A true cost comparison between piping systems should include installation time, jointing options, life span and SDR rating.
Polybutene-1 offers tangible benefits for piping systems compared to PEX and PE-RT
For building projects, the true cost variation of piping systems across competing materials is more than a per length cost comparison for the same outside pipe diameter.
Specifiers look at: ease of installation impacting onsite costs; jointing options, long-term system performance and projected life span; and Standard Dimension Ratio (SDR) comparing pipe materials for durability against pressure.
When compared to PEX and PE-RT systems, PB-1 offers significant benefits across a broad range of performance categories all contributing to make PB-1 piping systems the optimum choice for high performance piping installations.
Standard Dimension Ratio (SDR)
What is SDR?
SDR rates pipe durability against pressure and correlates a pipe's outside diameter and wall thickness.
The SDR or the Standard Dimension Ratio refers to the geometry of a pipe. SDR is a method of rating a pipe's durability against pressure and it describes the correlation between the pipe dimension and the thickness of the pipe wall. SDR 11, for example means that the outside diameter of the pipe is eleven times the thickness of the wall.
High SDR ratio
The pipe wall is thin compared to the pipe diameter
Low SDR ratio
The pipe wall is thick compared to the pipe diameter
SDR for a pipe with an outside diameter of 100mm and wall thickness of 5mm can be calculated as:
100mm / 5mm = SDR 20
Why does SDR matter for piping systems?
Due to the higher SDR ratio of PB-1 compared to either PEX or PE-RT, PB-1 piping systems deliver the following benefits because of its lower wall section requirements for the same pressure rating and outside pipe diameter:
- Less material for the same pressure capability
- Less weight per meter of pipe
- Lower outside pipe diameter for the same performance
Larger inside area for the same outside diameter providing:
- Higher flow rate at the same pressure
- Lower pressure loss, requiring less energy to run a system or pumps with lower capacity
SDR Classes and Pipe Dimensions
SDR classes quoted in National Standards for District Energy piping systems
(RU & NL)
The source for piping dimensions comparing materials PB-1, PEX and PE-RT
The current Russian standard for District Heating (GOST 56730 – 2015) and the Dutch guideline (BRL 5609 - and the draft of renewed BRL 5609) both include a comparison of 3 materials for District Heating piping systems: PB-1, PEX and PE-RT.
Both the Russian standard and the Dutch guideline have the same requirements in relation to the pipe dimensions and SDR classes of the 3 service pipe materials operating at pressures of 6 bar, 8 bar and 10 bar.
Per the Russian standard and the Dutch guideline the table (at right) is an excerpt of the relevant table showing the SDR classes for the listed materials at different pressure ratings. As indicated, for each operating pressure PB-1 is listed in the highest SDR class when compared to either PEX and PE-RT. The section below explains what this means, why standards refer to pipe dimensions and SDR classes and what are the benefits for pipe system specifiers.
Pipe Dimensions and SDR Classes
PB-1 pressure capability delivers benefits versus PEX and PE-RT
The higher SDR class of PB-1 delivers the following benefits:
• Thinner wall section
• Less material (less weight)
• Larger inside diameter and area
To illustrate the performance of PB-1, PEX and PE-RT in relation to the given operating pressure of 8 bar at the small pipe diameter of 50mm ø, the table and diagram below provide a comparison of the internal pipe dimensions required.
Example 1: Small pipe – 50mm diameter @ 8 bar
PB-1 is stronger than both PEX and PE-RT, and with an operating pressure of 8 bar and an outside pipe diameter of 50mm ø the required wall thicknesses are:
Per above, at the same water pressure, the larger inside diameter of PB-1 50mm outside ø pipe delivers a substantially higher flow rate than the other two materials. Taken the other way, at a given flow rate PB-1 pipes yield a lower pressure loss requiring less energy to run systems and/or pumps with a lower capacity.
As shown in the graphs above and for the purposes of comparison, PE-RT may be considered the benchmark at 100%. When comparing the inside cross-section area of a 50mm ø pipe (left graph) PB-1 clearly outperforms PE-RT with an additional 27% of volume. Also, in comparing the amount of material per meter for a 50mm ø pipe rated for 8 bar (right graph), PB-1 pipe uses 29% less material than PE-RT.
Once again for the purposes of comparison, PE-RT may be considered the benchmark at 100%. Per the above graph (left), using the same operating water pressure, a 50mm outside diameter pipe (8 bar) made from PB-1 delivers a substantially higher flow rate of +35% when compared to the identically rated PE-RT pipe of the same outside diameter.
Measured using the other comparison point (right): at a given flow rate (output) PB-1 pipes yield a 44% lower pressure loss versus PE-RT pipes. This means that PB-1 pipes require less energy to run a system - or - can accommodate pumps with a lower capacity for the same output.
Example 2: Large pipe – 160mm diameter @ 10 bar
Due to a higher SDR rating (and therefore a thinner wall section) a PB-1 pipe of 140mm ø delivers the same performance as a PE-RT pipe of 160mm ø, but with a smaller outside diameter and larger inside pipe cross-section area.
At a 10 Bar operating pressure pipe of 160mm outside diameter:
PE-RT @ SDR 6
60mm ø pipe has an internal cross section area of 8,958mm2
PEX @ SDR 7.4
160mm ø pipe has an internal cross section area of 10,605mm2
PB-1 @ SDR 9
With a smaller outside diameter of 140mm ø PB-1 has an internal cross section area of 9,263mm2
In addition, as shown in the graph (right), the weight of 160mm outside diameter PB-1 pipe rated for 10 bar is almost half of the weight for the same outside diameter and rating pipe made from PE-RT.
PB-1 Jointing Techniques
PB-1 is a versatile material for all available jointing techniques
The Bottom Line
Specifying PB-1 piping systems offers:
Substantial material saving opportunities, while at the same time increasing the capacity of the system
– thinner walls
– increase of the available inside cross section area
A higher degree of design freedom for projects including District Energy grids
– opportunity for using smaller outside pipe and fitting diameters
A clear opportunity for reduced integral installation cost and operating cost
– smaller pipe support frames
– use of less insulation material
– smaller pumps running at reduced energy consumption
– lighter overall weight for easier handling and lower shipping costs
- In addition: PB-1 can be fully re-used and recycled
PB-1 vs. PEX & PE-RT – download
Polybutene is not sold by PBPSA members for use in pipe applications intended for use in North America, and those parties require their customers or distributors not to sell products made from Polybutene into pipe applications for North America.