The Georg Fischer Piping Systems pressure/temperature diagrams are based upon a life expectancy of 25 years. They are valid for water and certain aqueous solutions which do not impact the plastic material properties. However, several aggressive chemical media may affect the plastic and could impact the lifetime of the system or operating parameters. A de-rating factor reduces the maximum pressure for a plastic/medium combination in order to maintain the material performance. De-rating factors are > 1 (typically in the range of 1–1.3; a few are higher). To use the de-rating factor, divide the maximum rated pressure by it to obtain the maximum sustainable pressure of the system, or multiply the pressure by it to obtain the maximum operating temperature.

Example: An aqueous medium in a polyethylene piping system (SDR 11) allows a maximum pressure of 9 bar (132 psi) at a temperature of 40 °C for a 25-year lifetime (see PT diagram: point A).

Hydrochloric acid 37% in polyethylene has a de-rating factor of 1.2. The maximum pressure of that system at a temperature of 40 °C is 9 bar / 1.2 = 7.5 bar (110 psi), point B on the graph. Additionally, if the system is operated at 9 bar, the de-rating factor times operating pressure (9 × 1.2 = 10.8 bar) corresponds to 30 °C, or point C on the graph, which represents the maximum operating temperature of the system at 9 bar. For further explanation, please contact PPS Engineering CZ.

ABS, PVC-U and PVC-C are typically cemented with Tangit. However, some aggressive media at higher concentrations require Tangit DTX as a chemically more resistant cement. The use of DTX brings about some restrictions: a de-rating factor, an upper temperature limit of 60 °C and a lifetime limitation.

The following chemicals and concentrations require Tangit DTX:

The quality and chemical resistance of a DTX joint depend upon proper processing. Please contact PPS Engineering CZ for further details.

Besides questions of chemical resistance, multiple organic media demand particular safety considerations due to their flammability and combustion properties. The database recommendations refer exclusively to chemical resistance considerations. They do not replace technical installation guidelines or restrictions. These guidelines are typically defined by legislation and standards such as ATEX, ASME, ASTM and NFPA. Some guiding principles are listed in the chapter “Plastic pipelines in highly combustible locations / Transport of explosive media” within the GF Planning Fundamentals. Ultimate compliance with these guidelines, however, must be ensured by the ordering party or the construction company.

Sealing materials are an essential part of the entire piping system. The choice of the gasket material depends not only on chemical resistance aspects but also on mechanical considerations. Even though a recommendation should always be made on an individual case-by-case basis, some general rules apply to our standard gasket materials:

The data are provided as is and there is no warranty or representation, either express or implied, that they are free from errors. We shall not be liable for damages of any kind that may result from the use of this data.

The successful operation of valves does not depend only on the chemical resistance of their materials and seals; a number of additional factors must be considered. Therefore, these data cannot be transferred without restriction to the operation of valves made from the same materials and/or combinations of materials.

This document serves only to provide technical information. We refer to our General Sales Terms. Subject to change without notice.