Hydraulic Machinery

Hydraulic machinery are machines and tools that use
fluid power to do the work.  Almost all types of
heavy equipment is a common example.  With this type
of equipment, hydraulic fluid is pumped to a high
pressure then transmitted through the machine to
various actuators.

The hydraulic pumps are powered by engines or electric
motors.  The pressurized fluid is controlled by the
operator with control valves and then distributed
through hoses and tubes.

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

Hydraulic power
The theory that lies behind hydraulic equipment is
fluid pressure.
1.  A force that acts on a small area can
create a bigger force by acting on a larger area
by hydrostatic pressure.
2.  A large amount of energy can be carried
by a small flow of highly pressurized fluid.

Pumps
A hydraulic pump will supply the fluid to the
components in the system. Pressure in the system
will develop in reaction to the load.  Pumps have
a power density of around ten times greater than
an electric motor.  The pumps are powered by an
electric motor or engine, which is connected through
gears, belts, or a flexible elastomeric coupling
to reduce the heavy vibration.

The common types of hydraulic pumps for hydraulic
machinery applications include:
1.  Gear pump - the gear pump is cheap,
durable, and simple.  It is less efficient, simply
because it is constant displacement and suitable
for pressures that are below 3,000 psi.
2.  Vane pump - vane pumps are cheap, simple,
and reliable.  They are good pumps for higher flow
low pressure output.

Hoses and tubes
A hydraulic hose is graded by pressure, temperature,
and compatibility of fluid.  A rubber interior is
surrounded by multiple layers of woven wire and
rubber.  The exterior of the hose is designed for
resistance against abrasion.

The bending radius of the hydraulic hose is
designed very carefully into the machine, since
a hose failure can be deadly, and violating the
minimum bend radius of the hose can also cause
failure.

A hydraulic pipe is thick enough to have threads
cut into it for connections.  It's rarely used
for high pressure systems though, which prefer to
have tubes or hoses.  The pipe itself lends to
weldings and can also be used to fabricate the
manifold.

Hydraulic pipes on the other hand are preferred
over hoses whenever possible, as they are simply
more durable.  Tubes are also preferred over pipes,
as they weigh a lot less.  Hydraulic tubes will
normally have flared ends and captive nuts to
make connections.  They can also be steel welded
with floating nuts and face seal fittings on the
ends.

Both tubes and pipes for hydraulic applications
traditionally haven't been plated or painted,
since the temperature and oil they operate under
drive away moisture and reduce the risk of rust.

Fittings
The fittings with hydraulic machinery serve
several purposes:
1.  To bride different standards, such
as the O-ring boss to JIC or pipe threads to the
face seal.
2.  Allows proper orientation of
components, as a 45 or 90 degree, straight, or
even swivel fitting will be chosen as it is
needed.  They are designed to be positioned in
the correct orientation and then tightened as
needed.
3.  To incorporate bulkhead hardware.
4.  A quick disconnect fitting may be
added to a machine without having to modify hoses
or valves.

How The Equipment Has Changed

There are many different opinions as to what
machines should actually be classified as earth
moving equipment.  There are many different types
of equipment that fall in this category, such as
excavators, backhoe loaders, dump trucks, and
even loaders.

Other machinery that falls in between are articulated
trucks, wheel and track tractors, and even
scrapers.  The thin line is normally drawn at
motor grades, which are more than capable or light
duty excavation, although they are mainly used
to level lots and grade roads.

If you take a glance at any equipment literature
from leading companies such as CAT, Komatsu, or
Case, you'll see right away that they believe the
biggest and most important change over the last
several years is increased productivity.  This is
normally followed by greater comfort and safety.

The increase in productivity is the result of
many different advancements.  CAT (Caterpillar)
cites that more powerful engines with a faster
rise in torque which allows machines to respond
faster to increased power demands.  Even though
this new generation is far more powerful, it
has a reduced impact on the environment as well.

Electronics
Most of the newer machines have electronic
control systems that will optimize both engine
and transmission performance, as well as fuel
consumption and hydraulic system performance.

Take for example the CAT mid sized G series
wheel loaders that feature electronically controlled
powershift transmissions.  Each and every
transmission offers autoshift capabilities that
ease the pressure on the operator, and an
electronic clutch pressure control that smooth
shifts the gears for longer life.

Comfort
In the industry, good operators are getting harder
and harder to find.  Manufacturers find themselves
stressing that operator comfort and convenience
need to be taken into account not only to make
the job easier, but also more efficient and
productive as well.

The new cab designs offer better visibility,
reduced noise and vibration, and improved comfort
as well.  The new control systems will require low
operator effort while also improving the control
of the machine for both the experienced as well
as the in-experienced operator.

Easier maintenance
Almost all new machinery offers electronic
monitoring systems that will provide constant
information on the health of the machine for the
operator.  These types of systems provide information
to technicians, including service modes that will
help them to diagnose conditions quickly.

Now days, machines are designed to make routine
maintenance easier.  With CAT's wheel loaders,
regular service points are easy to access from
ground level, with site gauges making it easier
to check the fluid of the radiator, hydraulic oil,
and transmission - without having to use dipsticks.

Changes for the better
If you compare the excavation equipment of today
with the machines of the past, you'll notice that
the changes are better.  The machines of the past
relied more on operator skill and technique, as
very few of them had electronic features.

Today, almost all types of heavy machinery offer
electronic features.  Electronics are a great
thing, as they can make the life of an operator
easier than ever.  You don't need to get out and
check the fluids anymore, as all you need to do
is take a look at your instrument panel, which can
help to save you a lot of time.

Operators who have a lot of experience know first
hand that machines of the past can't begin to
compete with machines of today.  With technology
always getting better, it just makes you wonder
what is in the future for heavy machinery.  Years
from now, one can only begin to wonder just great
heavy machinery will get - and what other features
will make the life of an operator even easier than
it is now.

Harvester

The harvester is a type of heavy machinery that is
employed in cut to length logging operations for
felling, buckling, and cutting up trees. Normally,
a harvester is employed alongside a forward that
will haul the logs and trees to a roadside landing.

Harvesters were developed in Sweden and Finland,
and today they do nearly all of the commercial
felling in these countries.  They work best for
less difficult terrain for the clear cutting area
of forest.  For steep hills or removing individual
trees, chain saws are normally preferred.  In
the nordic countries, small and agile harvesters
are used for thinning operations and manual cutting
is only used during extreme conditions or by self
employed owners of the forest or wooded area.

The leading manufacturers of harvesters include
Timberjack (which is owned by John Deere) and
Valmet, which is owned by Komatsu.

Normally, harvesters are built on a robust all
terrain vehicle, which can either be wheeled or
tracked.  Sometimes, the vehicle can be articulated
to provide tight turning around obstacles.  A
diesel engine will provide power for both the
vehicle and the harvesting mechanism through a
hydraulic drive.

An articulated, extensible boom that is similiar
to that of an excavator, will reach out from the
vehicle to carry the head of the harvester.  There
are even some commercial harvesters that are
adaptations of excavators with a new harvester
head, while the others are purpose built vehicles.

The normal harvester head may consist of:
1.  A chain saw to cut the tree at the
base and also to cut it to length.  The saw is
hydraulically powered rather than using a 2 stroke
engine of a portable version.  It offers a more
robust chain and a higher output power than any
saw carried by man.
2.  Two curved de-limbing knives that can
reach around the trunk to remove branches.
3.  Two feed rollers to reach out and grasp
the tree.  The wheels will pivot apart to allow
the tree to be embraced by the head of the harvester,
and pivot together to hug the tree tight.
4.  Two more curved knives for de-limbing.

All of this is controlled by an operator who sits
in the cab of the vehicle.  A control computer is
used to simplify mechanical movements and keep the
length and diameter of trees that have been cut.

The length is computed by counting the rotations
of the gripping wheels.  The diameter is computed
from the pivot angle of the gripping wheels that
hug the tree.

Harvesters are normally available for cutting trees
up to 900 mm in diameter, built on vehicles that
weight up to 20 t, with a boom that reaches up to
a 10m radius.  The larger, more heavier vehicles
do more damage to the forest, although a longer
reach will help by allowing more trees to be
harvested with less movements required by the
vehicle.

Front Loader

Also known as a front end loader, bucket loader,
scoop loader, or shovel, the front loader is a type
of tractor that is normally wheeled and uses a
wide square tilting bucket on the end of movable
arms to lift and move material around.

The loader assembly may be a removable attachment
or permanently mounted on the vehicle.  Often times,
the bucket can be replaced with other devices or
tools, such as forks or a hydraulically operated
bucket.

Larger style front loaders, such as the Caterpillar
950G or the Volvo L120E, normally have only a
front bucket and are known as front loaders,
where the small front loaders are often times
equipped with a small backhoe as well and called
backhoe loaders or loader backhoes.

Loaders are primarily used for loading materials
into trucks, laying pipe, clearing rubble, and
also digging.  Loaders aren't the most efficient
machines for digging, as they can't dig very deep
below the level of their wheels, like the backhoe
can.

The deep bucket on the front loader can normally
store around 3 - 6 cubic meters of dirt, as the
bucket capacity of the loader is much bigger than
the bucket capacity of a backhoe loader.  Loaders
aren't classified as excavating machinery, as
their primary purpose is other than moving dirt.

In construction areas, mainly when fixing roads
in the middle of the city, front loaders are
used to transport building materials such as
pipe, bricks, metal bars, and digging tools.

Front loaders are also very useful for snow
removal as well, as you can use their bucket or
as a snow plow.  They can clear snow from the
streets and highways, even parking lots.  They
will sometimes load the snow into dump trucks
which will then haul it away.

Unlike the bulldozer, most loaders are wheeled and
not tracked.  The wheels will provide better
mobility and speed and won't damage paved roads
near as much as tracks, although this will come
at the cost of reduced traction.

Unlike backhoes or tractors fitted with a steel
bucket, large loaders don't use automotive
steering mechanisms, as they instead steer by a
hydraulically actuated pivot point set exactly
between the front and rear axles.  This is known
as articulated steering and will allow the front
axle to be solid, therefore allowing it to carry
a heavier weight.

Articulated steering will also give a reduced
turn in radius for a given wheelbase.  With the
front wheels and attachment rotating on the same
axis, the operator is able to steer his load in
an arc after positioning the machine, which can
come in quite handy.  The problem is that when
the machine is twisted to one side and a heavy
load is lifted high in the air, it has a bigger
risk of turning over.

Forklift

Sometimes called a forklift truck, the forklift is
a powerful industrial truck that is used to lift
and transport material by steel forks that are
inserted under the load.  Forklifts are commonly
used to move loads and equipment that is stored on
pallets.  The forklift was developed in 1920, and
has since become a valuable piece of equipment in
many manufacturing and warehousing operations.

Types
The most common type of design with forklifts is
the counter balance.  Other types of designs
include the reach truck and side loader, both of
which are used in environments where the space is
at a minimum.

Control and capability
Forklifts are available in many types and different
load capacities.  In the average warehouse setting,
most forklifts have load capacities of around
five tons.

Along with the control to raise and lower the
forks, you can also tilt the mast to compensate
for the tendency of the load to angle the blades
towards the ground and risk slipping it off the
forks.  The tilt will also provide a limited
ability to operate on ground that isn't level.

There are some variations that allow you to move
the forks and backrest laterally, which allows
easier placement of a load.  In addition to this,
there are some machines that offer hydraulic
control to move the forks together or further
apart, which removes the need for you to get out
of the cab to manually adjust for a different size
load.

Another forklift variation that is sometimes
used in manufacturing facilities, will utilize
forklifts with a clamp attachment that you can
open and close around a load, instead of having
to use forks.  Products such as boxes, cartons,
etc., can be moved with the clamp attachment.

Safety
Forklifts are rated for loads at a specified
maximum weight and a specified forward type center
of gravity.  All of this information is located
on a nameplate that is provided by the manufacturer
and the loads cannot exceed these specifications.

One of the most important aspects of operating a
forklift is the rear wheel steering.  Even though
this helps to increase maneuverability in tight
cornering situations, it differs from the
traditional experience of a driver with other
wheeled vehicles as there is no caster action.

Another critical aspect of the forklift is the
instability.  Both the forklift and the load must
be considered a unit, with a varying center of
gravity with every movement of the load.  You
must never negotiate a turn with a forklift at
full speed with a raised load, as this can easily
tip the forklift over.

Normally, to drive a forklift, you'll need to
pass a basic test.  They aren't difficult to
operate, although you'll need to be safe when you
operate them.  Once you have operated one for a
while, you'll have no problems being safe.