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Why does vacuum in steam condenser reduce or drop??

  1-High exhaust temperature: Vacuum drops or maintains at lower side due to high exhaust steam temperature flow into steam condenser. This high exhaust temperature is mainly due to 1-Operation of Turbine at lower loads 2-More clearance in labyrinth seals 3-Not operating exhaust hood sprays 4-More load on condenser 5-Breaking of ejector U loop 2-Low circulating cooling water flow Vacuum in condenser reduces due to inadequate cooling water flow through steam condenser. This is mainly due to; 1-Problems associated with pumps 2-Air pockets in pipe line 3-Leakages in cooling water line 4-Stuck of discharge valve of pump 3-High cooling water temperature at condenser inlet Higher cooling water temperature at condenser inlet results into reduction of vacuum due to poor heat transfer from steam to water 4-Poor heat transfer in condenser Very less or poor heat transfer in steam condenser reduces vacuum to very low level resulting into high exhaust temperature &am

40- thumb rules/standards you must know in water treatment plant


1-Clarifier (HRSCC) outlet pH is 1 to 1.5 units lesser than inlet pH or out let pH is 10 to 15% lesser than inlet pH
2-Clarifier outlet water conductivity increases by 115 to 125% than its inlet water conductivity
3-Hardness of water at clarifier outlet decreases slightly (1 to 3 ppm) than its inlet water
4-Losses in clarifier = Inlet water X 2%
5-Detention time in clarifier =The time it takes for a drop of water to travel from inlet to outlet
Detention time = Clarifier tank volume M3 / Flow rate M3/day
Actually clarifiers are designed for detention time for 3 to 4 hours. If clarifier inlet flow increases detention time reduces & vice versa
6-For reverse osmosis
  • Permeate water pH=Inlet water pH X 80-85%
  • Permeate water conductivity =Inlet water conductivity X 5-15%
  • Reject water pH =Inlet water pH X 105 to 110%
  • Reject water conductivity = Inlet water conductivity X 325 to 350%
7-Pressure drop in RO cartridge filter will be 0.1 to 0.2 kg/cm2
Water treatment plant chemicals & their functions
8-RO membrane pores opening will be 0.0001 microns
9-UF membranes pores opening will be 0.01 to 0.1 microns
10-Ro plant recovery rate = (Feed water flow-Reject water flow) X 100 / Feed water
11-Salt passage in RO = Concentration in permeate water X 100 / Concentration in feed water
12-Salt rejection in RO = (1-Salt passage) X 100
13-In a RO plant reaction time for chemicals is minimum 15-20 seconds, so dosing taps should be at least 20 meter before the RO unit (RO inlet line)
14-For SAC: Outlet water pH = Inlet water pH X 70-75%
15-For SAC: Outlet water conductivity = Inlet water conductivity X 130-150%
16-For SBA: Outlet water pH = Inlet water pH X 140-150%
17-Feed water or Boiler water TDS = Conductivity X 50-60%
18-Standard pressure drop in DM plant vessels (SAC, SBA, MB etc) is 0.4 to 0.6 kg/cm2
19-Pressure drop in UF membranes is 0.1 to 0.3 kg/cm2
20-Whatman paper required for SDI is of cellulose nitrate membrane having pore size 0.45 microns & 47 mm diameter
21-Colloidal silica is in un-dissolved form & non reactive, it is removed in clarifier
22-Reactive silica is in dissolved form, is removed in RO, SBA & MB
23-A change of 1 pH value represents the change of 10 times in relative acidity or alkalinity.
For example: pH 4 is 10 times acidic than pH 5
24-Higher pH of water causes scaling & lower pH causes corrosion
25-Acids & alkalis have tendencies of increasing or decreasing the conductivity of water
For example: Water of pH 10 has more conductivity than that of pH 7
26-In DM plant SBA is always kept after SAC:
The cat ion resin is usually located before the anion resin. If the water contains any hardness traces, then it reacts with OH- of anion resin forming Hydroxide. And hydroxide has less solubility; it precipitates in the alkali environment.
27-For DM plant if DM plant Degasser is provided if inlet water has bicarbonates > 150 ppm, if it is less then there is no necessary of degasser tower.
28-On every 1 degree rise in water temperature its conductivity increases by 4 to 5 micS/cm
29-M alkalinity should be less than 20% of TDS
30-Silica in drum water = 0.4 X OH alkalinity
31-2 X P-M = 0 or negative, indicates no hardness in water
32-Conductivity = 6 X PO4 in drum water
50-Selected QnA for WTP operators & Chemists
33-Standard parameters of water in steam drum at various operating pressure
Sl No.
Parameter
UOM
P = up to 35 Kg/cm2
P=35-45 kg/cm2
P = 45-67 Kg/cm2
P =67-100 kg/cm2
P = >100 kg/cm2
1
pH in drum

9.5-10.2
9.5-10.2
9.5-10.2
9.5-9.8
9.5-9.8
2
Conductivity in drum
MicS/cm
500
250
150
100
50
3
TDS in drum
ppm
250
125
75
50
25
4
Hardness in drum
ppm
Nil
Nil
N
N
N
5
Silica in drum
ppm
<15
<10
<5
<1
<0.6
6
Chloride in drum
ppm
Nil
Nil
Nil
Nil
Nil
7
Oil & Grease in drum
ppm
Nil
Nil
Nil
Nil
Nil
8
Hydrazine (N2H4) in feed water
ppm
0.01-0.2
0.01-0.2
0.01-0.2
0.01-0.2
0.01-0.1
8
Residual phosphate in drum
ppm
18-20
15-18
10-15
6-10
5-7

34-Standard parameters of feed water/Condensate water

Sl No.
Parameters
UOM
Values
1
pH

8.5-8.8
2
Conductivity
MicS/cm
3-5
3
TDS
ppm
1.5-2
4
Hardness
ppm
Nil
5
Silica
ppm
0.02
6
Chloride
ppm
Nil
7
Oil & Grease
ppm
Nil

Also read Power plant thumb rules



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  1. That was a really good blog, the information you mentioned in your post is really good and useful. I like your blog please share more information with us. Water treatment San Antonio

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