Outlet; Start And Control Unit - Nederman L-PAK Serie Manual De Instrucciones

EN L-PAK 150, L-PAK 250
There is a vacuum limiting valve located close to the fan inlet which opens
when the vacuum becomes to great, figure 4. A weight (A) normally keeps
the valve cone (B) closed. At about - 20 kPa vacuum the cone lifts as shown in
the illustration, allowing air to flow into the fan. This is how the vacuum level,
power consumption and temperature are controlled.
NOTE! The valve must never be disabled.
The temperature rises sharply as the air passes through the side channel fan.
The temperature of the exhaust air increases with a high vacuum, i.e. a small
air flow and a high ambient temperature. To prevent the fan and motor from
running too hot, there is a thermal switch at the fan outlet. This trips at 125
°C (257°F) causing the filter cleaning plate to open to cool the fan. The unit
automatically restarts when the temperature has dropped to about 90 °C (194
°F) when the thermal switch automatically resets.
NOTE! The motor stops if the fan has not been cooled within 8 minutes.
4.6.3

Outlet

Air leaves the unit through the exhaust air silencer. The hot exhaust air should
be led off into the atmosphere. The air can be led to a heat exchanger.
CAUTION!
The air can be led to a heat exchanger, but there must be no dampers that can
obstruct the air flow. If the exhaust air duct is blocked the unit can create an
overpressure, which may cause major damage to the heat exchanger.
4.6.4

Start and control unit

Y/D-start or gradual start
L-PAK 150 is direct started (contactor). L-PAK 250 starts gradually (gradual start
equipment).
Automatic start/stop or continuous operation
The functions automatic idling (DIR function) and automatic starting and
delayed stopping (SSR function) are always included in the start and control
unit. To make proper use of the facilities all vacuum valves at workstations
must be fitted with a micro switch (AS set) connected to a pilot signal cable
that runs to the start and control unit.
Filter cleaning
Figure 5 shows the principle for filter cleaning A PLC controls a solenoid valve
(A) which in turn controls a compressed air cylinder (B) with a valve disc.
The principle requires negative pressure in the dust collector so that the
"accumulated vacuum", when the valve opens, gives a short but powerful blast
of reverse air through all the filter which will dislodge the dust deposited on
the outside of the filters, this will be repeated 3 times for each filter cleaning
cycle.
This method works best in installations with automatic vacuum valves at the
workstations. Filter cleaning occurs every time the L-PAK switches to idling on
installations that utilise the functions automatic idling and automatic starting
and stopping. This filter cleaning arises in addition to filter cleaning tripped by
the filter cleaning function in the PLC.
18
Risk of equipment damage.