Liquid jet Exhauster – Selection procedure

Typical sizing sample -1.

Type-A: Suitable for higher vacuum range.

A vacuum pump has to handle continuously 65m3/hr of air at 250mmHg vacuum against ‘0’ back pressure. Size the exhauster and motive flow required to be estimated for water temperature of 27ēC temp. Motive head available is 5kg/cm2

Refer table: At 250mmHg vacuum @ 4.5kg/cm2 pressure motive head @ 0kg/cm2 back pressure

Air suction rate is   4.5m3 /hr
Required air rate   65m3 /hr
Capacity ratio 65/4.5 = 14.44
Refer capacity ratio table for nearest higher CR 16
Select Liquid jet exhauster for CR =16    100mmNB
 Motive flow from table 3.2m3 /hr
 Motive flow required = 3.2m3 /hr (std) X 16 (CR) 51.2m3 /hr @ 4.5kg/cm2

Typical sizing Sample -2.

Type-B: Suitable for near atmosphere vacuum.

A  Vessel of volume 10m3 is to be evacuated to 0mmHg vacuum in 15min. Size & select the exhauster for the  available motive water pressure of 8kg/cm2.

A standard 1” exhauster @ 7.5 kg/cm2 motive water head 14.6m3 /hr @0mmHg and 0 back pressures evacuates
Required evacuation rate 10m3/(15 min/60)=40m3 /hr
Capacity Ratio 40/14.6 = 2.73
Refer CR Table (Nearest higher CR=4 for 50NB size exhauster) 50NB Size.
Standard motive Flow from table 4.0m3 /hr
Required motive flow 4x4=16 m3 /hr
Select 2” size exhauster