Lobe Blowers

Question 1

What is a lobe blower?

Answer 1

A lobe blower is rotary positive displacement machine used to move gas and air. mistakenly referred to as a compressor.

Question 2

What is the purpose of a lobe blower?

Answer 2

The 2 and the 3 Lobe blowers do not compress or reduce the volume of the air/gas, Instead they move air from one side to the other as the lobes rotate.

Question 3

How is pressure increased at the outlet?

Answer 3

Fixed volume of air is pushed into the discharge, the pressure at this point naturally increases causing the air or gas to flow. trapping and packing fixed volume of air with each rotation.

Question 4

How to increase efficiency on a lobe blower?

Answer 4

To increase efficiency, blowers are often two and three stages in a vacuum applications allowing a lower vacuum to be pulled.

Question 5

How do you further increase efficiency?

Answer 5

Often water or another liquid is injected into the vacuum stream increasing efficiency by sealing clearances within the blower.

Question 6

What other added advantage does injecting water into the vacuum stream has?

Answer 6

Serves as a coolant.

Question 7

Why was the three (3) lobe compressor developed?

Answer 7

It was developed to increase efficiency by reducing slip as compared to the two (2) lobe.

Question 8

What is also referred to as a hybrid between a blower and a compressor?

Answer 8

Cycloidal blower

Question 9

What is not a function of a love blower

Answer 9

Supplying Pneumatic Tooling.

Question 10

When referencing a lobe blower what is slip?

Answer 10

The discharge air leaking back towards the inlet

Question 11

The size of a blower is given as 7.15 what do the numbers refer to?

Answer 11

The seven is the diameter of the timing gear, 15 is the length of the lobe

Question 12

When performing a typical set of impeller to impeller clearance checks the preferred angle is?

Answer 12

45° from vertical

Question 13

Even though lobe blower does not produce substantial axial thrust, thrust bearings are required why?

Answer 13

To maintain rotor position relative to the end plates

Question 14

What is one critical criteria about timing gears?

Answer 14

They cannot have excessive backlash

Question 15

What should be done first before putting a compressor back into service after an overhaul or motor change?

Answer 15

You must check for correct rotation.

Question 16

What is the advantage of the helical lobe blower the two lobe blower?

Answer 16

Increased pressure and smoother air delivery.

Question 17

What types of bearings are found on lobe blowers?

Answer 17

• Single Row Ball Bearings
• Double Row Ball Bearings
• Deep Groove Ball Bearings
• Spherical Roller Bearings
• Cylindrical Roller Bearings
• Angular Contact Bearings

Question 18

What should be determined before resetting the timing gears on a lobe blower?

Answer 18

Before attempting to retime and set lobe clearances, you must determine whether the unit is unidirectional or bi-directional rotation. Always referred to “Manufacturer’s Operation Maintenance Manual”.

Question 19

At what position are lobe blowers clearances set?

Answer 19

• Between The Rotors
• Between The Rotors Tips And Casing
• Between The Ends Of The Impeller Rotors And End Plates.

Question 20

What should be done before starting a lobe blower after an overhaul?

Answer 20

Turn it over by hand to ensure that it rotates freely in the correct rotation.

Question 21

care should be taken to prevent what from happening during attempting to set lobe clearances in a blower?

Answer 21

Prevent injury to the fingers or hands cause by pinching from the gears or lobe rotors.