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SRD-Series Servomotor-Controlled,
Continuous Rotary Gear Pump Systems
Extremely accurate and fully
programmable, SRD-Series systems utilize
state-of-the-art PLCs and PCs, servomotor-control and coriolis mass
flowmeters for superior, closed-loop feedback ratio control. You can easily
select preset pour recipes for each of your parts by name or number at the
operator-interface. Setting digital presets for those recipes, including ratio,
shot-size, output rate, temperatures, vacuum and mixer-speed, can be made
with pushbuttons in seconds. The operator-interface is menu-driven for
easy operation.
  
Each of the positive-displacement rotary gear pumps on the
SRD-Series system is of the
highest quality available and each is driven with an independent, digitally-controlled
servomotor drive. The rotary pumps handle urethane, epoxy, polyester and cast nylon
formulations. Open-casting, VARTM (Vacuum-Assisted RTM) and closed-mold RTM resin
injection applications are also handled. Metering pump sizes are selected to match
your
ratio and output requirements. Accurate ratio settings are made by entering your
required
ratio at the LCD operator-interface. Typically, presets are also entered for shot-size,
output-
rate and mixer speed. You can save those presets to the PLC as process recipes for
later
use or you can enter and run each set of presets without saving them. Hundreds of
recipes
can be saved.
When the footswitch is depressed, the the servomotors turn the
rotary pumps, displacing
on-ratio streams of A and B component materials to the static (motionless) or dynamic
(motor-
driven) mixer. Various systems provide outputs from 1 to 50 lbs/min. Ratios
can range from
1:1 to 1:200. Two, three and four-component systems are standard and automatic
color-
component metering with one or more color pumps is standard.
Constant positive material feed pressure from the degassing
tanks feeds material to both pumps.
This positive air-free-material pressure from the tanks is created by nitrogen
over-pressure in
batch vacuum tanks or by mechanical feed pumps on constant-vacuum thin-film degassers.
These
mechanical rotary (or piston-type) feed pumps are submerged in the material or they are
mounted
under the degassing tanks for easier and cleaner access to the pumps.
Continuous recirculation is optionally provided at the mixer to keep
the material in constant
motion; continuously diverting the independent on-ratio streams of material back to their
respective material supply vessels whenever the machine is not in pouring mode. The
automatic
component injectors (2-way and 3-way valves) are located at the mixer and convenient
ratio-
taking ports (for manually checking ratio) are provided. See our optional Mass
Flowmeters for
automatic ratio monitoring and ratio correction, described below.
All heated compartments for the pumps and the mixer are made of removable slide-out panels
for easy access to all system components. Heaters are ceramic-enclosed
infrared type, which
allow the system to be more easily modified at a later date to include third and
fourth components
or to simply switch to different rotary pump sizes.
More Information - See Overview and items listed below.
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Rotary
Gear Pumps
Get precise, pulseless, repeatable flow. These positive
displacement
rotary gear pumps include just three moving parts. This means less
maintenance and more high-quality mixed material output. Various
pump sizes, for example, 1.2 ccs/rev to 100 ccs/rev and larger, match
any ratio and output requirement. |
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Servomotor
Drives
Eliminate mechanically connected gear pumps, backlash and the
need
to manually change gears in order to change ratio. Digital servomotor-
control offers much-improved controlled-rotation accuracy over variable-
speed DC and stepper-motor-driven metering systems especially
on
initial ramp-up and at the end of the pour, where linear-ratio streams
must maintain extreme accuracy. |
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Programmable
Logic Controller (PLC) & PC
The process control instructions and presets you enter
at the LCD operator-
interface are stored in the PLC (or optional Flat Panel IBM-PC.) When a
pour is initiated, that part's recipe instructions are passed on to the
servomotor amplifiers, which precisely control rotational movement of the
servomotor drives. Ratio, shot-size, output-rate, mixer-speed, pot-life alarm
time and other variables for each part are controlled via saved recipes in the
PLC or PC. |
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Coriolis
Mass Flowmeters
The rotary metering pumps included with our SRD-Series systems
provide
extreme accuracy and long service-life. The independent servomotors are
electronically (i.e., digitally) linked and this insures extremely close pump
rotation and speed control. Truly precise ratio control, however, needs to
rely and respond to continuous and near perfect measurement of the actual
flow from each metering pump to the mixer. Our optional mass flowmeters,
installed at each metering pump, provide the very best available, continuous,
closed-loop feedback, ratio correction and control. With mass flowmeters,
actual mass flows to the mixer are compared to the desired preset ratio.
This way, the difference is corrected by incrementally increasing and
decreasing the pump speed literally hundreds of times per second. Where
do pump output and ratio errors come from? Long-term internal wear on the
pumps, varying internal backpressures, notably from mixed-material
unavoidably curing in the mixer output line and from factory-built clearances
along each side of the pump's gears. Continuous ratio verification is
displayed at the operator interface and setpoints are easily entered for ratio
deviation alarms and automatic system shut-down. |
System
Specifications:
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1:1 to 1:200 |
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Typically,
batched and continuously degassed materials, air-free
and ready for metering, mixing and dispensing, flow by gravity.
However, low, medium and high pressure can be applied to deliver
higher viscosity materials to the precision metering pumps on the
SRD system. Mixed output pressure from the pumps can be as
low as a few PSI to 500 PSI and optionally, as high as 10,000 PSI. |
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To better than
0.5% |
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From a few
grams to more than 100 lbs/min. |
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1.4 cc (1:1
ratio) |
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Continuous
output; meaning hundreds or thousands of pounds. |
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Typically,
motor-driven dynamic mixers. Also, disposable static
tube mixers. Injectors for each component are controlled by
automatic 2-way and 3-way valves at the mix head for recirculated
and non-recirculating SRD systems. |
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One drive per
each metering pump. Two, three or four servomotors
on one metering system baseplate are standard. More than four can
be installed and PLC/PC controlled, as required. |
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