GB/T 35355-2017 in English

Background of Standardization and Technical Evolution

This standard is formulated in accordance with GB/T1.1—2009 and is managed by the National Technical Committee for Standardization of Marine Ships. The main drafting units include Shanghai Waigaoqiao Shipbuilding Co., Ltd. and China Shipbuilding Industry Comprehensive Technology and Economic Research Institute. This standard is applicable to the determination of salt content in water used for marine equipment (such as boiler water, cooling water, domestic fresh water, etc.), and the determination range does not exceed $0.400\%$.

With the rapid development of the shipbuilding industry, the requirements for water quality are becoming increasingly stringent, especially the control of salt content in water used for marine equipment, which directly affects the life and operating efficiency of the equipment. This standard provides an accurate and highly operable method for determining salt content by combining the standard sodium chloride method with conductivity determination.

Requirements for reagents and instruments

Electronic analytical balance: The minimum graduation value is $0.0001~g$, used for accurate weighing of sodium chloride.

Conductivity meter: The measurement range is $0~μS·cm^{-1}~10,000~μS·cm^{-1}$, and it must have a temperature correction function.

pH acidity meter: The graduation value is $0.01~pH$ unit, used to measure the pH value of water samples.

Key reagents:

• Sodium chloride storage solution: 1mL contains $0.1~g$ sodium chloride
• $0.1~mol/L$ hydrochloric acid solution
• $0.1~mol/L$ sodium hydroxide solution

Analysis steps and quality control

According to the standard requirements, the salt conductivity ratio working curve must meet the correlation coefficient of not less than $0.99$. By preparing sodium chloride standard solutions of different concentrations, measuring their conductivity and pH value, and establishing the working curve.

Quality Control:

• Check the effectiveness of the method once a week or every two weeks
• Recovery range: $90~110\%$ (salt content <0.01); $95~105\%$ (salt content 0.01~0.4)
• Out-of-control handling: Analyze the cause and recheck

Implementation suggestions

To ensure the effective implementation of the standard:

1. Equipment calibration:Regularly calibrate the conductivity meter and pH acidity meter to ensure measurement accuracy.
2. Staff training:Conduct systematic training for operators, focusing on mastering the preparation of standard solutions and the establishment of working curves.
3. Quality monitoring:Establish a long-term quality control plan and regularly evaluate the accuracy of the measurement results.
4. Record management: Record sampling information, analysis steps and results in detail to facilitate traceability and review.