LECTURE 24 TO 26 - HYDRAULIC CIRCUIT DESIGN
FREQUENTLY ASKED QUESTIONS
1. List three important considerations to be taken into account while designing a hydraulic
circuit
There are 3 important considerations in designing a hydraulic circuit.
Safety of machine and personal in the event of power failures
Performance of given operation with minimum losses
Cost of the component used in the circuit.
2. What are advantages of regenerative circuit?
The speed of the extension can be made greater than that of regular double acting cylinder. The
extending speed can be made greater than the retracting speed if the rod size is made small
enough.
3 Explain the Regenerative circuit for Drilling Machine:
C F LOAD
A B C – Double acting cylinder
D – 3 Position, 4 Way,
1 0 2 Regenerative center,
D P T solenoid actuated,
spring centered DCV
R – Relief Valve
E R F - Filter
P E – Electric Motor
F T T- Tank
T P - Pump
, Figure shows an application of regenerative circuit in a drilling machine. Here a 3-position, 4-
way , regenerative center directional control valve is used. When the DCV is in the spring-
centered position, port P is connected to A and B and tank port T is blocked. In this position
pump flow goes to A and flow from rod end of the cylinder also joins the pump flow to gives
rapid spindle advance ( no work is done during this period )
Why does the spring-centered position give rapid extension of the cylinder (drill spindle)? The
reason is simple. Oil from the rod end regenerates with the pump flow going to the blank end.
This effectively increases pump flow to the blank end of the cylinder during the spring-centered
mode of operation. Once again we have a regenerative cylinder. It should be noted that the
cylinder used in a regenerative circuit is actually a regular double-acting cylinder. What makes it
a regenerative cylinder is the way it is hooked up in the circuit. The blank and rod ends are
connected in parallel during the extending stroke of a regenerative center.
When the DCV shifts to 1st position, P is connected to A and B to T gives slow feed
(extension) when the drill starts to cut into the work piece. Similarly when the DCV shifts to 2nd
position, P is connected to B and A is connected to T, since the ring area is less the cylinder will
have fast return motion.
4 With the help of neat sketch explain the pump unloading circuit
F LOAD
C
A B
1 0
2
D P T
CV
P
U
F T
T
. Pump unloading circuit.
FREQUENTLY ASKED QUESTIONS
1. List three important considerations to be taken into account while designing a hydraulic
circuit
There are 3 important considerations in designing a hydraulic circuit.
Safety of machine and personal in the event of power failures
Performance of given operation with minimum losses
Cost of the component used in the circuit.
2. What are advantages of regenerative circuit?
The speed of the extension can be made greater than that of regular double acting cylinder. The
extending speed can be made greater than the retracting speed if the rod size is made small
enough.
3 Explain the Regenerative circuit for Drilling Machine:
C F LOAD
A B C – Double acting cylinder
D – 3 Position, 4 Way,
1 0 2 Regenerative center,
D P T solenoid actuated,
spring centered DCV
R – Relief Valve
E R F - Filter
P E – Electric Motor
F T T- Tank
T P - Pump
, Figure shows an application of regenerative circuit in a drilling machine. Here a 3-position, 4-
way , regenerative center directional control valve is used. When the DCV is in the spring-
centered position, port P is connected to A and B and tank port T is blocked. In this position
pump flow goes to A and flow from rod end of the cylinder also joins the pump flow to gives
rapid spindle advance ( no work is done during this period )
Why does the spring-centered position give rapid extension of the cylinder (drill spindle)? The
reason is simple. Oil from the rod end regenerates with the pump flow going to the blank end.
This effectively increases pump flow to the blank end of the cylinder during the spring-centered
mode of operation. Once again we have a regenerative cylinder. It should be noted that the
cylinder used in a regenerative circuit is actually a regular double-acting cylinder. What makes it
a regenerative cylinder is the way it is hooked up in the circuit. The blank and rod ends are
connected in parallel during the extending stroke of a regenerative center.
When the DCV shifts to 1st position, P is connected to A and B to T gives slow feed
(extension) when the drill starts to cut into the work piece. Similarly when the DCV shifts to 2nd
position, P is connected to B and A is connected to T, since the ring area is less the cylinder will
have fast return motion.
4 With the help of neat sketch explain the pump unloading circuit
F LOAD
C
A B
1 0
2
D P T
CV
P
U
F T
T
. Pump unloading circuit.
