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Polybutene-1 | Shipbuilding

In today's competitive shipbuilding market, companies are searching for new materials and systems that will extend the service life of their ships and on-board systems, reducing maintenance costs and improving the passenger experience. As a result, high quality, long lasting plastics such as Polybutene-1 (Polybutylene, PB-1) are increasingly being specified for onboard piping systems, particularly for the pressurized delivery of hot and cold water.
 

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The Cruise Industry

Seeking to reduce costs and extend the lifespan of onboard systems

The cruise industry hosts over 30 million passengers per year and has an annual global output of $134 Billion (2019 source: CLIA). When carrying large numbers of passengers across oceans, health and safety are basic requirements, along with high levels of comfort. These essential industry objectives come at significant cost. As a result, shipbuilding owners and contractors are focused on sustainably addressing the challenges related to onboard infrastructure, facilities and related energy usage as early as possible in the ship design process.
 


PB-1 Marine Applications

Polybutene-1 (Polybutylene, PB-1) is an excellent material for shipbuilding piping systems used for the following applications:

  • Hot and cold water pressurized systems
    - able to withstand constant temperatures from 0°C - 95°C @ 6 bar
  • Compressed air
  • Desalination
  • Reverse osmosis
  • Air conditioning lines
  • Heating and cooling
  • Condensation and/or recirculation lines
     

PB-1 Marine Products

PB-1 is specified for challenging environments

When compared to other polymers, Polybutene-1 (Polybutylene, PB-1) offers the most comprehensive list of physical capabilities across the mechanical properties spectrum. Products made from PB-1 used by shipbuilders include:

  • Pipes
    - able to be coiled and delivered in long lengths
    - offered as regular or multilayer pre-insulated pipes
  • Fittings
  • Ball valves
  • Diaphragm valves
  • Actuated valves
  • Measurement and control
     

PB-1 Benefits Summary

Fast and Efficient Installation
• Long lengths in coils
• Few tools required
• No flame or fluxes
• Flexible for tight areas
• Less connections

PB-1 piping systems are ideal for shipbuilding

High chemical resistance and corrosion free

  • resistant to solvents and chemical products
  • resistant to concentrated brine

High flexibility

  • allowing easy onboard handling and installation using coils and reducing connections
  • providing advantages for retrofit of new piping systems in tight areas in existing ship interiors

Low weight

  • significantly reducing the total deck weight vs. other plastics and metals

Pressure resistant and long-term burst resistant

  • under constant high temperatures

Best in class acoustic properties

  • with excellent sound dampening and low water hammer

Fast and efficient installation

  • lightweight and highly flexible PB-1 pipe in coils means easy shipping, less connections and easier onboard handling and installation into confined areas
  • few tools required and no flame, heat, fluxes or other chemicals needed, eliminating the need for hot work certificates
  • PB-1 systems' suppliers provide complete systems, optimising performance,  jointing integrity and choice
  • applicable for all current jointing techniques
  • PB-1 piping systems capabilities for offsite prefabrication radically reduces installation time on board and provides the ability to install at sea

Long life span

  • long system life spans along with low service and maintenance costs compared to other materials

Increased liquid flow rate

  • versus competitive plastics for the same outside pipe diameter
  • highest SDR classification allows the thinnest wall and therefore the largest internal cross section and flow rate

Suitable for cooling and air-conditioning

Low environmental footprint

  • compared to competitive polymers
  • recyclable

Meets International standards

Global availability of PB-1 piping systems
 


PB-1 Performance

Significant performance benefits for shipbuilding

Polybutene-1 piping systems (Polybutylene, PB-1) have an array of performance advantages which have made the material the latest generation choice for piping systems installed on ships

Performance benefits include lower thermal diffusivity than copper pipes which means water takes longer to freeze in them during cold weather.

If freezing does occur, the pipe expands to take account of the added volume, returning to its normal dimensions when the thaw comes. The same PB-1 thermal characteristic operates in reverse making them cool to the touch, even when high temperature water is being transported.

In marine environments PB-1 piping systems are corrosion-free and will not scale-up with hard water.

They absorb and suppress sound, rather than transmitting it and they are not subject to 'water hammer' particularly in areas noted for high water delivery pressures.

Welding technology with PB-1 offers additional opportunities to pre-fabricate sections off-site reducing logistical complexity and installation time.

Long-term ISO 9080 tests performed on Polybutene-1 pipes project service lifetimes of 50 years or more for PB-1 hot water pipes operating with water at 70°C, at 10 bar pressure.  ISO 9080 tests are carried out according to international protocols by independent and accredited test agencies such as EXOVA.
 

Explanation of the main qualities of Polybutene-1 as a material for plumbing and heating systems
Features Application Polybutene-1 (Polybutylene/PB-1)
Density Lower weight: facilitates handling, decreases the cost and reduces the environmental impact of its manufacturing process. Plastic systems in general benefit from its lightness compared to metal.
Thermal Conductivity It reduces heat loss and the possibility of condensation on the cold side. Again it is a typical characteristic of plastic systems, where PB-1 has the lowest value.
Thermal Expansion The expansion of plastic materials due to temperature changes is greater than that of metal: It must be taken into account for their compensation. Although PB-1 has a lower expansion than other plastic materials, these expansions must always be taken into account.
Elastic Modulus The much lower rigidity of the piping (lower elastic modulus) facilitates its usability in construction, and reduces the generation of stress linked the functioning of the installations: water hammer, fixed points and expansion, etc. It is the most elastic material of all those used for this application, and therefore it is the most manageable and generates the lowest stress.
Resistance to Pressure and Temperature The main characteristic that defines a piping system is its resistance to temperature and pressure. This information is characterised in the regression curves of the material, the DNA of the pipe. Polybutene-1 is the material with the best pressure resistance according to the temperature. This leads to lower thicknesses for the same required resistance, or a better resistance for the same thickness.
Creep Resistance Creep represents the deformity of the material over the course of time under constant load. It is fundamental in compression joints to ensure the dimensional stability of the pipe. PB-1 has minimum creep, preserving its dimensions under constant load.
Transmission of Sound As the material is very elastic, the transmission of sound and therefore noise through the physical medium made up of the piping network is far lower than that of other materials. It is the material that best insulates against noise transmission.
Expansion Stress The low elastic modulus of the material means that the stress generated by the expansion between fixed points of the installation is much smaller. PB-1 does not cause problems in installations due to expansion stresses.
Water Hammer The pressure peaks caused by instantaneous shut-offs of fluid flow are sources of problems in rigid piping systems. PB-1 is excellent at absorbing the stress associated with water hammer in installations.
Sustainability Sustainable construction requires systems manufactured with a lower consumption of resources. Polybutene-1 is the system that consumes less resources in its manufacture than metals or other plastics and causes less harm to the environment.

PB-1 Jointing Techniques

A comparison of available jointing techniques between piping systems polymers

PB-1 is a versatile material for all available jointing techniques

 


PB-1 Acoustic Properties

Acoustics is among the superior properties of Polybutene-1 piping systems

In consideration of the close proximity of passengers on ships  and with increased expectations of comfort, noise levels and acoustic properties of piping systems, acoustic properties are a significant consideration for shipbuilding. Piping systems that minimise fluid noise and water hammer where pipework passes through ceilings and walls are a key element in addressing passengers’ noise concerns.


Sound dampening

Among the superior properties of Polybutene-1 in comparison with other materials its excellent sound dampening. The combination of thinner pipe wall construction, low elastic modulus and low specific density in Polybutene-1 pipes (ρ = 0.9 g/cm3) leads to high absorption of “water hammer” and other noises associated with heating and cooling in pipe systems.
 

Sound velocity of materials
  Density (g/cm3) Elastic Modulus (MPa) Sound Velocity (m/s)
Soft Rubber 0.90 90 320
PB-1 (Polybutylene) 0.93 450 620
PE-X 0.95 600 800
CPVC 1.56 3,500 2,350

Resistance to Water Hammer

The higher the SDR Class the lower the water hammer at a given flow rate. PB-1 has the highest SDR Class compared to PP-H, PP-R, PE-RT and PEX

A column of moving water within a pipeline contains stored kinetic energy arising from its mass and velocity. Since water is essentially incompressible, this energy cannot be absorbed when a valve is suddenly closed.

The result is a high instantaneous pressure surge normally referred to as 'Water Hammer'.

With the inherent density of ship cabins the noise levels and acoustic properties of piping systems are a significant issue. Piping systems that minimise fluid noise and water hammer where pipework passes through the internal ship structure are a key element in addressing passengers' noise concerns.

Repetitive water hammer can be destructive to pipe systems. Beside the noise, water hammer can cause pipelines to break if the pressure is high enough.

The maximum theoretical value of pressure surge Ps is:

v0 · a · ρ = ps

v0 = velocity of the medium [m/s]
a = propagation rate of the pressure wave [m/s]
ρ = density of the medium [kg/m³]
ps = pressure surge – water hammer [N/m²]


The low elastic modulus of Polybutene-1, combined with reduced wall thickness gives rise to a low surge pressure for a given pipe OD and pressure rating. The table below compares maximum surge pressure for 38.1 mm (1-1/2") OD pipes of different plastic materials, designed for the same pressure service.
 

  E E DI t V Ps Ps
  [psi] [MPa] [mm] [mm] [ft/s] [psi] [bar]
PB-1 65000 450 32.5 (1.28") 3.8 (0.15") 5.0 49.5 3.4
PE-X 87000 600 28.9 (1.14") 5.6 (0.22") 5.0 72.4 5.0
PP 116000 800 26.7 (1.05") 6.6 (0.26") 5.0 93.0 6.4
CPVC 507000 3500 30.9 (1.22") 4.6 (0.18") 5.0 140.6 9.7

When compared to PP-H, PP-B, PE-RT and PEX, PB-1 has the highest SDR Class and delivers the best acoustic capabilities including the lowest level of water hammer.
 


Pipe Dimensions and Flow Rate

PB-1 pressure capability enables greater internal area and flow rate than PEX and PE-RT

To illustrate the performance of PB-1, PE-RT and PEX 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.

PB-1 is stronger than both PE-RT and PEX, 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.
 


PB-1 High Flexibility

Best in class flexibility lowers installation time

Flexibility is an advantage offered by a number of plastics in comparison with metals, however Polybutene-1 is clearly the plastic material of choice as illustrated in the following table, where typical flexural elasticity values of various polyolefin pipe materials are compared.
 

  PB-1 PE-X PE-RT PP-R PVC-C
Flexural Elasticity Modulus (MPa)
Method ISO 178
450 600 550-650 800 3500
(PE-RT - Raised Temperature Resistance Polyethylene)

The advantages of flexibility during the installation and service of Polybutene-1 piping systems are described in detail on this website and are particularly applicable to the requirements of shipbuilding. Obviously, the easier a pipe is to manipulate on site and in tight situations, the lower the installation time should be.

In this respect, the ease of cabling through drilled holes and threading through confined spaces, combined with long pipe runs available in coils and therefore a reduction in the number of fittings required, are all factors which contribute to the speed of installation and associated reduction in labour costs.

Although Polybutene-1 pipe is easily flexed, care should be taken not to bend the pipe to the point of 'kinking'. In this respect, a minimum bending radius of 8 times the pipe diameter is recommended.

The figure (above right) illustrates the recommended minimum bending radii for various Polybutene-1 pipe diameters.

 


PB-1 Piping Installation

PB-1 piping systems have revolutionised how pressurised hot and cold water systems are installed in ships. No bending tools, no flame, no fluxes, no chemicals.

Simple, fast and efficient

Piping systems from Polybutene-1 (Polybutylene, PB-1) have revolutionised how hot and cold water pressurised systems are installed in ships. With the installation of PB-1 piping, no bending tools are needed, no naked flame, and no fluxes or chemicals.

Polybutene-1 offers improved handling due to its flexibility, reduced pipe wall thickness and low memory effect. In addition to the potential cost savings of faster installation, polybutene-1 pipes provide opportunities for installation in tight, cramped spaces.

Pipework of up to 50mm in diameter is supplied in lightweight and easily handled long coiled lengths. Installations can be made in structures before ceilings and walls are fitted and flexible PB-1 pipe can be cabled around obstructions and cabled through tight areas making it perfect for shipbuilding refits. Continuous, flexible pipe means fewer joints providing greater system integrity.

With PB-1, many installations can be made without accurate pre-measuring, since it is easy to measure and cut in situ. Also, the light weight and ease of handling of PB-1 piping allows factory pre-fabrication and rapid on-board installation or when a cruise ship is underway when timing is critical.
 


 


Legionella

PB-1 piping reduces on board Legionella risk, due to:
• smooth internal pipe surface
• no metal corrosion
• optimum resistance at 70ºC
• suitable for chemical disinfection

Legionella is a bacteria occasionally naturally present in water distribution networks, and presents a potential danger to the health of the users of these installations.

The factors to combat to prevent the reproduction of this bacteria in piping systems in buildings are its reproduction temperature and the formation of a biofilm as a substrate for the feeding and colonisation of the bacteria.

The reproduction temperature of Legionella is between 20° and 50ºC, so water temperatures within this range must be avoided. On the other hand, the formation of a biofilm is aided by the accumulation of stagnant water, the temperature within the aforementioned range, the roughness of the piping and the possible corrosion of its metal.

The annihilation temperature of Legionella is established at 70ºC, and this is why thermal disinfection treatments require fluid to be heated to this temperature.

The international standards for production consider this working temperature for this application, where Class 2 is defined as applicable. The best choice of material for this problem is Polybutene-1, and with good design and appropriate maintenance of the installation, potential problems of Legionella can be avoided. PB piping, due to its low roughness, the lack of metal corrosion, and its optimum resistance at 70ºC (annihilation temperature of the bacteria) is ideal for preventing Legionella problems. They are, in addition, suitable for annual chemical disinfection treatments (30 ppm of Cl at 30ºC, 6 bar and for 2 hours), according to tests performed by the manufacturer of the raw material, LyondellBasell in independent laboratories.

 


Low Eco-Impact

Environmental impact study of piping materials by the Technical University of Berlin rated the impact of Polybutene-1 as low.

PB-1 classed as "environmentally friendly"

Piping systems' environmental impact and recycling potential are assessed in ‘cradle to grave’ studies. Such a study was conducted by the Technical University of Berlin on various drinking water pipe systems, including galvanised steel, copper, and plastics: cross-linked Polyethylene (PE-X), Polypropylene (PP-R), Chlorinated Polyvinylchloride (PVC-C) and Polybutene-1 (PB-1).

For all comparative indices, Polybutene-1 was rated as one of the products delivering the lowest levels environmental impact. Polybutene-1 is regarded highly in the area of sustainability, demonstrated by demanding national and international standards, and extensive long-term testing. PB-1 is classed as 'environmentally friendly' – consuming less energy during manufacture, conversion, installation and use than its competitors. As a non cross-linked polyolefin raw material, it can also be recycled.
 


 

Polybutene is often referred to as Polybutene-1, Polybutylene, PB-1 or PB.

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.