Control and Compensating Pressure Tap Locations

The pressure-sensing tap must go all the way through the wall— metal skin and refractory. Flare the refractory opening into a cone so that crumbs of refractory and 

WHEN FURNACE IS NOT IS USE, remove this observation port and tie it to this tag. O CLEAN OUT hole through wall very well. 

Clean glass (both sides), leave tag attached, and REPLACE OBSERVATION PORT, hand tight. 

The elevation of the pressure-sensing tap does not necessarily have to be at the elevation desired for the neutral pressure plane. The most desirable height for the zero pressure plane may be at a point that turns out to be bad for good measurement, for example, below the hearth, at a level where scale might plug the pressure tap, or in a place where liquid metal may splash into the tap. In such cases, a very workable solution is to locate the sensor tap at a convenient higher position and then adjust the controller s setpoint in accordance with the correction for the rise in pressure for the chosen higher elevation from table 6.2. (See example 6.2.) 

TABLE 6.2 Draft or chimney effect at various furnace ieveis and temperatures 

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