High oxygen content alarm value and high-high alarm value
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Under vacuum conditions, the internal oxygen content is measured. The process temperature is 170 degrees, and the lower explosion limit is 1.81% (at a temperature of 93 degrees). What are the alarm values and high-alarm settings for high oxygen content?
When designing this device, this key parameter must be included in the process package; why not refer to the data from that process package? The alarm points are set based on changes in the composition of the process medium; there are no ad-hoc settings for such things – this is a matter related to safety. Do you think subjective judgment can be relied on in this regard?
The foreigners specified 50% of the lower explosion limit; we have set it at 0.9% at present, but the plant shuts down automatically even with slight fluctuations in the readings.
The alarm value is not an interlock value; it can be set according to actual conditions. What is the purpose of setting it? Intervene manually to restore the parameters to a normal level, leaving sufficient margin and time. So the margin can be increased further, especially for the H in early warning; if \"there is even a slight fluctuation in the instrument, the system should trigger an automatic shutdown.\" The note indicates that a 0.9% margin is insufficient, and manual intervention is too late. It needs to be set based on the actual conditions and the specific parameters of the target. A larger margin can be used at first; once an alarm is triggered, manual intervention should be carried out immediately to make adjustments. After doing this a few times, it will be possible to determine roughly the value of H for which early warning is necessary. Additionally, more effort needs to be put into control and parameter adjustment.