CleaverBrooks Suggested Water Quality Level

ASME WATER QUALITY

Cleaver-Brooks requires industrial watertube boiler water quality to be maintained in strict accordance with ASME guidelines outlined below:

ASME Document No. CRTD (Vol. 34)

“Consensus On Operating Practices For the Control of Feedwater & Boiler Water Chemistry in Modern Industrial Boilers”

Table 1:

Suggested Water Chemistry Limits, Industrial Watertube, High Duty, Primary Fuel Fired, Drum Type

* as CaCO3

NS = not specified

ND = not detectable

VAM = Use only volatile alkaline materials upstream of attemperation water source. (10)

4.1.1- New Installations
A new hydronic system may contain various kinds of debris from the construction process, including weld slag, metal shavings, etc. The piping system should be thoroughly flushed with the boiler isolated from the system to ensure particulates do not enter the boiler.

During this and any subsequent cleaning or flushing of the system, take care to ensure that no debris enters the boiler during the cleaning process. Consult with the installation contractor and/or water treatment provider for filtration recommendations. A pre-start “boil out” of the vessel is not required; the interior boiler surfaces are cleaned following production of the pressure vessel.

  • With local heat fluxes >1.5 x 105 Btu/hr/ft2 (>473.2 kW/m2), use values for at least the next higher pressure range.
  • Minimum hydroxide alkalinity concentrations in boilers below 900 psig (6.21 MPa) must be individually specified by a qualified water treatment consultant with regard to silica solubility and other components of internal treatment. See section 6.6 of this document.
  • Maximum total alkalinity consistent with acceptable steam purity. If necessary, should override conductance as blowdown control parameter. If makeup is demineralized quality water and boiler operates at less than 1000 psig (6.89 MPa) drum pressure, the boiler water conductance should be that in table for 100-1500 psig (6.9-10.34 MPa) range. In this case, the necessary continuous blowdown will usually keep these parameters below the tabulated maximum values. Alkalinity values in excess of 10% of specific conductance values may cause foaming.
  • Not detectable in these cases refers to free sodium or potassium hydroxide alkalinity. Some small variable amount of total alkalinity will be present and measurable with the assumed congruent or coordinated phosphate-pH control or volatile treatment employed at these high pressure ranges.
  • Maximum values are often not achievable without exceeding maximum total alkalinity values, especially in boilers below 900 psig (6.21 MPa) with >20% makeup of water whose total alkalinity is >20% of TDS naturally or after pretreatment by lime-soda, or sodium cycle ion exchange softening. Actual permissible conductance values to achieve any desired steam purity must be established for each case by careful steam purity measurements. Relationship between conductance and steam purity is affected by too many variables to allow its reduction to a simple list of tabulated values.
  • Nonvolatile TOC is that organic carbon not intentionally added as part of the water treatment regime. See Section 6.4 of this document.
  • Boilers below 900 psig (6.21 MPa) with large furnaces, large steam release space, and internal chelant, polymer, and/or antifoam treatment can sometimes tolerate higher levels of feedwater impurities than those in the table and still achieve adequate deposition control and steam purity. Removal of these impurities by external pretreatment is always a more positive solution. Alternatives must be evaluated as to practicality and economics in each individual case.
  • Values in the table assume existence of a deaerator.
  • Achievable steam purity depends on many variables, including boiler water total alkalinity and specific and specific conductance as well as design of boiler steam drum internals and operating conditions [(Note 5)]. Since boilers in this category require a relatively high degree of steam purity for protection of the superheaters and turbines, more stringent steam purity requirements such as process steam restrictions on individual chemical species or restrictions more stringent than 0.1 ppm (mg/l) TDS turbine steam purity must be addressed specifically.
  • As a general rule, the requirements for attemperation spray water quality are the same as those for steam purity. In some cases boiler feedwater is suitable; however, frequently additional purification is required. In all cases the spray water should be obtained from a source that is free of deposit forming and corrosive chemicals such as sodium hydroxide, sodium sulfite, sodium phosphate, iron, and copper. The suggested limits for spray water quality are < 30 ppb (μg/l) TDS maximum, < 10 ppb (μg/l) Na maximum, < 20 ppb (μg/l) SiO2 maximum, and it should be essentially oxygen free.
  • Low pressure boilers frequently use feedwater that is suitable for use in higher pressure boilers. In these cases the boiler water chemistry limits should be based on the pressure range that is most consistent with the feedwater quality. See Sections 1 and 6.2 of this document regarding blowdown.
  • Conversion from ppm (mg/l) TDS values in the ABMA standards [12] used a factor of 0.65. See Section 6.7 of this document.

Boiler Inspection Checklist

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