Operation - LPG Loading Application Overview
Fusion4 MSC-L
Part No.: 4418309_Rev09
5 - 60
Installation & Operation Manual
Honeywell
The “Maximum limit point” is the point where “back pressure control”
starts throttling down flow rate. This point is above the “Minimum limit
point” and it can be adjusted via “Pressure control range factor”
parameter:
Maximum limit point = Minimum limit point * (1.0 + Pressure control
range factor)
NOTE: If the product vapour pressure (required for back
pressure control) cannot be determined for some
reason, for example in case of ‘Calculated’ vapour
pressure configuration and VCF calculations raising
exception, the flow rate target will be adjusted to zero
for safety reasons.
Back pressure control is implemented by applying a 'Setpoint
Adjustment Factor' (calculated) to the product flow rate setpoint. When
target setpoint is switched and if back pressure control is active, the
effective setpoint will be gradually changing (converging) from previous
value to a new value during the configured 'Pressure control ramp time'
interval, therefore smoothing out flow/pressure dynamics. An example
of Load Profile showing ‘ramping’ up when back pressure control is
active is shown in the figure below.
FIGURE 5-25
Load Profile showing ‘ramping’ up when back pressure control is active
For safety reasons, Fusion4 MSC-L features a number of alarms.
Relevant alarms can be configured and triggered if the flow rate is
reduced below meter’s “Minimum linear flow rate”. There are also
configurable pressure alarms that warn you about dropping pressure
conditions. MSC-L devices also support configurable pressure alarm
hysteresis in order to avoid oscillation of an alarm around the alarm
threshold.