CALORIMETERS An instrument for determining the percentage of moisture in steam is termed a calorimeter, two well known types being the throttling and separating calorimeters. The former receives steam at boiler pressure and allows it to expand to approximately atmospheric pressure, causing a condition of super heat. Neglecting radiation, the heat in the steam at boiler pressure will be represented in that at atmospheric pressure.
The separating calorimeter depends for its operation on changing the direction of the steam entering the calorimeter, causing the moisture, which is heavier than the steam, to be thrown out, due to inertia. The moisture thus separated is measured, as is also the remaining steam, which is condensed for this purpose, and the relation between the two is the indication desired.
The throttling calorimeter is accurate only when the percentage of moisture does not exceed about 3 %. A simple construction of this instrument can easily and quickly be made in the pipe shop, as shown in the following sketch.
The illustration explains itself. The W' nipple "g" is the sampling pipe; it should be short and should screw well into the pipe containing live steam, the moisture in which is to be measured. The best
results are obtained when that part of the sampling pipe projecting into the main steam line is well per forated by holes, the end being plugged. There should be a globe valve between the main steam line and the calorimeter.
The cap over the end of the sampling tube contains a IA" drilled hole, "o," as shown; on one side of this hole the steam will be at boiler pressure and on the calorimeter side • its pressure will be very nearly atmospheric, as shown in inches of water by the water gauge "b." The thermometer "q" should read to about F. for ordinary cases, and should rest on a small piece of waste at the bottom of the thermometer well; this well should be filled with cylinder oil. The nipple "e" should be about x io," and open at the bottom, as shown.
Allow the instrument to warm up thoroughly before taking readings, opening valve on sampling line slowly for this purpose.