This article tells mainly about the common Knowledge, questions and answers of PE irrigation pipes.

1. What are the components of PE irrigation pipes and what are the functions?
Polyethylene irrigation pipes are made by extrusion molding with polyethylene resin as the main raw material, adding a certain amount of heat stabilizers, colorants and processing aids. A heat stabilizer, also known as an antioxidant, is used to delay or inhibit the high-temperature oxidation of polyethylenes during the processing. A colorant which is also called a light stabilizer is generally black or blue for the polyethylene irrigation pipes' raw materials, which is mainly to prevent degradation and play a warning role. The role of processing aids is to improve the processing performance of polyethylenes.

2. What are the advantages of polyethylene pipes compared with metal pipes?
① Low energy consumption and light weight. They are recyclable. They belong to new products of environmental protection with long service life.
② The installation (connection) is reliable and convenient, which can meet the requirements of various special occasions. The requirements are low for the irrigation pipe base.
③ They have good flexibilities and strong resistances to the geological movement.
④ Excellent corrosion resistance.


3. What are the common polyethylene raw materials, like PE63, PE80 and PE100? What are the differences between them?

LPL, Mpa	The min required stregth MRS, Mpa	Number of material grades	Material name
6.3-7.99	6.3	63	PE63
8.00-9.99	8.0	80	PE80
10.00-11.19	10.0	100	PE100

4. What are the nominal pressure (PN), working pressure and design pressure? How are their relationships?
The nominal pressure refers to the working pressure of continuous water delivery at 20 ℃. If the water temperature is between 25 ℃ and 45 ℃, the working pressure should be corrected according to the different temperature drop coefficient. The working pressure refers to the maximum continuous movement pressure acting on the inner wall of irrigation pipes under normal working conditions, excluding the fluctuation pressure of water. The design pressure refers to the maximum instantaneous pressure of the pipeline system acting on the inner wall of irrigation pipes. Generally, the sum of working pressure and residual water hammer pressure is used. The relationships between them are as follows: nominal pressures ≥ working pressures. Design pressures = 1.5 × working pressures. The working pressure is calculated by the hydraulic calculation of pipe networks.

5. What is the water hammer pressure?
In the pipeline system, the instantaneous fluctuating pressure is caused by the sudden change of the water velocity.

6. What is SDR and what is its relationship with nominal pressure (PN)?
SDR is the standard size ratio, which is the ratio of the nominal outer diameter to nominal wall thickness, i.e. SDR = dn/en. The larger the SDR is, the lower the bearing capacity is. Conversely, the smaller the SDR is, the higher the pressure bearing capacity is. The relationship between SDR and PN of PE water supply pipelines is as follows:

Nominal pressure(MPA) of polyethylene (PE80) water supply pipelines

Standard Size ratio	SDR26	SDR21	SDR17	SDR13.6	SDR11
Nominal pressure	0.6	0.8	1.0	1.25	1.6

Nominal pressure (MPA) of polyethylene (PE100) water supply pipelines

Standard Size ratio	SDR33	SDR21	SDR17	SDR13.6	SDR11
Nominal pressure	0.4	0.6	0.8	1.0	1.25

7. What are the two common types of PE irrigation pipe connections?
The PE pipe connection mainly includes the following methods:
The hot melt connection includes: the hot melt butt joint connection, the hot melt socket connection and the hot melt saddle connection.
The electric fusion connection includes: electric fusion sleeve connection and electric melting saddle type connection.

8. Why and how to set exhaust valves in pipelines?
During the operation of the pipeline, the gas in the water will be accumulated at the high position of the pipeline, and even a gas resistance will be formed. When the water flow in the irrigation pipes fluctuates, an air bag will be formed on the bulge parts, which will be continuously compressed and expanded. After the gas is compressed, it will produce a great pressure, which is dozens or even hundreds of times higher than that of the water. At this time, the pipeline is easy to break, so the installation of exhaust valves is considered in the pipeline design. 

9. What types of raw materials are used for the water supply pipe production?
The raw materials for water supply pipe productions are PE80 and PE100.

10. Color classifications of polyethylene pipes?
PE water supply pipes: According to GB 13663, the polyethylene for water supply is specified as blue or black with blue strip.
PE polyethylene gas pipes: According to GB l5558.1, the color of polyethylene gas pipes is yellow or black with yellow strip.

11. The comparison between PE80 and PE100?
When the polyethylene is used for 50 years at 20 ℃ under long-term hydrostatic strength, the circumferential stress values of damaged materials are PE80 in the range of 8.0-9.99 MPa and PE100 in the range of 1.0-12.49 MPa.

The performance differenceS between them are as follows:
① The tensile property: The tensile yield strength of PE100 is 20% higher than that of PE80.
② The impact resistance: The impact resistance of PE100 is higher than that of PE80.
③ The bending property: The bending modulus of PE100 is 20% higher than that of PE80.
④ The bearing capacity: The pressure bearing capacity of PE100 is higher than that of PE80.
⑤ The crack growth resistance of PE100 is higher than that of PE80.