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Utilitiesman Basic Volume 02 - Manual for electric, plumbing, water and other utilities | Next
Methods of Treatment |
1. GASKET
6. PLUNGER SEATS.
11. FILTER NIPPLE.
2. TOP CAP HOLDING SCREW.
7. CO2 SCALE.
12. CONNECTION SAMPLING TUBE
3. TOP CAP
8 SCALE LOCKlNG SCREW.
TO FILTER NIPPLE.
4. PLUNGER CAP
9. RUBBER ASPIRATOR BULB
13 FILTER TUBE.
5. CONNECTOR TIP.
10. BOTTOM OF ANALYZER.
14. CONNECTION TUBING TO
UTB2f0127
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
1-25
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