Boiler Water Test


Corrosion and tube failure caused by water chemistry

Recommended ranges( Co-ordinated phosphate treatment for w/t boiler )

pH- 9.6 to 10.3
PO4- 4 to 20 ppm
N2H4- 0.01 to 0.03 ppm
TDS- < 150 ppm
Cond pH- 8.6 to 9.0
Cl- 20 ppm
O2- 10 ppb
Si- 10 ppb
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    Boiler water treatment

    Alkalinity

    Graph of corrosion and pH

    Treatment

    For pressures below 20 bar dissolved O2 in the feed does not cause any serious problems so long as the water is kept alkaline
    However cold feed should be avoided as this introduces large amounts of dissolved O2 are present, for pressures greater than 18.5 bar a dearator is recommended

    Feed Treatment Chemicals

    SodiumHydroxide
    CalciumBicarbonate (CaCO3 + Na2CO3)
    MagnesiumBicarbonate
    MagnesiumChloride.
    ..
    SodiumPhosphate
    CalciumCarbonate
    CalciumSulphate
    MagnesiumSulphate
    All in this column precipitated as hydroxide or phosphate based sludgesAll in this column form sodium salts which remain in solution
  2. Sodium Hydroxide




Oxygen Scavengers






Polymer Treatment

Polymer is a giant molecular built up by stringing together simple molecules

Amine treatment

Compounds containing nitrogen and hydrogen.

Neutralising amines

Hydrazine N2H4

Bramine ( cyclohexalamine )

(Bull & Roberts amine treatment)

Filming amines

Shows neutralising tendencies, main function however is to coat piping with a molecular water repellent protective film

Limits of density/pressure

Boiler presure/ chemical limits graph

Sludge conditioning agents



Treatment in boilers (non congruent)


LP tank blrs (<14 bar)

Na2CO3- precipitates salts, provides alkalinity
MgSO4- Sludge conditioners

Medium pressure tank blrs (<17.5 bar)

Na2CO3(3) + sodium phosphate(4) + sludge conditioners(1)

Medium to High pressure water tube <60 bar

Na2CO3 + Na2HPO4 +sludge conditioners

HP to UHP blrs (42 to 80 bar)

Due to level of decomposition of Na2CO3 . NaOH preferred for better controllability Na2HPO4

Permissible limits


ShellWTWTWTWTWT
TEST>PPM<17.5b<17,5b<32b<42b<60b<85b
HardnessCaCO3<=5<=5<=5<=1<=1<=1
P.alkCaCO3150-300150-300150-300100-15050-10050-80
T.D.S.CaCO3<=7000<=1000<=1000<=500<=500<=300
ClCaCO3<=1000<=300<=150<=100<=50<=30
PO4PO430-7030-7030-7030-5030-5020-30
N2H4N2H4------0.1 -1.00.1 - 1.00.1 - 1.0
SO3SO350-10050-10050-10020-50----
SiO2SiO2----------<=6.0
FeFe----------<=0.05
CuCu----------<=0.02
pHpH10.5-1110.5-1110.5-1110.5-1110.5-1110.3-11
Limits for feed water
ClCL<=10<=5<=1.0<=1.0<=1.0<=1.0
O2O2--------<=0.006<=0.003<=0.015<=0.01
NH3NH3----------------------<=0.5
FeFe-----------------<=0.01<=0.01
CuCu-----------------<=0.01<=0.01
pHpH------------8.5-9.28.5-9.28.5-9.2