Hydraulic intensifier
Encyclopedia
A hydraulic intensifier is a hydraulic machine for transforming hydraulic power
at low pressure into a reduced volume at higher pressure.
Such a machine may be constructed by mechanically connecting two piston
s, 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. 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 press
es, where a higher pressure is required and a suitable supply is already available.
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.
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.
In the example illustrated, the two pistons are approximately 1:2 ratio in diameter, giving a 1:4 increase in pressure. Note that it is the diameter of the effective piston, i.e. the seal diameter that matters. The cylinders here are relieved beyond the seal and are of greater diameter, for easy running. Although the moving cylinder's bore is around ¾ of the outer diameter, not ½, it is its seal diameter that matters, not its internal clearance bore.
The celebrated mechanical engineer Harry Ricardo
began his career by working in his grandfather, Alexander Rendel's, civil engineering
practice.
At the time they were involved in the construction of bridges in India, which required hydraulic lifting, hoisting and rivet
ing equipment. As the existing transport infrastructure was poor, all plant used on site needed to be lightweight and easily portable. Machines also needed to be connected to their hydraulic power source by flexible tubing, which limited their working pressure to around 500 psi. At this time, modern shipyard equipment was using pressures of up to 2000 psi. This high-pressure equipment was smaller and lighter than the bulkier low-pressure variety, a desirable feature for this construction work. Ricardo's innovation was to specify the use of portable hydraulic intensifiers for these tools, permitting the use of the improved high-pressure form, even where their supply was at low-pressure, through flexible hose. These intensifiers were so successful that eventually several hundred were supplied and used.
Hydraulics
Hydraulics is a topic in applied science and engineering dealing with the mechanical properties of liquids. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics is used for the generation, control,...
at low pressure into a reduced volume at higher pressure.
Such a machine may be constructed by mechanically connecting two piston
Piston
A piston is a component of reciprocating engines, reciprocating pumps, gas compressors and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tight by piston rings. In an engine, its purpose is to transfer force from...
s, each working in a separate cylinder
Hydraulic cylinder
A Hydraulic cylinder is a mechanical actuator that is used to give a unidirectional force through a unidirectional stroke. It has many applications, notably in engineering vehicles.- Operation :...
of a different diameter. As the pistons are mechanically linked, their force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
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
Mechanical work
In physics, work is a scalar quantity that can be described as the product of a force times the distance through which it acts, and it is called the work of the force. Only the component of a force in the direction of the movement of its point of application does 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. 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 press
Hydraulic press
A hydraulic is a machine using a hydraulic cylinder to generate a compressive force. It uses the hydraulic equivalenta mechanical lever, and was also known as a Bramah press after the inventor, Joseph Bramah, of England. He invented and was issued a patent on this press in 1795...
es, where a higher pressure is required and a suitable supply is already available.
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.
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.
In the example illustrated, the two pistons are approximately 1:2 ratio in diameter, giving a 1:4 increase in pressure. Note that it is the diameter of the effective piston, i.e. the seal diameter that matters. The cylinders here are relieved beyond the seal and are of greater diameter, for easy running. Although the moving cylinder's bore is around ¾ of the outer diameter, not ½, it is its seal diameter that matters, not its internal clearance bore.
The celebrated mechanical engineer Harry Ricardo
Harry Ricardo
Sir Harry Ricardo was one of the foremost engine designers and researchers in the early years of the development of the internal combustion engine....
began his career by working in his grandfather, Alexander Rendel's, civil engineering
Civil engineering
Civil engineering is a professional engineering discipline that deals with the design, construction, and maintenance of the physical and naturally built environment, including works like roads, bridges, canals, dams, and buildings...
practice.
At the time they were involved in the construction of bridges in India, which required hydraulic lifting, hoisting and rivet
Rivet
A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...
ing equipment. As the existing transport infrastructure was poor, all plant used on site needed to be lightweight and easily portable. Machines also needed to be connected to their hydraulic power source by flexible tubing, which limited their working pressure to around 500 psi. At this time, modern shipyard equipment was using pressures of up to 2000 psi. This high-pressure equipment was smaller and lighter than the bulkier low-pressure variety, a desirable feature for this construction work. Ricardo's innovation was to specify the use of portable hydraulic intensifiers for these tools, permitting the use of the improved high-pressure form, even where their supply was at low-pressure, through flexible hose. These intensifiers were so successful that eventually several hundred were supplied and used.