What is a interlock bypass?

The function of bypassing is to suppress the interlock that would otherwise occur, so that even if an interlock takes place, there is no change in the output

Is there a difference between this and the situation where interlock automatically switches to manual mode when there is a production anomaly?

Bypassing involves masking the corresponding interlock input conditions to prevent unnecessary interlocks; it is mainly used when, under normal operating conditions of the process, an instrument failure causes the process parameters to approach the interlock values, and it is necessary to bypass that interlock circuit in order to repair the instrument. Some devices are equipped with a MOS (Maintenance Bypass Switch) to enable bypass operation in case of instrument failures or for preventive maintenance ； OOS (Process Bypass Switch) is used to implement bypassing when the process conditions are not met prior to startup. For example, if it is required that the reactor feed flow be at a certain level or higher, but no feed is available to the reactor before startup and thus the flow rate will be low, it is necessary to use the OOS function first. Some devices do not have a MOS setting; in such cases, a \"forced\" bypass operation must be carried out within the SIS system to ensure that the input conditions or output results remain unchanged. Such use is also subject to approval.

There is a difference. Well, although it’s all interlocking, as you just mentioned, it generally involves switching between control modes; you can still turn things on and off through the panel. In contrast, bypassing interlocking means that even if you try to turn things on and off manually via the panel, the equipment on site will not respond accordingly.

It can be understood that once a bypass is in place, even if your process parameters reach the interlock values, the interlock will not be triggered. Therefore, bypass operations must be handled with extreme caution

Bypass means removal, and there are odd explanations regarding interlock as well as manual and automatic modes.

An interlock bypass is a logic mechanism designed to prevent the interlocks from being triggered, either when instrument failures require maintenance (maintenance bypass) or when the unit cannot be started without bypassing the interlocks (operation bypass). The bypass can only be implemented after undergoing strict approval and evaluation

Learn a bit to gain a deeper understanding of bypasses.

Bypassing means cutting it out; by bypassing the interlock, it’s as if that interlock no longer exists, and the material flows only through the auxiliary line, just like in the case where it doesn’t flow through the main line.