What is the SDR and why it is important for polypropylene piping
ISO 15874 standard, which defines the characteristics of ‘Plastic piping systems for hot and cold water installations-Polypropylene (PP)’, dimensionally classifies pipes by defining the Series (S) according to ISO 4065.
In technical manuals or literature used in the plumbing industry, in order to dimensionally classify plastic pipes, SDR (Standard Dimension Ratio) is frequently used.
So let’s discover what SDR is, how it is calculated, its relevance when choosing PP-R pipes and an analysis of the SDRs available for Aquatechnik’s Fusio-technik pipes.
What is SDR?
SDR is a standardized ratio used to describe the relation between the outer diameter and the nominal wall thickness of a pipe. It is an essential indicator of a pipeline’s hydrostatic resistance, used to dimensionally classify polymer pipelines. The concept of SDR is simple: the higher the value of SDR, the thinner the pipe will be with the same outer diameter and, consequently, the lower its ability to withstand pressure and temperature. On the contrary, a lower SDR value indicates a thicker wall, which generally results in a higher operating pressure or temperature for the pipe.
How is the SDR value calculated?
The calculation of the SDR is defined by the following formula:
SDR=De/s
Where:
- De is the pipe outer diameter
- S is the pipe wall thickness
This value is directly related to the hydrostatic resistance in case of pressurized pipelines and to the annular stiffness of the pipe for non-pressurized applications as well.
How is the S value calculated?
The calculation of the S value is defined by the following formula:
S=SDR-1/2
Why SDR is essential for Polypropylene pipes
PP pipes, known for their mechanical, chemical and thermal resistance, are widely used in plumbing, heating and fluid distribution systems. The SDR classification of a PP pipe is essential because it directly influences its performance in terms of pressure and temperature resistance and life expectancy.
Ability to withstand pressure
The most significant characteristic related to the SDR value of a PP pipe is pressure resistance. For example, a PP pipe with an SDR of 7.4 will have a thicker wall than a pipe with an SDR of 17.6 and will therefore provide greater resistance to higher internal pressures.
Application versatility
SDR ratings allow PP-R pipes to be customized for specific applications. For example, in a residential plumbing system where water pressure and operating temperatures are low, a pipe with a higher Standard Dimension Ratio could be used. However, in a commercial or industrial environment, where the required pressure or operating temperature is higher, it is better to choose a pipe with a lower SDR.
What is the difference between SDR and DR?
SDR is basically used in the European context, which generally refers to the ISO 15874 standard, while the DR (Dimension Ratio) value is defined in the corresponding standard used in the North American territory, the ASTM 2389. The two values are essentially similar.
Selecting PP pipes according to SDR
When choosing polypropylene pipes for a given application, SDR classification is a crucial factor. These are some key considerations:
- Pressure requirements, that is, determine the maximum operating pressure the pipe will have to handle. For high-pressure applications, choose a pipe with a lower SDR (thicker walls).
- Temperature conditions. The operating temperature of the fluid being transported must be considered. Higher temperatures may require pipes with lower SDRs to ensure that the material is able to withstand both pressure and thermal stresses.
- Cost constraints to balance material costs with performance requirements. Pipes with a higher Standard Dimension Ratio are generally less expensive because they are made with less material, but not suitable for high-pressure applications.
All SDRs of Aquatechnik Fusio-technik pipes
Aquatechnik’s Fusio-technik system offers a wide range of pipes and fittings with an already outstanding base material, PP-R 80. This system has been further improved over the years for superior performance, first with PP-R 80 Super, and later with the new generation of fibre-reinforced PP-RCT WOR pipes.
Fusio-technik pipes are available in different SDR classifications, each suitable for specific applications.
Fiber-reinforced pipes
They feature a multi-layer composition combining an inner surface made of PP-RCT (modified crystallinity random copolymer polypropylene) with the addition of state-of-the-art antioxidant additive packages, a middle layer made of PP-RF (fibre-reinforced copolymer polypropylene), and an outer layer made of PP-R 80 Super.
1.Fusio-technik Faser FIBER-T 7.4
- Application: ideal for high pressure systems such as domestic water distribution in residential, commercial, industrial buildings.
- Characteristics: the low SDR of 7.4 indicates a thicker wall, which offers superior pressure resistance and durability, together with WOR (White Oxidation Resistance) technology that increases the performance and strength of the pipe.
2. Fusio-technik Faser FIBER-COND 11
- Application: particularly suitable for mechanical systems. WOR technology allows it to be used in applications that also require high temperatures and medium operating pressures.
- Characteristics: with an SDR of 11, this pipe offers an optimal combination of flexibility and strength.
3. Fusio-technik Faser FIBER-LIGHT 17.6
- Application: designed for mechanical applications at medium pressure and temperatures.
- Characteristics: the higher SDR of 17.6 provides a thinner wall, making the pipe lighter and more flexible.
4. Fusio-technik Faser UVRES 7.4 and 11
- Application: pipes designed for outdoor use, for installations with direct sun exposure.
- Characteristics: available in SDR 7,4 and SDR 11, they offer options for high and medium pressure applications with increased UV resistance.
5. Fusio-technik Faser FIRES 7.4 and 11
- Application: designed for fire sprinkler systems (where such use is permitted by regulation/legislation), these pipes must withstand high pressures.
- Characteristics: available in both SDR 7.4 and SDR 11, they provide the necessary pressure resistance required in safety-critical installations.
Single layer pipes
Aquatechnik’s single-layer polypropylene pipes are synonymous with reliability and flexibility, with a wide range of solutions for various applications. Performance and strength guaranteed by PP-R 80 Super.
- Application: ideal for plumbing installations in industrial or commercial environments.
- Characteristics: with an extremely low SDR of 6, it offers the highest wall thickness, ensuring the highest pressure rating in the Fusio-technik range.
- Application: versatile and resistant, it is particularly suitable for transporting aggressive fluids.
- Characteristics: for SDR 7.4, it was possible to reduce the wall thickness of the pipe by increasing the flow rates by about 20%, passing all tests required by the SDR 6 pipe standards.
- Application: an SDR of 11 is a versatile choice for a wide range of applications.
- Characteristics: range of homogeneous single-layer pipes in PP-RCT WOR (random copolymer polypropylene with modified crystallinity and increased oxidation resistance)
- Application: specifically designed for rainwater collection and recycling systems.
- Characteristics: SDR 11 classification provides suitable pressure resistance while maintaining flexibility. High resistance to low PH and alkaline phenomena.
Total reliability of PP-R piping systems with the most suitable SDR
SDR is more than just a technical specification: it helps maximize installations efficiency. Choose from several Standard Dimension Ratio options and get all the reliability of Aquatechnik, working alongside designers and installers for high-quality system solutions for almost 40 years. Contact us for more information on Standard Dimension Ratio and discover all the benefits of our systems.
