What permanent markings must be on the exposed orifice plate indicator tab or nameplate?

• A. Orifice diameters and indication of the flow direction.
• B. The foam concentrate type and supplier name.
• C. The maximum system temperature and pressure.
• D. The model number and serial.

Answer: (A)

The key idea is that the orifice plate must carry the information critical to how the foam-water system will perform and be serviced. The exact size of the orifice diameter determines the flow restriction, which directly affects the proportioning of foam concentrate and the overall discharge characteristics. Knowing the flow direction is essential to install the plate correctly; installing it backward would change the discharge pattern and foam mix, compromising system performance. Other details like foam concentrate type or supplier, or system temperature/pressure and model/serial, belong on other labels or documentation, not on the plate itself. So, the permanent markings that matter for operation and maintenance are the orifice diameters and the flow direction.