What does the diagram in HG/T20505-2014 represent?
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I’ve never been able to figure out what TZY means in Figure 6.3.1 on page 89 of HG/T20505-2014. What is the purpose of TZY-400, and what does the 2003 in the corner represent?
TZY-400: T stands for temperature, that is, the parameter being measured (triggered) is temperature； Z is an adjective that indicates the temperature in the SIS system; together, they denote the temperature of the safety instrument system ； Y here represents the operation ； 2oo3 means taking 2 out of 3, that is, selecting two of the three temperatures being measured. It is considered true only if any two of the three temperatures are true.
Thank you for the explanation. I would like to ask whether there are any provisions in HG20505 regarding this model 2003. I have 5 high-level tanks, with a level gauge installed in each of them. One pipeline is used to supply liquid to all 5 tanks, and there is a shut-off valve installed on this main pipeline. The requirement is that whenever the level in any one of the tanks reaches a certain threshold, the shut-off valve should activate and stop the supply of liquid. Does this mean that only one tank at a time can be considered, and therefore the code 1005 should be used?
This post was last edited by myface on 2021-9-14 08:45. The 3 and 2 in 3 out of 2 refer to the same measurement value, which is done to increase reliability. Out of the three measurement values, two values are selected according to certain rules as the accurate ones for evaluation. It doesn’t refer to the five measurement points here. All five of these values can be used; it’s just that in terms of the interlock action logic, they are connected in an or relationship. Such specific logical relationships are generally not shown on PID diagrams.
This is a redundancy issue in instrument testing; for important parameters such as temperature and pH value, or those in environments where measurement results are prone to interference, triple redundancy should be employed, with a two-out-of-three voting system used for parameter control or output.
Is it 2003 or 2oo3? Should there be a zero in the middle, or is it a capital O? Or was it printed incorrectly – should it be a lowercase o?
2oo3: 2 out of 3; the middle character is the letter o, not the number 0.
TZY-400A/B are solenoid valves for the pneumatic pipeline of control valves, used for interlock purposes; a loss of air pressure causes the control valve to open fully