K-Patents SeedMaster 2 - Manual (Page 18)

3 THE SEEDMASTER 2 CRYSTALLIZATION TRANSMITTER … 18
18
the refractometer has (depending on the model used) two, or only a single current output. It is possible to use
an independent temperature sensor and standard current transmitter to transmit temperature data to
SeedMaster 2 as well. SeedMaster 2 has 2 (optional) RTD Pt100 type (Resistance Temperature Detector)
inputs as well. In these cases the temperature sensor should be located as close to the refractometer sensor
head as possible in order to measure the same sample temperature. From time to time re-calibration of the
temperature transmitter is advised.
Temperature measured by the refractometer can be transmitted (together with concentration data) by using
digital data communication (COM1, COM2, COM3 and ETHERNET ports), too.
All data input versions listed with concentration data input (3.5.1) are available.
NOTE:
It is preferred to use temperature data measured by the refractometer.
3.5.3 Selecting the “THIRD INPUT” transmitter
Whenever available a “THIRD INPUT” transmitter should be used. If there are more than one available from
those already listed, massecuite density or solids content data are preferred. From these two the one offering
higher accuracy and stability should be used. Based on practical experience it is rather difficult to calibrate
and verify these devices. It is possible to make slight corrections in the data provided by them in SeedMaster
2 itself in order to achieve a better match with more accurate refractometer and laboratory data.
If stirrer motor data are used it is preferred to use motor power consumption (kW) data, because they better
reflect the mechanical power required to drive the stirrer (voltage fluctuations and the changing power factor
are also taken into account). As a last resort, motor current data can also be used.
NOTE:
The use of stirrer motor power or current consumption as “Third input” is limited to batch vacuum
pans operating without strike cut(s), that is without discharging some part of the massecuite before
the end of the strike. The trend of motor consumption data should look like one of those shown in
Fig. 7.5 or Fig. 7.6.
3.5.4 Using laboratory data instead of “THIRD INPUT”
It is always preferred to have on-line feedback (that is: on-line information from one of the instruments listed).
However, if there is no instrument available to use as “THIRD INPUT”, laboratory data on crystal content (%
by volume) at the end of a strike can be used with batch vacuum pan applications. In this case the instrument
carries out involved calculations in order to simulate the process of crystallization on-line. Based on
occasional crystal content data from the laboratory, the simulated process of crystallization is adapted by the
instrument using these data from the laboratory. All features of SeedMaster 2 are available.
3.5.5 Optional data input
An optional LEVEL transmitter can be connected to one of the analogue input channels of SeedMaster 2.
The level data may come from a PCS via digital communication, too. The use of level data is optional: if
available, they are used to refine some of the calculations and to implement a smooth transition from one
feed syrup to an other one, if feed syrups with different purities are used in the same batch strike. It can
.provide additional information on site for the pan operator, too. If there is no on-line data on level, instead of
level mean crystal size will be displayed on the Main Display.
3.6 Digital inputs
The 2 digital inputs (per pan) are typically contact (relay or switch) types. An “ACTIVE” digital input can be
configured either as an OPEN, or CLOSED relay (or switch) contact.
3.6.1 “STRIKE ACTIVE” input DIN1
SeedMaster 2 can be operated in “Stand-by”, or in “Active” mode (Fig. 3.4). In Stand-by mode it waits for the
start of a new strike (batch pans) and no calculations are performed. Displayed data might be not correct.
The Active mode should be evoked by the start of a new strike (feeding syrup in the pan begins), and should
usually end with the drop of the charge and motor switch OFF. In the time between two active strikes
(SeedMaster 2 in Stand-by mode) the pan is usually washed and is under normal pressure. Temperature and
concentration data can be quite far from their normal ranges.
Information on the “ACTIVE “status of a pan or crystallizer might come from 3 sources, namely:
•
from a relay or switch contact (digital input DIN1), or