Many process plants handle harmful and corrosive liquids. To assure the best possible protection of life and property, operators need to focus special attention to their inventory- or day-tanks. These vessels are the points with the highest accumulation of dangerous fluids on their facilities.
The right combination of dedicated sensors and controllers can be used to design a redundant filling level control monitoring system; their continuous and limit switches which are taking care of crucial filling levels.
Continuous Level Control
Ultrasonic, radar or hydro static level sensors generate a continuous signal which allows precise filling and emptying control. They are used e.g. in batching or mixing processes but also for simple inventory control. The sensors directly control the process during daily operations.
Even most advanced continuous technologies can be prone to measurement errors or malfunctions. But the handling of harmful fluids does not leave any room for loss of control. That is where limit switches play an important role as a redundant safety system.
At least one pair of limit switches is placed into a tank – one at the maximum and another one at the lowest allowed filling level. Most limit switches are designed to react as soon as they get in physical contact with the process media – as soon as the minimal or maximum level had been reach. This usually only happens if the continuous sensor fails. Still the environment is safe due to the fact that the switches directly connect to the power supply of the pump or the valve of the inlet.
Only by applying both technologies operators can guarantee protection of life and equipment, even if one system may fail.
Refrigeration and Cooling plants in general using plastic pipe as the carrier system offer complete corrosion resistance and a cost effective solution compared to traditional metal materials.
Pressure ratings for thermoplastic pipe are always quoted for water at 20 °C. It can be used at higher temperatures but it is a fundamental principle in thermoplastic pipework that if the working temperature is increased then the working pressure must be reduced.
The design and installation of thermoplastic pipe systems requires designers and installers alike to take into account the fact that plastics have different physical characteristic to metal.
As a general rule for designing and installing plastics one of the major differences is that plastics can and should be allowed to move after commissioning i.e. move under the influence of temperature fluctuation and pressure changes. For instance using pipe brackets that allow horizontal movement and not clamping the system in place is a must for plastic piping installations.
Polybutene has the least thermal expansion of all the plastics. The low expansion forces (30 times less than steel and 10 times less than composite piping) means that the material can absorb the expansion in itself.
This, in turn, saves on expansion legs or joint and makes it possible to use standard fasteners, so clean and aesthetically pleasing installations can be built, even where space is limited.
- space-saving installation
- no maintenance
- easy to install
- the flexibility of polybutene enables making smaller changes in direction without the use of fittings. This saves on parts and valuable on-site time.
- polybutene retains its flexibility and easy handling even at low temperatures
- pre-fabricated riser pipes can be transported in coils and installed in shafts on site easily and quickly
- very durable due to its high resistance to chemicals
Planning and installation of piping systems is a true engineering task, necessitating the organisation of a multitude of requirements and goals. For piping installations, simple, critical and aggressive media in each case require suitable materials. The idea is to especially cover the requirements of functionality, operating safety, optimal service life, environmental conditions and adequate profitability. Included in this are overall ecological, technical and economic assessments. High-performance plastics for piping installations are proven and implementable where special endurance problems in connection with the media need solving.
Environmental protection is an important responsibility affecting us all. Each one of us, businesses and industrial concerns alike have to meet this great challenge.
Ecological balance for plastic piping systems
- Raw material requirements
- Energy requirements
- Impact on:
– Hygienically safe | Air | Water | Disposal
– Economic | Technical | Ecological
- Product use
– Long service life | Proven in practice | Good recycling characteristics | High chemical resistance properties | Simple handling | Negligible piping losses | Cost-effective
An analysis of the individual positions for an ecological balance, it can be demonstrably established that plastic piping systems are not only economical, but also technically and especially ecologically profitable when compared with other material systems.
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.
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).
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.
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.
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.
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.
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