Graco BetaCell 241D, Operation

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39
Overview
Buffer tanks Great emphasis is always placed on the outlet of the metering pump such as
the flow and pressure produced; however, the importance of the inlet side of
the pump cannot be overlooked. If the metering pump is not properly
supplied, cavitation will result. This may cause damage to the pump and
most certainly will lead to an “
off ratio ” condition.
To assure an adequate supply of material at the proper temperature, the
BetaCell 241 includes temperature conditioned and pressurized buffer
tanks.
Temperature conditioning is accomplished by surrounding the tank with an
oil filled jacket. A submersible 1800-watt heater heats the oil and the
program within the PLC control maintains the operator-selected
temperature. A low RPM mixer moves the material in contact with the
heated walls of the tank to assure an even temperature gradient.
To assure adequate pressure at the inlet to the metering pump, the tank is
pressurized with Nitrogen or dry air at 60 psi. Since the two components
are chemically reactive, check valves isolate the two air streams.
Should the pressure in the tank exceed 70 psi, an operator settable pressure
relief valve is provided to bleed the pressure.
A completely separate factory set and sealed safety relief valve is also
provided to dump the tank should the maximum pressure of 100 psi be
exceeded.
The level in the tank is automatically maintained between 80% and 90%
full by the AutoFill system. A visual reference is also provided. Should the
tank level fall below the factory set limit of 10% full, operation will
automatically freeze and be accompanied by audible and visual alarms.