Pumps Flashcards
(22 cards)
What are two categories of pumps?
- Non-positive displacement
2. Positive displacement
What is the function of a hyd. gear pump?
To create oil flow
How do non-positive pumps create flow?
Create centrifugal force to push oil
Positive displacement pumps:
Use teeth to seal, and are always building pressure
What is pressure rating?
Identifies the maximum pressure a pump can safety withstand without damage
What are two basic types of gear common in this industry
- External gear
2. Internal gear
Which port on a gear pump is the larger?
The inlet
Unidirectional pumps operate:
In one direction only
What is maximum allowable vacuum at pump inlet?
5 in Hg
A direct pressure relief valve is;
Normally closed valve that senses pressure
What is relief valve cracking pressure?
The pressure at inlet port when ball is moved off of seat.
What is full flow pressure?
Pressure required to fully open the relief valve
What is Pressure override?
Is the pressure difference between cracking pressure and full flow pressure
What are the 3 common control valve configurations?
- Spool type
- Rotary type
- Poppet type
What is feathering?
When spool is partially moved making it act like a variable orifice
What are most common methods of of valve actuation?
- Mechanical
- Pilot
- Electrical
What are the two common types of directional control valve center conditions?
- Open center
2. Closed center
What is difference between open center and closed center?
Open center P is connected to T.
Closed all ports are blocked
What are to basic types of hydraulic cylinders are:
Single acting
Double acting
Which portion of a telescoping cylinder lifts first?
The largest portion moves first
What is volumetric efficiency?
Term used to express the amount of flow lost due to internal leakage.
Equation for volumetric efficiency
VE= actual flow rate/ theoretical flow rate
