Water distribution systems consist of an interconnected series of pipes, storage facilities, and components that convey water for cities, homes, schools, hospitals, businesses, industries and other facilities. A common trend in this industry is metal replacement with technopolymers mainly driven by the restricted amount of lead allowed by the law within these systems. Water distribution applications have very specific requirements such as good mechanical properties retention after long term water contact with chlorine (disinfectants) as well as long-term dimensional stability and oxidative degradation resistance. Most common applications in this field are water filtering, water softeners and metering systems, submersible pumps or shut-off valves.
Using DOMO’s TECHNYL® SAFE range in water system designs ensures systems are lead-free and compliant with water regulations. It also means significant system savings compared to the high cost of processing and machining new brass alloys and the high environmental impact of end-products manufactured in foundries.
In these systems, long term dimensional stability, mechanical properties, and resistance to chlorine at ambient temperatures are required. The chlorine concentration levels can significantly influence the long-term resistance to oxidative degradation of engineering plastics based on aliphatic PA if not properly stabilized and could affect the reliability of the water meter’s performance during its lifetime.
Water meters are normally expected to last over 20 years and they need to be metrologically reliable and resistant to cracks and failure over such a lifetime. With an average consumption per household (comprising four people) of around 200m3 of water per year, some 4000m3 of water will pass through a meter over its lifetime.
Premature failure must be avoided because of the high replacement costs (normally water meters are wall cased).
Drinking water typically has a chlorine content of 0.5 ppm. One of the standard tests DOMO performs on water meters involves the use of water with a chlorine content of 10 ppm, flowing through the meter at a rate of 0.7m3/h for up to 1500h.
The above graphs show that TECHNYL® SAFE grades exhibit the same level of retention of mechanical properties in distilled water and chlorinated water.
The TECHNYL® SAFE D grades (PA 6.10) exhibit better performance retention than TECHNYL® SAFE A (PA 66) due to less water uptake at saturation, which leads to:
- Better retention from DAM of the mechanical performance (67% for PA 6.10 GF50 vs. 53% for PA 66 GF50)
- Less surface degradation in chlorinated water
In addition to these points, the TECHNYL® SAFE D grades (PA 6.10) offer the following advantages vs. PA 66:
- Better dimensional stability after water uptake (see water uptake graph fig.3)
- Better surface finish
All these advantages make long chain PA6.10 TECHNYL® SAFE D a suitable engineering material for water meter and water distribution applications, and more generally, water management systems.
PA6.10-based TECHNYL® SAFE D can also successfully replace high transition temperature PPA with the same glass fiber content in cold water meter body and top plate applications with the following benefits:
- Better dimensional stability after water uptake
- Better roughness and surface finish
- Easier processing (wider processing window + lower temperature setting on barrel and mold): no need to build oil heated mold, as well as less energy consumption of the injection machine
- Lower density material with the possibility of lighter products bringing advantages in terms of handling and transport of final products
- Better Material Environmental Footprint (GWP)
- Superior performance on cyclic pressure test (fatigue)
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