Questions about the draft guidelines for the installation of on-site safety monitoring equipment at major hazard sources (tank farms)?
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Draft Specification for the Installation of On-site Safety Monitoring Equipment in Sites with Major Hazard Sources (Tank Areas) 4.3.3 At least two levels of pressure alarms should be installed; the threshold for the first level alarm is set at the upper limit of the normal operating pressure, while the threshold for the second level is 80% of the container’s design pressure. The first-level alarm serves as an on-site alert and does not require reporting to the higher-level authorities or the **safety supervision or emergency response center. However, alarms at the second level and above must be reported in real time to the higher-level authorities or the **safety supervision or emergency response center. From the perspective of device design, this is problematic to understand! “Can “the first-stage alarm threshold is the upper limit of the normal operating pressure” be understood as meaning that the first-stage alarm threshold is the maximum operating pressure? In container design, the design pressure is generally set at 1.1 times the maximum operating pressure. Thus, if the maximum operating pressure is 1 MPa, then according to these standards, the alarm value for the first stage is 1 MPa, while the alarm value for the second stage is 1.1*1*0.8=0.88 MPa. Is the alarm value for the second stage lower than that of the first stage? But according to these specifications, should the secondary alarm threshold be higher than the primary alarm threshold? How to understand it?
The normal operating pressure is different from the maximum operating pressure; the latter refers to the highest value under abnormal conditions. For example, the design pressure for a liquefied petroleum gas tank is 17.6 kilograms, while the maximum operating pressure is 16 kilograms. The normal operating pressure is 6 kilograms, and in some cases it is only around 3 kilograms. As mentioned above, an alarm level 1 can be set at around 8 kilograms, and an alarm level 2 at 12.08 kilograms
If what was said above is true, the device may have already stopped working by the time a level 2 alarm is triggered! Since my design pressure is only 11 kilograms, the maximum allowable operating pressure for the equipment might be lower than the 12.08 kilograms mentioned above! When the pressure secondary alarm is triggered, the equipment has already failed, and the pressure alarm turns into an accident alarm!
Design pressure > Maximum operating pressure > Normal operating pressure. The design pressure is the allowable pressure for the material; exceeding this pressure can lead to an explosion at any time. The maximum operating pressure is the highest pressure at which a device or instrument can operate; exceeding this pressure will cause the instrument to fail and lose control, leading to accidents. The normal operating pressure is the pressure at the safe state.
The last edit to this post was made by lyhh9024 on 2010-3-17 at 06:04. There is a difference between the concept of normal operating pressure and maximum operating pressure. Different processes that use the same pressure vessels have different values set for normal operating pressure; however, the basic maximum operating pressure and the design pressure are the same
There is a difference between the normal operating pressure and the maximum operating pressure; LZ has confused these concepts
{:3_46:} The person above is right; the upper limit of work pressure is determined by the upper limit of your control parameters. You can’t exceed the upper limit of those control parameters, which in turn represents the upper limit of the equipment’s operational capacity
Citing post 1, in response to friends in posts 4, 5, 6, and 7: If the normal operating pressure is 0.9 MPa and the maximum operating pressure is 1 MPa, then according to the standards (draft for comments), the alarm setting for the first stage is 0.9 MPa, while the alarm setting for the second stage is 1 * 1.1 * 0.8 = 0.88 MPa. Is there any contradiction in this situation? Therefore, the question raised by the original poster does exist! Please ask the original poster to contact the relevant authorities!