Bucket Wheel Excavators

BUCKET-WHEEL EXCAVATOR

Bucket-wheel excavators (BWEs) 

are heavy equipment used in surface mining and mechanical engineering/civil engineering. The primary function of BWEs is to act as a continuous digging machine in large-scale open pit mining operations. What sets BWEs apart from other large-scale mining equipment, such as bucket chain excavators, is their use of a large wheel consisting of a continuous pattern of buckets used to scoop material as the wheel turns. They are among the largest vehicles ever constructed, and the biggest bucket-wheel excavator ever built, Bagger 293, is the largest terrestrial (land) vehicle in human history according to the Guinness Book of World Records.

History

Bucket-wheel excavator in the open-pit mining Garzweiler (Video, 1:40 Min., ca. 9 MB)

Bucket-wheel excavators have been used in mining for the past century, with some of the first being manufactured in the 1920s.^[They are used in conjunction with many other pieces of mining machinery (conveyer belts, spreaders, crushing stations, heap-leach systems, etc.) to move and mine massive amounts of overburden (waste). While the overall concepts that go into a BWE have not changed much, their size has grown drastically. BWEs built since the 1990s, such as the Bagger 293, have reached sizes as large as 96 metres (314.9 feet) tall, 225 metres (738.2 feet) long, and as heavy as 14,200 tons (31.3 million lb). The bucket-wheel itself can be over 70 feet in diameter with as many as 20 buckets, each of which can hold over 15 cubic metres of material. BWEs have also advanced with respect to the extreme conditions in which they are now capable of operating. Many BWEs have been designed to operate in climates with temperatures as low as -45°C (-49°F). Developers are now moving their focus toward automation and the use of electrical power.

Structure

A bucket wheel excavator (BWE) consists of a superstructure to which several more components are fixed.

The bucket wheel from which the machines get their name is a large, round wheel with a configuration of scoops which is fixed to a boom and is capable of rotating. Material picked up by the cutting wheel is transferred back along the boom. In early cell-type bucket wheels, the material was transferred through a chute leading from each bucket, while newer cell-less and semi-cell designs use a stationary chute through which all of the buckets discharge.

A discharge boom receives material through the superstructure from the cutting boom and carries it away from the machine, frequently to an external conveyor system.

A counterweight boom balances the cutting boom and is cantilevered either on the lower part of the superstructure (in the case of compact BWEs) or the upper part (in the case of mid-size C-frame BWEs). In the larger BWEs, all three booms are supported by cables running across towers at the top of the superstructure.

Beneath the superstructure lay the movement systems. On older models these would be rails for the machine to travel along, but newer BWEs are frequently equipped with crawlers, which grant them increased flexibility of motion.

To allow it to complete its duties, the superstructure of a BWE is capable of rotating about a vertical axis (slewing). The cutting boom can be tilted up and down (hoisting). The speeds of these operations are on the orders of 30 m/min and 5 m/min, respectively. Slewing is driven by large gears, while hoisting generally makes use of a cable system.

Size

The scale of BWEs varies drastically and is dependent on the intended application. Compact BWEs designed by ThyssenKrupp may have boom lengths as small as 6m, weigh 50 tons, and move 100 fm3/hr of earth. Their larger models reach boom lengths of 80m, weigh 13,000 tons, and move 12,500 fm3/hr. The largest BWE ever constructed is TAKRAF's Bagger 293, which weighs 14,200 tons and is capable of moving 240,000 cubic metres of overburden every day. Excavations of 380,000 cubic metres per day have been recorded.The BWEs used in the United States tend to be smaller than those constructed in Germany.

Bucket chain excavators

Bucket chain excavators (BCEs) are similar in structure and function to BWEs. However, instead of the buckets being placed in a ring, they are strung out in a manner reminiscent of a trencher. They remove material from below their plane of movement, which is useful if the pit floor is unstable or underwater. TAKRAF's BCEs travel on rails rather than crawlers.

Operation

BWEs are used for continuous overburden removal in surface mining applications. They use their cutting wheels to strip away a section of earth (the working block) dictated by the size of the excavator. Through hoisting, the working block can include area both above and below the level of the machine (the bench level). By slewing, the excavator can reach through a horizontal range.

The overburden is then delivered to the discharge boom, which transfers the cut earth to another machine for transfer to a spreader. This may be a fixed belt conveyor system or a mobile conveyor with crawlers similar to those found on the BWE. Mobile conveyors permanently attached to the excavator takes the burden of directing the material off of the operator.The overburden can also be transferred directly to cross-pit spreader which reaches across the pit and scatters overburden at the dumping ground.

Automation

Automation of the BWEs requires integrating many sensors and electrical components such as GPS, data acquisition systems, and online monitoring capabilities. The goal of these systems is to take away some of the work from the operators in order to achieve higher mining speeds. Project managers and operators are now able to track crucial data regarding the BWEs and other machinery in the mining operations via the Internet. Sensors can detect how much material is being scooped onto the conveyor belt, and the automation system can then vary the speed on the conveyor belts in order to feed a continuous amount of material.

Applications

Bucket wheel excavators and bucket chain excavators take jobs that were previously accomplished by rope shovels and draglines. They have been replaced in most applications by hydraulic excavators, but still remain in use for very large-scale operations, where they can be used for the transfer of loose materials or the excavation of soft to semi-hard overburden.^\

Lignite mining

The primary application of BWEs is in lignite (brown coal) mining, where they are used for soft rock overburden removal in the absence of blasting. They are useful in this capacity for their ability to continuously deliver large volumes of materials to processors, which is especially important given the continuous demand for lignite.

Because of the great demand for lignite, lignite mining has also been one of the areas of greatest development for BWEs. The additions of automated systems and greater maneuverability, as well as components designed for the specific application, have increased the reliability and efficiency with which BWEs deliver materials.

Materials handling

Bucket wheel technology is used extensively in bulk materials handling. Bucket wheel reclaimers are used to pick up material that has been positioned by a stacker for transport to a processing plant. Stacker/reclaimers, which combine tasks to reduce the number of required machines, also use bucket wheels to carry out their tasks.

In shipyards, bucket wheels are used for the continuous loading and unloading of ships, where they pick up material from the yard for transfer to the delivery system. Bucket chains can be used to unload material from a ship's hold. TAKRAF's continuous ship unloader is capable of removing to 95% of the material from a ship's hold, owing to a flexibly-configured digging attachment.

Heap leaching

An extension of their other uses, BWEs are used in heap leaching processes. Heap leaching entails of constructing stacks of crushed ore, through which a solvent is passed to extract valuable materials. The construction and removal of the heaps are an obvious application of stacking and reclaiming technology.

GIANT KOMATSU EXCAVATOR PC8000

The PC 8000 of Komatsu

Komatsu's hydraulic front shovel excavators are in the lead everywhere. The Japanese PC 8000 had been hit number one in the world chart for quite some time. The peculiarity of this giant is its electric undercarriage. The PC 8000 is moved by 6600-volt electric motors and not by hydraulic motors like its rivals. Two 3516 EUIS Caterpillar turbocharged aftercooled diesel engines drive the generator and the hydraulic system. Together, these two 16-cylinder aggregates deliver a massive 3,730 HP at 1,800 RPM. Despite the tremendous power, with its top speed of 2.2 kph no wonder this monster is not the vehicle for high speed car chases. Depending on track width ground pressure is about 2.5 bar. At full work speed the hydraulic pumps drive 8280 litres of oil through the cylinders with work pressure of 310 bar. In order to operate this giant there must be fuel and hydraulic oil, and lots of them. The fuel tank has an amazing capacity of 14,000 litres while the hydraulics tank is trying to keep up with its 11,500-litre capacity. The larger shovel bucket has the capacity of 44 cubic meters and weighs a decent 58.2 tons while its break-out force is 2,000 kN.

Liebherr R9800

A highly detailed model of a Liebherr R9800 mining excavator with gooseneck boom.

-the scale is set to 'real world' and the dimensions are set according to manufacturer's specifications.

-the level of detail is suitable for the most extreme close-ups - the clean topology, makes it possible for you to further subdivide the model according to your needs.

-there are no coplanar faces and no coincident vertices

-all the parts of the model are grouped in individual logically named groups.

-all the materials and textures are logically named.

-the main parts of the model are unwrapped (as seen in the previews).

-the textures used for the unwrapped parts of the model are 4096x4096

-the textures that are applied on the model using simple projection mapping are the following (the size are specified on the right of each texture):

The model is available in max (version 9), fbx and obj formats, but it can be converted for free, on request, to any format you may need.
The max version contains both standard and vray materials.

*the polycount is shown for 0 meshsmooth iterations.

HYDRAULIC MACHINERY

An excavator; main hydraulics: Boom cylinders, swingdrive, cooler fan and trackdrive

Fundamental features of using hydraulics compared to mechanics for force and torque increase/decrease in a transmission.

Hydraulic machines are machinery and tools that use liquid fluid power to do simple work. Heavy equipment is a common example.

In this type of machine, hydraulic fluid is transmitted throughout the machine to various hydraulic motors and hydraulic cylinders and which becomes pressurised according to the resistance present. The fluid is controlled directly or automatically by control valves and distributed through hoses and tubes.

The popularity of hydraulic machinery is due to the very large amount of power that can be transferred through small tubes and flexible hoses, and the high power density and wide array of actuators that can make use of this power.

Hydraulic machinery is operated by the use of hydraulics, where a liquid is the powering medium.

Force and torque multiplication

A fundamental feature of hydraulic systems is the ability to apply force or torque multiplication in an easy way, independent of the distance between the input and output, without the need for mechanical gears or levers, either by altering the effective areas in two connected cylinders or the effective displacement (cc/rev) between a pump and motor. In normal cases, hydraulic ratios are combined with a mechanical force or torque ratio for optimum machine designs such as boom movements and trackdrives for an excavator.

Examples

Two hydraulic cylinders interconnected

Cylinder C1 is one inch in radius, and cylinder C2 is ten inches in radius. If the force exerted on C1 is 10 lbf, the force exerted by C2 is 1000 lbf because C2 is a hundred times larger in area (S = πr²) as C1. The downside to this is that you have to move C1 a hundred inches to move C2 one inch. The most common use for this is the classical hydraulic jack where a pumping cylinder with a small diameter is connected to the lifting cylinder with a large diameter.

Pump and motor

If a hydraulic rotary pump with the displacement 10 cc/rev is connected to a hydraulic rotary motor with 100 cc/rev, the shaft torque required to drive the pump is 10 times less than the torque available at the motor shaft, but the shaft speed (rev/min) for the motor is 10 times less than the pump shaft speed. This combination is actually the same type of force multiplication as the cylinder example (1) just that the linear force in this case is a rotary force, defined as torque.

Both these examples are usually referred to as a hydraulic transmission or hydrostatic transmission involving a certain hydraulic "gear ratio".

The equivalent circuit schematic.

For the hydraulic fluid to do work, it must flow to the actuator and or motors, then return to a reservoir. The fluid is then filtered and re-pumped. The path taken by hydraulic fluid is called a hydraulic circuit of which there are several types. Open center circuits use pumps which supply a continuous flow. The flow is returned to tank through the control valve's open center; that is, when the control valve is centered, it provides an open return path to tank and the fluid is not pumped to a high pressure. Otherwise, if the control valve is actuated it routes fluid to and from an actuator and tank. The fluid's pressure will rise to meet any resistance, since the pump has a constant output. If the pressure rises too high, fluid returns to tank through a pressure relief valve. Multiple control valves may be stacked in series [1]. This type of circuit can use inexpensive, constant displacement pumps.

Closed center circuits supply full pressure to the control valves, whether any valves are actuated or not. The pumps vary their flow rate, pumping very little hydraulic fluid until the operator actuates a valve. The valve's spool therefore doesn't need an open center return path to tank. Multiple valves can be connected in a parallel arrangement and system pressure is equal for all valves.

Constant pressure and load-sensing systems

The closed center circuits exist in two basic configurations, normally related to the regulator for the variable pump that supplies the oil:

Constant pressure systems (CP-system), standard. Pump pressure always equals the pressure setting for the pump regulator. This setting must cover the maximum required load pressure. Pump delivers flow according to required sum of flow to the consumers. The CP-system generates large power losses if the machine works with large variations in load pressure and the average system pressure is much lower than the pressure setting for the pump regulator. CP is simple in design. Works like a pneumatic system. New hydraulic functions can easily be added and the system is quick in response.

Constant pressure systems (CP-system), unloaded. Same basic configuration as 'standard' CP-system but the pump is unloaded to a low stand-by pressure when all valves are in neutral position. Not so fast response as standard CP but pump lifetime is prolonged.

Load-sensing systems (LS-system) generates less power losses as the pump can reduce both flow and pressure to match the load requirements, but requires more tuning than the CP-system with respect to system stability. The LS-system also requires additional logical valves and compensator valves in the directional valves, thus it is technically more complex and more expensive than the CP-system. The LS-system system generates a constant power loss related to the regulating pressure drop for the pump regulator:

The average is around 2 MPa (290 psi). If the pump flow is high the extra loss can be considerable. The power loss also increases if the load pressures vary a lot. The cylinder areas, motor displacements and mechanical torque arms must be designed to match load pressure in order to bring down the power losses. Pump pressure always equals the maximum load pressure when several functions are run simultaneously and the power input to the pump equals the (max. load pressure + Δp_LS) x sum of flow.

Five basic types of load-sensing systems

(1) Load sensing without compensators in the directional valves. Hydraulically controlled LS-pump.

(2) Load sensing with up-stream compensator for each connected directional valve. Hydraulically controlled LS-pump.

(3) Load sensing with down-stream compensator for each connected directional valve. Hydraulically controlled LS-pump.

(4) Load sensing with a combination of up-stream and down-stream compensators. Hydraulically controlled LS-pump.

(5) Load sensing with synchronized, both electric controlled pump displacement and electric controlled valve flow area for faster response, increased stability and less system losses. This is a new type of LS-system, not yet fully developed.

Technically the down-stream mounted compensator in a valveblock can physically be mounted "up-stream", but work as a down-stream compensator.

System type (3) gives the advantage that activated functions are synchronized independent of pump flow capacity. The flow relation between 2 or more activated functions remains independent, of load pressures even if the pump reach the maximum swivel angle. This feature is important for machines that often run with the pump at maximum swivel angel and with several activated functions that must be synchronized in speed, such as with excavators. With type (4) system, the functions with up-stream compensators have priority. Example: Steering-function for a wheel loader. The system type with down-stream compensators usually have a unique trademark depending on the manufacturer of the valves, for example "LSC" (Linde Hydraulics), "LUDV" (Bosch Rexroth Hydraulics) and "Flowsharing" (Parker Hydraulics) etc. No official standardized name for this type of system has been established but Flowsharing is a common name for it.

Open and closed circuits

Open loop and closed loop circuits

Open-loop: Pump-inlet and motor-return (via the directional valve) are connected to the hydraulic tank.The term loop applies to feedback; the more correct term is open versus closed "circuit".

Closed-loop: Motor-return is connected directly to the pump-inlet. To keep up pressure on the low pressure side, the circuits have a charge pump (a small gearpump) that supplies cooled and filtered oil to the low pressure side. Closed-loop circuits are generally used for hydrostatic transmissions in mobile applications. Advantages: No directional valve and better response, the circuit can work with higher pressure. The pump swivel angle covers both positive and negative flow direction. Disadvantages: The pump cannot be utilized for any other hydraulic function in an easy way and cooling can be a problem due to limited exchange of oil flow. High power closed loop systems generally must have a 'flush-valve' assembled in the circuit in order to exchange much more flow than the basic leakage flow from the pump and the motor, for increased cooling and filtering. The flush valve is normally integrated in the motor housing to get a cooling effect for the oil that is rotating in the motor housing itself. The losses in the motor housing from rotating effects and losses in the ball bearings can be considerable as motor speeds will reach 4000-5000 rev/min or even more at maximum vehicle speed. The leakage flow as well as the extra flush flow must be supplied by the charge pump. Large charge pumps is thus very important if the transmission is designed for high pressures and high motor speeds. High oil temperatures, is usually a major problem when using hydrostatic transmissions at high vehicle speeds for longer periods, for instance when transporting the machine from one work place to the other. High oil temperatures for long periods will drastically reduce the lifetime for the transmission. To keep down the oil temperature, the system pressure during transport must be lowered, meaning that the minimum displacement for the motor must be limited to a reasonable value. Circuit pressures during transport around 200-250 bar is recommended.

Closed loop systems in mobile equipment are generally used for the transmission as an alternative to mechanical and hydrodynamic (converter) transmissions. The advantage is a stepless gear ratio (continuously variable speed/torque) and a more flexible control of the gear ratio depending on the load and operating conditions. The hydrostatic transmission is generally limited to around 200 kW maximum power, as the total cost gets too high at higher power compared to a hydrodynamic transmission. Large wheel loaders for instance and heavy machines are therefore usually equipped with converter transmissions. Recent technical achievements for the converter transmissions have improved the efficiency and developments in the software have also improved the characteristics, for example selectable gear shifting programs during operation and more gear steps, giving them characteristics close to the hydrostatic transmission.

Hydrostatic transmissions for earth moving machines, such as for track loaders, are often equipped with a separate 'inch pedal' that is used to temporarily increase the diesel engine rpm while reducing the vehicle speed in order to increase the available hydraulic power output for the working hydraulics at low speeds and increase the tractive effort. The function is similar to stalling a converter gearbox at high engine rpm. The inch function affects the preset characteristics for the 'hydrostatic' gear ratio versus diesel engine rpm.

Components

Hydraulic pump

An exploded view of an external gear pump.

Hydraulic pumps supply fluid to the components in the system. Pressure in the system develops in reaction to the load. Hence, a pump rated for 5,000 psi is capable of maintaining flow against a load of 5,000 psi.

Pumps have a power density about ten times greater than an electric motor (by volume). They are powered by an electric motor or an engine, connected through gears, belts, or a flexible elastomeric coupling to reduce vibration.

Common types of hydraulic pumps to hydraulic machinery applications are;

• Gear pump: cheap, durable (especially in g-rotor form). , simple. Less efficient, because they are constant (fixed) displacement, and mainly suitable for pressures below 20 MPa (3000 psi).
• Vane pump: cheap and simple, reliable.Good for higher-flow low-pressure output.
• Axial piston pump: many designed with a variable displacement mechanism, to vary output flow for automatic control of pressure. There are various axial piston pump designs, including swashplate (sometimes referred to as a valveplate pump) and checkball (sometimes referred to as a wobble plate pump). The most common is the swashplate pump. A variable-angle swashplate causes the pistons to reciprocate a greater or lesser distance per rotation, allowing output flow rate and pressure to be varied (greater displacement angle causes higher flow rate, lower pressure, and vice versa).
• Radial piston pump A pump that is normally used for very high pressure at small flows.

Piston pumps are more expensive than gear or vane pumps, but provide longer life operating at higher pressure, with difficult fluids and longer continuous duty cycles. Piston pumps make up one half of a hydrostatic transmission.

Control valves

Directional control valves route the fluid to the desired actuator. They usually consist of a spool inside a cast iron or steel housing. The spool slides to different positions in the housing, intersecting grooves and channels route the fluid based on the spool's position.

The spool has a central (neutral) position maintained with springs; in this position the supply fluid is blocked, or returned to tank. Sliding the spool to one side routes the hydraulic fluid to an actuator and provides a return path from the actuator to tank. When the spool is moved to the opposite direction the supply and return paths are switched. When the spool is allowed to return to neutral (center) position the actuator fluid paths are blocked, locking it in position.

Directional control valves are usually designed to be stackable, with one valve for each hydraulic cylinder, and one fluid input supplying all the valves in the stack.

Tolerances are very tight in order to handle the high pressure and avoid leaking, spools typically have a clearance with the housing of less than a thousandth of an inch (25 µm). The valve block will be mounted to the machine's frame with a three point pattern to avoid distorting the valve block and jamming the valve's sensitive components.

The spool position may be actuated by mechanical levers, hydraulic pilot pressure, or solenoids which push the spool left or right. A seal allows part of the spool to protrude outside the housing, where it is accessible to the actuator.

The main valve block is usually a stack of off the shelf directional control valves chosen by flow capacity and performance. Some valves are designed to be proportional (flow rate proportional to valve position), while others may be simply on-off. The control valve is one of the most expensive and sensitive parts of a hydraulic circuit.

• Pressure relief valves are used in several places in hydraulic machinery; on the return circuit to maintain a small amount of pressure for brakes, pilot lines, etc... On hydraulic cylinders, to prevent overloading and hydraulic line/seal rupture. On the hydraulic reservoir, to maintain a small positive pressure which excludes moisture and contamination.
• Pressure regulators reduce the supply pressure of hydraulic fluids as needed for various circuits.
• Sequence valves control the sequence of hydraulic circuits; to ensure that one hydraulic cylinder is fully extended before another starts its stroke, for example.
• Shuttle valves provide a logical or function.
• Check valves are one-way valves, allowing an accumulator to charge and maintain its pressure after the machine is turned off, for example.
• Pilot controlled Check valves are one-way valve that can be opened (for both directions) by a foreign pressure signal. For instance if the load should not be held by the check valve anymore. Often the foreign pressure comes from the other pipe that is connected to the motor or cylinder.
• Counterbalance valves are in fact a special type of pilot controlled check valve. Whereas the check valve is open or closed, the counterbalance valve acts a bit like a pilot controlled flow control.
• Cartridge valves are in fact the inner part of a check valve; they are off the shelf components with a standardized envelope, making them easy to populate a proprietary valve block. They are available in many configurations; on/off, proportional, pressure relief, etc. They generally screw into a valve block and are electrically controlled to provide logic and automated functions.
• Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low, or safely vent fluid if pressure becomes too high.
• Auxiliary valves in complex hydraulic systems may have auxiliary valve blocks to handle various duties unseen to the operator, such as accumulator charging, cooling fan operation, air conditioning power, etc. They are usually custom valves designed for the particular machine, and may consist of a metal block with ports and channels drilled. Cartridge valves are threaded into the ports and may be electrically controlled by switches or a microprocessor to route fluid power as needed.

Actuators

• Hydraulic cylinder
• Swashplates are used in 'hydraulic motors' requiring highly accurate control and also in 'no stop' continuous (360°) precision positioning mechanisms. These are frequently driven by several hydraulic pistons acting in sequence.
• Hydraulic motor (a pump plumbed in reverse)
• hydrostatic transmission
• Brakes

Reservoir

The hydraulic fluid reservoir holds excess hydraulic fluid to accommodate volume changes from: cylinder extension and contraction, temperature driven expansion and contraction, and leaks. The reservoir is also designed to aid in separation of air from the fluid and also work as a heat accumulator to cover losses in the system when peak power is used. Design engineers are always pressured to reduce the size of hydraulic reservoirs, while equipment operators always appreciate larger reservoirs. Reservoirs can also help separate dirt and other particulate from the oil, as the particulate will generally settle to the bottom of the tank.

Some designs include dynamic flow channels on the fluid's return path that allow for a smaller reservoir.

Accumulators

Accumulators are a common part of hydraulic machinery. Their function is to store energy by using pressurized gas. One type is a tube with a floating piston. On one side of the piston is a charge of pressurized gas, and on the other side is the fluid. Bladders are used in other designs. Reservoirs store a system's fluid.

Examples of accumulator uses are backup power for steering or brakes, or to act as a shock absorber for the hydraulic circuit.

Hydraulic fluid

Also known as tractor fluid, hydraulic fluid is the life of the hydraulic circuit. It is usually petroleum oil with various additives. Some hydraulic machines require fire resistant fluids, depending on their applications. In some factories where food is prepared, either an edible oil or water is used as a working fluid for health and safety reasons.

In addition to transferring energy, hydraulic fluid needs to lubricate components, suspend contaminants and metal filings for transport to the filter, and to function well to several hundred degrees Fahrenheit or Celsius.

Filters

Filters are an important part of hydraulic systems. Metal particles are continually produced by mechanical components and need to be removed along with other contaminants.

Filters may be positioned in many locations. The filter may be located between the reservoir and the pump intake. Blockage of the filter will cause cavitation and possibly failure of the pump. Sometimes the filter is located between the pump and the control valves. This arrangement is more expensive, since the filter housing is pressurized, but eliminates cavitation problems and protects the control valve from pump failures. The third common filter location is just before the return line enters the reservoir. This location is relatively insensitive to blockage and does not require a pressurized housing, but contaminants that enter the reservoir from external sources are not filtered until passing through the system at least once.

Tubes, pipes and hoses

Hydraulic tubes are seamless steel precision pipes, specially manufactured for hydraulics. The tubes have standard sizes for different pressure ranges, with standard diameters up to 100 mm. The tubes are supplied by manufacturers in lengths of 6 m, cleaned, oiled and plugged. The tubes are interconnected by different types of flanges (especially for the larger sizes and pressures), welding cones/nipples (with o-ring seal), several types of flare connection and by cut-rings. In larger sizes, hydraulic pipes are used. Direct joining of tubes by welding is not acceptable since the interior cannot be inspected.

Hydraulic pipe is used in case standard hydraulic tubes are not available. Generally these are used for low pressure. They can be connected by threaded connections, but usually by welds. Because of the larger diameters the pipe can usually be inspected internally after welding. Black pipe is non-galvanized and suitable for welding.

Hydraulic hose is graded by pressure, temperature, and fluid compatibility. Hoses are used when pipes or tubes can not be used, usually to provide flexibility for machine operation or maintenance. The hose is built up with rubber and steel layers. A rubber interior is surrounded by multiple layers of woven wire and rubber. The exterior is designed for abrasion resistance. The bend radius of hydraulic hose is carefully designed into the machine, since hose failures can be deadly, and violating the hose's minimum bend radius will cause failure. Hydraulic hoses generally have steel fittings swaged on the ends. The weakest part of the high pressure hose is the connection of the hose to the fitting. Another disadvantage of hoses is the shorter life of rubber which requires periodic replacement, usually at five to seven year intervals.

Tubes and pipes for hydraulic applications are internally oiled before the system is commissioned. Usually steel piping is painted outside. Where flare and other couplings are used, the paint is removed under the nut, and is a location where corrosion can begin. For this reason, in marine applications most piping is stainless steel.

Seals, fittings and connections

Main article: Seal (mechanical)

In general, valves, cylinders and pumps have female threaded bosses for the fluid connection, and hoses have female ends with captive nuts. A male-male fitting is chosen to connect the two. Many standardized systems are in use.

Fittings serve several purposes;

1. To bridge different standards; O-ring boss to JIC, or pipe threads to face seal, for example.
2. To allow proper orientation of components, a 90°, 45°, straight, or swivel fitting is chosen as needed. They are designed to be positioned in the correct orientation and then tightened.
3. To incorporate bulkhead hardware.
4. A quick disconnect fitting may be added to a machine without modification of hoses or valves

A typical piece of heavy equipment may have thousands of sealed connection points and several different types:

• Pipe fittings, the fitting is screwed in until tight, difficult to orient an angled fitting correctly without over or under tightening.
• O-ring boss, the fitting is screwed into a boss and orientated as needed, an additional nut tightens the fitting, washer and o-ring in place.
• Flare fittings, are metal to metal compression seals deformed with a cone nut and pressed into a flare mating.
• Face seal, metal flanges with a groove and o-ring are fastened together.
• Beam seals are costly metal to metal seals used primarily in aircraft.
• Swaged seals, tubes are connected with fittings that are swaged permanently in place. Primarily used in aircraft.

Elastomeric seals (O-ring boss and face seal) are the most common types of seals in heavy equipment and are capable of reliably sealing 6000+ psi (40+ MPa) of fluid pressure.

GIANT KOMATSU EXCAVATOR PC3000 WORKING IN INDONESIA

Komatsu PC4000 Loading Cat 785B's

ACCOMPLISHED AREAS (ACCESSIBILITY)

    namely infrastructure that belongs to the work area. Is it easy in the delivery of heavy equipment (mechanical equipment). If there is no way that could not be reached then it must be created first and it will be influential terhdap tool cost of ownership (cost of ownership) and operating costs (operating cost) of the mechanical equipment. If there is a focal area of ​​roads, need to know first-class roads, whether rural roads, or a provincial road. This is to maintain the carrying capacity of roads in accordance with dipersyratkan to bring a mechanical device into the working area.

RECOGNITION OF TOOLS
the factors that determine the use of heavy equipment are:

•    power required (power reguired)
•    power available (power available)
•    power that can be used (power usable)                           

the relationship between power required, power available and power that can be used is very important to know, because we can determine the capacity beberapat tool that should we choose for any work performed.Several things affect the amount of energy that can be used from the machine is described as follows:
    PLANT STATE (VEGETATIAN)
    of trees that grow on the field work necessary to know, whether it is the diameter of the tree, the number poho, average height and a variety of trees. This is to consider clearing the working field. So it can be determined that the equipment will be used pruning the tree.

    WEATHER (CLIMATIC CONDITION)
    weather effects on an area of ​​work needs to be known. Because it would be expected during the last year for how many days of rain. On a rainy day use of mechanical devices can not work effectively even can not be used at all.

     
ALTITUDE (ALTITUDE)
    that the mean is the location / place of work tools to the sea. Should note that the work will affect the performance of a device. The higher the work of sea level (pal-sea level), the pressure of the atmosphere decreases. Because atmospheric pressure decreases the density of air is also decreased, which resulted in the amount of oxygen in the workplace is also reduced. This will result in decline in power for combustion engines "ic engine" (internal combustion engine). To overcome these problems, heavy equipment / heavy to be used to do the correction of horsepower (hp-horse power) of the heavy equipment. To the engine 4 (four cycle engine) would decrease by 3% from hp (horse power) at sea level (sea level) of each in use on a work area with an altitude of 1000 ft first.

    To minimize the reduction of energy / power (hp), then the machine is equipped with a "turbocharger" that serves to supply air to the machines. When the engine using a turbocharger is the correction of horse power, draw bar pull: dbp or rimpul done when the machine is used at a place that has a height of more than 5000 ft above the pal (surface seawater).

    Example:
    wheel tractor tire (wheel tractor) 100 hp at pal (sea level) is equipped with 4 stroke engine "turbocharger". What is the hp correction, if wheel tractor "is in use at an altitude of 15000 ft.?
    Answer:
    correction hp at 15000 ft. = 100 hp-(15000-5000) / 1000 x 3% x 100 hp
    = 100 hp-30 hp = 70 hp

    "taktor" 4 stroke engine, the first gear can provide a 30 000 lb "draw bar pull" (dbp) to pal (sea level). What is the dbp in first gear when the tractor is used on the field working with the elevation of 10000 ft above the pal (sea level)?
    Answer:
    dbp at 10000 ft = 30 000 lb-(10000-1000) / 1000 x 3% x 30 000 lb
    = 30 000 lb-8100 lb
    = 21 900 lb

    TEMPERATURE (TEMP)

    rising temperatures could lead to decreased efficiency of the engine (engine efficiency). When air rises it temeperatur density (density) of air is going down, this causes a decrease in the amount of oxygen that is in each volume of air and will result in efficiency will decrease.

    Horse power (hp) engines vary according to the state of air temperature and local air pressure. Horse power (hp) is a standard based on the temperature and standard atmospheric pressure. The influence engine power loss due to temperature are: engine power is reduced by 1% for every 10O f air temperature rises above the standard temperature of 60O f, or 1% increase engine power when the air temperature falls below the temperature of each standard 10O f 60O f.

    Therefore that when the heavy equipment used in areas of temperature and air pressure is different from the standard hp engine is in need of correction. The formula used is:

    HAUL ROADS, SLOPE AND DISTANCE (HAUL ROAD, GRADE AND DISTANCE)
    the state of roads, distances, road slope and road carrying capacity will strongly influence the production of means of conveyance.

    ROADS TRANSPORT (HOUL ROAD)
    this haul road to be seen of its existence, whether wet or strong, or fairly rough surface. This all needs to review, because the state road transport will affect the size of the rolling resistance (rr) caused by the surface haul road wheel / tire removal of mechanical equipment.

    THE SLOPE (GRADE)
    grad is the slope of the haul roads, the flatness or kecuramannya greatly affects production (output) a conveyance, sebap the slope of the road (grade) raises detainee incline (grade rasistance) that must be addressed by a conveyance engine.

    TRANSPORT DISTANCE (DISTANCE)
    distance transport should also be taken into consideration in determining the speed of the conveyance rate. Conveyance speed of the faster rate, the production (output) the conveyance is also getting bigger and it relies on gravity (rimpull-rp) which is available on the machine. While the tensile strength (rp) the amount determined by the prisoners glinding (rolling resistance - rr) and the slope resistance (grade rasistance - gr) the greater rp available on the machine then the speed of conveyance rate also accelerated, resulting in the production (output) devices the freight rate besar.kecepatan next conveyance determined by the tensile force (rp) on the machine, is also limited by its short and long-distance road transport.

    CYCLE PRODUCTION (PRODUCTION CYCLE COMPONENT)
    mechanical removal of soil on the production cycle can include:

•     loading (loading)
•     transportation (hauling)
•     hoarding (dumping)
•     return (return)
•     put yourself (spot)
•     loading (loading)

    is the process of material loading and unloading the excavation by tool-loading equipment (power shovels, drag line back hoe) that load on a conveyance (hauling equipment). Sizes and types of loading equipment used shall be in accordance with field conditions and the state of transport means. The berpengaru of production (output) and unloading equipment (loading equipment) is:

•     kind / type and condition of the load (including capacity)
•     type / kind of material that will be done
•     the capacity of means of conveyance (hauling equipment)
•     fit the pattern
•     skill of the operator
•     the carrier (hauling)

    is the work of transporting the material. Production (output) of the transport work is influenced by:
    condition of its road transport
    many / her not incline
    the ability of the driver
    and other matters that affect the speed of conveyance (hauling equipment)

    HOARDING (DUMPING)
    is a hoarder of work material. Accumulation of work affected by the landfill, easy to maneuver whether or not the conveyance tersebutselama hoarding, and it influenced and was influenced by:
    how to perform accumulation (dump side, rear or bottom dump dump)
    condition of the material to be in the shed (fragmentation and kelengketannya).

    RETURN (RETRUN)
    is the work of the means of transport to return to the loading point in dumping charges after the spill site (landfill site). So time to go back (retrun time) is also affected by the same things with the time for transporting (hauling time).

    PLACEMENT ITSELF (SPOT)
    a placement away from the means of conveyance (haulage unit). And easy way whether haulage unit (eg truck) positioned to be loaded by means of unloading (loading equipment), is determined by:

    TYPES OF LOADING (LOADING MACHINE)
    LOCATION OR POSITION OF TOOL LOADING (LOADING EQUIPMENT).