Lab Flashcards
(22 cards)
four methods of energy transmission
mechanical (drive shaft), electrical (motor), hydraulics (crushing car), pneumatics (air tools)
who first defined the fundamental law of hydraulic system
Pascal
what fluid was used in the earliest hydraulic system and why
water - plentiful and easy to get
what type of fluid is now used in hydraulic systems and why?
oil
5 modern applications of hydraulic power transmission
landing gear, construction equipment, scissor lift, cranes, plows, presses, etc.
pressure in a hydraulic system
created by the resistance of the system (pressure=resistance)
resistance
caused by friction, diameter of hose, viscosity of fluid (temp.), length of hose, number of fittings, load, directional control valve (pressure drop)
relief valve
safety device - sets the highest pressure so that way no components get damaged
flow
describes the movement of gases, any fluid that can flow can transmit power
velocity and friction
when velocity increases, friction decreases
minimize frictional losses
increase pipe diameter, reduce the surface toughness, minimize length of piping
flow control valve
- operate by offering a restriction or partial blockage in a line (manual variation of the size of an orifice)
- flow through orifice depends on size of orifice, pressure differential across orifice, & temperature
3 types of valves
directional control valve, flow control valve, and pressure control valve
check valve
allows fluid to flow in one direction
working relationship
there is a working relationship between flow control valve and simple relief valve
meter in
controlling flow rate into cylinder, control extension speed, restricts amount of fluid going into the cylinder
meter out
controls the flow rate out of the cylinder so it controls extension speed in a backwards way, cylinder is prevented from overrunning, maintains constant back pressure, important for drilling applications
bleed off circuit
flow to cylinder is regulated by sending some of the pump flow to the tank, more efficient than meter in/meter out
rapid traverse circuit/feed circuit
extends quickly (rapid traverse) until the cam button is pushed and then it extends slower (feed), only extension is affected
cracking pressure
when a check valve reaches cracking pressure, it will open
isothermal
stays at the same temperature
pilot operated check valve
although it only allows flow in one direction, if there is enough pressure from the pilot line, the no flow direction can be made into flow
