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9.3 Pressure loss of internal nozzles
There are two nozzles in MV. Carrier gas is supplied to the secondary side through these
two nozzles. Therefore, the carrier gas flow rate is restricted by the nozzles. The
nozzles having a diameter of 0.4 mm reduce the flow rate to 1.4 LM at an N
2
supply pressure
of 0.1 MPa (G), 2.2 LM at 0.2 MPa (G) and 3 LM at 0.3 MPa (G). To increase the diluted
gas flow rate higher than these values, it is necessary to dilute the gas in the piping on the
secondary side of MV or replace the MV nozzles with those having a larger diameter (0.7 or
1mm).
9.4 Valve travel for set temperature
The travel of the control valve used in MV changes under the influence of the set
temperature of MV. Before shipment, we adjusted the valve travel and check for seat
leakage at the MV temperature at which the designated liquid material can be vaporized
under the specified conditions. Therefore, when using the equipment, keep the
temperature within the temperature specified by us
10
C. If the set temperature is lower
than the specified temperature, the valve travel will become larger to cause seat leakage.
On the contrary, if the set temperature is higher, the valve travel will decrease, the response
speed may lower, and the flow rate of the liquid material may be decreased.
9.5 Purging
procedures
When the piping is evacuated to purge the liquid material, if the piping is evacuated from the
secondary side through MV, it is evacuated through the control valve. Since the valve is a
throttle part and there are nozzles in the piping, the material may not be purged completely.
Therefore, for a material having an excessively low vapor pressure, it is recommended to
provide a branch line for evacuation on the piping for supplying the liquid material to MV and
evacuate the liquid supply piping together with the MV secondary side when purging the
material.
9.6 Temperature
control
When MV starts vaporization, the heat in MV is removed by the vaporization latent heat of
the liquid material. Fluctuation of MV temperature during vaporization affects the stability of
vaporization flow rate. Therefore, stable temperature control is required not only to
maintain the temperature when vaporization is not performed, but also to stabilize the
temperature during vaporization. Except when the temperature lowers at the beginning of
vaporization, the temperature fluctuation during vaporization must be within
1
C, and the
fluctuation period must be 30 seconds or more. Select temperature regulators in
consideration of the following points.
Control cycle : When using temperature regulators of voltage or contact output type,
select regulators having an output cycle of 1 second or less. For stable
control, current control type (power control type) temperature regulators
are recommended.
PID control : Use temperature regulators that are capable of PID control of heater
output. Use temperature regulators whose PID constants can be
automatically tuned.
9.7 Setting of pressure of liquid supply tank
When the liquid supply tank and MV differ in installation level, if the tank is installed at a
lower level, the supply pressure to MV is reduced owing to the weight of the liquid material.
When they are different in level, determine the drop of supply pressure caused by the
