From practice

Boiler tubes are damaged by pitting corrosion

  • Dosing of oxygen scavenger is insufficient
  • Low temperature in feedwater tank - thermic deaeration does not work well
  • Oxygen scavenger is inconvenient for the system
  • Oxygen scavenger is already old
  • Aerated or non-functional dosing of chemicals
  • Pulse watermeter does not work. Dosing pump is connected to it.
  • Control unit of dosing to system is fault

Boiler tubes are scaled, fair colour

  • Ion-exchanger (Reverse osmosis) does not work
  • Quality of condensate is low and parameters of boiler feed water worsens
  • Condensate can be worsen either resprays or it is polluted during road by damaged interchanger from which condensate receives raw water, or other substance from production
  • Low or zero concentration of phosphates or another scale inhibitor or isn´t dosed at all
  • Inconvenient scale inhibitor is used for this type of boiler water
  • Aerated or non-functional dosing of chemicals
  • Pulse water meter does not work. Dosing pump is connected to it.
  • Control unit of dosing to system is fault

Boiler is full of sludges, colour is red

  • Probably to many phosphates is dosed into boiler feed water
  • Condensate worsens quality of boiler feed water. Hardness comes to system and and it leads to phosphates sludge creation.
  • Boiler water is thickening or blow-down is too low and sludge stay in boiler

  • Operation of blow-down does not work sufficiently or automatic blow-down is set up badly
  • Control unit of dosing to system is fault

kaly

Boiler after half-year polymeric continual cleaning, sludge is almost gone and it stays only protective phosphate layer

Boiler carryover

  • Blow-down is too low
  • Bad quality of condensate can be caused by carryover. Another problem is increasing risk of clogging boiler thanks to shoddy boiler feed water althoughion-exchanger in supplemental water works well
  • Increasing fuel consumption of boiler as a result of shoddy boiler feed water and thereby low cycles of concentration in boiler water
  • Boiler water is thickening or blow-down is too low and sludges stay in boiler
  • Operation of blow-down does not work sufficiently or automatic blow-down is set up badly
  • Pulse water meter does not work. Dosing pump is connected to it
  • Control unit of dosing to system is fault

Condensate is yellow colored , red or contains black sediments

  • Condensate pipeline is affected by corrosion
  • Except food production system should be treated by volatile amines
  • Chemicals for protection of condensate pipeline increase condesate´s pH around 9 also they passivate an iron surface and create protective layer

Steam generator is damaged by pitting corrosion

  • Dosing of oxygen scavenger is insufficient
  • Dosing of oxygen scavenger is sufficient however reaction without catalyzer is too slow for elimination. Inconvenient oxygen scavenger is used for the device
  • Temperature in boiler feed tank is too low
  • Pump of oxygen scavenger is synchronised with pump of feed water to boiler and it is not given sufficient period for chemical reaction to oxygen´s elimination
  • Because of incrusts on tubes
  • Aerated or non-functional dosing pump of chemicals
  • Pulsa watermeter do not work. dosing pump is connected to it.
  • Control unit of dosing to system is fault

Steam generator is scaled

  • It is neccesary to find if deposits contain mainly phosphate or calcium carbonate
  • Firstly too large amount of phosphate is dosed at low quality of feed water. Phosphate sludge is created
  • Secondaly too low amount of phosphates or another scale inhibitor is dosed and it is not sufficient to hardness elimination, which remains behind ion-exchanger and create the scale in the coil
  • Ionexchanger (Reverse osmosis) does not work well
  • Ion-exchanger (Reverse osmosis) works but the parameters of condensate are poor and it worsens parameters of boiler feed water
  • System can be clog by iron compounds, which come from condensate´s pipeline or corroded supply tank
  • Aerated or non-functional dosing pump of chemicals
  • Pulse watermeter does not work. Dosing pump is connected to it.
  • Control unit of dosing to system is fault
  • Ideal for steam producers is fully polymeric technology of water treatment without sludge creation. Thanks to small average of screw feeder minimizes the risk of clogging or blockage even with temporary worsening quality of boiler feed water because of ion-exchanger fault.

Condenser is scaled

  • Scale inhibitor is not applied to system or it is dosed in low concentration.
  • Thickening of cooling water is too high and LSI of the water system has tendency to scale formation
  • Ion exchanger does not work correctly.
  • When acid is dosed for modification of pH, maybe probe for measuring pH does not work
  • Parameters of hardness dosing water changed against original project Pulsating watermeter works badly. Dosing inhibitor is connected to watermeter or
  • pump does not work.
  • System is too thickened because of incorrectly setup the automatic blow-down
  • Control unit of dosing to system is fault

 

vodnikamen

Typical scale on condenser. On exposed parts is obvious corrosion as a result of unsuitable treament by sulphuric acid

Condenser is corroded

  • Condenser was cleaned chemically after unsuitable treatment
  • Dosing of sulphuric acid for pH treament is irregular. Probe of pH works badly or dosing of acid is too high.
  • Water source with high content of chlorides and sulphates is used. It create corrosion during thickening although LSI has a positive valued
  • Chlorides in cooling water come from source and adding of hypochlorites together allowed high chloride concentration and then water is corrosive
  • Source with high content of iron is used. It precipitates in tubes
  • Condenser is treated unsuitable chemically
  • Thanks to too high or too low pH of cooling water zinc layer dissolve and iron corrodes
  • Tower is treated bybad biocide, there is a corrosion in system because of present biofilm
  • Control unit of dosing to system is fault

szk1

Strong corroded condenser

ozvjpz

Protective layer of zinc is damaged.

smpo

The same place after passivation and suitable permanent anti-corrosion protection.

Condenser is damaged by white corrosion (protective zinc layer diluted)

  • pH of system water is too low or too high
  • pH usually should be from 7 to 8,5, depending on requirements of manufacturer
  • Dosing of sulphuric acid for pH treament do not work correctly
  • Control unit of dosing to system is fault

bilakoroze

White corrosion
“White corrosion is defined as fast creating of unprotected areas zinc carbonate on the surface of galvanized steel”. These sediments show as spots of white powder and they are considered a byproduct of zinc corrosion. These areas are porous and support creation of continous corrosion of non-passive galvanized areas. This type of corrosion outweighs on evaporative cooling devices. It should be noted that not all white deposits that appear are caused by white corrosion. Consequently, content of inorganic sediments must be determined necessarily

dok

Well treated condenser


Condenser is full of  biofilm

  • Insufficient biological treatment
  • Aerated pump of sodium hypochlorite
  • Unsuitable biocide is used
  • Control unit of dosing to system is fault

High consumption of water

  • Current supplier sets too low thickening treatment. It is possible to hold clean system and consumption of chemicals is higher too. However it has huge costs for water
  • Current supplier used chemicals, which are not able to hold hardnees of water at i higher concentration and put ignorance of the tower´s owner
  • Opportunity to reduce consumption of water if pH treatment is not used.
  • Opportunity to reduce consumption of water because ion-exchanger is not used.
  • Automatic blow-down works badly
  • System has not automatic blow down

Tower is full of scale

  • The same dosing of scale inhibitor is not applicable to the system or low concentration is dosed
  • Thickening of cooling water is too high and LSI of the system thanks to it is high that responds creation ofscale.
  • Ion- exchanger doesn´t work correctly. It softs make-up water insufficiently
  • When acid is dosed for modification of pH, maybe probe for measuring pH doesn´t work
  • Parameters of hardness of make-up water changed against original project and this is not measured regularly
  • Puls watermeter works badly. Dosing inhibitor is connected to water hydrometer or pump does not work.
  • System is to thickened because of incorrectly set up of automatic blow-down
  • Fault is on control unit of dosing to system???

Tower carries  corrosion deposits

  • Refrigerating water is turbid or contains increasing concentration of iron (if we calculate ratio of make-up water and its thickening)
  • Too soft or osmotic water with low thickening is used
  • Water source with high content of chlorides and sulphates is used. It create corrosion during thickening although LSI has a positive value
  • Source with high content of iron is used. It precipitates in a system.
  • Tower is treated chemically unsuitable
  • If sulfuric acid is dosed for treatment pH either once or long-term it leads to excessive reduction of water system pH. After it is strogly corrosive
  • Tower is treated biocide badly there is a corrosion in system because of present biofilm
  • on Control unit of dosing to system is fault

korozeveze

There is a picture from pipeline of refrigerating water. You can see deposits which are corrosive.

Tower is full of  biological biofilm

  • Insufficient biological treatment
  • Air in the pump of sodium hypochlorite
  • Unsuitable biocide is used
  • Control unit of dosing to system is fault

zelen

Slime at the bottom of micro-tower

High consumption of water

  • Current supplier sets too low thickening treatment. It is possible to hold clean system and consumption of chemicals is higher too. However it has huge costs for water
  • Current supplier used chemicals, which are not able to hold hardnees of water at higher concentration and put ignorance of the tower´s owner
  • Automatic blow-down works badly
  • System has not automatic blow down
  • System has not ion-exchanger

System contents more metals, for example Fe and Cu, Zn or Al

  • System is threatened by a galvanic corrosion

  • Important damage threatens of colorful metal´s parts and their alloys (cooper, brass) and corrosion of system iron parts too.

  • It proves expressive increasing content of dissolved Cu and other colorful metals in system water.

  • Treatment by chemicals based on azole is necesarry. Common anti-corrosion chemicals don´t work.

  • Regular treatment is necesarry by biocide, ideally by nonoxidizing biocide

 

   Fe Al  Zn  Cu influencing metals
Fe  O B
Al A O A C
Zn C B O C
Cu  O

Influenced metal
(water trickles)

     

A – influencing adversely
B – influencing mildly
C – influencing strongly
O – without influence

Galvanic corrosion

It arises by joining two dissimilar metals and their exposure to the corrosive enviroment. Nobler metal (cathode) corrodes slower than it would corrode itself. Less noble metal (anode) on the contrary corrodes faster than it isn´t connect conductively with second. This phenomenon is used in practice for cathodic protection of anode sacrificed. In our case, it is completely undesirable phenomenon

 

Non-softened water is used

  • System is threatened to scale forming.

  • Low flow threatens, low efficiency of cooling to the complete destruction of equipment.

  • Acidic cleaning can be inevitable, but it is always a significant risk of damage to the iron parts of the system.

  • According to the temperature in the system and content of hardness to the supplemental water suffices either regular treatment with the help of dispersant scale, or it is necessary to treat the water by using of cation ion-exchanger

 

 

vkvt

There is a scale in pipe of untreated system. Evidently there are vestiges of corrosion under deposits, that means you can´t rely on anti-corrosion protection using the scale there is rarely corrosion completely without control and opportunity of treatment under its.

 

Completely softened water or osmotic water is used

  • System is threatened by corrosion of iron parts

  • It can prove yellowing, turbidity or redness of water system.

  • Water can be clear if it is reguraly exchange. After there is a higher danger that risk will be underestimated by service because water looks clearly.

  • It is often necessary in connection with other parameters of the supplemental water "cut" to reduce its corrosion.

  • Treatment by anti-corrosion chemicals is necesarry

  • Nowdayds the most effective chemicals are based on molybdenum and silicates supplemented by azoles for present protection of colorful metals.

  • If nitrites are used like a catcher of oxygen, oxidizing biocide can’tusn´t be use together.

Corrosion

koroze

Corrosion is spontaneous, gradual excitement of metal or metals by chemical or electrochemical reaction with the environment. It can pass off take in the atmosphere or other gases, in water and other liquids, soils and various chemical substances that are in contact with the material. This excitement can prove differently; from changes in appearance to a complete breakdown of integrity.

Corrosion is caused by electrochemical processes. The main factor of corrosion is atmospheric oxygen, respectively. hydroxide group (OH), followed by anions, which arised from acids (CO32-, Cl-, NO2-, SO42-, etc.) Hydrogen ions of acids are replaced with metal ions to produce the salts.

Biocide treatment isn´t practised regurally

  • System is threatened by corrosion of iron parts and grow of biofilm.

  • Surface of system proves like a smooth, slimy which are under the water. We can try a bath with reserve water.

  • Water can be pure if it is often exchanged. Usually water can be greenish or yellowish to reddish because of corrosion under biofilm´s places.

  • Regular biocide treatment is necesarry. If the system wasn´t treat for a long time it would be needful intensive cleaning from corrosion and biological deposits. This cleaning is possible do during operation but with caution.

Unsuitable biocide is used

  • In spite of biocide treatment system is full of biofilm and biological deposits

  • System water is colored by dissolved iron into yellowish or reddish.

  • It´s necessary to check all parameters and put on biocide treatment, which correspond to existing conditions.

  • Very effective sodium hypochlorite can be unsuitable in some cases. It affects strong corrosion.

  • On the contrary nonoxidative biocides don´t have to be always effective or wrong type of biocide is chosen because of parameters of the water system.

biocid

Comparision of water from sort with water from system affects by corrosion due the insufficient biocide treatment.

Biological (organic) pollution is caused especially by bacteria, eventually blue-green algae or algae depends on the type of system.
Because of it is necessary to cultivate and identify which types of microorganisms in a system dominate and by this put on a biocide protection. Generally always effective, sodium hypochlorite can be unsuitable for the system because of its considerable corrosion, especially where isn´t frequent replacement of the water. Amount of chloride ions is carrying into system, and it is really dangerous for iron systems. For service is often confusing that system can be also affected even it is completely closed and only water is supplemented to its. In closed systems there are ideal conditions for biological growth thanks to optimum temperature of water, eventually thanks to present substances, which are food for the organisms so they can reproduce.

System is treated by unsuitable chemicals

  • High pressure on low price of treatment leads to hire a firm without sufficient experience eventually a firm without suitable chemicals in its portfolio.

  • The most common mistake is treatment by the same chemicals, which are used in opened cooling systems or steam boilers.

  • They are not allowed to protect system for a long time against corrosion, which is higher risk of this treatment.

  • Water is usually turbid and is colored in yellow and red if it isn´t exchanged regularly.

  • System is fauled by scale and other deposits. Supplier often apologizes that treatment of system won´t be better or oxygen treatment is a common part of service.

np

 

An extreme example of closed loop treats by unsuitable chemicals. System is affected by galvanic and general corrosion and currently excessive amount of microorganisms was found and they accelerate the process of corrosion.

Watermeter supplemental water is missing of or it is not monitored

  • In the system there are the water losses due by leaks or defects which can remain undetected for a long time.

  • This leads to increased payment for water or scale formation because of increasing amount of hardness.

  • If the water is softened, the system can be threaten by corrosion, which is masked by the fact that water is periodically rotated to losses, which reduces the effective amount of dissolved iron in the system water - water looks clear, even if the system is highly corrosive.

vodomer

Finding the place, where water is lost can be a hard peanut. Cracked pipes or faulty seals don´t have to be the main problem. Human factor is good to be checked too. An extreme case happened in a factory, where the softened water from the system is  used for car wash of employees. Watermeter after installation wasn´t allowed turn off and culprits were quickly discovered.

 

Nitrites are used like a  oxygen scavengers

  • Pitting corrosion threatens in system water when we don´t stand required concentration of oxygen scavengers.

  • Nitrites are delecious food for microorganisms and unsuitable biocide treatment causes that is not possible to dose them sufficiently and speed of corrosion strongly rises.

dusicnany

Typical picture of pitting corrosion

Najdete nás

  • Starobělská 1063/13
    Ostrava – Zábřeh
    Česká republika 700 30
  • +420 702 181 700
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