Hydrualic 5 Tonne Jack Flashcards
Hydraulic jacks have what type of ram to provide high lift?
Telescopic
What are the 3 advantages of a hydraulic jack?
Load is raised with minimum effort- through a lever
The load is under control at all times- achieved by the suction/delivery valve
No danger of hack retracting under load, achieved by the release valve and mechanical locks
What are the 3 main assemblies of a hydraulic jack
Hydraulic body
Trestle type
Towbar assembly
What type of component is common to all jacks?
Hydraulic body
The hydraulic body consists of what components?
Reservoir
Pump assembly
Hydraulic cylinder
What component makes sure the jack is perpendicular
Spirit level
What type of fluid does the reservoir of jack have?
OM 18
The base of the reservoir is fitted with what?
Drain screw and the top is fitted with a bush which has the dipstick and air valve
Why is the thread partially relived on the bush?
To provide an air path between the reservoir and atmosphere
What does the air valve prevent?
Formation of a vacuum when raising or pressure when lowering in the reservoir
Also prevent dirt ingress when it is out of use
What is the mechanical actuator used to give?
Unidirectional force in a unidirectional motion
The rod gland prevents what?
Pressurised oil from leaking past the interface between the rod and the head
This area is called the rod gland
The rod wiper prevents what?
Contaminants from entering the cylinder when extended and retracted
Why must the safety locking nut be fully wound down when the ram is fully extended?
The ram needs to be raised to release them
What type of seals are fitted to the pump?
Seals , o ring seals and sealing washers
How is the plunger raised and lowered?
By the pump handle through a fulcrum - adjusted by the rotating spigot
What does closing the relief valve do?
Isolates the hydraulic cylinder from the reservoir enabling it to be pressurised?
What does unscrewing the release valve do?
Allows pressurised fluid in the cylinder to return to the reservoir
The jack is protected from excess pressure by what?
Pre set overload valve that must not be adjusted
This also limits the load lifting capacity
What is the weight overload valve set to?
5.3-5.7 tonnes
What is the purpose of the overload valve
To protect components and personnel
Do not adjust screw
What are the 5 things you should do when storing the jack?
Open the air valve one revolution
Fully extend both rams and lightly lubricate
Retract rams
Close air valves
Close release valve
What will unscrewing the release valve do when lowering the jack?
Uncontrolled decent
What is the standard serviceability test?
Check rams raise to full extent
Check rams fully retract
How do you bleed a jack?
Open release valve and air valve
Pump vigorously
