two stage hydraulic pump diagram free sample

A two-stage hydraulic pump is two gear pumps that combine flow at low pressures and only use one pump at high pressures.  This allows for high flow rates at low pressures or high pressures at low flow rates.  As a result, total horsepower required is limited.

Pumps are rated at their maximum displacement.  This is the maximum amount of oil that is produced in a single rotation.  This is usually specified in cubic inches per revolution (cipr) or cubic centimeters per revolution (ccpr).  Flow is simply the pump displacement multiplied by the rotation speed (usually RPM) and then converted to gallons or liters.  For example, a 0.19 cipr pump will produce 1.48 gallons per minute (gpm) at 1800 rpm.

Simply put, gear pumps are positive displacement pumps and are the simplest type you can purchase. Positive displacement means that every time I rotate the shaft there is a fixed amount of oil coming out.  In the diagram shown here, oil comes in the bottom and is pressurized by the gears and then moves out the top.  The blue gear will spin clockwise. These pumps are small, inexpensive and will handle dirty oil well.  As a result, they are the most common pump type on the market.

A piston pump is a variable displacement pump and will produce full flow to no flow depending on a variety of conditions.  There is no direct link between shaft rotation and flow output.  In the diagram below, there are eight pistons (mini cylinders) arranged in a circle.  The movable end is attached to a swashplate which pushes and pulls the pistons in and out of the cylinder.  The pistons are all attached to the rotating shaft while the swashplate stays fixed.  Oil from the inlet flows into the cylinders as the swashplate is extending the pistons.  When the swashplate starts to push the pistons back in, this oil is expelled to the outlet.

So, we don’t actually turn one of the pumps off.  It is very difficult to mechanically disconnect the pump, but we do the next best thing.  So earlier in the article I mentioned that pumps move oil they don’t create pressure.  Keeping this in mind, we can simply recirculate the oil from the pressure side back to the tank side.  Simple.   So, let’s look at this as a schematic.

Luckily, turning off the pump is quite simple and only involves two components: a check valve and an unloader valve.  The check valve is there to keep the higher-pressure oil from the low flow pump separate from the oil in the high flow pump.  The higher-pressure oil from the low flow pump will shift the unloader valve by compressing the spring.  This allows flow from the high flow pump to return to the suction line of the pump.  Many pumps have this return line internal to the pump, so there is no additional plumbing needed.  At this point, the high flow pump uses little to no power to perform this action.  You will notice that the cylinder speed slows dramatically.  As the log splits apart, the pressure may drop causing the unloader valve to close again.  At this point, the flows will combine again.  This process may repeat several times during a single split.

The graph above shows the overlay of a performance curve of a piston pump and two stage gear pumps.  As you can see, the piston pump between 700 psi and 3000 psi will deliver the maximum HP that our engine can produce and as a result, it will have maximum speed.  Unfortunately, it will also have maximum cost.  If we are willing to sacrifice a little performance, the two-stage pump will work very well.  Most of our work is done under 500 psi where the two pumps have identical performance.  As pressure builds, the gear pump will be at a slight disadvantage, but with good performance.  The amount of time we spend in this region of the curve is very little and it would be hard to calculate the time wasted.

After the pump on my log splitter died, I replaced it with a two-stage pump.   While I was missing out on the full benefits of the piston pump, there was a tremendous increase in my output (logs/hr.).  I noticed that instead of me waiting on the cylinder to be in the right position, I was now the hold up.  I couldn’t get the logs in and positioned fast enough.  What a difference!

As you go from a standard two-stage pump to your own custom design, you will find that you will need to add the check valve and unloader separately.  However, there are many available cartridges manifold out there already that make this simple.  Some even have relief valves built in!

Two stage pumps are wonderful creations!  They allow for better utilization of pressure, flow and power by giving you two performance curve areas.  They also show their versatility in conserving power which leads to energy savings while remaining inexpensive.  A lot of these pumps come pre-made and preset, but you can make your own!  See if your next project can get a boost from one of these wonderful devices.

Hydraulic pumps are mechanisms in hydraulic systems that move hydraulic fluid from point to point initiating the production of hydraulic power. Hydraulic pumps are sometimes incorrectly referred to as “hydrolic” pumps.

They are an important device overall in the hydraulics field, a special kind of power transmission which controls the energy which moving fluids transmit while under pressure and change into mechanical energy. Other kinds of pumps utilized to transmit hydraulic fluids could also be referred to as hydraulic pumps. There is a wide range of contexts in which hydraulic systems are applied, hence they are very important in many commercial, industrial, and consumer utilities.

“Power transmission” alludes to the complete procedure of technologically changing energy into a beneficial form for practical applications. Mechanical power, electrical power, and fluid power are the three major branches that make up the power transmission field. Fluid power covers the usage of moving gas and moving fluids for the transmission of power. Hydraulics are then considered as a sub category of fluid power that focuses on fluid use in opposition to gas use. The other fluid power field is known as pneumatics and it’s focused on the storage and release of energy with compressed gas.

"Pascal"s Law" applies to confined liquids. Thus, in order for liquids to act hydraulically, they must be contained within a system. A hydraulic power pack or hydraulic power unit is a confined mechanical system that utilizes liquid hydraulically. Despite the fact that specific operating systems vary, all hydraulic power units share the same basic components. A reservoir, valves, a piping/tubing system, a pump, and actuators are examples of these components. Similarly, despite their versatility and adaptability, these mechanisms work together in related operating processes at the heart of all hydraulic power packs.

The hydraulic reservoir"s function is to hold a volume of liquid, transfer heat from the system, permit solid pollutants to settle, and aid in releasing moisture and air from the liquid.

Mechanical energy is changed to hydraulic energy by the hydraulic pump. This is accomplished through the movement of liquid, which serves as the transmission medium. All hydraulic pumps operate on the same basic principle of dispensing fluid volume against a resistive load or pressure.

Hydraulic valves are utilized to start, stop, and direct liquid flow in a system. Hydraulic valves are made of spools or poppets and can be actuated hydraulically, pneumatically, manually, electrically, or mechanically.

The end result of Pascal"s law is hydraulic actuators. This is the point at which hydraulic energy is transformed back to mechanical energy. This can be accomplished by using a hydraulic cylinder to transform hydraulic energy into linear movement and work or a hydraulic motor to transform hydraulic energy into rotational motion and work. Hydraulic motors and hydraulic cylinders, like hydraulic pumps, have various subtypes, each meant for specific design use.

The essence of hydraulics can be found in a fundamental physical fact: fluids are incompressible. (As a result, fluids more closely resemble solids than compressible gasses) The incompressible essence of fluid allows it to transfer force and speed very efficiently. This fact is summed up by a variant of "Pascal"s Principle," which states that virtually all pressure enforced on any part of a fluid is transferred to every other part of the fluid. This scientific principle states, in other words, that pressure applied to a fluid transmits equally in all directions.

Furthermore, the force transferred through a fluid has the ability to multiply as it moves. In a slightly more abstract sense, because fluids are incompressible, pressurized fluids should keep a consistent pressure just as they move. Pressure is defined mathematically as a force acting per particular area unit (P = F/A). A simplified version of this equation shows that force is the product of area and pressure (F = P x A). Thus, by varying the size or area of various parts inside a hydraulic system, the force acting inside the pump can be adjusted accordingly (to either greater or lesser). The need for pressure to remain constant is what causes force and area to mirror each other (on the basis of either shrinking or growing). A hydraulic system with a piston five times larger than a second piston can demonstrate this force-area relationship. When a force (e.g., 50lbs) is exerted on the smaller piston, it is multiplied by five (e.g., 250 lbs) and transmitted to the larger piston via the hydraulic system.

Hydraulics is built on fluids’ chemical properties and the physical relationship between pressure, area, and force. Overall, hydraulic applications allow human operators to generate and exert immense mechanical force with little to no physical effort. Within hydraulic systems, both oil and water are used to transmit power. The use of oil, on the other hand, is far more common, owing in part to its extremely incompressible nature.

Pressure relief valves prevent excess pressure by regulating the actuators’ output and redirecting liquid back to the reservoir when necessary. Directional control valves are used to change the size and direction of hydraulic fluid flow.

While hydraulic power transmission is remarkably useful in a wide range of professional applications, relying solely on one type of power transmission is generally unwise. On the contrary, the most efficient strategy is to combine a wide range of power transmissions (pneumatic, hydraulic, mechanical, and electrical). As a result, hydraulic systems must be carefully embedded into an overall power transmission strategy for the specific commercial application. It is necessary to invest in locating trustworthy and skilled hydraulic manufacturers/suppliers who can aid in the development and implementation of an overall hydraulic strategy.

The intended use of a hydraulic pump must be considered when selecting a specific type. This is significant because some pumps may only perform one function, whereas others allow for greater flexibility.

The pump"s material composition must also be considered in the application context. The cylinders, pistons, and gears are frequently made of long-lasting materials like aluminum, stainless steel, or steel that can withstand the continuous wear of repeated pumping. The materials must be able to withstand not only the process but also the hydraulic fluids. Composite fluids frequently contain oils, polyalkylene glycols, esters, butanol, and corrosion inhibitors (though water is used in some instances). The operating temperature, flash point, and viscosity of these fluids differ.

In addition to material, manufacturers must compare hydraulic pump operating specifications to make sure that intended utilization does not exceed pump abilities. The many variables in hydraulic pump functionality include maximum operating pressure, continuous operating pressure, horsepower, operating speed, power source, pump weight, and maximum fluid flow. Standard measurements like length, rod extension, and diameter should be compared as well. Because hydraulic pumps are used in lifts, cranes, motors, and other heavy machinery, they must meet strict operating specifications.

It is critical to recall that the overall power generated by any hydraulic drive system is influenced by various inefficiencies that must be considered in order to get the most out of the system. The presence of air bubbles within a hydraulic drive, for example, is known for changing the direction of the energy flow inside the system (since energy is wasted on the way to the actuators on bubble compression). Using a hydraulic drive system requires identifying shortfalls and selecting the best parts to mitigate their effects. A hydraulic pump is the "generator" side of a hydraulic system that initiates the hydraulic procedure (as opposed to the "actuator" side that completes the hydraulic procedure). Regardless of disparities, all hydraulic pumps are responsible for displacing liquid volume and transporting it to the actuator(s) from the reservoir via the tubing system. Some form of internal combustion system typically powers pumps.

While the operation of hydraulic pumps is normally the same, these mechanisms can be split into basic categories. There are two types of hydraulic pumps to consider: gear pumps and piston pumps. Radial and axial piston pumps are types of piston pumps. Axial pumps produce linear motion, whereas radial pumps can produce rotary motion. The gear pump category is further subdivided into external gear pumps and internal gear pumps.

Each type of hydraulic pump, regardless of piston or gear, is either double-action or single-action. Single-action pumps can only pull, push, or lift in one direction, while double-action pumps can pull, push, or lift in multiple directions.

Vane pumps are positive displacement pumps that maintain a constant flow rate under varying pressures. It is a pump that self-primes. It is referred to as a "vane pump" because the effect of the vane pressurizes the liquid.

This pump has a variable number of vanes mounted onto a rotor that rotates within the cavity. These vanes may be variable in length and tensioned to maintain contact with the wall while the pump draws power. The pump also features a pressure relief valve, which prevents pressure rise inside the pump from damaging it.

Internal gear pumps and external gear pumps are the two main types of hydraulic gear pumps. Pumps with external gears have two spur gears, the spurs of which are all externally arranged. Internal gear pumps also feature two spur gears, and the spurs of both gears are internally arranged, with one gear spinning around inside the other.

Both types of gear pumps deliver a consistent amount of liquid with each spinning of the gears. Hydraulic gear pumps are popular due to their versatility, effectiveness, and fairly simple design. Furthermore, because they are obtainable in a variety of configurations, they can be used in a wide range of consumer, industrial, and commercial product contexts.

Hydraulic ram pumps are cyclic machines that use water power, also referred to as hydropower, to transport water to a higher level than its original source. This hydraulic pump type is powered solely by the momentum of moving or falling water.

Ram pumps are a common type of hydraulic pump, especially among other types of hydraulic water pumps. Hydraulic ram pumps are utilized to move the water in the waste management, agricultural, sewage, plumbing, manufacturing, and engineering industries, though only about ten percent of the water utilized to run the pump gets to the planned end point.

Despite this disadvantage, using hydropower instead of an external energy source to power this kind of pump makes it a prominent choice in developing countries where the availability of the fuel and electricity required to energize motorized pumps is limited. The use of hydropower also reduces energy consumption for industrial factories and plants significantly. Having only two moving parts is another advantage of the hydraulic ram, making installation fairly simple in areas with free falling or flowing water. The water amount and the rate at which it falls have an important effect on the pump"s success. It is critical to keep this in mind when choosing a location for a pump and a water source. Length, size, diameter, minimum and maximum flow rates, and speed of operation are all important factors to consider.

Hydraulic water pumps are machines that move water from one location to another. Because water pumps are used in so many different applications, there are numerous hydraulic water pump variations.

Water pumps are useful in a variety of situations. Hydraulic pumps can be used to direct water where it is needed in industry, where water is often an ingredient in an industrial process or product. Water pumps are essential in supplying water to people in homes, particularly in rural residences that are not linked to a large sewage circuit. Water pumps are required in commercial settings to transport water to the upper floors of high rise buildings. Hydraulic water pumps in all of these situations could be powered by fuel, electricity, or even by hand, as is the situation with hydraulic hand pumps.

Water pumps in developed economies are typically automated and powered by electricity. Alternative pumping tools are frequently used in developing economies where dependable and cost effective sources of electricity and fuel are scarce. Hydraulic ram pumps, for example, can deliver water to remote locations without the use of electricity or fuel. These pumps rely solely on a moving stream of water’s force and a properly configured number of valves, tubes, and compression chambers.

Electric hydraulic pumps are hydraulic liquid transmission machines that use electricity to operate. They are frequently used to transfer hydraulic liquid from a reservoir to an actuator, like a hydraulic cylinder. These actuation mechanisms are an essential component of a wide range of hydraulic machinery.

There are several different types of hydraulic pumps, but the defining feature of each type is the use of pressurized fluids to accomplish a job. The natural characteristics of water, for example, are harnessed in the particular instance of hydraulic water pumps to transport water from one location to another. Hydraulic gear pumps and hydraulic piston pumps work in the same way to help actuate the motion of a piston in a mechanical system.

Despite the fact that there are numerous varieties of each of these pump mechanisms, all of them are powered by electricity. In such instances, an electric current flows through the motor, which turns impellers or other devices inside the pump system to create pressure differences; these differential pressure levels enable fluids to flow through the pump. Pump systems of this type can be utilized to direct hydraulic liquid to industrial machines such as commercial equipment like elevators or excavators.

Hydraulic hand pumps are fluid transmission machines that utilize the mechanical force generated by a manually operated actuator. A manually operated actuator could be a lever, a toggle, a handle, or any of a variety of other parts. Hydraulic hand pumps are utilized for hydraulic fluid distribution, water pumping, and various other applications.

Hydraulic hand pumps may be utilized for a variety of tasks, including hydraulic liquid direction to circuits in helicopters and other aircraft, instrument calibration, and piston actuation in hydraulic cylinders. Hydraulic hand pumps of this type use manual power to put hydraulic fluids under pressure. They can be utilized to test the pressure in a variety of devices such as hoses, pipes, valves, sprinklers, and heat exchangers systems. Hand pumps are extraordinarily simple to use.

Each hydraulic hand pump has a lever or other actuation handle linked to the pump that, when pulled and pushed, causes the hydraulic liquid in the pump"s system to be depressurized or pressurized. This action, in the instance of a hydraulic machine, provides power to the devices to which the pump is attached. The actuation of a water pump causes the liquid to be pulled from its source and transferred to another location. Hydraulic hand pumps will remain relevant as long as hydraulics are used in the commerce industry, owing to their simplicity and easy usage.

12V hydraulic pumps are hydraulic power devices that operate on 12 volts DC supplied by a battery or motor. These are specially designed processes that, like all hydraulic pumps, are applied in commercial, industrial, and consumer places to convert kinetic energy into beneficial mechanical energy through pressurized viscous liquids. This converted energy is put to use in a variety of industries.

Hydraulic pumps are commonly used to pull, push, and lift heavy loads in motorized and vehicle machines. Hydraulic water pumps may also be powered by 12V batteries and are used to move water out of or into the desired location. These electric hydraulic pumps are common since they run on small batteries, allowing for ease of portability. Such portability is sometimes required in waste removal systems and vehiclies. In addition to portable and compact models, options include variable amp hour productions, rechargeable battery pumps, and variable weights.

While non rechargeable alkaline 12V hydraulic pumps are used, rechargeable ones are much more common because they enable a continuous flow. More considerations include minimum discharge flow, maximum discharge pressure, discharge size, and inlet size. As 12V batteries are able to pump up to 150 feet from the ground, it is imperative to choose the right pump for a given use.

Air hydraulic pumps are hydraulic power devices that use compressed air to stimulate a pump mechanism, generating useful energy from a pressurized liquid. These devices are also known as pneumatic hydraulic pumps and are applied in a variety of industries to assist in the lifting of heavy loads and transportation of materials with minimal initial force.

Air pumps, like all hydraulic pumps, begin with the same components. The hydraulic liquids, which are typically oil or water-based composites, require the use of a reservoir. The fluid is moved from the storage tank to the hydraulic cylinder via hoses or tubes connected to this reservoir. The hydraulic cylinder houses a piston system and two valves. A hydraulic fluid intake valve allows hydraulic liquid to enter and then traps it by closing. The discharge valve is the point at which the high pressure fluid stream is released. Air hydraulic pumps have a linked air cylinder in addition to the hydraulic cylinder enclosing one end of the piston.

The protruding end of the piston is acted upon by a compressed air compressor or air in the cylinder. When the air cylinder is empty, a spring system in the hydraulic cylinder pushes the piston out. This makes a vacuum, which sucks fluid from the reservoir into the hydraulic cylinder. When the air compressor is under pressure, it engages the piston and pushes it deeper into the hydraulic cylinder and compresses the liquids. This pumping action is repeated until the hydraulic cylinder pressure is high enough to forcibly push fluid out through the discharge check valve. In some instances, this is connected to a nozzle and hoses, with the important part being the pressurized stream. Other uses apply the energy of this stream to pull, lift, and push heavy loads.

Hydraulic piston pumps transfer hydraulic liquids through a cylinder using plunger-like equipment to successfully raise the pressure for a machine, enabling it to pull, lift, and push heavy loads. This type of hydraulic pump is the power source for heavy-duty machines like excavators, backhoes, loaders, diggers, and cranes. Piston pumps are used in a variety of industries, including automotive, aeronautics, power generation, military, marine, and manufacturing, to mention a few.

Hydraulic piston pumps are common due to their capability to enhance energy usage productivity. A hydraulic hand pump energized by a hand or foot pedal can convert a force of 4.5 pounds into a load-moving force of 100 pounds. Electric hydraulic pumps can attain pressure reaching 4,000 PSI. Because capacities vary so much, the desired usage pump must be carefully considered. Several other factors must also be considered. Standard and custom configurations of operating speeds, task-specific power sources, pump weights, and maximum fluid flows are widely available. Measurements such as rod extension length, diameter, width, and height should also be considered, particularly when a hydraulic piston pump is to be installed in place of a current hydraulic piston pump.

Hydraulic clutch pumps are mechanisms that include a clutch assembly and a pump that enables the user to apply the necessary pressure to disengage or engage the clutch mechanism. Hydraulic clutches are crafted to either link two shafts and lock them together to rotate at the same speed or detach the shafts and allow them to rotate at different speeds as needed to decelerate or shift gears.

Hydraulic pumps change hydraulic energy to mechanical energy. Hydraulic pumps are particularly designed machines utilized in commercial, industrial, and residential areas to generate useful energy from different viscous liquids pressurization. Hydraulic pumps are exceptionally simple yet effective machines for moving fluids. "Hydraulic" is actually often misspelled as "Hydralic". Hydraulic pumps depend on the energy provided by hydraulic cylinders to power different machines and mechanisms.

There are several different types of hydraulic pumps, and all hydraulic pumps can be split into two primary categories. The first category includes hydraulic pumps that function without the assistance of auxiliary power sources such as electric motors and gas. These hydraulic pump types can use the kinetic energy of a fluid to transfer it from one location to another. These pumps are commonly called ram pumps. Hydraulic hand pumps are never regarded as ram pumps, despite the fact that their operating principles are similar.

The construction, excavation, automotive manufacturing, agriculture, manufacturing, and defense contracting industries are just a few examples of operations that apply hydraulics power in normal, daily procedures. Since hydraulics usage is so prevalent, hydraulic pumps are unsurprisingly used in a wide range of machines and industries. Pumps serve the same basic function in all contexts where hydraulic machinery is used: they transport hydraulic fluid from one location to another in order to generate hydraulic energy and pressure (together with the actuators).

Elevators, automotive brakes, automotive lifts, cranes, airplane flaps, shock absorbers, log splitters, motorboat steering systems, garage jacks and other products use hydraulic pumps. The most common application of hydraulic pumps in construction sites is in big hydraulic machines and different types of "off-highway" equipment such as excavators, dumpers, diggers, and so on. Hydraulic systems are used in other settings, such as offshore work areas and factories, to power heavy machinery, cut and bend material, move heavy equipment, and so on.

Fluid’s incompressible nature in hydraulic systems allows an operator to make and apply mechanical power in an effective and efficient way. Practically all force created in a hydraulic system is applied to the intended target.

Because of the relationship between area, pressure, and force (F = P x A), modifying the force of a hydraulic system is as simple as changing the size of its components.

Hydraulic systems can transfer energy on an equal level with many mechanical and electrical systems while being significantly simpler in general. A hydraulic system, for example, can easily generate linear motion. On the contrary, most electrical and mechanical power systems need an intermediate mechanical step to convert rotational motion to linear motion.

Hydraulic systems are typically smaller than their mechanical and electrical counterparts while producing equivalents amounts of power, providing the benefit of saving physical space.

Hydraulic systems can be used in a wide range of physical settings due to their basic design (a pump attached to actuators via some kind of piping system). Hydraulic systems could also be utilized in environments where electrical systems would be impractical (for example underwater).

By removing electrical safety hazards, using hydraulic systems instead of electrical power transmission improves relative safety (for example explosions, electric shock).

The amount of power that hydraulic pumps can generate is a significant, distinct advantage. In certain cases, a hydraulic pump could generate ten times the power of an electrical counterpart. Some hydraulic pumps (for example, piston pumps) cost more than the ordinary hydraulic component. These drawbacks, however, can be mitigated by the pump"s power and efficiency. Despite their relatively high cost, piston pumps are treasured for their strength and capability to transmit very viscous fluids.

Handling hydraulic liquids is messy, and repairing leaks in a hydraulic pump can be difficult. Hydraulic liquid that leaks in hot areas may catch fire. Hydraulic lines that burst may cause serious injuries. Hydraulic liquids are corrosive as well, though some are less so than others. Hydraulic systems need frequent and intense maintenance. Parts with a high factor of precision are frequently required in systems. If the power is very high and the pipeline cannot handle the power transferred by the liquid, the high pressure received by the liquid may also cause work accidents.

Even though hydraulic systems are less complex than electrical or mechanical systems, they are still complex systems that should be handled with caution. Avoiding physical contact with hydraulic systems is an essential safety precaution when engaging with them. Even when a hydraulic machine is not in use, active liquid pressure within the system can be a hazard.

Inadequate pumps can cause mechanical failure in the place of work that can have serious and costly consequences. Although pump failure has historically been unpredictable, new diagnostic technology continues to improve on detecting methods that previously relied solely on vibration signals. Measuring discharge pressures enables manufacturers to forecast pump wear more accurately. Discharge sensors are simple to integrate into existing systems, increasing the hydraulic pump"s safety and versatility.

Hydraulic pumps are devices in hydraulic systems that move hydraulic fluid from point to point, initiating hydraulic power production. They are an important device overall in the hydraulics field, a special kind of power transmission that controls the energy which moving fluids transmit while under pressure and change into mechanical energy. Hydraulic pumps are divided into two categories namely gear pumps and piston pumps. Radial and axial piston pumps are types of piston pumps. Axial pumps produce linear motion, whereas radial pumps can produce rotary motion. The construction, excavation, automotive manufacturing, agriculture, manufacturing, and defense contracting industries are just a few examples of operations that apply hydraulics power in normal, daily procedures.

One of the more challenging aspects of developing pasture and grazing land is providing access to a reliable water supply for livestock. In some cases, existing streams, creeks, or ponds provide drinking water for the livestock. When a surface water source is not available, wells can be drilled and pumps installed to provide water for the animals. In some instances, surface water may be available, but not accessible to the livestock due to water quality issues, steep access slopes, or fencing issues.

Providing an electrical power source to such a location for a pump can be cost-prohibitive. Utilizing a pump powered by an internal combustion engine can require inspection and attention several times each day and regular fuel supply runs. Nose pumps and sling pumps may be used effectively in some of these situations, but these pumps will not work if the elevation difference between the water source and grazing area is greater than twenty feet. Solar-powered pumps are an excellent option but can be expensive depending on the flow rate and pressure needs of the system.

Figure 1. A 3/4-inch homemade hydraulic ram pump made with PVC fittings. Water flows from right to left during operation. Image credit: W. Bryan Smith, Clemson University.

One possible solution to providing livestock drinking water in remote locations is the hydraulic ram pump. The first development work of the hydraulic ram is reported to have been completed by John Whitehurst in 1772, with the first automatic version of the hydraulic ram developed by Joseph Montgolfier in 1796.1 Various companies in England and the United States have been producing cast-iron versions of the hydraulic ram since the early 1800s. Hydraulic ram pumps can lift water over a considerable elevation, and do not require any external power source.

Commercially sold hydraulic ram pumps last for decades but are quite expensive. A simple, homemade PVC (polyvinyl chloride) hydraulic ram pump (figure 1) may be constructed for $150 to $200 depending on material costs in your area and size of pump constructed. These homemade pumps will last for several years if not longer and can allow a farmer to see how such a pump would work before investing in a more expensive commercial unit.

Hydraulic ram pumps operate by utilizing pressure developed by a “water hammer” shock wave. Any object in motion has an inertial force. Energy is required to place the object in motion, and energy will also be required to stop the motion, with more energy being required if the motion is started or stopped quickly. A flow of water in a pipe also has inertia (or momentum) that resists sudden changes in velocity. Slowly closing a valve allows this inertia to dissipate over time, producing very little pressure increase in the pipe. Closing a valve very rapidly will create a pressure surge or shock wave as the flowing water stops, which moves back up the pipe – much like a train stopping, with individual train cars hitting the coupling in front of them in rapid succession as the brakes are applied. The more quickly the valve is closed, the larger the shock wave produced. A faster water flow will also produce a larger shock wave when a valve is closed, since more inertia or momentum is involved. A longer pipe will also produce a larger shock wave for the same reason.

A hydraulic ram relies on a non-pressurized flow of water in a pipe placed from the water source to the pump (called a “drive” pipe). This flow is produced by placing the hydraulic ram some distance below a water source and running the drive pipe from the water source to the pump. The hydraulic ram employs two check valves, which are the only moving parts in the pump.

Figure 2. Step 1: Water (blue arrows) starts flowing through the drive pipe and out of the “waste” valve (#4 on the diagram), which is open initially. Water flows faster and faster through the pipe and out of the waste valve. Image credit: W. Bryan Smith, Clemson University.

Figure 3. Step 2: At some point water is moving so quickly through the waste valve (#4) that it pushes the valve’s flapper up and slams it shut. The water in the pipe was moving quickly and had considerable momentum, but all the water weight and momentum is stopped by the valve’s closure. That creates a high-pressure spike (red arrows) at the closed waste valve. The high-pressure spike forces some water (blue arrows) through the check valve (#5 on the diagram) and into the pressure chamber. This increases the pressure in that chamber slightly. The pressure “spike” in the pipe also begins moving away from the waste valve and up the drive pipe (red arrows) at the speed of sound and is released at the drive pipe inlet. Image credit: W. Bryan Smith, Clemson University.

Figure 6. Step 5: When the low-pressure wave reaches the drive pipe inlet, a normal pressure wave travels down the drive pipe to the valves. Normal water flow due to the elevation of the source water above the ram follows this pressure wave, and the next cycle begins. Image credit: W. Bryan Smith, Clemson University. The hydraulic ram pump cycle described in figures 2-6 may repeat from forty to ninety times per minute depending on elevation drop to the hydraulic ram pump, drive pipe length from the water source to the ram pump, and drive pipe material used. Image credit: W. Bryan Smith, Clemson University.

Figure 7. A typical hydraulic ram pump installation, with (a) drive pipe, (b) delivery pipe, and (c) hydraulic ram pump placement noted. Image credit: W. Bryan Smith, Clemson University.

In its simplest form, a hydraulic ram pump installation includes a drive pipe to bring water from the water source to the pump, the hydraulic ram pump, and a delivery pipe to take water from the pump to the water trough or site where water is needed (figure 7).

The drive pipe size determines the actual pump size and also determines the maximum flow rate that may be expected from the pump. Since the pump efficiency depends on capturing as much of the water hammer shock wave as possible, the best drive pipe material for a hydraulic ram pump installation is galvanized steel pipe. Most livestock producers use PVC pipe instead due to the lower cost and the difficulty in placing and assembling galvanized steel pipe. Hydraulic ram pump installations using a PVC drive pipe will work well, but the elasticity of the pipe will allow some of the water hammer shock wave to dissipate slightly with pipe wall expansion. If PVC pipe is used for the drive pipe installation, choose PVC piping with a thicker wall. Schedule 80 PVC pipe would be the better choice, with Schedule 40 PVC pipe being a secondary choice.

The best drive pipe installation would place the pipe on a constant slope from the water source to the hydraulic ram pump, with no bends or elbows, and anchor it with bolts and/or galvanized tie-downs to large rocks or concrete pads to prevent movement. This would allow the most efficient shock wave development. The Gravi-Chek Company suggests the optimum drive pipe slope is one foot of drop for every five feet of length, which corresponds to a 20% slope.2 However, this is not always practical in livestock water supply installations. The ram pump will work with piping that is not installed on a constant slope, as long as all piping slopes are either level or downward toward the pump (figure 8). There can be no “humps” or up-and-down installation points in the drive pipe, since this will allow air to be captured in the pipe, which will allow shock wave dissipation.

Figure 8. A PVC drive pipe placed in a stream bed. Galvanized steel was not an option due to the bed topography and geometry. The hydraulic ram pump worked well, but each bend allowed a tiny portion of the shock wave to dissipate. A straight, galvanized steel pipe would have captured a larger shock wave and provided more pressure. Image credit: W. Bryan Smith, Clemson University.

If a choice must be made between installing the drive pipe on a constant slope and using a more rigid drive pipe (such as galvanized steel), choose the more rigid drive pipe. This will have a larger impact on pump performance than the drive pipe slope.

There is a range of allowable drive pipe lengths for each pipe size used. If the drive pipe is too short or too long the pressure wave that allows the pump to cycle will not develop properly.

The publication Hydraulic Rams for Off-Stream Livestock Watering gives the following equations developed by N. G. Calvert for minimum and maximum drive pipe length.3

Rife Ram Company literature offers a different method of drive pipe length selection.4 The Rife method does not consider pipe size but is based solely on vertical elevation drop or fall from the water source to the hydraulic ram pump. Values are presented in table 2.

Figure 9. A hydraulic ram pump installation with a (a) standpipe and (b) supply pipe to allow a longer piping solution from water source to ram pump location. Image credit: W. Bryan Smith, Clemson University.

The Rife recommendations in table 2 maintain a given pipe slope for each range of elevation falls. Either method (table 1 or table 2) may be used to determine mainline length; satisfying both methods may provide the best ram pump performance.

There are installation solutions if the maximum drive pipe length allowed is not long enough to reach the water source from the hydraulic ram pump placement. One option is to install a “standpipe” at the maximum drive pipe distance from the ram pump (figure 9). This standpipe should be three pipe sizes larger than the drive pipe and should be open at the top to allow the water hammer shock wave to dissipate at that point. The standpipe should be installed vertically, with the top of the standpipe a foot or so above the level of the water source. Supply piping, which should be at least one pipe size larger than the drive pipe, is then run from that point to the water source.

Figure 10. Use of a carpenter’s level and a measuring stick to determine elevation drop from the water source to the proposed hydraulic ram pump location. Image credit: W. Bryan Smith, Clemson University.

Hydraulic ram pumps operate based on an amount of elevation drop or fall from the water source to the site where the ram pump is placed. The amount of drop will determine the performance of the ram pump. The amount of drop or fall available at a given location can be measured using a measuring stick and a carpenter’s level. Start at the site where the hydraulic ram pump will be placed. Hold the measuring stick vertically, placing one end on the ground. Place the carpenter’s level on the measuring stick, holding it level, with the top even with the top of the measuring stick. Look along the top of the carpenter’s level at the slope going up to the water supply, and sighting along the top of the level, pick a spot on the slope (figure 10). That point is the height of the measuring stick above the starting point. Move to that spot and repeat the sighting process, continuing up the slope after each sighting until the water supply is reached. Count the number of times the measuring stick was placed on the ground, multiply that number by the measuring stick’s length, add any partial stick measurement for the last sighting (see figure 10), and the result will be the elevation drop or fall from the water source to the ram pump location.

Hydraulic ram pumps are very inefficient, generally pumping only one gallon of water for every eight gallons of water passing through the ram. They will, however, pump water up ten feet (or more in some cases) of vertical elevation for every foot of elevation drop from the water source to the hydraulic ram. For instance, if there is an elevation drop of seven feet from the water source to the hydraulic ram, the user can expect the hydraulic ram to pump water up to seventy feet or more in vertical elevation above the ram. Higher delivery elevations do decrease the pump flow – the higher the elevation difference between the hydraulic ram and the delivery pipe outlet, the smaller the delivered water flow will be.

In this equation, Q is the available drive flow in gallons per minute, F is the fall in feet from the water source to the ram, E is the elevation from the ram to the water outlet, and D is the flow rate of the delivery water in gallons per minute. 0.6 is an efficiency factor and may differ somewhat between various ram pumps. For example, if a flow rate of twelve gallons per minute is available to operate a ram pump (Q), the pump is placed six feet below the water source (F), and the water will be pumped up an elevation of twenty feet to the outlet point (E), the amount of water that may be pumped with an appropriately-sized ram pump is:

The same pump with the same drive flow will provide less flow if the water is to be pumped up a higher elevation. For instance, using the data in the previous example but increasing the elevation lift to forty feet (E):

The pump inflow rate, Q, will always be determined by the drive pipe size, drive pipe length, and the elevation of the water source above the hydraulic ram.

Table 3 uses the Rife equation to list some flow rate ranges for various sizes of hydraulic ram pump based on the friction loss found in Schedule 40 PVC pipe. The pump flow ranges in the chart are based on a fall (F) of five feet of elevation and an elevation lift (E) of twenty-five feet. Changing the values of E or F will change the expected performance of the ram pump.

Some of the delivery flow rates listed in table 3 are quite small, but even the 3/4-inch ram pump will deliver a considerable amount of water over time. Hydraulic ram pumps operate twenty-four hours per day, seven days per week, so even at the minimum pump inflow the 3/4-inch ram pump will provide (0.10 gpm x 60 minutes x 24 hours =) 144 gallons of water per day, which would supply the daily water need of four to five 1,200 pound cattle.

If more flow is desired, either a larger hydraulic ram may be used, or another hydraulic ram may be installed with a separate drive pipe, and then plumbed into the same delivery pipe to the water trough as long as there is sufficient water flow in the water source to supply this demand.

Figure 11. A schematic diagram for homemade hydraulic ram pump Design 1. Table 4 contains item descriptions. Image credit: W. Bryan Smith, Clemson University.

There are a number of designs for a homemade hydraulic ram. The University of Warwick has some excellent designs developed for use in developing countries where standard plumbing parts may not be readily available.5

This publication will address two similar designs. The first design was developed by Mark Risse of the University of Georgia and was presented by Frank Henning in University of Georgia Extension Service publications #ENG98-0023 and #ENG98-003.6 Figure 11 provides a schematic of the design, and table 4 provides a parts list for a 1 1/4-inch hydraulic ram pump.

This is a very simple design that only requires assembly of basic plumbing fittings. The air chamber (#14–16) acts like a pressure tank for a well, using compressible air captured in the tank to buffer shock waves and provide a steady outlet pressure. The air initially captured in this air chamber, however, will be absorbed by the water flowing through the pump over time. When this happens there will be a much more pronounced shock to the pump and piping during each cycle (this condition is described as a water-logged pump), and material fatigue and failure will follow. In order to keep air in the chamber over time, a bicycle or scooter inner tube may be filled with air until it feels “springy” or “spongy,” and then folded and inserted into the pressure chamber before the cap (#16) is glued on to the pipe. This will retain air in the chamber and prevent pump failure.

Fittings 1–4 in the diagram must be the same size as the drive pipe in order for the pump to work properly. The spring-loaded check valve (#5) and the pipe nipple (#12) should also be the same size as the drive pipe, but the pump should work if they are reduced to the same size as the delivery pipe.

Figure 12. A brass swing check valve. Note the free-swinging flapper in the outlet port. The swing check valve should be placed vertically for best pump performance. Image credit: W. Bryan Smith, Clemson University.

Valve #1 in figure 11 is used to stop or allow flow to the pump and can be used to turn off water flow if the pump needs to be removed or serviced. Valve #7 is turned off while the pump is started, then gradually opened to allow water to flow after the pump is operating. The pump will operate for thirty seconds or more with this valve completely closed, and if the valve is left in the closed position the pump will reach some maximum pressure and stop operating. The ram pump requires approximately 10 psi of back pressure to operate, so if the delivery pipe outlet is not at least twenty-three feet above the ram pump, valve #7 can be used to throttle the flow and maintain the required back pressure.

The pressure gauge (#11) is used to determine when valve #7 may be opened during pump start-up and can be used to determine how much valve #7 should be closed during normal operation if throttling is needed. The pipe cock (#10) is optional but can be turned off to protect the gauge from failure over time due to repeated pulses.

The air chamber size is dictated by the expected flow rate of the hydraulic ram pump. University or Warwick documentation suggests the optimum pressure chamber volume is twenty to fifty times the expected volume of water delivery per cycle of the pump.5 Table 5 provides some minimum lengths of piping required for a pressure chamber based on this information. The table is based on a hydraulic ram that will operate sixty pulses or cycles per minute.

The second design presented in figure 13 is one commonly found on the internet in YouTube videos.7 It is very similar to the first design, but this design incorporates a homemade “snifter” valve that allows a small amount of air to be added to the air chamber with each pumping cycle, which eliminates the need for an inner tube in the air chamber.

Figure 13. A schematic diagram for homemade hydraulic ram pump Design 2 with air snifter. Tables 4 and 6 contain item descriptions. Image credit: W. Bryan Smith, Clemson University.

The difference in the two designs is the vertical placement of the spring-loaded poppet check valve (#5) just below the air chamber, and the addition of a small hole in the vertically-oriented coupling (#20) just below that check valve (some designs suggest drilling the hole in the lower part of the check valve instead, below the flapper). A cotter pin (#21) is placed in the hole to reduce water loss (and pressure loss) to some degree when a pressure cycle occurs, but still allow air to be drawn into the pipe to be pushed into the air chamber in the next cycle. Fitting size and material information are the same as for Design 1 except for the following: pipe coupling (or nipple) #20 used for the snifter hole should be galvanized steel to prevent wear by the cotter pin over time, and galvanized steel is a better material choice for elbow #19 for structural strength.

The size of the snifter hole is critical to pump operation. The University of Warwick has an extensive discussion concerning this property in their hydraulic ram pump documentation.5 Their information suggests drilling a 1/16-inch hole and increasing the size slightly if necessary. A 1/8-inch snifter hole or smaller with an appropriately sized cotter pin inserted may be a good option instead as a starting point. If the hydraulic ram should become waterlogged, a slightly larger snifter hole may be needed.

The advantage of this design is that if the snifter hole is sized correctly, the pump should never become waterlogged due to a leaking inner tube in the air chamber. The disadvantages are the trial-and-error approach to obtaining the correct hole size, the need for additional support for the pump’s increased vertical height, and the possibility that the snifter hole, being very small, may freeze over and close in cold weather.

Figure 14. A 3/4-inch hydraulic ram pump (Design 1) in operation. The image was taken just at waste valve closure. The concrete block is in place to support the air chamber. Image credit: W. Bryan Smith, Clemson University.

Both pump designs are started using the same steps. Attach the assembled ram pump to the drive pipe, close valve #7, then open valve #1 to allow water flow. The waste valve (#4) will almost immediately forcefully close. The flapper in the waste valve must be pushed down manually a number of times to initially start automatic pump operation. This process purges air from the system and builds up the pressure in the air chamber required for the pump to operate. Pressing the flapper down twenty to thirty times is expected to start a ram pump. If the pump does not start operating after pressing the flapper down more than seventy times, there is an issue somewhere in the system. The flapper on a smaller pump (1/2-inch, 3/4-inch, etc.) can be pressed down with a thumb fairly easily, but larger pumps may require the use of a metal rod of some type to push the flapper down, especially if there is considerable elevation drop between the water source and the hydraulic ram pump.

After the pump has started operating (figure 14), gradually open valve #7 to allow water to flow uphill to the water trough. The pump must have 10 psi or more back pressure to operate, so gradually open valve #7 while watching the gauge to maintain 10 psi of back pressure. Pressure will build as the water fills the delivery pipe as it is pumped uphill.

The pump will operate continuously after starting as long as water flows freely to the pump and is flowing out of the delivery pipe. If water flow is stopped at the water trough, the ram will pump up to some maximum pressure and stop, and then must be manually restarted. The pump will not restart itself. This means that if water is supplied to a single water trough, a float valve cannot be used. Some provision must be made to drain overflow away from the trough after it fills, since the water must flow continuously for the pump to remain in operation. A simple gravel-filled trench or another method may be used to direct the excess water away from the water trough.

Since water continuously flows out of the pump’s waste valve, some consideration must also be given to water drainage at the pump site. If the pump is placed near a stream downstream of a pool or other water source, this will not be an issue. If, however, it is placed on dry ground away from the water source, drainage must be considered.

There are no restrictions on the size or type of delivery pipe used beyond normal piping design practice. Galvanized steel pipe, PVC pipe, rubber hose, or a simple garden hose may be used to deliver water to the water trough, provided it is sized to deliver the anticipated flow rate. Some ram pump installation guidelines indicate the delivery pipe should be one half the size of the drive pipe, but this has no bearing on the pump performance. The delivery pipe should be sized based on flow rate and friction loss.

Table 7 provides some maximum recommended flow rates for various pipe sizes. These flow rates are based on a maximum flow velocity of five feet per second in the delivery pipe, which will help prevent water hammer development in the delivery pipe. Smaller flows than those listed will allow the water to be piped longer distances or to higher elevations within reason, since less pressure will be lost to pipe friction. Pipe friction loss charts for the appropriate pipe material used may be utilized to determine the actual friction loss for a given installation.8 Larger delivery pipes will reduce friction losses but will also increase costs. Smaller delivery pipes will cost less but can decrease the ram pump flow rate. If friction losses are not calculated, use half the allowable flow rates (or less) listed in table 7 to select a delivery pipe size.

Water will run continuously through a hydraulic ram pump since the pump runs constantly. If the water source for the pump is a shallow pool in a flowing stream or creek this will not be an issue, since water flows continuously in those water bodies. There may be a problem, though, if a small pond is used as a water source for a hydraulic ram pump.

For example, say that a farmer decides to use a small, 1/2-acre pond to supply a hydraulic ram. The pond history shows that it seems to stay fairly full except during times of severe drought. The farmer wants a flow rate of 1 gpm (gallons per minute) to his livestock water trough, and therefore places a 1 1/2-inch hydraulic ram pump behind the pond. The ram pump requires a flow of approximately 9 gpm to produce the desired 1 gpm flow to the water trough.

The ram pump runs twenty-four hours per day, seven days per week, withdrawing 9 gpm from the pond. This flow rate will remove (9 gpm x 60 minutes x 24 hours =) 12,960 gallons of water per day from the pond. That is the equivalent of approximately one inch of water removed from the pond each day. If the stream or spring that fed the pond was just adequate to keep the pond full before the ram pump was installed, the pond water level will begin to fall one inch each day. Over a month’s time the pond level could fall as much as thirty inches.

There are methods described in the next section that allow the use of a hydraulic ram pump using a pond as a water source without breaching the dam. The farmer, though, must first determine if the springs or streams supplying the pond will be adequate to maintain the pond’s water level before installing a ram pump. This may prevent draining a good pond to non-useable levels.

If a hydraulic ram pump is installed behind a pond dam, the farmer should also consider drainage requirements to remove the expelled drive water from behind the pond. This will prevent the development of a wet area or possible soil erosion over time.

Some type of siphon assembly may be used to draw water from a pond and deliver it over the dam to a hydraulic ram pump. However, this siphon cannot be directly connected to the drive pipe without some provision for pressure and siphon release. The siphon will interfere with the development of the pressure wave in the drive pipe. If a siphon is used, the water may be delivered by the siphon pipe to a trough or barrel open to the atmosphere behind the pond dam, with a ram drive pipe plumbed directly into the trough or barrel. This will prevent the siphon action from affecting pressure wave development.

There are only two moving parts in the home-made hydraulic ram pump – the waste valve and the spring-loaded check valve (#4 and #5 in figures 11 and 13). Over time one or both of these valves may fail simply due to wear. The wear will be more extensive in rams utilizing sandy or silty water, and in rams that have a more rapid cycle time. Farmer reports indicate that home-made hydraulic ram check valves seem to last between three months and two years depending on these two factors. The two unions in the figures 11 and 13 (#1 and #8) are there to allow pump removal for maintenance if needed.

If there is detritus in the water source and an inlet screen is not used, there may be an issue with a small stick or twig becoming caught between the waste valve flapper and the valve seal, preventing proper valve closure. In some cases, this might make it miss a cycle and then the stick may be flushed away, but in other cases the stick may become lodged. If the hydraulic ran pump is the only source of water for your livestock it should be checked daily – in most cases the farmer can simply drive near the site, roll down a window (or turn the tractor off), and listen for the regular “click” to confirm the pump is operating. The best inspection is always to visit the operating pump, but a second option is simply to visit the water trough to make sure water is flowing.

If a ram pump is used during winter months, care should be taken to insulate as much of the pump and above ground piping as possible. The constant flow of water through the pump should help prevent freezing, but ice may still build up around the waste valve outlet in colder temperatures and might stop the pump. If Design 2 is used, inspection of the snifter hole is a must in cold weather to ensure it has not frozen closed.

If a hydraulic ram pump is installed in or near a small stream bed, care should be taken to make sure the pump is anchored sufficiently to a concrete pad or other heavy, non-moveable items to prevent loss during a major storm event. Some type of shield or shelter from branches or other detritus flowing downstream during such an event should also be considered. A better placement would be to position the ram pump on dry ground near the stream, but out of the potential flood plain for average storm events, with drainage provisions for the waste or drive water to return to the stream.

There are two methods that may be used to “tune” or adjust a hydraulic ram pump to increase or decrease pump pressure and flow rate. The first tuning method is to simply change the position of the waste valve (#4 in figures 11 and 13). This valve should normally be placed vertically for best pump performance. If the grower desires to lower the pressure, the tee the valve is attached to (#2 in figures 11 and 13) may be rotated slightly to one side, which will allow the waste valve flapper to drop slightly into the valve body. The valve body should be oriented as shown in figure 12 to allow the flapper to descend into the water flow path. Rotating the valve slightly will allow the flapper to close at a slower water velocity, which will create a smaller water hammer shock wave and result in a lower pump pressure. Rotating the valve too far, as illustrated in figure 12, will cause the pump to stop operating, since the water velocity in the drive pipe will be too slow when the valve closes to create a useful water hammer shock wave.

The second tuning method can be used to increase the pressure developed by the ram pump, and in doing so increase the flow rate. The waste valve flapper (shown in figure 12) will close when a certain water velocity is reached in the pipe. The weight of the valve flapper determines the water velocity needed to close the flapper. If weight is added to the flapper, a higher water velocity will be necessary to close the flapper. The University of Warwick’s “How Ram Pumps Work” publication provides a detailed description on flapper weights and closing water velocities.9

Common methods of increasing flapper weight include using screws or epoxy to attach washers or other small weights to the flapper. Care must be exercised to attach weights so that they remain firmly attached and they do not interfere with normal valve closure. The grower must also consider how much pressure may be obtained by tuning the pump in this manner. It is possible to increase the water velocity in the pipe to where the increased water hammer shock wave may cause actual damage to the piping or the pump.

The Ram will not start: (a) In most cases this is due to the fact that the correct size check valve for the waste valve was not installed. That valve and tee must be the same size as the drive pipe. Using a PVC check valve or a metal check valve that is spring-loaded instead of a free-swinging check valve will also cause this issue; (b) Another problem could be a lack of elevation difference between the ram pump and the water source. While some commercially made ram pumps will operate with as little as twenty inches of elevation fall, these home-made units are less efficient and require approximately five feet of vertical elevation drop to operate dependably; (c) the air has not been purged from the system. Pushing the waste valve flapper down twenty to fifty times is normal to start a hydraulic ram pump; (d) a flexible hose was used for the drive pipe. The drive pipe must be made of a rigid material.

The ram pumps for a few cycles and stops: (a)This is usually due to a drive pipe that is too long or too short for the hydraulic ram pump size. A drive pipe that is too long or too short can interfere with or prevent the development of th