We asked Javier Eiriz, export manager for Nueva Terrain, to elaborate on why the company's PB-1 piping systems range has been so well received, particularly for demanding construction and end-use environments (hot and cold climates) that often present challenges to other materials.
Q: Mr. Eiriz, how would you summarise the material advantages of Polybutene-1 versus other competitive materials for pressurised piping systems ?
A: We could sum up the main material advantages of PB versus others, such as PP-R as follows:
1. The high material flexibility of PB-1, while at the same time providing excellent hot water and pressure resistance, combined with the lowest wall thicknesses of all piping systems, makes PB-1 the premium performer for ease of installation, and problem-free performance under high levels of continuous heat and pressure.
2. The use of PB-1 is highly recommended for installations requiring 24/7 hot water running lines. Nueva Terrain has considerable project experience for hotels, hospitals and high-rise buildings and PB-1 offers significant advantages for these pressurised systems
3. The extreme water hammer resistance of piping systems made from PB-1 (due to high material flexibility and reduced wall thicknesses) is a critical factor in the extended lifetime of the installation. It's interesting to note that many competitive piping systems don’t achieve the “theoretical” calculated lifetime due to this issue.
Nueva Terrain recommends PB-1 for 24/7 hot water running lines.
"To wrap up the reasons for our commitment to PB-1 as the premium piping systems material – they are:"
- Ease of installation and handling
- Long lifetime under heat and pressure
- Service reliability and low (or no) maintenance costs
These are the crucial elements for every piping system and our experience tells us that “cheaper per meter" inevitably becomes "considerably more expensive" over the lifetime of the system.
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To expand on the question "Why Polybutene-1?" put to Javier Eiriz of Nueva Terrain, included below is a recently published article from Nueva Terrain comparing the performance of PB-1 versus other competitive polymers across the key performance indices for pressurised piping and plumbing systems .
POLYBUTENE-1 DELIVERS FOR PIPING SYSTEMS
When it comes to plastic materials marketed for piping systems, there are key differences affecting the life-span, operational capabilities and ongoing maintenance requirements of installed systems. The wrong choice can ultimately be costly.
KEY ARTICLE POINTS
PB-1 is the most advanced material for continuous pressure hot water recirculation systems.
- The high material flexibility of Polybutene-1 (also referred to as PB-1, "PB-H", Polybutylene or PB), combined with its excellent hot water and pressure resistance; and lowest wall thickness requirement of all thermoplastic piping (based on pressure ratings), makes PB-1 the optimum choice for continuous pressure hot water recirculation systems typically required in hospitals, hotels and high-rise projects.
- PB-1 offers superior water hammer resistance due to its high material flexibility and reduced pipe wall thickness that arrests and absorbs the pressure surges which create water hammer.
- Both benefits combine to provide best-in-class lifetime expectancy when compared to other harder plastic piping materials. Please note that many piping systems, due to the water hammer impacts, do not achieve the “theoretical” calculated lifetime and as a result are not included in several of the presented comparisons.
Next to the structure, a plumbing system is the one of the most important parts of every building and a long-term investment. This is particularly true for hospitals, hotels and high rise buildings where reliable systems are key to smooth daily operations. Repairs can be expensive, along with business downtime. Pipes in these structures are installed to be concealed behind or inside walls, floors, false ceilings, shafts and other difficult to access areas often providing expensive service issues in the case of leakages.
The right choice of piping material can help to avoid long-term problems and future costs.
Considering that the actual material costs of pipes and fittings (not including installation, valves, pumps, insulation and other plumbing items) is less than 0.3% of the total building project cost, it makes good sense to select the most advanced material available for the piping system.
Our focus for this article is hot water pressure piping which is subject to the most rigorous physical stresses. Operating requirements at high temperatures and under continuous pressure, in combination with pressure surge relating to repetitive water hammer events combine to accelerate the aging process and substantially reduce the lifetime of plastic piping systems.
The right choice of piping material at the planning stage by architects, engineers, consultants and building owners can help to avoid long-term problems and considerable future costs in building maintenance and downtime.
Unlike other thermoplastics, modification is not needed by PB-1 for pressurised piping.
In contrast to other competitive thermoplastics used in pressurised piping applications, performance modification of the material via compounding, cross-linking or copolymerisation is not necessary for PB-1 piping systems to fulfil the stringent performance standards applied to their use.
Compared to other polyolefins, PB-1 has a higher level of resistance to strain with continually applied stress under heat over long periods of time.
Piping material performance comparison
The matrix below shows a comparison of the main thermoplastic materials used in plumbing services and piping systems. Each column represents an important performance criterion for piping systems.
Piping material stress comparison
PB-1 delivers the highest hoop stress values across all standardised application classes.
By using standardised dimensional criteria, as presented in ISO 10508, maximum allowable hoop stress of alternative polyolefin pipes can be compared over standardised applicational temperature classes.
The table below shows that PB-1 polymers deliver the highest hoop stress values across all standardised application classes. The intrinsic stress bearing advantage of PB-1 is between 35% and 90% higher, depending on application class and material. At equivalent thickness, pipes made from PB-1 offer a significant safety factor over alternative plastic materials for installed systems.
Piping material strength comparison
As clearly indicated in the Figure 2 above, PB-1 provides a much higher tensile strength than other polyolefin materials. As a result, and as shown in Figure 3 below, PB-1 pipes can resist considerably higher pressures with the same wall thickness.
Comparison – Different wall thicknesses at the same pressure and temperature
Due to the lower material strength (Figures 2 and 3) of other materials, they require higher wall thickness than PB-1 to withstand similar service pressures at equal temperature rates. When compared to PP-R, PP-RCT, PE-RT and PEX, PB-1 has the highest SDR Class which means it needs the lowest wall section to meet the same pressure requirement.
Note: SDR = Standard Diameter Ratio (correlation between pipe OD and wall thickness)
PB-1 has the lowest surge pressure for a given pipe outside diameter and pressure rating.
A column of moving water within a pipe contains kinetic energy, according to its mass and velocity. Since water is an almost incompressible fluid, this energy cannot easily be absorbed when a valve is closed suddenly. The result is a high instantaneous overpressure, generally known as water hammer. Problems associated with water hammer are one of the most frequent causes of failures in metal pipes, due to their rigidity.
In plastic piping, due to its low elastic modulus, especially in the case of PB-1, the pressures generated are lower and therefore, in general do not cause problems in installations to the same extent.
In the case of Polybutene-1, its low elastic modulus (high flexibility), combined with reduced wall thickness, versus other materials gives rise to a low surge pressure for a given pipe outside diameter (OD) and pressure rating.
The table below compares maximum surge pressure for 25 mm OD pipes of different piping materials. Repetitive water hammer, that is very common in risers and bathrooms of plumbing services, can reduce the lifetime of a piping system if the appropriate material is not used. As shown, in the comparison a 25mm Ø PB-1 pipe with a given water flow rate of 0.6l/s and a corresponding flow velocity, PB-1 has the lowest surge pressure by a significant margin.
Lifetime comparison between PB-1 and PP-R pipes / 24/7 @ 70°C
As calculated per EN ISO 9080 for the same continuous (24/7) service conditions at 70ºC temperature, with an included security factor of 1.5, the table below indicates the lifespan benefits achieved using PB-1 in piping systems. A continuous 70ºC operating temperature (or higher) avoids the potential of Legionella developing in the piping system.
Lifetime comparison between PB-1 and PP-R pipes / 24/7 @ 80°C
As calculated per EN ISO 9080 for the same continuous (24/7) service conditions at 80ºC temperature, with an included security factor of 1.5. While not common, the comparison at continuous 80°C temperature shows the clear temperature resistance advantage that PB-1 provides which translates into a longer lifetime for the system as well as peace of mind to the property owner.
CONCLUSION (Figures 6 & 7)
- A pressure increase of just a few bars substantially reduces the lifetime of a piping system. PB-1 has the highest pressure resistance of thermoplastic polymers.
- Lifetime comparison of SDR 6 and SDR 7.4 pipes shows PB-1 delivers a longer lifespan than PP-R which requires a higher wall thickness. When maximum lifetime and low maintenance is a key requirement (as is the case in high-rise buildings, hospitals and hotel projects) pipes made from Polybutene-1 are an excellent choice.