WHAT IS ‘HYDRAULIC’
Hydraulic Gate controls Dams helps irrigation Hydraulic System supplies water to Villages and HomesThe Historian think that the word Hydraulic may have come from Greek word “Hydor”, which means ‘Water’.
Further, the Greek word Aulos means Pipe. The word ‘Hydor’ and ‘Aulos, later somehow became ‘Hydrolous’ to commonly pronounced today in Europe and North America as ‘Hydraulics’.However, close to pronouncing HYDROLOUS is still not uncommon in Spain, Latin and South America. Thousands of year back, Dams and Gates were used for irrigation and domestic use. Water wheels were a common phenomenon then. With the advent of oil exploration in previous centuries and later the technique of refining the mineral oil, resulted in the explosion of industrial invention. In the early 19th century, we learnt how to create huge monumental Power/Force to move loads, through managing mineral oil rather than Water. Both Water and Oil are infinitely flexible, and can readily change its shape. Both mediums can be infinitely manipulated, to push and pull load and get the ultimate work done. However, the physical properties of Water being too thin and lack of lubrication capabilities, a thickermedia like Oil is used for creating higher pressure and consequently Power. Moreover, Oil has inherent lubrication capabilities. This helps in self-lubricating various mating dynamic components with in a system. Therefore, the modern day’s Hydraulic system run on mineral Oil with specific qualifications and is preferred, over Water . However, high intensified pressure application with low volume of water still exist, for Example, Water Jet Cutting Machines. The whole concept of Fluid Power’, is based upon the principal of Pressure at any point in a static fluid is the same, in every direction and exerts equal force on equal areas. This is the Pascal Law, which will be further expanded later in this book. Understanding of term Pressure and Volume is very important in order to comprehensively appreciate the applications of any Hydraulic Pump/Motor
As shown below, A container of 1 diameter (A1) filled with fluid. Aforce/load of 1 lb (W1) applied on the one square inch area (A1), which is connected with yet Pressure (Symbol P) is the Force per unit area applied in direction 90 degree to the surface of an object
another container with 10 diameter. When the load on 1 diameter container is pushed down for 10, this creates a force of 10 pound per square inch to lift the load of 10 pounds thru I in the larger container with 10 diameter
When the load on 1” diameter container is pushed down for 10”, this creates a force of 10 pound per square inch to lift the load of 10 pounds thru I” in the larger container with 10” diameter
Basically, what happens is that 1 pound load on a confined fluid area of 1 square inch creates a force of 1 pound per square inch (psi) equally in all direction. The 1psi now directly works underneath a 10 square inch area. Every square inch area now has 1pound force. Thus creating cumulatively 10 pound per square inch force under the 10” diameter container, which in turn can now lift a load of 10 pound by 1inch height.
The phenomenon of fluid in a confined container works in all direction with equal force is further amplified blow. This the basic fundament based on which all modern hydraulic equipment and applications are built. The following example is the further simplification and amplification in Mechanical engineering/Physics terms. This is very basic Physics.
when there is an “increase in pressure at any point in a confined fluid, there is an equal increase at
every other point in the container”. The height of fluid in a tube, as the length increases pressure at the
bottom of the tube too increases due to fluid mass, as shown in the following example. The container below is full with fluid. Due to the increased mass the pressure in the column increases as the length of
the column. The basic Physics is the common base for all Hydraulic pump/motor applications
HISTORY OF HYDRAULICS PUMPS
The ancient history indicates that in the First Century AD, the Greek inventor called “Hero of Alexandria” developed the first concept pump. It seems that Piston Type Pump was first evolved/developed, than a Vane Type Pump
The piston and cylinder combination were used in Geece raise water from well. The Romans later adopted this principle and improved upon this device.
Evidences exit that the Piston type reciprocating pumping system was developed first. Early on, these reciprocating piston type pumps were made out of wood and bamboo, without any valves. A “Rag-Tag Piston” was created by wrapping around substances like cloth/leaf etc. at the end of a stick (Which would apparently be called as the “Piston Rod’), then inserted in a hollow bamboo bore (Apparently the cylinder). There will be hole at the front end of the bamboo cylinder. The water would be drawn up below the piston, by pulling up the piston, rod, and thus creating vacuum at the piston head end.
Even though, historian believes that the Egyptian developed some kind of Pumping device thousands of years BC. However, there is no solid evidence of that. Nevertheless, it may be correct to assume that there was some kind of liquid transferring device early on in the Human evaluation and civilization process.
HOW IT ALL STARTED
However, ever since in 1653, the French thinker, mathematician and scientist BLAISE PASCAL established the “PASCAL LAW”,the need for a hydraulic Pump emerged As explained with examples earlier, the Pascal law defines that when fluid is in rest in a confined area, the pressure on any surface exerts a force perpendicular to the surface and independent of the direction of orientation of surface.
As shown in the following example, A 10 LB force on 1 square inch area can result into 10 POUND PER SQUARE INCH in all direction in the following example. Later, based on this principle, the Industrial usage of HYDRAULIC SYSTEM was born. Obviously, to convert the hydraulic energy to mechanical energy, the hydraulic fluid needed to be moved from one point to another.
.This is the emerging point of a device called PUMP. Blaise Pascal, never may have dreamt the future development of his principle translated in to wide use of Hydraulic system, and the design and invention of the related relevant components to put his law into functional reality in wide variety of modern day applications.
With the dawn of industrial revolution through out the 10 to 15th century, the need for such devices increasingly evolved to drain mines and supplying power to Cranes and Hoists etc.
Therefore, it is quite possible a similar elements, that we call ”PUMP” was available in the ancient centuries.
The first ever centrifugal pump said to have been developed byone DENIS PAPIN, around in 1689. The name of the device subsequently became a modern day PUMP. Obviously, it isbelieved that name PUMP may have come after Mr. PAPIN
History says that around 1851, the centrifugal pumps took its root and widely used in the industries. During the renaissance of 19th century, Oil hydraulic application took its real root. Subsequently rapid modernization of hydraulic pumps took place, and variety of pumps were designed and developed to meet the MODERN DAY industry’s need.
Real development of higher volume positive displacement pumps, with pressure range capacity beyond 1000 psi took place between the Ist and 2nd world wars (1900 and 1940).
Three legendary pioneers in the early 19th century pave the ways for the invention of modern days Pumps and Motors.
(Current company- Parker Hannifin)
(Current Company- Parker Denison)
Harry Vickers among others, played significant key role in research and development of wide range of hydraulic Pumps and Motors, as well other relevant Elements
There are however other individuals, who contributed greatly in the evaluation process of the entire Fluid Power industry.
Around the advent of the 2nd world war Mr. Harry Vickers first devised the concept rotary centrifugal fluid transfer device and subsequently developed the first Vane type Pumps for a Press and Power steering application.
However, the early design of Gear, impellor and crescent type rotaryfluid transfer devices, were developed in stagesbetween 12th to 18thcentury. All these fluid transfer devices were good enough for low resistance, low force and lower load moving capability. As the industries grew the requirements for heavy load handling also grew simultaneously. This opened the flood gate of invention of variety of today’s all types of pumps, for high Volume and higher pressure and way beyond 150 Gallon Per Minute (GMP) and 10000 Pounds Per Square Inch (PSI) range.
Late in thirties of the 20th century, as mentioned briefly earlier Mr. Harry Vickers established a company called Vickers Incorporated in California. Around the WW II, he moved the company to Detroit and developed and manufactured all kind of early Vane pumps. Mr. Vickers needed funding for his future design and development program for Hydraulic pumps and other related components. Therefore, he sold
his company to Sperry Corporation. The new company became to be known as ”Sperry Vickers” world wide, the pioneers of modern hydraulic product line
It is during the “Sperry Vickers” period, the company developed most of the current Vane and
Piston pumps and continuously improved upon them, to meet the industry’s demand.
Subsequently, many other inventor and designer emerged and further consolidated the Vane and Piston Pump capabilities. Pioneers and entrepreneurs like Mr. Denison, Parker Hannifin, Sundstrand, Racine and Rexroth (In Europe) emerged continuously to boost and improve the Pump design and helped the industry and the fluid power application growth.
During this time and the renascence period of evolving technology, the demand for fluid power technology, became increasingly popular
THE NECESSITY IS THE MOTHER OF INVENTION:
As we all know and the title suggests, all inventions are need based. Many mechanical machine tool, agricultural equipment manufacturers in the early period of the renascence felt the necessity of better productivity. Thus they look for ways to improve their machinery and equipment performance.
The medium of the Industrial Hydraulic application is mineral Oil, a by-product of petroleum products. Therefore, underground oil exploration during the late 18th century helped keeping the Fluid Power Technology alive and what it is T0-Day.
Around the period California and Texas coast Mineral oil exploration also become very active. The invention of internal combustion engine by Mr. Mercedes also accelerated the mineral oil processing By late eighteenth and early Nineteenth century the oil exploration gained further momentum and refining process also evolved. Therefore, the “Bi- Product named mineral oil came in existence. The utilization of this “Bi-Product, helped to grow the fluid power industry rapidly.
Early on, the available mineral oil had all kind of impurities. Therefore Pumps and other components used with the mineral oil then available, will not last long. This is how, evolving process of newer pump design started, along with the mineral oil purification techniques.
Mineral oil purification process with variety of added additives helped to develop, all kind of different viscosity of oils.
Between the WW I & II the Caltex (California and Texas) refineries started producing variety of mineral hydraulic oil, with wide range of viscosity range, and with built in additives. As the oil refining technology and process improved, the mineral oil with better lubrication, rust preventive qualities, started become available to the industry.
This provided an immediate boost to oil Hydraulic product manufacturers, to design and develop improved and efficient hydraulic Pumps, Motors and Valves.
This resulted into many original equipment manufacturer (OEM) like Caterpillar, John Deere, Jones and Lampson, Gidding and Lewis, Brown and Sharpe, Sundstrand, Oil Gear and many other in Europe, developed their own Hydraulic Pumps (Vane and Piston types), as well other controls, for their own use. Some of their products are extinct today or hard to find. However, few like Oil Gear, Sundstrand are still a name to reckon with, in the Hydraulic pump market.
All these pump and control manufacturers were really machinery and equipment manufacturers.
Since then, significant invention evolved in the process of developing various kind of HYDRAULIC PUMPS, and subsequently all other components, downstream of a PUMPS, Such as the followings to make a complete and comprehensive hydraulic circuits.
- Pressure Control Valves – Sequence, unloading, Counterbalance etc.
- Directional Control Valves – Checkvalves etc.
- Servo Valves, single and two stage, Flapper and Jet type etc.
- Proportional Valves (Most recent development)
- Flow Control Valves
- Cylinders, Accumulators, Strainers, Filters etc. etc.
The Hydraulic Pumps have gone through a revolutionary change over last 50 years. From a simple fluid transferring device to, it has become a complete Power pack, within itself. Later, the close loop pumps and transmissions, very useful for the new equipment and applications.