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Frequently Asked Questions (FAQs)

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Is elongation of PE pipes problematic?
No, various types of pipes undergo longitudinal expansion and contraction with temperature variations. This process should be understood to take necessary measures. The longitudinal expansion of PE pipes is calculated from the formula, 0.2 mm/m.K. It means an elongation of 0.2 mm per meter when temperature increases by 1 ̊C.
What is SDR?

Standard dimensional ratio (SRD) represents numerical naming of a pipe series where a proper rounded number is approximately equal to the ratio of nominal outer diameter (dn) to nominal wall thickness (en). See the national standard INSO 14427-1.

Do the surface scratches damage the pipe?
Scratches up to 10% of the pipe wall thickness are acceptable.
How should PE pipes be stored?

See the relevant instruction in P.E.S website.

Can adhesives be used to connect PE pipes?
No, PE pipes can be connected by butt fusion and electrofusion or mechanical fittings.
How PE pipelines are tested?
See the pressure test manual for PE pipelines in P.E.S website.
Are PE pipes resistant to water hammer and how they work compared to other pipes?

Due to flexibility, PE pipes are more resistant than other pipes to water hammer. PE pipes with SF=1.25 withstand up to 150% of nominal working pressure.

The pressure induced by water hammer at different velocities in different pipes:

 

PVC-U

DN 200  -  PN10

PE 225* 20.5

PN 12.5

GGG

DN 200 * 8

V= 0.5 m/s  Speed

1.45 bar

0.61 bar

5.99 bar

V= 1.0 m/s  Speed

2.90 bar

1.22 bar

11.98 bar

V= 1.5 m/s  Speed

4.36 bar

1.83  bar

17.98 bar
 
Pipes of what diameter can be shaped as coil?
According to PE100 Plus Association, PE pipes up to a diameter of 180 mm produced from PE100 raw materials can be shaped as coil. However, PE pipes up to a diameter of 110 mm are produced and packaged as coil. P.E.S is able to produced coil pipes up to a diameter of 125 mm.
Do PE pipes need cathodic protection?
No, PE pipes do not suffer from rusting by galvanization and thus do not need cathodic protection unlike metal pipes.
What is the internal roughness of PE pipes in terms of Hazen-Williams? How does it change over the years of operation compared to DI pipes?
The factor C for PE100 pipes equals 150. The internal roughness reported by manufacturers of DI pipes is 140. Most consultant engineers believe that the internal roughness of DI pipes is reduced to 120 and even 100 over the years. However, the internal roughness of HDPE pipes does not change due to lack of corrosion as pointed out in MSS Handbook by American Water and Wastewater Association (AWWA).
What are the minimum and maximum depths for placement of PE pipes?
The appropriate depth for placing PE pipes ranges from 1 to 7 m taking into account SDR, soil type, soil impaction and permissible out of roundness. P.E.S is ready to provide specialized consulting services regarding these calculations.
What is the bend radius of PE pipes?

Cold PE pipes can be bent according to the formula R=a*OD where R is bend radius, OD outer diameter and a is bending ratio.

Bending ratio of pipe a

SDR Pipe

20

7.4

25

11

27

17

34

26

50

41
 
Are PE pipes suitable for transferring drinking water?
Yes, PE pipes have health certificates and are suitable for transferring drinking water.
What are the minimum and maximum working temperatures of PE pipes?
PE pipes can be used from -40 ̊C to +45 ̊C. In special cases, PE pipes can be even used at +60 ̊C.
Does sunlight damage PE pipes?
No, black PE pipes contain permissible carbon black content and thus are resistant to UV radiation. So, sunlight does not damage PE pipes.
What is the lifetime of PE pipes?
The lifetime of first and second-generation PE pipes, i.e. PE63 and PE80 is 50 years. With the advent of the third-generation PE pipes, PE100, a lifetime of 100 years is predicted for this type of PE pipes.
How one can find pipe dimensions such as outer diameter, wall thickness and inner diameter?
See P.E.S website or national standard INSO 14427-1 or international standards.
Does the welding edge in the pipe reduce water velocity?

Weld edge has a negligible impact on water flow in the pipe. The welding edge is circular with a small height compared with inner diameter of the pipe.

This is taken into account in the Hazen-Williams of 155 for PE pipes. According to field tests, welding edge does not affect pressure drop or water velocity.

Are PE pipes suitable for transferring chemical fluids?
PE pipes are resistant to most organic solvents. Given the diversity of chemicals, refer to the table on chemical resistance of PE pipes in P.E.S website.
How PE pipes are packaged?
PE pipes up to a diameter of 110 mm are packaged as 100m coils. Pipes with a diameter larger than 110 mm are produced as 12m braches. For other lengths, please contact Sales Department of P.E.S.
Can PE80 pipes be welded to PE100 pipes?
PE pipes produced from PE80 can only be welded by electrofusion using coupler to PE100 pipes of the same outer diameter and different SDR.
What is the difference between PE63, PE80 and PE100 raw materials? Which is better?

Since invention in 1957, three generations of raw materials have been provided for PE pipes.

Minimum Required Strength (MRS°)

Raw materials

6.3 MPa

PE63

8 MPa

PE80

10 MPa

PE100

MRS= Minimum Required strength

PE63 raw materials are no longer used, but pipes produced from PE63 are still working without damage around the world. In the mid-1980s, the second generation, PE80, was introduced to the market, Ten years later in the mid-1990s, the third generation, PE100, with improved specifications than the previous two generations was introduced to the market. A lifetime of 100 years has been predicted for PE100 pipes.

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