In the past, the pipes used for water supply were mainly cast iron pipes. The outdoor mainly uses sand mold cast iron pipe, the interior uses galvanized cast iron pipe, and can be divided into cold (electric) galvanizing and hot galvanizing. China has stipulated that the sand-casting pipe fittings and cold-galvanized cast iron pipes will be eliminated on June 1, 2000, and the use of hot-dip cast iron pipes will be gradually restricted, and aluminum-plastic composite pipes and plastic pipes will be promoted. Therefore, there are three main types of pipelines currently in use. The first category is metal pipes, such as hot-dip cast iron pipes, steel pipes, stainless steel pipes, etc. The second category is plastic-plastic pipes, such as plastic-coated steel pipes and aluminum-plastic composite pipes. The third category is plastic pipes, such as PP-R (crosslinked polypropylene high density mesh engineering plastics).
The state also stipulates that all kinds of pipes and fittings involving drinking water pipelines must be approved by the health department before they can be sold.
Commonly used plastic code and meaning in water supply pipeline:
PP-R cross-linked polypropylene high-density mesh engineering plastic
PE high density polyethylene
PP polypropylene
PB polybutene
PEX cross-linked polyethylene
Comprehensive performance requirements for water supply pipelines:
As a water supply pipe, it is required to be hygienic, safe, energy-saving and convenient. Therefore, testing a pipeline should be investigated from four aspects. That is, hygiene: pipes and fittings must be free from any damage to the human body. Safety: It has sufficient strength and excellent mechanical properties as well as anti-aging and heat resistance. Energy saving: the inner wall is smooth, corrosion resistant, low in fluid resistance and good in heat preservation performance. Convenient: connection, construction is convenient, reliable, and has the possibility of promotion and use.
If the above four requirements are not met, it will damage the user's physical health and property safety.
Introduction to several water supply pipes:
1. Aluminum-plastic composite pipe
The aluminum-plastic composite pipe is the first water supply pipe to replace the cast iron pipe. The basic structure should be five layers, that is, plastic, hot melt adhesive, aluminum alloy, hot melt adhesive and plastic from the inside to the outside.
The aluminum-plastic composite pipe has good thermal insulation performance, and the inner and outer walls are not easy to corrode. Because the inner wall is smooth, the resistance to the fluid is small; and because it can be bent at will, the installation and construction are convenient. As a water supply pipe, the aluminum-plastic composite pipe has sufficient strength, but if the lateral force is too large, it will affect the strength, so it should be used for the construction of the pipe or buried in the wall, but it should not be buried in the ground. The connection of the aluminum-plastic composite pipe is ferrule type, so the first one in the construction is to pass the strict pressure test to check whether the connection is firm. The second is to prevent frequent vibration and loose the ferrule. Third, the length should be sufficient to install, so as not to pull off.
2, plastic copper tube
The plastic copper tube is made of pure copper (copper) and is covered with PE plastic. From the perspective of comprehensive performance, the plastic copper tube is slightly better than the aluminum-plastic composite tube. For example, the strength is better, the life is longer, and the heat resistance is better. However, the insulation performance is slightly worse.
Pure copper has a very high corrosion resistance. After a period of use, a layer of green oxide will appear on the inner surface. But it has little effect on the life, flow, and resistance to the fluid. The patina is not detrimental to human health and has a certain ability to kill bacteria.
The installation method of the plastic copper tube is ferrule type and welded type, and the welding type is more reliable.
Copper tube, stainless steel tube:
In addition to poor insulation performance, other types of pipes such as strength and life resistance to fluids are good, and should be used as cold water pipes. If used for hot water delivery, insulation jacket should be added. The connection method is mainly ferrule type, and the copper tube can also be welded.
Inner plastic galvanized cast iron pipe:
That is to say, a layer of plastic is placed on the inner wall of the ordinary galvanized pipe, so that it has the characteristics of corrosion resistance, small resistance and good heat preservation, and has the characteristics of high strength of the galvanized pipe itself. Most of these pipes are ribbed.
plastic pipe:
Plastic pipes can have sufficient strength, longevity, safety and hygiene as long as the materials are selected to meet the requirements of the standard. It is the best insulation performance of all pipes. The plastic pipe is hot-melt welded, and the reliability is high. As long as the construction is correct, the pipe welding at the normal pressure test will not leak and fall off.
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