Hydronix Hydro-Control VI, Руководство по установке

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Chapter 5 System Design
Hydro-Control VI Installation Guide HD0455 Rev 1.9.0 57
1.3
Example
Metric units:
If a 1m 3 mixer has only a coarse valve and the water flow rate through the valve is 10 L/s with
an on/off cycle time of 1 sec, then water can only be added in 10 L steps. With a full load (~
2200 Kg) then the smallest moisture step is approx. 0.5%, which is too coarse for adequate
control.
If the same system was also fitted with a fine valve which had a flow rate of 1 L/sec with an
on/off time of 1 sec, then using this valve would permit water addition in steps of approx. 1 L or
0.05% giving good control.
US units:
If a 35ft
3
mixer has only a coarse valve and the water flow rate through the valve is 3 Gal/s with
an on/off cycle time of 1 sec, then water can only be added in 3 Gal steps. With a full load (~
4800 lbs) then the smallest moisture step is approx. 0.5%, which is too coarse for adequate
control.
If the same system was also fitted with a fine valve, which had a flow rate of 0.3Gal/sec with an
on/off time of 1 sec, then using this valve would permit water addition in steps of approx. 0.3Gal
or 0.05% giving good control.
Note that a higher water flow rate should normally allow a shorter mix cycle time for an efficient
mixer, provided the valve is fast enough to control the dose (on/off time is short). A slow flow
rate and slow valve will provide the same dosing accuracy but will take longer to complete a
mix.
It is also possible to add water too fast to a mixer, which creates a large ball of water which
moves around the mixer with the raw material rather than being mixed in. To compensate for
this, it is recommended to add water using a spray bar arrangement instead of from a single
outlet.
1.4
Leaking Water Valve Alarm
If the water flow meter outputs pulses when there are no valves open, this will trigger the
Leaking Water Valve Alarm.
2 Flow Measurement
2.1
Flow Meter
The flow meter should be specified to give a pulse rate of between 1 and 10 Hz. For a system
that is adding 60 litres in a 30 second dose, this would mean 2 litres per second, so a flow meter
giving 2 pulses per litre would be suitable (this would pulse 4 times per second).
2.2
Weighed Water
In Weighed Water Mode, a tank is filled to a known level (the high level point), and held ready
for the water addition phase. A weigh cell analogue input is used and the reading is zeroed
when the tank reaches the high level point. As the tank empties the weight of water that has
been dosed into the system can be read from the change in the input, and this can be used to
determine the quantity of water dosed.
2.3
Timed Mode
In Timed Mode, the water is added for a time specified in the recipe. The water pressure must
be constant for results in this mode to be repeatable. It is not recommended to design a system
to use this mode, but it can be useful to keep a plant running when there is a problem with the
flow meter.