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 Steel Pipe |
 Home>Products>Steel Pipe |
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| Construction of water supply and drainage pipes used | | |
| 1. Plastic Pipe |
Plastic tube is a synthetic resin additive made by melt molding the products. Additives are plasticizers, stabilizers, fillers, lubricants, colorants, UV absorbers, modifier.
Plastic pipe commonly used are: hard PVC pipe (PVC-U), high density polyethylene pipe (PE-HD), cross-linked polyethylene pipe (PE-X), random copolymer polypropylene tube (PP-R), Polybutylene pipe (PB), engineering plastics acrylonitrile - butadiene - styrene copolymer (ABS) and so on.
The composition of the raw materials of plastic pipe determines the characteristics of plastic pipe. The main advantages of plastic pipe:
(1). Chemical stability, free from environmental factors and medium components of pipe, good corrosion resistance.
(2). Small thermal conductivity, low thermal conductivity, thermal insulation, energy-saving effect is good.
(3). Hydraulic properties, pipe, smooth wall, the resistance coefficient is small and difficult to fouling, tube flow area does not change with time, channel blocking probability small.
(4). Relative to the metal pipe, density, light weight, transport, easy to install, flexible, simple and easy maintenance.
(5). May have a natural bent or cold performance, the coil supply means can be used to reduce the number of pipe joints.
The main disadvantages:
(1). Poor mechanical properties, impact resistance, poor, poor rigidity, straight sex was bad, and thus control the density of high cards and hanger.
(2). Retardant poor, most of the combustible plastics, pyrolysis and combustion, it releases toxic gases and smoke.
(3). Coefficient of thermal expansion, flexible compensation must be very stressed.
Therefore, in the promotion of plastic pipe, it is also a need to develop technologies to overcome its shortcomings.
1.1 Performance of Plastic Pipe
1.1.1 Physical Properties:
The physical properties of plastic pipe and plastic composite pipe, steel pipe, copper pipe is shown in table 1:
|
Unit
PVC-U
PE
PE-X
PP
PB
ABS
PAP
鋼
銅 |
Density
g/cm
1.50
0.95
0.95
0.90
0.93
1.02
7.85
8.89 |
Thermal conductivity
w/mk
0.16
0.48
0.40
0.24
0.22
0.26
0.45
50
400
|
Coefficient of thermal expansion
mm/m°C
0.07
0.22
0.15
0.16
0.13
0.11
0.36
0.012
0.018 |
Coefficient of thermal expansion
MPa
3000
600
600
900
350
2500
210000
110000 |
Tensile strength
MPa
40
25
>25
28
17
40
700
150 |
Hardness
R
120
70
100
60
230HB |
Temperature ° C
0-60
-60-60
-60-95
-20-95
-20-95
-20-80
-60-95 |
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| Note: PAP (PEX-AL-PEX), said plastic composite pipe, aluminum plastic composite pipe is crosslinked XPAP.
The physical properties of plastic pipe pipeline mode, use of compensation measures and pipe insulation and so on. Such as:
(1). PVC-U, PP, ABS, PAP relatively high mechanical properties, be regarded as "rigid control", install better tomorrow. On the contrary, PE, PE-X, PB as a "flexible tube" for Concealed.
(2). Plastic tubes and heat resistance temperature determines the PVC-U, PE, ABS, PAP only be used for cold water pipes, and PE-X, PP, PB, XPAP may act as a hot water pipe. When building a water supply system and hot and cold water pipes when the heat resistance of a uniform as a major target.
(3). Plastic tube for the high coefficient of thermal expansion, especially in the plastic pipe as a water pipe, with flexible interfaces, expansion joints or bends of various compensation measures such as more heat. Among them, PE, PP and other polyolefins most. If this is not the time construction and installation of adequate attention, and to take appropriate technical measures, is extremely vulnerable due to the interface of expansion joints and pull off the problem.
(4). Because of low thermal conductivity, thermal insulation performance of plastic pipes superior in turn can reduce the thickness of insulation or no insulation. When different between the plastic pipe insulation thermal conductivity of more than, but also with their respective wall thickness.
1.1.2 Pressure Performance:
Performance is concerned with the pressure in the plastic pipes under certain conditions, to withstand the internal pressure and the destruction of time under constant pressure. To determine the design parameters and related to the quality of the pipe evaluation and monitoring. General conduct two tests: hydraulic pressure test and long-term high-temperature hydraulic pressure test. The performance of various pipe pressure Table 2
|
Pipe Material
Working Pressure/MPa
Sample test pressure/MPa
Connector seal test/MPa
Burst pressure/MPa |
UPVC
1.6
42/h
De≤90，4．2PN
De＞90，3．36PN |
PEX
1.0/95℃
1.6/Room temperature
1.2
2.5
3.5
5.6 |
ABS
1.0
3.8/h
4～8
|
PB
1．6～2．5／ColdWater
1.0/Hot water
|
PP-R PP-C
2.0/Room temperature
0.6/75℃
20℃，11h，16MPa
80℃，48h，4.8MPa
80℃，170h，4.2MPa
|
HDPE
1.0/Hot water1.6/Cold water
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1.1.3 Health and Performance:
Physical health indicators. Where PE, PE-X, PP, PB and ABS easy to compliance. The PVC-U pipe should be used in the production of non-toxic PVC resin and stabilizers to meet health and hygiene performance requirements.
1.2 Application of Plastic Pipe for Water
A single structure, materials and performance of many different varieties. Common characteristics of plastic pipe water supply are listed below:
|
| Variety |
Advantages |
Disadvantages |
Connection |
| PVC-U |
Strong anti-corrosion, easy to glue, cheap, hard texture |
UPVC monomers and additives are leaking, does not apply to water transport; joint bonding technique for high, long curing time |
Bonding, thread |
HDPE |
Good toughness, good fatigue strength, resistance to temperature, good performance; lightweight, flexible and impact performance is good |
Welding power required; mechanical connection, connections large |
Squeeze clamp, hot melt together, fused together |
| PEX |
Good heat resistance, creep resistance, good |
Can only be used to connect metal parts; can not be recycled recycling |
Squeeze Clamp |
| PB |
Good heat resistance, good tensile strength, compressive strength, impact resistance, low creep, high flexibility |
till no PB resin raw materials, dependence on imports, high prices |
Squeeze clamp, hot melt together, fused together |
| PP-R |
Good heat resistance |
Under the same pressure and medium temperature conditions, the thickest wall
|
Melt together |
| ABS |
Strength, impact resistance |
Poor UV resistance, adhesive curing time longer |
Bonding, thread, fused together |
|
| General PVC pipe as low cost, without considering the water quality impacts, water supply systems are preferred in the cold water pipe, and when the temperature is high, can be used or cross-linked polyethylene pipes and polyethylene pipes, polypropylene pipes, polybutylene tube.
1.3 Application of plastic pipe drainage
Single material: PVC
Structure in various forms: core layer foam pipe and air wall pipe, spiral pipe, spiral core layer foam and air wall spiral.
The existence of some problems:
(1). Thermal expansion coefficient, need to set the expansion compensation device to solve.
(2). Stiffness of small, straight, poor management need to encrypt card, frame, hanger to solve.
(3). Poor heat resistance, softening temperature is low, should limit water temperature control and limit the use of space and distance to solve the heat source.
(4). Retardant poor, across the floor, the Master roof roof, firewall, pipe shaft lining department needs to set fire ring and fire sleeve to solve.
(5), poor resistance to mechanical impact, need to strengthen the construction technology and careful construction to resolve.
(6), poor sound insulation, plastic pipe noise is greater than cast iron pipe, pipeline installation and pipeline located near Ming bedroom, the problem is particularly prominent. Noise reduction methods to improve the sound insulation pipe material, core layer foam pipe blank wall pipe is developed based on this idea; noise of the other way is to change the flow conditions, spiral pipe is developed based on this idea of. The idea of combining two methods is foam core layer spiral coil and air-wall development.
Under the same conditions, different structural forms of plastic drainage pipe, the noise determination results:
General management> core layer foam pipe> empty wall pipe> Spiral
Application of plastic drainage tube drainage in the Place of the work carried out in cast iron pipe. Currently, plastic drainage pipe has a height of 100m in under construction for use in buildings, but very uneven progress in various areas. When the building height greater than, equal to 100m of high-rise buildings and not suitable for plastic drainage pipe of the occasion, cast iron drainage pipe can be used flexible earthquake.
2. Metal tubes
2.1 Galvanized steel
Galvanized steel pipe is not meant to replace metal pipes have been replaced, nor that galvanized steel water supply in the area of the building be replaced.
Galvanized steel as cheap, excellent performance, fire performance, long life, but also in the fire water supply system, particularly the application of automatic sprinkler system. And the plastic tube (pressure small) should not be in the Fire water supply system and life - fire, the production - a total system of fire application.
2.2 Copper
Metal pipe is the most dominant copper, brass applications longer, more advantages, pipes and fittings are complete, the interface methods varied, more applications in hot water pipe, the main problem is that the existing copper fold amount of easily exceeded.
2.3 Cast Iron Pipe
Cast iron pipe and pipe water supply is not easy compared to corrosion, low cost and good durability, suitable for burying. Drawback is crisp, the weight of large and small length. Connections commonly used socket connection.
Clamp-style cast iron pipes is building a new drainage pipe, 60's entered the international market, after decades of promotion and application, this pipe has been widely recognized by the international community. This pipe socket with a traditional style cast iron drain pipes have many advantages in comparison, is a replacement product, but because the pipe and fittings for relatively expensive, it has not been popular in the country to promote.
2.4 Other:
Stainless steel tube is also favored by engineers and technicians, are being reduced wall thickness from the lower prices set in order to facilitate promotion.
Aluminum alloy tube is introduced to the water supply and drainage sector of new varieties.
Nickel-plated steel and galvanized steel pipe is the nature of recent, and corrosion resistance far beyond the original galvanized steel pipe, coating the solution to reduce costs and pipe construction site of the fracture after nickel process, is expected to be adopted within a certain range.
Coated steel is promising in the metal pipe in a pipe, and pipe layout and installation, interface methods and the construction and installation are the same with galvanized steel pipe, this pipe is most likely to be accepted. Because of its thin coating, low price, most likely to be extended.
3. Composite pipe:
Complex including a lining of lead pipe, rubber lined pipe, glass pipe. Composite pipe mostly by working-level (which requires water corrosion), supporting layer, protective layer (requires corrosion-resistant) form.
Generally metal composite pipe for supporting material, lined with epoxy resin and cement based, it is characterized by light weight, smooth wall, low resistance, corrosion resistance performance is good; also to the support of high-strength soft metal, and non-metallic pipe internal and external sides, such as aluminum plastic composite pipe, which is characterized by corrosion and scaling pipeline wall will ensure that water quality; also have metal pipes in the medial and lateral non-metallic tube, such as plastic coated copper pipe, which is the use of plastic poor thermal conductivity from thermal insulation and protection.
According to the metal material can be divided into:
(1). Steel-plastic composite pipe
(2). Stainless steel - plastic composite pipe, plastic covered stainless steel
(3). Plastic coated copper pipe
(4). Aluminum-plastic composite pipe, aluminum plastic composite pipe cross-linking
(5) lined aluminum tube
It should be said composite pipe is the pipe diameter ≥ 300mm or more to the best sewer pipe. It combines a metal pipe strength, rigidity and non-metallic pipe corrosion advantages. But it is the slow development of a pipe. This is because: (1). Two pipes together higher than the price of a single pipe. (2). Two kinds of material difference between the larger coefficient of thermal expansion, such as the adhesive is not strong and the ambient temperature and medium temperature change has more intense, easily torn off, which led to lower quality.
Composite pipe connections should use cold, thermal processing methods likely to cause the plastic liner stretching, deformation or even melting. Generally threaded, ring, clamp and other connections.
As the composite pipe is still a new pipe, our country has not had a unified design, construction and acceptance. Design and construction workers are often applied to galvanized pipe design and construction process, so not to enumerate here.
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