1. GASKET

2. TOP CAP HOLDING SCREW.

3. TOP CAP

4. PLUNGER CAP

5. CONNECTOR TIP.

6. PLUNGER SEATS.

7. CO₂ SCALE.

8 SCALE LOCKlNG SCREW.

9. RUBBER ASPIRATOR BULB

10. BOTTOM OF ANALYZER.

11. FILTER NIPPLE.

12. CONNECTION SAMPLING TUBE TO FILTER NIPPLE.

13 FILTER TUBE.

14. CONNECTION TUBING TO SAMPLING TUBE.

Figure 1-27. - CO₂ meter (analyzer).

water. This chemical treatment prolongs the useful life of the boiler and results in appreciable savings in fuel, since maximum heat transfer is possible with no scale deposits.

SCALE

Crystal clear water, satisfactory for domestic use, may contain enough scale-forming elements to render it harmful and dangerous in boilers. Two such scale-forming elements are precipitates of hardness and silica.

Scale deposited on the metal surfaces of boilers and auxiliary water heat exchange equipment consists largely of precipitates of the HARDNESS ingredients - calcium and magnesium and their compounds. Calcium sulfate scale is, next to silica, the most adherent and difficult to remove. Calcium and magnesium carbonates are the most common. Their removal requires tedious hand scraping and internal cleaning by power-driven wire brushes. When deposits are thick and hard, the more costly and hazardous method of inhibited acid cleaning must be used. Scale deposits are prevented by the following: removal of calcium and magnesium in the feedwater to the boiler (external treatment); chemical treatment of boiler water (phosphate, organic extracts, etc.); and changing scale-forming compounds to form soft nonadherent sludge instead of scale that can be easily removed from the boiler by blowdown (internal treatment).

SILICA in boiler feedwater precipitates and forms a hard, glossy coating on the internal surfaces. In the feedwater of high-pressure boilers, such as those used in electric generating plants, a certain amount of silica vaporizes under the influence of high pressure and temperature. The vapor is carried over with steam and silica deposits on the intermediate and low-pressure blading of turbines. In boilers operating in the range of 10- to 125-psig pressure, the silica problem is not so troublesome. When the water is low in hardness, contains phosphate that prevents calcium silicate scale