Download The TEC Interlock & Slow Control System

4 Question 3.3: Data requirements
Identity the data elements and logical data groupings that will be stored and processed by the control system.
Include archiving data requirements and sensitivity of data.
All available information must be logged and archived in a data base.
Easy access to all information is necessary, i.e. a user interface must be provided to browse the data base.
A tool to display archived data (e.g. temperature versus time) must be provided.
Data must be stored in common format (e.g. ascii, XML, or any well documented, easily readable binary format)
such that tools for further analysis can be developed by the users (e.g. with Root).
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Question 3.4: Functional requirements
Delineate, at a detailed level, control system requirements within the context of the processes it must support. This
is supported by a process model, which may be included, where all the actions to be performed by the process
control are to be specified. This section also includes the controls in terms of “IF .. THEN” events handling.
Under certain conditions, the interlock should take action, i.e.
a.) ramp down the bias voltage and/or send a signal to the low voltage control system to switch off the low
voltage;
and/or
b.) act on the cooling system, i.e. switch off or ramp down/up the cooling machine for systems 1 and 2; act on
the cold room for system 2; give feedback to the tracker cooling system or, if this is possible, close valves to
certain cooling loops for system 3;
c.) act on the dry gas flushing system.
In the following, a list of failures is given. For each failure, the cuts on which the interlock should react are listed
and the demanded reaction is outlined. The list is neither exhaustive nor final. In particular for the cuts, it is felt
that at the moment no numbers (temperatures, humidities, change rates) can be given. Clearly, some experience
with stability and uniformity of the temperature and humidity inside the tracker is necessary here. These numbers
shall anyway be easily changeable by the expert user.
Also the reaction time still has to be specified; it of course depends directly on the frequency of sensor readings
that can be implemented.
This discussion is divided into two parts: in section 5.1, it is assumed that the tracker relies on the hardware
interlock from the PLC. In section 5.2 then the same failures are listed for the case that a software interlock is
available as well.
5.1
Cases for a hardware interlock (PLC)
a.) Global cooling failure
– The PLC should get information from the chiller for system 1, the cold room and chiller for system 2,
and the global cooling system for system 3.
– Cut on the mean temperature T of the temperature sensors that are connected to the PLC, and the
change of the temperature d T /dt.
– Action: for the whole system (TEC), the LV should be switched off and the HV ramped down.
b.) Global stop of Nitrogen flow
– For system 3, the PLC should get information from the gas flushing system. In systems 1 and 2 the gas
flushing system will provide information as to whether the gas is flushing or not, as well as (for system
2) the dew point temperature for gas arriving at the TEC.
– Cut on the mean relative humidity H, and the change of the humidity d H /dt, as well as H and
dH/dt of the sensors nearest to the N 2 outlet.
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