Most hydraulic fluids are oils, with a huge number of different types available. Different hydraulic systems, pumps and valves will require a different viscosity of fluid. Sometimes, in applications where any flammable liquid poses a risk, the hydraulic fluid may be water based. Both ends of the hydraulic cylinder need a mounting interface; one at the base and one at the head. The mounting interface depends entirely on the customer requirements and application of the fabrication. Different mountings include:.
The hydraulic tube needs to be sealed at both ends to stop oil leaking and keep the pressure in. One end of the tube is sealed off with a base.
However, the other end needs to be open to allow the rod to move in and out of the tube. At this end the tube is sealed with a neck gland that allows the rod to move in and out.
The neck gland material would be chosen during design, with seals on both the rod and the tube. Hydraulic fluid needs to enter and exit the cylinder via ports, with one port at either end of the cylinder tube and the hydraulic piston between the two ports.
These must be secure, as a weak port can cause a dangerous leak of hydraulic fluid under intense pressure. Seals are used throughout the hydraulic cylinder. They can be made of a wide variety of different materials, depending on the function and type of hydraulic cylinder. They need to be hard wearing, able to survive multiple repetitions of the rod moving in and out of the barrel, removing any contamination. Hydraulic cylinder designers will select the right seal for the cylinder application, taking multiple factors into account.
Cylinders that operate at very high temperatures will require seals that are not prone to melting, and so they may select a material such as Viton. Zurcon and PTFE seals may be chosen for circumstances where seals are required to withstand the friction associated with very quick repetitions, such as in a factory environment.
Specialist seals can also be designed with back up rings for seals working under intense pressure and seals with an extremely tight closure for very thin hydraulic fluid that can leak out of standard seals. Valves and pumps are connected to the hydraulic cylinder via feed pipes and hoses. These are highly specialised, having to work under extreme pressures. They also need to be able to resist corrosion, so will be made of a material suitable for the outside environment as well as the relevant hydraulic fluid.
Filtration is vital to the hydraulic system. Hydraulic fluid must be kept entirely free of contaminants in order to ensure that seals are not damaged, and the system remains working well.
There are a number of filters throughout the hydraulic system and depending on the environment of the machinery, these will need to be regularly changed. Some highly contaminated locations, such as factories, may benefit from bypass filtration units, which allow the filters to be changed without stopping the machinery. The filtration system can be isolated from the rest of the hydraulic system — the filters can be changed quickly and easily and then the system reattached.
This has been found to increase the lifespan of the hydraulic system without the need for expensive services. Read more about our experience with hydraulic rams within the case studies below. Read more about our sector experience associated with hydraulic cylinders below. Please find related images below…. Replacement Cylinder Manufacture for Commercial Linkspan. For example, you must have a pond on a hillside so that you can locate the pump below the pond.
You run a pipe from the pond to the pump. The pump has a valve that allows water to flow through this pipe and build up speed. The delivery pipe can rise some distance above both the pump and the source of the water. For example, if the pump is 10 feet below the pond, the delivery pipe might be up to feet above the pump. You can see that the one big disadvantage of a ram pump is that it wastes a lot of water.
The rest flows out of the pump as the water builds momentum. There is nothing magical happening in a ram pump. A different design that accomplishes the same thing might work like this:. This design has more moving parts, but it accomplishes the same thing and has the advantage that it scales to any size very easily.
The idea of using the energy of flowing water has been around for a long time! Sign up for our Newsletter! Impulse Valve - There are a number of types impulse valves that may be used.
The weighted-bolt-impulse valve is durable, easy to maintain, and the principles are easy enough for anyone to understand.
Less weight means there will be a quicker stroke and less water pumped. More weight means slower strokes and more water pumped. Delivery Valve - Also known as a check valve W.
Only allows fluid to travel one direction. Types of check valves include: ball, swinging, diaphragm, lift-check. Pressure Vessel - A large surge in pressue from the water compresses the air inside the Pressue Vessel.
This surge in pressure is known as the known as the water hammer effect W [8]. Water Source - Typically stream or spring. Must have adequate flow rate. Higher elevation is better more head. Must be able to measure flow rate. For smaller flows one may contain water using a dam or containment area.
It is necessary to prevent dirt and debris from entering the pump and drive pipe. Grates, Filters and often times a supply tank or sediment tank is used.
Ram Housing - A security cover or housing may be prefered to prevent exterior damage or theft. The hydram body requires to be firmly bolted to a concrete foundation, as the beats of its action apply a significant shock load. The hydram should be located so that the waste valve is always located above flood water level, as the device will cease to function if the waste valve becomes submerged.
Reservoir Tank - A storage tank is usually included at the top of the delivery pipe to allow water to be drawn in variable amounts as needed. Multiple Hydrams - Where greater capacity is needed, it is common practice to install several hydrams in parallel. This allows a choice of how many to operate at any one time so it can cater for variable supply flows or variable demand. The size and length of the drive pipe must be in proportion to the working head from which the ram operates.
Also, the drive pipe carries severe internal shock loads due to water hammer, and therefore normally should be constructed from good quality steel water pipe. Hydrams are mostly intended for water supply duties, in hilly or mountainous areas, requiring small flow rates delivered to high heads. They are less commonly used for irrigation purposes, where the higher flow rates required will usually demand the use of larger sizes of hydram having 6-inch or 4-inch drive pipes.
Traditional hydram designs, such as in Figure 3, developed a century ago in Europe, are extremely robust. They tend to be made from heavy castings and have been known to function reliably for 50 years or more.
However, although a number of such designs are still manufactured in Europe and the USA in small numbers, they are relatively expensive, although generally speaking the drive-pipe, delivery pipe and civil workings will be significantly more expensive than even the heaviest types of hydram.
Lighter designs, fabricated using a welded sheet steel construction, were developed first in Japan and are now in production in other parts of SE Asia including Taiwan and Thailand. These are cheaper, but only likely to last a decade or so as they are made from thinner material which will eventually corrode. Nevertheless they offer good value for money and are likely to perform reliably.
The 2" Papa ram pump, manufactured from a high-spec engineering composite, weighs only 2kg compared to a traditional 2" hydram which weighs in the region of 96kg. Some simple designs that can be improvised from pipe fittings have also been developed by aid agencies Figure 4 , and some interesting versions have also been quite crudely improvised using scrap materials, such as a unit which is being produced in some numbers in southern Laos from materials salvaged from bombed bridges and using old propane cylinders for the air chamber.
Needless to say, such devices are very low in cost but the pipes in the end cost considerably more than the hydram. They are not always as reliable as traditional designs, but are usually acceptably reliable with failures separated by many months rather than days, and are easy to repair when they fail. While the commercial pumps are more expensive they can handle the constant abuse associated with the hammer effect and high pressures. While the initial investment for a pump and the corresponding system may be seem high there are no fuel costs and low maintenance costs associated with hydrams.
This includes delivery hose assembly, ball valve, pressure vessel and filtration. Rams Pumps are known for continuously running while having minimal maintenance.
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