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# What is the recommended maximum operating pressure for a PE pipe?

The relationship between the maximum operating pressure (MOP), the minimum required strength of the PE pipe grade (MRS) and the pipe geometry (SDR standard dimension ratio) is given by the following industrially recognised and applied formula;

MOP = (20 x MRS) / (C x (SDR-1))

Where C is the ‘overall service (design) coefficient, or Safety Factor.

It is generally recommended by our customers and design institutes that for water applications the minimum value of C is 1.25 and for gas applications the minimum value of C is 2.0. The designer may apply higher coefficients depending upon national codes of practice or judgment of local conditions and the critical nature of the application.

Example 1: What is the maximum operating pressure of a PE100 SDR11 water pipeline?

MOP = (20 x MRS) / (C x (SDR-1))

MRS = 10 MPa, SDR = 11, C = 1.25

MOP = (20 x 10) / (1.25 x (11-1))

MOP = 16 bar

Example 2: What is the maximum operating pressure of a PE100 SDR17 gas distribution main?

MRS = 10 MPa, SDR = 17, C = 2.0

MOP = (20 x 10) / (2.0 x (17-1))

MOP = 6.25 bar

(Note, other factors such as resistance to rapid crack propagation (RCP) are suggested to be taken into account, particularly for gas applications, to confirm that the calculated MOP can be applied. Refer to EN 1555-1/2 and ISO 4437-1/2)

## References

• EN ISO 12162:2009 Thermoplastics materials for pipes and fittings for pressure applications - Classification and designation - overall Service (Design) coefficient
• EN 1555-1:2010 Plastics piping systems for the supply of gaseous fuels. Polyethylene (PE) - Part 1 General.
• EN 1555-2:2010, Plastics piping systems for the supply of gaseous fuels. Polyethylene (PE) - Part 2 Pipes
• ISO 4437:2007 Buried polyethylene (PE) pipes for the supply of gaseous fuels - Metric series - Specifications
• EN 12201-1:2011, Plastics piping systems for water supply, and for drainage and sewerage under pressure - Polyethylene (PE) - Part 1: General
• EN 12201-2:2011, Plastics piping systems for water supply, and for drainage and sewerage under pressure - Polyethylene (PE) - Part 2: Pipes
• ISO 4427-1:2007, Plastics piping systems – Polyethylene (PE) pipes and fittings for water supply – Part 1: General
• ISO 4427-2:2007, Plastics piping systems – Polyethylene (PE) pipes and fittings for water supply – Part 2: Pipes
Created Sunday 08 February 2009
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