Question regarding the claim that “the signal for a remote water level display device cannot be obtained from primary instruments”
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“The signal for a remote water level display device cannot be taken from the primary instrument. In boilers where the water level is monitored using such a remote display device, there should be two reliable remote water level display devices in the control room; moreover, it is necessary to ensure that one direct-reading water level gauge is functioning properly at all times during operation. ” The aforementioned sections are taken from the 1996 version of the Safety Inspection Regulations for Steam Boilers. Why can’t they be taken from the primary instruments? Then where does the remote water level signal come from? Also, what is a primary instrument?
In other words, one watch corresponds to one display device.
Primary instruments refer to those that are installed on-site and in direct contact with the process medium, such as Bourdon tube pressure gauges and glass tube level gauges. In other words, the signal point for the remote water level display device should be taken from another location within the boiler, rather than at the water level gauge. Once the water level gauge shows an incorrect water level, the remote water level display will also show the same incorrect level.