Difference between Surging and Choking

 COMPRESSOR 
Mechanical device which imparts kinetic energy to the fluid in impeller and conversion of this energy into pressure by decreasing velocity in diffuser.

  SURGING    
According to the standard operating curve of compressor, maximum discharge pressure is obtained at minimum flow rate. So, if maximum head capacity is reached, then pressure in diffuser will be greater than pressure at impeller outlet, this will prevent fluid from moving towards discharge and cause the fluid in diffuser to flow back towards impeller. Reversal of flow takes place.

 IT CAN 

• Damage bearings.
• Damage other rotating parts.
• Cause high vibrations.

 REMEDY 

• Anti-surge valve.

 CHOKING 

According to the given below graph, compressor run in between of surge point and stonewall point which also known as Choking point. As it is described in the above para that if flow is decreased and pressure is increased Surging will occur. Now, flow increases and discharge pressure decreases which means less back pressure on fluid and less resistance to flow as a result flow increases to a velocity approachable to MACH=1 also known as Sonic velocity and choking occurs.

 IT CAN 

• May cause very severe damage to the compressor.

 REMEDY 

• Anti-choke valves.

Scaling and Fouling

In Short :

Scaling is depositing of dissolved minerals on equipment surface.

Fouling can be caused by garbage collection for the pump suction grid in the pits, the growth of algae in lighted areas, and mucus in the shadows or dark areas of water systems. The material can clog pipes or other parts of the system, after he has escaped and migrated to the flow of water.

Difference between Flashing and Cavitation

DIFFERENCE
Flashing happens in the control valve if the liquid pressure drops to the value below its vapor pressure hence it may form vapor component (like bubble). Similar to flashing, the vapor is formed in cavitation in the same way, the difference is that the liquid pressure is increasing to a value over its vapor pressure during pressure recovery in which makes the vapor turn back into liquid state afterwards.
REMEDY
Flashing could be anticipated by hardened material trim therefore to overcome flashing, the selected control valve shall have hardened material trim. However, hardened material trim is not sufficient to handle cavitation. Anti-cavitation trim shall be used otherwise the system design itself should be changed so  cavitation is avoided.