hot  water  heaters.  Shore  water  is  usually  hard water  which  contains  high  concentrations  of dissolved  solids  and  silica.  Although  it  can  have either high or low pH, in a boiler, shore water usually causes high pH. High concentrations of dissolved solids lead to boiler water carryover with the steam. Silica may be deposited on the boiler watersides and in the steam system as it vaporizes. Water hardness leads to excessive usage of boiler water treatment chemicals which causes cor- rosion, scale, and sludge buildup. Excessively high pH  causes  caustic  embrittlement  and  subsequent erosion of boiler metal parts. Firetube and watertube auxiliary boilers are natural circulation boilers. The water treatment for natural circulation auxiliary boilers is main- tained in the same manner as the propulsion boiler water.  Section  21  of  Naval  Ships’  Technical Manual,  chapter 220, volume 2, describes this water treatment. The control parameters for aux- iliary  boiler  water  are  alkalinity,  phosphate,  and chloride. In auxiliary boilers, the alkalinity of the auxiliary  boiler  water  is  measured  instead  of  the pH because its higher alkalinity level can be more easily measured by the alkalinity test than by the pH  meter  test.  The  alkalinity  range  is  equivalent to a pH range of 11.0 to 11.3. The auxiliary boiler limits are given in table 7-1. The  same  treatment  chemicals,  trisodium phosphate  dodecahydrate  (TSP)  and  disodium phosphate anhydrous (DSP), are used for aux- iliary boiler water treatment except that a higher level   must   be   maintained   due   to   the   lower operating pressures. The TSP provides alkalin- ity  and  phosphate.  The  DSP  provides  additional Table 7-1.—Auxiliary Boiler Water Limits For Firetube and Natural  Circulation  Water  Tube  Auxiliary  Boilers Alkalinity: 1.0 - 2.0 epm (1.0 - 2.0 meq/L) Phosphate: 200 - 400 ppm (200 - 400 mg/L) Chloride: 10.0 epm (10.0 meq/L) maximum Chapter  7—AUXILIARY  MACHINERY phosphate  without  significantly  affecting  the alkalinity. Initial Treatment The boiler is initially half-filled with feedwater to  partially  dilute  the  treatment  chemicals  which must be added. The treatment chemicals are then added to bring the boiler water conditions to near the upper limits. The necessary amounts of treat- ment chemicals are weighed, dissolved in feed- water, and injected into the boiler. WARNING:  TSP  solutions  are  corrosive  and cause  burns  to  skin,  eyes,  and  body  tissues. Affected personnel should flush skin with cold water. If TSP or its solutions enter the eyes, flush with cold water and obtain immediate medical attention. TSP is added to bring the alkalinity to 2.0 equivalents per million (epm) (2.0 meq/L) and to provide some of the needed phosphate. DSP is added to bring the phosphate to 300 parts per million (ppm) (300 mg/L) and not to the upper limit of 400 ppm (400 mg/L). In order to deter- mine the amount of chemicals needed, the volume of water requiring chemical treatment must be known.  This  information  is  sometimes  available in the instruction manual for the boiler. If the weight of water at normal steaming level while steaming is given, divide the weight in pounds by 8.33 to determine volume in gallons. If the boiler weight data gives only the dry weight and the wet weight of the boiler, determine the boiler water chemical treatment volume as follows: 1.  Subtract  the  boiler  dry  weight  from  the boiler wet weight to obtain a weight of cold water in the boiler. 2. Divide the weight of cold boiler water in pounds  by  9.30  for  boilers  operating  at  125 pounds per square inch (psi) or 8.87 for boilers operating  at  35  psi  to  obtain  the  boiler  water volume,  in  gallons,  for  chemical  treatment.  This volume  times  the  initial  chemical  treatment  fac- tors (ounces per gallon) given in table 7-2 deter- mines the ounces of TSP and DSP required. Enter the volume to the nearest gallon and the calculated dosage  to  the  nearest  one-half  ounce  in  the appropriate columns. 7-9