Chapter 8 - Hydraulic and Pneumatic Power Systems (B)

Question 1

On a constant displacement pump, how is the output pressure regulated?

Answer 1

It must have some form of regulator or relief valve in the system to relieve the pressure that builds up when the pump moves more fluid that the system can use.

Question 2

What is the safety feature on the micronic filter assembly?

Answer 2

Relief valves across both elements to prevent over-pressurizing the return if, for any reason, the pressure drop across the elements become excessive.

Question 3

What is good about the cuno filter?

Answer 3

They are able to be used on the pressure side of the system

Question 4

On a variable displacement pump, how is the output pressure regulated?

Answer 4

By controlling the amount of fluid that the system will accept

Question 5

What is the main purpose for pressurizing hydraulic reservior?

Answer 5

To operate at higher altitudes to compensate for the decrease air pressure.

Question 6

Name some reasons for the quick disconnect coupling.

Answer 6

• Prevents loss of fluid when units are removed
• It can be used interchagably with other systems
• Automatically closes when a line has been disconnected from it

Question 7

What pump is connected to the standpipe?

Answer 7

Handpump

Question 8

Which three things maintain pressure in a hydraulic system? Which part has the lowest pressure?

Answer 8

Thermal relief valve - highest psi

Accumulator - lowest psi

system relief valve - medium psi

Question 9

Name the three types of fluids

Answer 9

Vegatable based fluids: MIL-H-7644

• Not interchagable
• blue dyed
• castor oil and alcohol made

Mineral based fluids: MIL-H-5606

• Kerosene type petroleum
• Red dyed

Synthetic fluids: Skydrol

• Non-petroleum based/phosphate easter base
• Not compatable with neoprene or Buna-N
• Light purple

Question 10

What is a one way seal?

Answer 10

The seal will stop the flow of fluid on one direction only

Question 11

What precaution should be used when removing a pressurized hydraulic reservior cap?

Answer 11

All of the pressurizing air must be released before removing the reservior cap

Question 12

On a wet style pump, what else is required?

Answer 12

Oil seperator

Question 13

What is a sequence valve used for?

Answer 13

To permit actation only when specific prior events have occured

Question 14

What is a priority valve used for?

Answer 14

Does not allow flow until a preset pressure is reached. They are opened by a hydraulic pressure rather than by mechanical contact.

Question 15

How do you remove moisture from a compressor?

Answer 15

Removed from a moisture seperator with final last traces dried out with a desiccant or chemical dryer

Question 16

What is a moisture seperator?

Answer 16

Collects the water that is in the air on a baffle, holds it until the system shuts down, and blows it overboard through a drain valve. An electrical heater prevents water from freezing, and later a chemical dryer removes any last traces of water.

Question 17

Wht is the purpose of a relief valve?

Answer 17

Prevents excess pressures from damaging the system through spring tension that can be overcomed to open the valve if pressure is too high

Question 18

What is the purpose of a check valve?

Answer 18

A one directional flow-control valve

Question 19

What are some characteristics of the pneumatic system

Answer 19

Dual compressor

shuttle valve

moisture sperator - 98%

Desiccant - 2%

Question 20

What are two broad categories of engine driven hydraulic pumps?

Answer 20

Constant displacemnt

variable displacement

Question 21

What causes chattering of a hydraulic pump?

Answer 21

Air

Question 22

Name the different seal fluid’s base

Answer 22

Natural rubber seal

• vegetable based fluids
• if combined with petroleum based or phosphate easter base, the seals break down

Neoprene seal MIL-H-5606

• mineral base fluids

Butyl seals

• Skydrol phosphate ester base
• sythetic fluids

Question 23

How is packing protected during installation?

Answer 23

Placing tape over the thread

Question 24

What is the most common used two-way seal?

Answer 24

The o-ring which may be used as either a gasket or a packing or a packing and needs to squeeze or pinch the groove.

Question 25

What is an unloading valve?

Answer 25

A line between the pump and the selector valve that returns fluid back to the reservior

Question 26

What is the characteristics of the open center selector valve?

Answer 26

• It’s an open center poppet type valve used in an open center hydraulic system
• When in neutral fluid flows straight through the next selector valve and on to the reservior

Question 27

The instruments used to measure
the viscosity of a liquid are known as

Answer 27

viscometers or viscosimeters