Pressure surges in water hammer: solutions with multilayer and PP-R pipes by Aquatechnik
One of the most common hazards for designers and installers of water and heating systems is water hammer. The mass of fluid flowing through the pipes is in constant motion and reacts to any change in flow rate or pressure.
If not taken into account, this phenomenon can compromise the strength and durability of the pipes, reduce the efficiency of the system and increase maintenance costs. However, it is a phenomenon that can be prevented and controlled through the correct choice of materials and the correct mechanical dimensioning of the pipes.
Let’s analyze the causes and consequences of pressure surges, its key role, and the most effective solutions.
What is water hammer: the phenomenon of pressure surges
Water hammer is a pressure surge resulting from a sudden change in velocity and pressure. It is essentially a transient pressure surge that occurs when a moving fluid stops or slows down rapidly inside pipes and pipelines.
Typical examples and causes include:
- rapid closure of a valve;
- sudden shutdown or start-up of a pump;
- sudden change in flow rate in a distribution network;
- flushing and emptying of pipes and supply tanks.
This pressure surge wave propagates along the pipes, generating high and rapid overstressing of the pipe walls themselves, as well as vibrations and other types of mechanical stress. If the system is not designed to absorb them, negative effects are inevitable:
- deformations and breakages at the weakest points;
- high and annoying noise from the system;
- loosening or failure of fittings;
- micro-cracks that reduce the service life of the pipes.
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The importance of material selection in water and heating distribution systems
It is well known that water hammer and the resulting sudden pressure surges are related to the material used in the piping.
Rigid materials, such as metal pipes, produce pressure surges that are significantly higher than those generated by materials with a viscoelastic response, such as polymers.
In summary, the viscoelastic behaviour typical of a polymeric material allows for a reduction in the maximum pressure surge generated in conjunction with a water hammer, as the structural characteristics of the material allow the pressure surge wave to be absorbed by the pipe, which is able to deform elastically. On the other hand, metal pipes elastically return the entire pressure wave generated, as they are unable to dissipate this wave due to their extremely limited deformation.
The consequences are that, for the same pressure wave, the maximum pressure reached by a fluid transported in polymer pipes is significantly lower than the pressures reached by the fluid transported in metal pipes. This difference depends on a typical feature of materials such as the elastic modulus (E), which for polypropylene, for example, is approximately 1 GPa, while for steel it is approximately 200 GPa.
This allows the use of polymer pipes with thicknesses similar to those of metal pipes and less stringent clamping conditions.
The importance of pipe clamping in water and heating distribution systems
Pipe clamping does not have a purely ‘mechanical’ support function: they are a dynamic element of the system.
When designed and installed correctly, clamping points:
- limit the effects of pressure surges;
- absorb part of the vibrations caused by water hammer;
- reduce the linear thermal expansion of the pipes;
- prevent oscillations and contact noise with walls or structures;
- improve acoustic comfort and overall efficiency.
On the contrary, clamps that are not correctly sized or distributed can amplify the effects of pressure surges and turn water hammer into a permanent problem for the system.
Safety system clamping and design with multilayer pipes
Aquatechnik catalogues contain precise tables of recommended clamping values based on pipe diameter and material.
Some basic rules:
- distribute clamping points at regular intervals, avoiding unsupported sections that are too long;
- observe the maximum distances based on the operating temperature;
- use anti-vibration supports to reduce noise transmission;
- provide fixed and sliding points to control expansion and movement.
The integration of multilayer pipes, Safety fittings and correctly designed clamps is the most effective solution for managing pressure surges.
Fusio-technik PP-R pipes: strength and reduced clamping
In addition to multilayer pipes, Aquatechnik offers the Fusio-technik range in fibre-reinforced PP-R, ideal for complex systems and large networks.
Concrete advantages during clamping
- Fewer fixing points for faster and more economical installation;
- control of thermal expansion thanks to the fibre-reinforced structure;
- better acoustic performance and reduction of noise induced by pressure surges.
Integrated solutions against water hammer
Pressure surges management requires an integrated approach that combines materials, design and components.
- Choice of the right pipe: multilayer for plumbing and domestic heating systems; PP-R Fusio-technik for large networks and high temperatures in particular.
- Use of certified fittings: Safety for multilayer pipes, Fusio-technik welded fittings for PP-R.
- Optimized clamps: calculated based on diameter, temperature and length of the lines.
- Protective accessories: check valves, expansion tanks, anti-water hammer devices in the most critical cases.
With this approach, systems are safer, quieter and longer lasting. Only conscious project management, with technologically advanced systems, can prevent damage, costs and inconvenience.
Aquatechnik has been supporting designers and installers for over 40 years with solutions that meet your needs: from multilayer pipes to Safety-plus and Safety-metal fittings, to fibre-reinforced PP-R Fusio-technik systems.
Turn a weak point such as water hammer in systems into a competitive advantage with the best solutions.
For further information and customized advice, please contact our Technical Department.
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