I would like to ask what high alarm and very high alarm mean

High alarm and very high alarm refer to the situation where a monitored value exceeds a certain threshold, indicating that it has surpassed a higher warning threshold and an extremely high warning threshold, respectively. Generally, a high alarm indicates that the monitored value has reached the upper limit of the safety threshold, requiring attention and prompt action ； A high alarm level indicates that the monitored value has significantly exceeded the safety threshold, requiring immediate emergency actions to ensure safety. The meanings of high alarm and very high alarm are specified in relevant specifications and standards; for details, refer to the relevant monitoring and alarm standards. For example, in the oil and gas industry, high alarms and very high alarms are incorporated into various safety measures and emergency response plans to ensure the safety of equipment and personnel. .

When an electrical component fails and cannot operate properly, a high-high alarm or a low-low alarm is triggered, and the corresponding protection circuit is activated to prevent the equipment from being damaged.

It is an upper limit alarm within the range set for temperature variation (proposed by the process; usually, it triggers interlocking)

What is the interlock mechanism? Does it start automatically as soon as a high-level alarm is triggered?

This post was last edited by sun_fm on 2023-5-9 08:27. Before answering this question, let’s confirm a few points first: 1. Under what circumstances is it necessary to set up alarms? According to Chapter 9 of HGT20507, alarms should be installed for variables that affect production and safety; additionally, reference can be made to 4.1.6 of GB/T 50892-2013, which states that parameters affecting production safety should be equipped with alarms and/or safety interlock functions. Reference can also be made to clause 5.8.3.1(2) of GBT51273, which outlines the standards and process requirements regarding when two-level alarms are necessary; for example, GBT50493 requires two-level alarms for gases, while AQ 3036 specifies two-level alarms for temperature and pressure ； For alarms in actual process operations, just like setting an alarm clock, does one need to set two alarms for waking up? The same phone can have multiple alarms set up, each for different scenarios such as getting up, brushing teeth, eating, and going out. But with so many settings, isn’t it annoying? 3. Why are HH, H/L, and LL often seen in flowcharts? Generally, HH and LL are used for interlock purposes, but the instrument tag numbers in flowcharts usually do not indicate S. 4. The interlock is directly set to HH (interlock value); then why is H (prediction) also set? An interlock that provides no warnings or signs has a significant impact, and generally, if manual intervention is possible, the interlock function is not activated. A pre-alarm refers to setting an alarm point before the interlock alarm point for a certain interlock parameter, with an alarm being issued when this alarm point is reached. Interlock alarm refers to the alarm issued when an interlock action occurs. A pre-alarm is a warning to the operator that an interlock action is about to occur, and they should be prepared. After a pre-alarm occurs, an interlock action does not necessarily take place; only the possibility of such an action occurring exists. Pre-alarm provisions are mentioned in HTG20511, GBT50892, and GBT50770. As specified in 3.1.2 of HGT20511, alarms should be provided for the processes involved in interlocking, and pre-alarms are advisable.

It depends on the specific requirements of the process; the DCS interlock program can be implemented

Simply put: an alarm is triggered when the value is overreported, indicating the need for manual intervention； When the time is reached, the interlock activates the corresponding controller to directly cut off the fluid flow or shut down the machine, etc. In this case, there is no human intervention; it is the system that takes action automatically.

Alarms are issued through sensory signals such as sound and light to indicate that there are deviations in the production process； Interlocking is the automatic intervention by the system in the production process in case of an emergency ； These are two different concepts; an alarm does not necessarily trigger interlocking ； High/low alarms and high-high/low-low alarms are both types of alarms; typically, they represent different degrees of deviation from normal production conditions. Different alarm levels can be indicated by various sensory signals; for example, changes in color and flashing of production parameters indicate high/low alarms, while changes in color and flashing accompanied by sound (such as a siren) indicate very high/very low alarms. The diagram does not indicate whether interlock information is available, so it is impossible to determine.

From a process perspective, I believe that the operator responsible for high-level alarms can manually start or shut down the relevant automatic valves in the control room. High-high level alarms should interlock with those automatic valves to protect the equipment and other components.