Due to its non-polar nature as a hydrocarbon of high molecular weight, polyethylene shows a high resistance against chemical attack. PE is resistant to acids, alkaline solutions, solvents, alcohol and water. Fat and oil swell PE slightly. PE is not resistant against oxidising acids, ketones, aromatic hydrocarbons and chlorinated hydrocarbons.
For additional information, please refer to the detailed list of chemical resistance tool on the GF Piping Systems website.
If polyethylene is exposed to direct sunlight over a long period of time, it will, like most natural and plastic materials, be damaged by the short wave UV portion of sunlight together with oxygen in the air, causing photo-oxidation. Because of this, GF black polyethylene grades are effectively stabilised against UV light by adding carbon black.
PE also has excellent resistance against abrasion. As a result, PE piping systems are used in numerous applications for transporting solids and slurries.
The medium transported basically determines the selection of valves. Pressure and temperature are important criteria. The valve best suited for a particular pressure and temperature can be determined from the technical data of the respective valve.
The selection of the material for the valve seals needs to be selected. This is best decided by consulting the chemical resistance list.
Also to be considered is compressible media.
Suitable materials for compressible media are those that under standard conditions and at low temperatures do not tend toward brittle fractures owing to their ductility.
Such materials include polyethylene (PE) and acrylonitrile-butadiene-styrene (ABS). All other raw materials such as polypropylene (PP-H), polyvinyl chloride (PVCU/-C) or polyvinyliden fluoride (PVDF) are to be limited to ≤ 0.1 bar with respect to the operating pressure of gases. Higher pressures are possible if secondary containment piping systems are used (for environmental protection, brittle effects, gas shocks, intoxication).
Georg Fischer Piping Systems would like to wish you a safe and enjoyable Christmas, and New Year. We look forward to a busy 2014 for all.
Please note that our blog will be not be monitored during the festive season from COB Friday 20 December 2013, until Monday January 6, 2014.
Please note our offices throughout Australia will be closed from COB, Friday 20 December 2013, and will reopen for business on Thursday January 2, 2014. If you have any urgent inquiries during this time, please contact Simon Naef on 0418 214 037.
The Butterfly Valve controls flow by using a circular disk or vane with its pivot axis at right angles to the direction of flow in the pipe. The butterfly valve requires a minimum of space and is used both for on-off and throttling services.
The different markets
Because of the aggressive environment of many applications in the chemical industry, production and transport processes in this segment pose a particular challenge to piping systems regarding safety and quality. When dosing, mixing and batching chemicals – even under the most difficult conditions – good flow and linear control characteristics are basic requirements for efficient and safe processes. Contamination must be prevented in all process steps, especially surface treatment.
Integrating the right system components is therefore crucial; the butterfly valves provide high flow performance and precise process control and regulation.
The majority of all processes in microelectronics take place under strictly controlled cleanroom conditions.
Particularly high demands are placed on the consistent purity of the process water as well as the transport of ultrapure water within the manufacturing process. The butterfly valve with a consistent thermal expansion behaviour at the same time increases safety and consequently reduces the need for costly maintenance.
Economical and sustainable water treatment is becoming more and more important, especially in light of today of increasing scarcity of resources. In water treatment applications butterfly valves are mainly implemented to transport the water.
The innovative design, flow efficiency and control characteristics, for which the butterfly valves are known, are especially appreciated in cooling applications in energy production.
Compared to conventional materials, plastics offer the following general advantages:
• Low weight – low density offers low weight Plastic 0.9 – 1.5 g/cm³
• High elasticity – Resistant against impact and bending stresses
• Chemical resistance – equates to no corrosion
• Low heat conduction equals small thermal loss
• Smooth surfaces ensure low pressure losses and no encrustation
Plastics are materials which are created by chemical conversion of natural products or in a synthetic manner from organic compounds.
The main components are the elements carbon (C) and hydrogen (H). The basis of most plastics are carbon-hydrogen compounds, from which the single components of plastics, the so-called monomers, are produced.
1) Synthesis: production of a chemical compound from different elements or simple molecules. Synthesis is the opposite of analysis.
2) Organic media are pure non-metals of natural occurrence, e. g. petroleum, coal, wood, natural gas. Inorganic media are compounds of metal and non-metals, e .g. minerals, ores etc.
3) Monomers are the basic molecules, i. e. the smallest components of which plastics are built.
A chemical exposure accident may cause injuries to eyes, face and other parts of a human body. The emergency shower is a necessary first aid response to minimise the effects of a chemical exposure accident.
The initial 10 to 15 seconds after exposure to a hazardous substance, particularly a corrosive one, are crucial. Delaying treatment, even for a few seconds, may cause severe injury. Even more critical is the delivery temperature of the water and wait the time taken for water to flow from a cool source to the safety shower which on a long run may be considerable. Imagine an exposed steel pipe in the Australian summer heating up in the midday sun. The affected person would not only receive burns from the chemical exposure but potentially from the hot water in the supply pipeline as well.
In accordance with the AS 4775 -2007 Emergency Eyewash and Shower Equipment, flushing fluid shall be tepid, in which the optimum temperature range is between 15.6oC and 37.8oC. Tepid-water systems can become a source of Legionella; therefore, the emergency shower shall be operated weekly by the user to make sure it works and also to clean the line of microbial hazards (flushing of stagnate water from plumbed fixtures). For each test, a signed and dated record should be kept with the facility and maintained by the user.
The affected body part should be flushed for a minimum of 15 minutes using a large and clean supply of flushing fluid under low pressure.
A preinsulated pipe line and fittings can prevent the water at the safety shower and eye wash stations from being outside the Australian Standards.
What piping systems are you installing for your safety showers and eye wash stations?
The chemical resistance of a substance is a complex property which depends (inter alia – amongst other items) on its chemical composition and on the way it has been processed / manufactured.
The chemical resistance of a polymer pipe depends predominantly on its chemical structure, on additives, on its crystalline structure and on the condition of its surfaces. As chemical resistance depends, ultimately, on the possibility of chemical reactions occurring (reaction kinetics), the conditions under which they take place (pressure, temperature, radiation, mechanical loads, concentration of chemicals and the duration of contact with them, etc.) are also decisive. According to the existing standards (DIN 16888, Parts 1 and 2), there are three categories for a thermoplastic pipe’s behaviour under chemical attack: “resistant”, “conditionally resistant” and “not resistant”.
Whilst our blog attempts to give general guidance and we take care not to publish any misleading content, sometimes it is difficult to manage all different standards for the various code classifications across different countries.
Our last blog “Why use Thermoplastics” implied that thermal insulation was not required. We have altered the 5th point to say one of the key benefits of thermoplastics is Low thermal conductivity has improved thermal performance over traditional materials.
This point was altered as one of blog readers cited standard AS/NZS 3500:4:2003 Table 8.1 Piping connected to storage water heater piping Minimum thermal insulation “R” Value Internal locations 0.3; for external locations :- Climate Region (A 0.3) (refer to fig 8.1 New South Wales) Climate region (B 0.6) Climate region (C 1.0).
Table 8.2 Heated Water Piping has similar requirements, and notes the following(3a) 13 mm of closed cell polymer R= 0.3 (3b) 25 mm of closed cell polymer R=06 (3c) 38 mm closed cell polymer R=1.0
It is understood that the R values relate to water temperatures of 60◦C.
From this information we (the reader) are inclined to believe that thermal insulation is at least recommended by AS/NZS 3500, and possibly also other regulation boards.
Use of correct pipe insulation can also result reduced energy costs; a desirable advantage.
The point we (the writer) were trying to make was to compare thermal conductivity between copper and PP-R for instance.
It is great to receive comment.
This is a wrap of the key benefits of using thermoplastics
- No incrustation thanks to smooth internal surface
2. Chemical resistance
- Good compatibility with chemicals
- Most economical solution for your requirements
3. Low total cost of installation
- Reduced pipe sizes
- Reduced welding times
4. Low material weight
- Low density – no machinery required to carry material
- Low anchor forces save installation costs
5. Low thermal conductivity
- Improved thermal performance over traditional materials
- No corrosion due to less condensation and higher resistance results in cost savings
6. No electrical conductivity
- No corrosion
- No additional earthing required