Fluid
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Hydraulic
Oil Usage
Hydraulic
System Pressure (Setting)
Hydraulic
Pump Operation
Hydraulic
System Operation
Hydraulic
System Design
Pneumatic
System Design
Hydraulic
Oil Usage
Temperature Guidelines
For normal operation (0-1500 psi, 130¼
F), use oil with a fluid viscosity of 150
SSU @ 100¼ F.
For
higher pressures and temperature (up to 150¼
F), use oil with a fluid viscosity of 225-325
SSU @ 100¼ F.
For
cold startup applications down to 0¼
F, ATF Type A fluid will prove satisfactory.
Hydraulic
Setting System Pressure
System pressures should be set as low as possible
to prevent unnecessary fluid heating; on some
applications, this setting may be from 50
to 200 psi above necessary working pressures
to overcome dynamic pressure drop or to achieve
proper acceleration.
If
system is equipped with a pressure compensated
pump, adjust the pressure using the pump compensator.
If
system is equipped with a fixed displacement
pump, adjust the pressure using the system
relief valve.
Hydraulic
Pump Operation
Eliminating Pump Noise
Pump noise (crackling) is often caused by
air entering the pump suction. The tightening
of fittings on the suction side of the pump
will usually eliminate such problems.
Pump Won't Prime
If pump fails to prime, vent pump discharge
to atmosphere by loosening a discharge fitting
until you see a steady stream of flow, then
tighten.
Hydraulic
System Operation
Power Unit Cleaning after Startup
After the first few hours of operation of
a new power unit, foreign material from the
system plumbing will be flushed back to the
reservoir.
It is good practice to drain and replace the
initial fill, then clean the reservoir and
suction strainer, followed by replacing with
new hydraulic fluid.
As
an alternative, an offline re-circulating
pump and filter can be used to accomplish
this task.
Beware High Temperatures
For most industrial applications, an operating
temperature of 150¼ F is considered
maximum.
At
higher temperatures, difficulty is often experienced
in maintaining reliable and consistent hydraulic
control, component service life is reduced,
hydraulic fluid deteriorates, and a potential
danger to operating personnel is created.
If
system is running at 150¼ F or higher,
shut down the system, and determine the cause
of the elevated temperature.
Maintenance Intervals
At least once a year or every 4,000 hours
of operation, the reservoir, suction strainer,
and air vent filter should be cleaned. At
this time, check the entire system for possible
future difficulties.
Some
application or environmental conditions may
dictate such maintenance be performed at more
frequent intervals.
If
system is equipped with filters having visual
or electrical indicators, service the filters
whenever the indicators show a by-pass condition.
Hydraulic
System Design
Pump Sizing
Size the pump to the average oil flow plus
10%. There is no need to size the pump for
peak load when using an accumulator.
Reduce System Pressure Drop
Use adequate pressure and return lines with
a minimum number of 45¼ and 90¼
joints. These joints induce unnecessary pressure
drops.
Accumulator Sizing
When designing for multiple components and
operations, use an accumulator. It should
be sized at least 10 times larger than the
change in volume of oil.
Accumulator Pre-Charge
Pre-charge accumulators to 80% of system pressure.
Any oil in the accumulator that is not being
used is reducing its effectiveness.
The
gas bubble should be as large as possible
as long as there is always some oil in the
accumulator.
Maximizing Cylinder Control
Locate valves as close as possible to cylinders
to maximize control.
Maximize Cylinder Control
Locate accumulators as close to the valve(s)
as possible.
Cylinder Control in Proportional Circuits
For maximum control of the cylinder (in proportional
systems), do not use flexible hose between
the valve and the cylinder.
Maximizing Hose Life
Never bend hose past its listed bend radius
(can be found in manufacturer's catalog).
Maximizing Hose Life
Bend hose in one plane only to avoid twisting
its wire reinforcement, which would reduce
the hose's pressure capability.
If
you must bend a hose in more than one plane,
install hose clamps between bends, and provide
enough length on both sides of the clamp to
relieve strain on the hose's reinforcement
wires.
Maximizing Hose Life
80% of hose failures are attributable to external
physical damage, with abrasion cited as the
major culprit.
To
prevent abrasion, use clamps to secure hose
in place and keep it from rubbing against
adjacent surfaces.
Additional
protection can be provided by sleeves. Sleeves
can be metal to prevent crushing, or fabric
to keep abrasive particles way from the hose.
And
always use a hose with an abrasion-resistant
cover if at all possible.
Maximizing Hose Life
Excessive heat can dramatically reduce hose
life, so it is important to keep hose away
from any external sources of heat.
Pneumatic
System Design
Sizing Pneumatic Motion Systems
To correctly size pneumatic motion systems,
every component must be taken into account.
Using only the flow coefficient (CV) is not
enough. Every component in the system must
be considered to ensure high performance and
minimal losses.
A
good rule of thumb for sizing a cylinder for
speed is to make it large enough to provide
two times the calculated force requirement.
Sizing Pneumatic Cylinders
A good rule of thumb for sizing a cylinder
for speed is to make it large enough to provide
two times the calculated force requirement.
Sizing Pneumatic Valves
You want to size pneumatic valves by determining
the average flow rate through the exhaust
port, and likewise, through the supply port
during motion. These exhaust and supply flows
will be used to estimate all other component
pressure drops in the circuit.
You
want a pneumatic valve that has a pressure
drop between 2 psi and 10 psi. A valve that
has a lower the pressure drop provides a more
efficient circuit.
You
also need to determine pressure drops across
the exhaust valve fitting, exhaust air line,
exhaust and supply flow controls, cylinder
exhaust fitting, cylinder, cylinder supply
fitting, supply air line, supply valve fitting,
and the valve supply port. Please call or
e-mail for the necessary equations.
With
this information, you can calculate the delay
time before motion begins when retracting/extending
the cylinder. This will also give you an initial
time estimate when combined with the valve
shift time, PLC scan time, and the valve solenoid
time. Then you can resize and adjust components
accordingly to give you the proper system
response you need.
Using
this type of method to determine valve and
cylinder requirements may result in space
and cost savings as opposed to using the old
CV style of pneumatic component sizing. Also,
cylinder times are more predictable, and cylinders
and valves can be sized to minimize air consumption.
Pneumatic Dryers
Eliminating the cost of replacement parts,
labor, standby inventory, and downtime can
offset the cost of installing and operating
air dryers.
Dryers
remove water vapor from the air and lowers
the dew point of air (the temperature to which
air can be cooled before condensate forms).
The four basic types of compressed air dryers
are deliquescent, regenerative desiccant,
refrigeration, and membrane.
Deliquescent
dryers contain a chemical desiccant that absorbs
moisture in the air. This chemical desiccant
is consumed in the water-removal process and
must be replenished periodically. The solution
that must be drained from this type of dryer
contains both water and the chemical, so disposal
may be a problem. Due to differing environmental
regulations in each area, these dryers are
the least popular of the four types.
Regenerative
desiccant dryers work much like deliquescent
dryers. The main difference is that a porous
desiccant, usually silica gel, is used instead
of a chemical. The porous desiccant does not
react chemically with the water, so there
is no need for replenishment or disposal of
the chemical. The desiccant has to be dried,
or regenerated, periodically for this dryer
to function properly. This type of dryer is
further divided up into two types, the heatless
regenerative dryer and the heat regenerative
dryer. The major difference between these
two is the cycle time, and amount of energy
consumption to complete a regenerative cycle.
The
refrigeration dryer types condense moisture
from the compressed air by cooling the air
in heat exchangers chilled by refrigerants.
These types can only produce dew points in
the 35-50 at normal operating pressure (compared
to -100 to 65 for the previously mentioned
dryers). There are three types of refrigeration
dryers. Tube-in-tube dryers operate by cooling
a mass of aluminum or bronze that in turn
cools the compressed air. Water-chiller refrigerators
use a mass of water for cooling. An extra
heat exchanger is needed to maintain chilled
water if cold water is not available on-site.
Direct-expansion refrigerators use a refrigerant-to-air
cooling process to produce dew points as low
as 35. No recovery period is necessary with
this type, so direct-expansion dryers can
run continuously.
Membrane-type
air dryers are gas-separation devices. They
consist of miniature tubes made of plastic
compounded to allow water vapor to pass through
when there is a pressure differential. This
type of dryer is very rugged, with some lasting
years while drying continuously. This type
of dryer also delivers the most consistent
level of drying protection that follows the
change in inlet dew point temperature. The
membranes of the dryer never become saturated,
so there is no need for regeneration. The
also contain no moving parts to wear out.
They also are non-electric, use no refrigerant
in the cooling cycle, make no noise, and can
be mounted in any orientation. This is probably
the best type of air dryer for most applications
among the four.
The
two questions to ask yourself in determining
what dryer is right for you is 1) How dry
must the air be? and 2) What type of dryer
should be used?. For more information in determining
these two criteria, please contact Indiana
Fluid Power.
Filters, Regulators, Lubricators
Air is a simple medium to use for motion control.
It's clean, ready available, and simple to
use. However, it can be the most expensive
form of energy in your facility. A good rule
of thumb to use is that for every 2 psi increase
in operating pressure, there is a corresponding
1% increase in the energy cost to compress
this air. FRL's are needed in your pneumatic
system to ensure that every tool, cylinder,
or process is receiving a clean, lubricated
supply of compressed air at the proper pressure
to provide peak performance to decrease your
energy cost.
Filters
are used to maximize reliability and longevity
of your supply of air and components in your
motion control system. Filters are used to
clean out condensed water, oil carryover from
compressors, solid impurities, and wear particles
from your air supply. The most likely component
in your system to be affected by dirty air
is pneumatic valves.
The
manufacturers of pneumatic valves normally
require certain air ratings in order for the
valve's to perform effectively. You want to
match your point of use filters to your most
demanding component of clean air. Filters
are rated according to the minimum particle
size that their elements will trap. Finer
filter ratings will increase the pressure
drop through the filter, which equates to
higher energy cost to compress the air. That
is why it is extremely important to match
your filter to your application to keep your
energy costs in line. Finer filtration over
what is needed isn't necessarily better. These
filters should be selected based on required
air flow, acceptable pressure drop, and pipe-connection
size.
A
pressure regulator is used to reduce supply
pressure to the level required for efficient
operation of downstream pneumatic equipment.
Once you have determined a minimum suitable
operating pressure for your application, it
is essential to supply the air at a constant
pressure, regardless of upstream flow and
pressure fluctuations. Selecting the best
type of regulator for a specific application
first requires a choice among regulator styles
(unbalanced poppet, diaphragm, balanced poppet).
The next consideration becomes primary (supply)
pressure versus secondary (output) pressure.
Finally, desired airflow rate must be selected.
Although several models may appear to be acceptable
for a given airflow and pressure, a larger
body size regulator will produce better setting
sensitivity and less pressure drop than a
smaller body model under the same set of operating
conditions.
Many
system components and almost all pneumatic
tools perform better when lubricated with
oil. Injecting an oil mist into the air-stream
which powers them can continuously lubricate
for proper operation and longer service life.
Correct application of most airline lubricators
requires mounting close to a single component
or tool. Too little oil can allow excessive
wear and cause premature failure. Excessive
oil in the pipeline is wasteful and can become
a contaminant in the ambient area as it exits
out of tools and valves by the air exhaust.
Finally, intermittent lubrication is the worst
condition of all because oil film can dry
out and form sludge or varnish on the internal
surfaces of your equipment. Lubricators are
generally selected based on pipe connection
size, oil reservoir capacity, and acceptable
pressure loss versus flow rate. Remember to
account for this added downstream pressure
loss when setting the pressure regulator.
If
you need any explanation on how F-R-L's work
and how to properly size them for your application,
please contact Indiana Fluid Power.
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