Application of 304 Stainless Pipe in Drinking Water Pipe
Article 5.7.6 of my country’s “Code for Design of Building Water Supply and Drainage” (GB50015-2003) clearly states that drinking water pipes should be made of thin-walled stainless steel pipes, thin-walled copper pipes, and high-quality plastics that are resistant to corrosion, have smooth inner surfaces and meet food-grade sanitation requirements. Tube and so on.
304 stainless steel is a universal stainless steel material. The chemical grade of 304 stainless steel is 06Cr19Ni10, which contains 19% chromium and 8-10% nickel. The anti-rust performance of 304 stainless steel is stronger than that of 200 series stainless steel materials. High-temperature resistance is also better, and the general use temperature limit is less than 650°C.
Therefore, 304 stainless steel is widely used in life, such as some high-end stainless steel tableware, stainless steel drinking water pipes, and outdoor stainless steel railings. 304 stainless steel is a nationally recognized food-grade stainless steel.
The 304 stainless steel pipe that meets the national standard has a dense passivation oxide film on the surface, so it has high corrosion resistance, and the film can be automatically repaired by oxygen in the atmosphere or water after the film is damaged. Therefore, 304 stainless pipes can basically adapt to various water quality including the use of soft water and has a wide range of applications.
304 stainless steel has excellent corrosion resistance and good resistance to intergranular corrosion. For oxidizing acids, it is found in the experiment that 304 stainless steel has strong corrosion resistance in nitric acid with a concentration of ≤65% and a temperature of ≤100°C. It also has good corrosion resistance to alkaline solutions and most organic and inorganic acids. At the same time, it can withstand high flow rates, even if the flow rate reaches 30m/s,
Its annual corrosion rate is still within 0.003mm/year. However, the contact between stainless steel and iron and other metals with a potential difference must be insulated to prevent electrochemical corrosion.
The current applications in developed countries are as follows:
1. Japan’s tap water supply pipes have entered a standardized track
Before 1955, galvanized pipes were commonly used in tap water supply pipes in Tokyo, Japan. From 1955 to 1980, plastic pipes and steel-plastic composite pipes were widely used. Although the water quality and leakage problems of galvanized pipes have been partially solved, the water leakage phenomenon of Tokyo’s water supply pipe network is still very serious. The problem is gradually reflected in that plastic pipes and steel-plastic composite pipes cannot meet the basic requirements of environmental protection.
The Tokyo Water Supply Bureau has conducted a large number of experiments on water leakage for more than 10 years. According to analysis, 60.2% of water leakage is caused by insufficient water pipe material strength and external forces, 24.5% of water leakage is caused by unreasonable pipe joint design, 8.0 % Of the water leakage is caused by the unreasonable design of the pipeline circuit due to the excessive expansion of plastics.
For this reason, the Japan Waterworks Association recommends improving water pipe materials and connection methods. Beginning in May 1980, all water supply pipes with diameters below 50mm used stainless steel pipes, pipe joints, elbows, and faucets from the auxiliary water supply trunk line to the water meter. As a result, the problem of water leakage was fundamentally solved. In 1982, Japan developed the stainless steel bellows. The pipe users can easily bend to any angle, greatly reducing the number of joints or even completely eliminating the joints, saving installation time and cost.
Today, in Tokyo, Japan, the penetration rate of stainless steel water supply pipes has reached almost 100%. All residential areas have installed stainless steel pipes, which greatly improve water quality and enhance earthquake resistance. Moreover, a large number of dual-purpose water bridges (both as water pipes and as passage bridges) are also widely constructed of 304 or 316 stainless steel. Since 1983, nearly 3,000 stainless steel water bridges have been built.
Japan has used stainless steel pipes for 40 years. Now stainless steel pipes have been recognized by the Japanese as the “best drinking water content material”.
2. The U.S. government promotes the development of stainless steel water pipes
The use of stainless steel pipes in the United States began in the 1960s and prevailed in the 1990s.
The latest 2003 edition of the American International Standards Committee’s water pipe and residential standards again include this content, indicating that the use of stainless steel water pipes has been officially approved by the United States. Other countries such as Health Canada, the Dutch Health Appraisal Board, and the World Health Organization have also confirmed this standard. More and more countries now require that the pipes and system components of drinking water systems must meet the above standards as the basis for health assurance. The first batch of materials that meet the requirements of this standard is 304, 304L, 316, and 316L stainless steel.
In the United States, stainless steel has been successfully used in more than 100 drinking water treatment plants and delivery systems. New York’s water supply system has adopted stainless steel since the 1960s. The original drinking water distribution system in New York City was aging and outdated and could not meet the demand. Based on a 15-year evaluation of alternative materials, the authorities adopted large-diameter risers and other pipelines for urban water pipelines on a large scale in 1993. 304L stainless steel, its goal is to make the system live up to 100 years.
Stainless steel water pipes have also been used in the water supply transformation of the Washington area on a large scale. The main water supply pipeline of the water supply system in the Ford Stadium, a large-scale new stadium in Detroit, which cost 300 million, includes the direct drinking water pipelines of various sales outlets, all of which are made of 304 stainless steel. In addition, stainless steel pipes have become standard materials for more than 1,600 urban sewage treatment plants built in the United States over the past 30 years.
3. European stainless steel water pipes are gradually becoming popular
Since 1995, Italian cities have generally adopted a technology that does not require trenching to replace the main water pipelines with stainless steel pipelines. Experience has shown that stainless steel pipelines are corrosion-resistant, high-strength can withstand ground subsidence and earthquakes, and have a lifespan of at least 70 years. Substitute pipes such as plastic pipes are more economical.
After 10 years of experimentation in Karls Koga, Sweden, the ductile iron and PVC buried water supply main pipelines have all been replaced with 316 stainless steel pipelines. British hospitals (Scotland) used copper water pipes in the past, but the soft water quality in Scotland caused corrosion and failure of the copper water pipes, causing serious water leakage.
The government spent a huge amount of money to study the causes and solutions of the failure, and later all the hot and cold water pipes were replaced with stainless steel water pipes and joints. After more than ten years of use, the hot and cold water pipes were disassembled to investigate the use of stainless steel pipes and joints. The results showed that the stainless steel pipes and joints were in excellent condition and there was no sign of corrosion.