hydraulic intensifier

A hydraulic intensifier is a hydraulic machine for transforming hydraulic power at low pressure into a reduced volume at higher pressure.

Explanation and Working

   Such a machine may be constructed by mechanically connecting two pistons, each working in a separate cylinder of a different diameter. As the pistons are mechanically linked, their force and stroke length are the same. If the diameters are different, the hydraulic pressure in each cylinder will vary in the same ratio as their areas: the smaller piston giving rise to a higher pressure..As the pressure is inversely proportional to the area, it will be inversely proportional to the square of the diameter.The working volume of the intensifier is limited by the stroke of the piston. This in turn limits the amount of work that may be done by one stroke of the intensifier.These are not reciprocating machines (i.e. continually running multi-stroke machines) and so their entire work must be carried out by a single stroke. This limits their usefulness somewhat, to machines that can accomplish their task within a single stroke.

Applications

They are often used where a powerful hydraulic jack is required, but there is insufficient space to fit the cylinder size that would normally be required, for the lifting force necessary and with the available system pressure.Using an intensifier, mounted outside the jack, allows a higher pressure to be obtained and thus a smaller cylinder used for the same lift force. Intensifiers are also used as part of machines such as hydraulic presses, where a higher pressure is required and a suitable supply is already available

Intensifiers  with Stepped Piston 

Some small intensifiers have been constructed with a stepped piston. This is a double-ended piston, of two different diameters, each end working in a different cylinder.This construction is simple and compact, requiring an overall length little more than twice the stroke. It is also still necessary to provide two seals, one for each piston, and to vent the area between them.A leak of pressure into the volume between the pistons would transform the machine into an effective single piston with equal area on each side, thus defeating the intensifier effect.

Concentric cylinder hydraulic intensifier

A mechanically compact and popular form of intensifier is the concentric cylinder form, as illustrated. In this design, one piston and cylinder are reversed: instead of the large diameter piston driving a smaller piston, it instead drives a smaller moving cylinder that fits over a fixed piston.This design is compact, and again may be made in little over twice the stroke. It has the great advantage though that there is no "piston rod" and the effective distance between the two pistons is short, thus permitting a much lighter construction without risk of bending or jamming.

Shock Absorbing Characteristics

Types Commonly used Accumulators

there are three different types of accumulator Commonly used.

Hydraulic Accumulator

"A type of power storage devices,functioning as a temporal storage tank of fluid energy  to provide or absorb momentary flow". 

An accumulator can serve as

• an auxiliary power source,
• a pulsation absorber,
• a shock damper,
• a leakage makeup source, and
• a thermal expansion compensator

Functions of an Accumulator

• Energy storage
• Pulsation absorption
• Shock cushioning
• Supplementing pump flow
• Maintaining pressure
• Fluid dispensing  

Spring Loaded Accumulators

In a spring loaded accumulator, a change in fluids volume is proportional to its pressure.

As the spring compression increases as fluid enters the chamber and decreases as the accumulator is discharged, the pressure is not constant.

Gas Charged Accumulators

In a closed chamber, a change in gas volume must result in an identical fluids volume.  It can maintain a constant fluid pressure.

 Six Stages of Operation

1. 
   

    empty - no gas charge
2. 
   

    precharged with dry nitrogen
3. 
   

     system pressure exceeds precharge pressure, and hydraulic fluid flows into accumulator.
4. 
   

   system pressure peaks, maximum fluid has entered accumulator, and system relief opens
5. 
   

     system pressure drops, precharge pressure forces fluid from accumulator and into system
6. 
   

     system pressure reaches 

Sizing Accumulators

Hydraulic accumulators are normally sized in terms of specific applications.  For example