Manitowoc 3900W - Operation

© 1996 Manitowoc Engineering Co.
Rev. 06-14-96 Folio 525-1
AIR SYSTEM DEICER
SERVICE INFORMATION
Table of
Contents
Operation
(Figure 1)
The deicer meters deicant into the air line only when there is a flow of air through
the deicer. Air flowing through the deicer passes around flow sensor (10) to the
downstream system. Inlet pressure is admitted to the reservoir through check
(charge) valve (11). When air is flowing, a small pressure drop occurs across the
flow sensor. The outlet (lower) pressure is sensed in sight feed dome (6a) through
nozzle passage (A). This establishes a pressure drop across metering orifice (B)
and, as a result, deicant at inlet pressure flows upward through siphon tube (12)
into the sight feed dome where it drips into the nozzle passage and then into the
deicer throat. Adjusting knob (6) controls the deicant drip rate. The deicant drops
are atomized by the high velocity air flowing past the flow sensor and are carried
downstream. Check ball (13) prevents back flow of deicant into the reservoir
during periods of no flow.
Flow sensor (10), in effect, functions as a variable restrictor in the throat of the
deicer to produce a pressure drop of up to 5 psi (0.3 bar) that is proportional to the
rate of air flow through the deicer. These variations in outlet pressure, sensed in the
sight-feed dome, cause a like variation in the pressure drop across the metering
orifice as a function of air flow. Thus, for a given drip rate setting at some average
air flow, a lower air flow will cause a proportionally higher drip rate.
Charge valve (11) controls the rate of reservoir pressurization and allows rapid de-
pressurization for refilling without shutting off the air pressure. When the deicant
plug is loosened, a bleed orifice is exposed which immediately reduces the
reservoir pressure. This pressure drop causes the charge valve to close and restrict
air flow into the reservoir to eliminate blow-back when adding deicant. When the
fill plug is replaced, the reservoir re-pressurizes through the charge valve at a
nominal rate. The charge valve opens fully when inlet pressure is reached.
Operation......................................................................1
Adjusting.......................................................................2
Maintenance.................................................................3
Filling ............................................................................4
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