-
E-mail
2803218312@qq.com
-
Phone
18166600153
-
Address
Room 2804-2805, 28th Floor, T3 Building, Qidi Center, No. 67 Keji 2nd Road, High tech Zone, Xi'an City, Shaanxi Province
Xi'an Yingrun Environmental Protection Technology Group Co., Ltd
Water quality testing of heating hot water boilers: core parameters and maintenance strategies
Date: 2025-12-15Read: 2
Heating hot water boiler is an important core equipment in modern building heating systems. Its long-term stable operation is not only related to heating efficiency, but also directly affects energy efficiency, equipment lifespan, and even operational safety. However, many people may overlook a key factor: boiler water quality. Poor water quality is the main culprit that leads to boiler scaling, corrosion, decreased heat transfer efficiency, and even safety accidents. Therefore, regular and scientific testing and management of the water quality of heating hot water boilers is the cornerstone to ensure the efficient and safe operation of the heating system. So, what specific parameter indicators need to be tested? This requires us to have a deep understanding of the impact of relevant national standards and water quality on boiler operation.
What are the key parameters that need to be tested for water supply?
Supply water, also commonly known as feedwater, is a water source that is continuously replenished during boiler operation. The quality of its water directly determines the foundation of the internal water environment of the boiler. According to the national standard GB/T 1576-2018 Industrial Boiler Water Quality, the following parameters must be strictly tested and controlled for the supply water of heating hot water boilers:
1. Hardness: Why is it the primary concern?
Hardness is an indicator of the total amount of calcium and magnesium ions in water. These ions are highly prone to decompose and form scale in the high-temperature and high-pressure environment of the boiler, and adhere to the heating surface. The thermal conductivity of scale is extremely low, only 1/100 to 1/200 of that of steel, which means that even if a thin layer of scale is formed, it will significantly reduce heat transfer efficiency, leading to increased fuel consumption and higher operating costs. More seriously, scale can also cause metal overheating and even lead to pipe burst accidents. According to the GB/T 1576-2018 standard, for industrial boilers with a rated outlet steam pressure less than 3.8 MPa, the total hardness of the feedwater should be strictly controlled. For example, for hot water boilers, the total hardness of the feedwater is usually required to be no higher than 0.6 mmol/L.
2. pH value: How does pH affect boiler safety?
The pH value reflects the acidity and alkalinity of the water body. The low pH value (acidic) of boiler feedwater can lead to metal corrosion of the boiler, especially acidic corrosion, which can accelerate equipment wear and shorten boiler life. However, a high pH value (alkaline) may cause caustic embrittlement, damage metal grain boundaries, and also threaten boiler safety. The ideal pH value of the make-up water should be maintained between 7.0 and 9.0 to ensure neutral or weakly alkaline water quality and effectively inhibit the occurrence of corrosion.
3. Turbidity: What are the hazards of suspended solids in water?
Turbidity refers to the measurement of the degree of light scattering and absorption by suspended solids in water. Excessive turbidity in the supply water indicates the presence of a large amount of suspended impurities such as sediment, colloids, and microorganisms. After these impurities enter the boiler, they not only deposit on the heating surface to form scale, but also block the pipes, affect water circulation, and even form sludge inside the boiler, leading to local overheating. Therefore, the turbidity of the supply water should be as low as possible, usually requiring no more than 5 NTU.
4. Iron content: Where do iron ions come from and what are their hazards?
The iron in the supply water mainly comes from the corrosion of the water source itself or the water pipeline. After entering the boiler, iron ions undergo hydrolysis at high temperatures, resulting in the precipitation of iron hydroxide and the formation of hard iron scale, which adheres to the heating surface and also reduces heat transfer efficiency and causes metal corrosion. The national standard also has clear restrictions on the iron content in the supply water, generally requiring no more than 0.3 mg/L.
5. Dissolved oxygen: How do invisible killers corrode boilers?
Dissolved oxygen is the oxygen dissolved in water. It is an 'invisible killer' of boiler metal corrosion. Oxygen is corrosive to carbon steel at high temperatures and can undergo electrochemical reactions with boiler metal to form iron oxide, leading to pitting and overall corrosion, posing a serious threat to the integrity of boiler walls. Therefore, before the feedwater enters the boiler, the dissolved oxygen content must be reduced through deoxygenation equipment, usually requiring no more than 0.1 mg/L. For high parameter boilers, even lower requirements are required, such as no more than 0.05 mg/L.
What are the key parameters that need to be tested for boiling water?
Boiler water refers to the water circulating inside the boiler, and its water quality directly reflects the operating environment and water treatment effect inside the boiler. Unlike supply water, boiler water undergoes a series of physical and chemical changes under high temperature and pressure, so its detection parameters and control standards are also different. According to GB/T 1576-2018 Industrial Boiler Water Quality and actual operating experience, the following parameters are the focus of boiler water testing:
1. pH value: How to maintain the balance of acidity and alkalinity in pot water?
The pH value of boiler water is the core indicator for maintaining the stability of the internal water chemical environment of the boiler. A reasonable pH range (usually between 10.0 and 12.0) can effectively inhibit metal corrosion and promote the softening and precipitation of scale forming substances, making it easier to remove pollutants. If the pH value of the boiler water is too low, it will exacerbate acidic corrosion; If it is too high, it may lead to caustic embrittlement and foaming. Therefore, it is crucial to accurately control the pH value of the boiler water by adding chemicals such as phosphate and sodium hydroxide.
2. Phosphate radical: How to effectively prevent scaling?
Phosphate radical (PO ₄³ ⁻) is a commonly used anti scaling agent in boiler water treatment. It reacts with calcium and magnesium ions in water to produce calcium phosphate and magnesium phosphate precipitates that are easy to slag, thereby preventing hardness scaling. The concentration of phosphate ions in the boiler water needs to be maintained within a certain range, usually 5-10 mg/L. If it is too low, the anti scaling effect will be poor, while if it is too high, it may lead to phosphate scaling or waste of chemicals. Regular monitoring of phosphate content is key to ensuring the effectiveness of water treatment in the furnace.
3. Iron: What do iron ions in boiling water mean?
The iron ions in boiler water mainly come from the corrosion products of the boiler body and pipelines. A high content of iron ions indicates serious corrosion problems inside the boiler. These iron ions can form secondary scale on the heating surface, affecting heat transfer efficiency and even causing local overheating. Therefore, the iron content in the boiler water should be strictly controlled, generally not exceeding 0.3 mg/L. Continuous monitoring of iron content helps to detect and solve corrosion problems in a timely manner.
4. Oil: What impact does oil pollution have on boiler operation?
The oil stains in the boiler water mainly come from lubricating oil leakage, condensed water with oil, etc. After entering the boiler, oil stains will form an oil film on the water surface, hindering the normal release of steam and causing bubbling in the boiler water. In severe cases, it can cause steam water azeotropy and affect steam quality. In addition, oil stains can also adhere to the heating surface, forming oil deposits, reducing heat transfer efficiency, and even causing metal overheating. Therefore, the oil content in the boiler water should be as low as possible, usually not exceeding 2 mg/L.
5. Phenolphthalein alkalinity: How to evaluate the alkalinity of boiler water?
Phenolphthalein alkalinity (P alkalinity) is an indicator of the alkalinity of hydroxides and carbonates in boiler water, reflecting the effective alkalinity of the boiler water. Maintaining appropriate phenolphthalein alkalinity is crucial for inhibiting corrosion and promoting scale softening. Low phenolphthalein alkalinity may lead to acidic corrosion, while high alkalinity may cause caustic embrittlement. According to the type and operating parameters of the boiler, the phenolphthalein alkalinity is usually controlled within a certain range. For example, for a hot water boiler, the phenolphthalein alkalinity can be controlled between 14-18 mmol/L.
6. Dissolved oxygen: Why is oxygen in boiler water a hidden danger?
Although the feedwater has undergone deoxygenation treatment, a small amount of dissolved oxygen may still enter the boiler. In the high-temperature environment inside the boiler, dissolved oxygen accelerates the corrosion of metals, especially pitting corrosion. Therefore, the dissolved oxygen content in the boiler water also needs to be strictly controlled, generally not exceeding 0.05 mg/L. Chemical deoxygenation by adding chemicals (such as sodium sulfite) inside the furnace is an effective means of maintaining low dissolved oxygen levels in the boiler water.
Why is it necessary to conduct regular water quality testing?
Regular and professional testing of the water quality of heating hot water boilers is not an optional additional burden, but a necessary guarantee to ensure the safe, economical, and efficient operation of the boiler system. Neglecting water quality management may not be apparent in the short term, but the long-term accumulated harm will be enormous.
1. Extend the service life of the boiler:
Scale and corrosion are the two major killers of boiler lifespan. The formation of scale can cause metal to overheat, leading to a decrease in strength, and even deformation, bulging, and pipe bursting. Corrosion will cause thinning of the boiler wall and perforation leakage. Regular monitoring of water quality parameters can detect water quality abnormalities in a timely manner and take corresponding treatment measures, such as adjusting dosage and discharging, effectively controlling scaling and corrosion, significantly extending the service life of boilers, and reducing the frequency and cost of equipment replacement.
2. Improve energy utilization efficiency:
The presence of scale can seriously hinder heat transfer. Research has shown that when the fouling thickness on the heating surface reaches 1 millimeter, fuel consumption will increase by about 10%This means that poor water quality directly leads to significant energy waste. By precisely controlling water quality and keeping the heating surface clean, thermal efficiency can be improved, fuel consumption can be reduced, and energy conservation and emission reduction can be achieved.
3. Ensure safe operation:
Poor water quality is one of the important causes of boiler accidents. Metal overheating caused by scaling, leakage and even explosion caused by corrosion can result in serious casualties and property damage. Strictly following national standards for water quality testing and control is the key to preventing such accidents from occurring. For example, according to the Regulations on Safety Supervision of Special Equipment, boiler users must conduct daily supervision and management of boiler water quality, and regularly conduct water quality inspections.
4. Reduce operation and maintenance costs:
The scaling and corrosion caused by water quality issues will increase the frequency and difficulty of boiler cleaning and maintenance. For example, chemical cleaning of scale is not only costly, but also causes certain damage to the boiler body. Through daily water quality testing and treatment, these expensive maintenance tasks can be effectively reduced, lowering overall operating costs.
List of hazards of boiler water quality parameters exceeding the standard
In order to better understand the potential hazards of exceeding various water quality parameters, the following table summarizes them:
| parameter indicators | Excessive hazards | Typical data (taking hot water boilers as an example) |
| Supply water | ||
| hardness | Scaling, decreased heat transfer efficiency, metal overheating, increased risk of tube bursting | >0.6 mmol/L |
| PH value | Acidic corrosion (too low), caustic embrittlement (too high) | <7.0 or>9.0 |
| turbidity | Mud deposition, pipeline blockage, local overheating | >5 NTU |
| iron | Iron scale formation, decreased heat transfer efficiency, and intensified corrosion | >0.3 mg/L |
| dissolved oxygen | Oxygen corrosion, pitting corrosion, perforation leakage | >0.1 mg/L |
| Boiling water | ||
| PH value | Acidic corrosion (too low), caustic embrittlement, foaming (too high) | <10.0 or>12.0 |
| phosphate radical | Phosphate scaling (too high), poor anti scaling effect (too low) | <5 mg/L or>10 mg/L |
| iron | Corrosion intensifies, forming secondary scale | >0.3 mg/L |
| oil | Bubbling, azeotropic boiling of soda water, formation of oil stains, and decreased heat transfer efficiency | >2 mg/L |
| phenolphthalein alkalinity | Acidic corrosion (too low), caustic embrittlement (too high) | <14 mmol/L or>18 mmol/L |
| dissolved oxygen | Oxygen corrosion, pitting corrosion, perforation leakage | >0.05 mg/L |
How to effectively conduct water quality testing and management?
Effective boiler water quality testing and management is a systematic project that involves not only measuring a few parameters, but also the entire process from water source assessment, water treatment plan design, daily monitoring, abnormal handling to regular maintenance. Professional boiler water quality analysis instruments, such as the ERUN-ST seriesLaboratory desktop boiler water quality analyzerAccording to national standards such as GB/T 1576-2018 Industrial Boiler Water Quality, turbidity, hardness pH、 Accurate detection of various parameters such as conductivity, dissolved oxygen, oil, iron, phosphate, sulfite, chloride ions, etc. provides scientific basis for boiler water quality management. In addition, establishing a sound water quality management system, equipping professional water quality testing personnel, and regularly inspecting and maintaining water treatment equipment are key to ensuring the long-term stable operation of heating hot water boilers.
By strictly monitoring and scientifically regulating the key parameters of the supply water and boiler water, we can not only effectively prevent common problems such as boiler scaling and corrosion, but also significantly improve the operating efficiency of the boiler, extend the service life of equipment, and ultimately achieve safe, economical, and environmentally friendly operation of the heating system. Water quality management is an important part of the operation of heating and hot water boilers, and deserves more attention and professional expertise.