PVC and the Weather

Testing and past field experience studies have concluded that when conventional Type I, Grade I (Cell Classification 12454) rigid PVC pipe is exposed to UV radiation from sunlight the following conditions have been noted:

  • The effects of exposure to UV radiation results in a colour change to the product, slight increase in tensile strength, slight increase in modulus of tensile elasticity, and a slight decrease in impact strength.
  • UV degradation occurs only in the plastic material directly exposed to UV radiation and to extremely shallow penetration depths (frequently less than 0.001 inch). UV degradation does not continue when exposure to UV is terminated.
  • UV radiation will not penetrate even thin shields such as paint coatings, clothing or wrapping.

Based on these studies, it maybe recommended that PVC and CPVC piping products (i.e. pipe, duct and shapes) exposed to the direct effects of UV radiation be painted with a light coloured acrylic or latex paint that is chemically compatible with the PVC/CPVC products. Compatibility information should be confirmed with the paint manufacturer. The use of oil-based paints is not recommended.

When painted the effects of exposure to sunlight are significantly reduced, however, consideration should be given to the effects of expansion/contraction of the system caused by heat absorption in outdoor applications. The use of a light coloured, reflective paint coating will reduce this affect, however, the system must also be designed and installed in such a manner to reduce the effects of movement due to thermal expansion. Information concerning expansion and contraction, proper hanger support spacing and other design criteria can be found in this engineering and installation guide.

Thermal Expansion & Contraction

All piping systems expand and contract with changes in temperature.

Thermoplastic piping expands and contracts more than metallic piping when subjected to temperature changes. This issue must be addressed with appropriate system design to prevent damage to the piping system. The degree of movement (change in length) generated as the result of temperature changes, must be calculated based on the type of piping material and the anticipated temperature changes of the system. The rate of expansion does not vary with pipe size. In many cases this movement must then be compensated for by the construction of appropriate sized expansion loops, offsets, bends or the installation of expansion joints.
These configurations will absorb the stresses generated from the movement, thereby minimizing damage to the piping. The effects of thermal expansion and contraction must be considered during the design phase, particularly for systems involving long runs, hot water lines, hot drain lines, and piping systems exposed to environmental temperature extremes (i.e. summer to winter).

Helping the Carbon Footprint

The key to sustainable and environmentally friendly products is to keep the entire product life cycle in mind when developing them; all the factors that could potentially impact the environment should be taken into account. Starting with effects or influencing variables in the area of procurement, continuing with manufacturing and use up to disposal or product recycling – all the stages should be reviewed. It is important to identify potential effects at an early stage of the process and to find innovative solutions to minimize the environmental impacts.
The market demands system solutions that generate added value and mutual benefit for all stakeholders along the supply chain. In this respect, ecological responsibility also includes the choice of business partners such as suppliers.

Corrosive waste piping systems

When installing a drainage system being corrosive free is essential. Metals have been traditionally used in laboratory and industrial DWV applications and can generally fail due to corrosion. Polypropylene plastic waste systems are suitable for use in chemical and industrial plants as well as in food and beverage, hospital and university laboratories, anywhere where mixtures of acids, bases and solvents are drained. Polypropylene is resistant to the corrosive action of alkalis, alcohols, acids, solvents and salt solutions.

So what then is CPVC

Chlorinated polyvinyl chloride (CPVC) is created by subjecting PVC resin to a post chlorination reaction that results in additional chlorine atoms on the base molecule; this results in an amorphous thermoplastic material similar to PVC with added advantages: a higher heat distortion temperature and improved fire performance properties at relatively low cost compared to alternate materials. As with PVC, the physical properties of CPVC can be altered considerably to provide desirable properties by compounding techniques.

What is PVC

Polyvinyl Chloride (PVC) is an amorphous thermoplastic material that can be formulated or “compounded” to target a specific application.
Minor ingredients must be blended with PVC resin to create a PVC compound that is processable into a finished product. The physical properties of PVC can be altered considerably to provide desirable properties by compounding techniques. Additives such as impact modifiers, stabilizers, lubricants, processing aids, pigments and other ingredients can be modified to obtain desirable properties.
As such, PVC is available in a wide range of products from flexible tubing, film packaging materials, and vinyl siding, through various blends that can be used to produce rigid PVC pressure piping.

Hydraulic Shock

Hydraulic shock is the term used to describe the momentary pressure rise in a piping system which results when the liquid is started or stopped quickly. This pressure rise is caused by the momentum of the fluid; therefore, the pressure rise increases with the velocity of the liquid, the length of the system from the fluid source, or with an increase in the speed with which it is started or stopped.

Examples of situations where hydraulic shock can occur are valves, which are opened or closed quickly, or pumps, which start with an empty discharge line. Hydraulic shock can even occur if a high speed wall of liquid (as from a starting pump) hits a sudden change of direction in the piping, such as an elbow. The pressure rise created by the hydraulic shock effect is added to whatever fluid pressure exists in the piping system and, although only momentary, this shock load can be enough to burst pipe and break fittings or valves.

Christmas Post 2015

GF Piping Systems would like to wish you a safe and enjoyable Christmas, and New Year. We look forward to a busy 2016 for all.

Please note that our blog will be not be monitored during the festive season from COB Wednesday 23 December 2015, until Wednesday January 6, 2016.

Please note our offices throughout Australia will be closed on Thursday December 24, 2015, and will reopen on Monday January 4, 2016. Contact our customer service team to ensure we can meet your requirements before we close for the festive season.

Effective handling and transporting of pipes

Vehicles used to transport pipes must be capable of accommodating the full pipe length. The pipes must be supported to prevent them bending or deforming. The area where pipes rest (including side supports) should be lined with padded sheeting or corrugated cardboard to avoid damage by protruding rivets or nails. To prevent damage, pipes and fittings must not be slid over the transport vehicle’s loading area, nor should they be dragged along the ground to their place of storage.

Due care must be taken with loading and unloading. If lifting gear is used, this must be fitted with special pipe grips. Throwing pipes and parts down from the cargo surface is unacceptable.

Impacts must be avoided at all cost, especially at ambient temperatures below 0°C where many plastics (e.g. PVC) have significantly lower impact resistance.

Pipes and fittings must be transported and stored so that they cannot be soiled by earth, mud, dirty water, etc. It is recommended sealing pipes with protective end caps to prevent dirt entering the pipes.

 

Pressure loss with valves and fittings in pipelines

The pressure losses depend upon the type of fitting as well as on the flow in the fitting. The so-called ζ-value is used for calculations.

To calculate the total pressure loss in all fittings in a pipeline take the sum of the individual losses, i. e. the sum of all the ζ-values. The pressure loss can then be calculated.

The kv factor is a convenient means of calculating the hydraulic flow rates for valves. It allows for all internal resistances and for practical purposes is regarded as reliable.

The kv factor is defined as the flow rate of water in litres per minute with a pressure drop of 1 bar across the valve.