hydraulic system types Flashcards
what is the definition of a hydraulic system
all of the interconnected components mounted on a vehicle or piece of equipment
what is a hydraulic circuit
a group of interconnected components within a hydraulic system that perform a specific function
what is an open center hydraulic system
one that allows pump flow to return to the reservoir when the directional control valve in in the neutral position
another name for a open center hydraulic system with fixed displacement pump is
constant flow
what type of equipment would use the constant flow type hydraulic system
wheel loader
another name for open center hydraulic system with pressure compensated pump
constant horse power
how dose a constant horsepower type hydraulic system work
destroke the pump as pressure rises to limit maximum power that the pump can draw from the engine
closed center hydraulic systems are often called
demand type or load sensing
what are the advantages of load sensing hydraulic systems
provide minimum wasted energy . precise control of actuator motion
what is margin pressure
the pumps outlet pressure is kept slightly higher than the actuator load pressure ( 150 to 450 ) psi
what would use the closed center load sensing hydraulic system
dozer
HST stands for
hydrostatic transmission
what are the four basic hydrostatic configurations
open circuit ( loop ) with fixed displacement or variable displacement pumps and closed circuit ( loop ) with fixed or variable displacement pumps
what is the most common type of HST system used
closed loop with variable displacement reversible pump
what would use the hydrostatic transmission system
compactor
when pumps are connected front to back what pump is the driven pump and what pump is the idler
the pump connected to the engine is the driven and the rear pump is the idler
power shift pressure has what effect on the main hydraulic pump
as power shift pressure decreases pump output increases. as power shift pressure increases pump output decreases
open center hydraulic systems are most often used
when the hydraulic operations are not a high percentage of the machines duty cycle
constant hoarse power open center hydraulic systems maintain a constant power draw from the engine by varying
pump displacement proportional to the load on the system
the identifying characteristics of a closed center hydraulic system is
the directional control valve always blocks pump oil flow in neutral position
why are closed center systems equipped with pressure compensated pumps often called demand type systems
because flow is only provided when there is work to preform
the most commonly used HST in mobile heavy equipment is
closed circuit system with a variable displacement reversible pump
