Extreme Environments

DID YOU KNOW?

Temperatures in unshaded bunds can easily exceed the safe working limits for PVC pipes, valves & fittings. PVC-U piping systems are generally considered to have a maximum pressure of 15 Bar at a temperature of 23°C but this drops to 3.3 bar at 60°C.

In this photograph, taken in NSW  summer 2016, the temperature of the valve was 74°C!

These high temperatures are a result of direct sunlight plus reflected heat from the white concrete bund & floor.
Repeated exposure to excessive temperature will ultimately reduce significantly the working life of the entire system. To operate so far in excess of the design parameters risks sudden catastrophic failure due to excessive expansion imposing undue stress at fittings. Leakage at threaded joints & “O” ring seals. Even normal system operating pressures will exceed permissible levels at elevated temperature & pressure surges due to dosing pump and valve operation can easily cause significant damage.
PVC is selected for pipe systems often because of its ability to handle aggressive chemicals & the consequences of significant failure to the safety of personnel and environmental contamination are very serious indeed.
These are not brand specific issues we have seen failures of installations using fittings from all the well known manufacturers, it is a fundamental principle that systems must be designed to operate within the manufacturer’s published pressure/temperature limitations.
Roofing to provide effective shading of the PVC installation is an obvious solution or using CPVC piping systems if shading is not cost effective. Double containment can also be considered for difficult applications.
These web links will take you to our data sheets for a more detailed explanation of temperature/pressure effects and provision for thermal expansion.
http://www.merrimancontrols.com/uploads/category_pdf/ThermalMovement.pdf

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