrate and detrimental because it causes damage to the compressor parts. Compressor surge only occurs in dynamic compressors (Axial and Centrifugal) due to their nature. To understand compressor surge, a solid understanding of how a compressor actually works is needed.

A centrifugal compressor is a machine that imparts energy to the gas flowing through it. This energy is in the form of velocity and is imparted from compressor impeller to the gas. Kinetic energy of the gas is then converted to pressure head when gas is diffused, slowed down.

Answer / raj ratnam

Due to increase in load on the compressor, mass flow rate
decreases. it would again tend to increase the flow rate.
This to and fro motion of the fluid causes pulsation in the
compressor called surging.

Answer / ahmed zaky

Surge occurs at the lower extreme of the compressor flow
range where the gradient of a compressor’s pressure
characteristic becomes positive; therefore any reduction
in mass flow rate will result in a reduction in the outlet
pressure from the compressor accompanied by a reversal of
the high pressure flow downstream of the compressor.

Answer / sameera

I guess, surging is entry of less air flow because of
reduced pressure drop. it can be corrected by reducing flow
area (i.e. by decreasing c/s area of casing) opposite of
surging is choking wherein there is excessive air flow. Not
sure though

Answer / mayur amipara

srging basically means reversal flow fluid from compressor
to evaporator...it occurs when the pressure is
increased.And to avoid this reversal flow a check valve
must be provided in the suction line.

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