Fully
automated closed loop spray system provides
outstanding monitoring and control capabilities
 A
carpet manufacturer needed an automated spray system to apply a
latex-based solution as an anti-slip backing on their carpets. To
keep their operations running at peak efficiency, they needed a
system that provided outstanding monitoring and control capabilities.
Problem:
The customer needed to control the application rate of the dry product
in a specific range with the application rate remaining constant
even at line speeds which varied between 15 m/min and 25 m/min (49
ft/min and 82 ft/min). Since the product being sprayed is very tacky
and plant safety is an issue, it was imperative to minimize spray
drift, avoid overspray and install an effective rinsing system to
keep the system clean. The control system also needed to account
for three different carpet widths on the same machine. Finally,
the control system needed to monitor two latex spray tanks and determine
when a tank was empty so that the other one could be activated.
Solution: A fully automated spray system was designed and installed
by AutoJet Technologies. The Model 2250 AutoJet Spray Controller
met all of the customer's needs using powerful SprayLogicTM
software. The controller detects the various carpet widths through
proximity switches and automatically switches on the appropriate
bank of stainless steel 1/4JAUH AutoJet spray guns (3 spray gun
banks in total). A speed dependent closed loop flow rate control
system was implemented.
The
latex flow rate is measured with an electro-magnetic flowmeter and
the Model 2250 spray controller continuously adjusts the flow rate
to the spray guns by regulating the RPM of an eccentric worm pump
with a frequency driven motor. The continuous flow rate calculations
are based on six factors:
- The
setpoint for the desired dry product application rate
- The measured flow
- The speed signal coming from the customer's PLC that
controls the speed of the production line
- The dilution ratio of the latex
- The specific gravity of the latex
- The measured carpet width
In
order to prevent clogging of the spray tips, a fully automated rinsing
system was implemented. When the system stops spraying for longer
than a predetermined length of time, a piston-activated stainless
steel rinsing gutter is automatically positioned under the spray
nozzles and either a latex spray cycle or a complete rinsing cycle
is performed.
Operating
conditions such as flow rate, liquid and air pressures, tank levels
and carpet widths are constantly monitored by the AutoJet spray
system. Fault detections were established using SprayLogic software
which allow the controller to generate alarms and to shut the entire
system down under specific conditions.
 The
"System Integrity Checking" program automatically detects
spray nozzles that are clogged or worn. The Model 2250 controller
then generates alarm messages such as: "Check clogged nozzles"
or "Check worn nozzles". The spray controller has also
a built-in algorithm that prevents the pump from running dry.
The
custom AutoJet spraying system has allowed the customer to gain
a competitive advantage by adding the anti-slip feature to his carpets,
while keeping up with existing production throughput. The automated
rinsing system has minimized maintenance and all environmental and
safety requirements for applying latex have been met.
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