TABLE OF CONTENTS Fans are used to raise the pressure by about 3% [12 in. (30 cm) water], blowers raise to less than 2.75 barg (40 psig), and compressors to higher pressures, although the blower range is commonly included in the compressor range.
For vacuum pumps use the following:
| Reciprocating piston Type | down to 133.3 Pa (1 torr) |
| Rotary piston type | down to 0.133 Pa (0.001 torr) |
| Two lobe rotary type | down to 0.0133 Pa (0.0001 torr) |
| Steam jet ejectors | 1 stage down to 13.3kPa (100torr) 3 stage down to 133.3 Pa (1torr) 5 stage down to 6.7 Pa (0.05torr) |
A three-stage ejector needs 100 kg steam/kg air to maintain a pressure of 133.3 Pa (1 torr).
In-leakage of air to evacuated equipment depends on the absolute pressure (torr) and the volume of the equipment, V in m 3(ft), according to W = kV 2/3kg/h (lb/h), with k = 0.98 (0.2) when P > 90 torr, k = 0.39 (0.08) when P is between 0.4 and 2.67 kPa (3 and 20 torr), and k = 0.12 (0.025) at p less than 133.3 Pa (1 torr).
Theoretical adiabatic horsepower
where T 1 is inlet temperature in Rankine, R = F + 460 and a = {k - 1 )/k,k = Cp/C v. Theoretical reversible adiabatic power = mz 1RT 1[({P 2/P 1} a
