According to Georg Fischer Piping Systems , growing concerns with regard to the environment have prompted federal, state and local regulators to create guidelines, to protect the environment from industrial pollution. Many regulations provide penalties for owners, managers and employees for environmental damage and safety infractions caused by chemical spills and leaks. The penalties are particularly for cases where leaks from piping system failures at workplaces result in damage to equipment, the environment and/or cause harm to people.
The risk of harming the surroundings, equipment and people, can be eliminated with the use of double containment piping systems, wherever environmentally hazardous media must be conveyed. Double containment piping systems used in conjunction with moisture detector sensors are a cost-effective solution for the controlled conveyance of aggressive media. There are three solutions that are available.
The first is a retrofit system (Contain It) where split pipe of a PVC pipe is fitted over existing pipe work (thermoplastic, thermosets or metal). If the inside carrier pipe work fails, the outside containment pipe will allow the leaking fluid to flow into a designated annular space before isolation is achieved without any leakage to the environment. The retrofit system was developed primarily for the petro-chemical industry where all fuel lines were required to be double contained to meet federal regulations such as the UST laws.
Since then it has been used by companies such as Boeing, Intel, Hyundai, Honda, Fujitsu, Kanto Chemical, Northwest Airlines and Borden Chemical for protecting the conveyance of various media including fuel and acids as well as biomedical waste in hospitals.
Installation of the Contain It system is simple. Two half shells of clear PVC pipes are fitted around the outside of existing pipe, up to 4”. The shells are aligned through a tongue and groove construction, which is positioned around the internal carrier pipe with internal spacers. This is secured with an adhesive system to seal the units. The fittings are assembled in a similar manner using stainless steel pins to align and secure the fittings before bonding. The pipe and fitting joints are then welded together through an injection bonding process. Once all welds are complete, final containment inspection is achieved through a low pressure air or a hydrostatic test.
The second system, Contain It Plus, is used for new systems or to replace existing systems. It uses a method where the external containment pipe is also pressure rated. If a leak occurs, the fluid will be contained in the outer protective pipe until the damage can be located and attended to.
The Contain It Plus system is designed for conveyance of aggressive and non-aggressive media, and utilises industrial grade plastics for the internal carrier pipe and fittings. The plastic carrier piping materials used (PVC-U, PVC-C, PE100, PP and PVDF) are suitable for acids and alkalies with temperatures ranging from -40ºC to 140ºC, and are selected depending on the system parameters such as the chemical conveyed, the working pressure and temperature. These systems are available in sizes up to 225mm.
The internal pipe is joined through standard methods such as solvent cemented/butt or socket welded, depending on the material and pipe size. The external containment pipe is a PE100 material and is joined through electro fusion. The principle of the patented double containment pipe jointing technology is based on the inner pipe being jointed first. This technology enables the double pipeline to be joined similarly to a single pipeline. The fittings are manufactured as a combined internal/external fabrication.
For a fitting, using the example of 90 degree elbow, the carrier part of the elbow is PVC, which is housed in a PE100 material. This design enables solvent cementing of the PVC internal material and then electro fusion of the outside PE100 material at a later time. Prior to solvent cementing of the PVC pipe and fittings, the external PE100 pipe slides over the internal pipe and is positioned through spacers prior to the internal pipe and fittings being joined.
The external PE100 pipe is cut 60mm shorter to the distance left after the internal PVC pipe is joined. A 30mm gap is then left between the fitting and the exterior PE pipe, which allows for visual inspection during pressure testing of the PVC carrier pipe.
After the completion of a pressure test, a PE100 snap ring is inserted into the 30mm gap and the electro fusion fitting slides into place over the joint area and fused. This leaves a sealed and pressure rated system for the medium and containment pipe.
The third system, designed for drainage, utilises a DWV pattern design to allow double containment of a gravity line. This can be done using the Fuseal range of PP or PVDF.
Using electro-fusion technology, and a combination of resin materials, drainage lines to 12” can be contained in this Imperial product group with secondary piping to 16”. The specific design of these systems allow for leak detection, gravity flow, and processing of fluids through dilution and neutralisation tanks.
Visual or electronic leak detection units can be installed through a termination fitting. The termination fittings also allow for isolated leak detection sectors to be established, while maintaining a continuous inner pipe. All containment systems can be fitted with moisture detection sensors that enable alarms and/or automatic system shutdown or isolation to be activated if a leak occurs.
Double containment piping systems exhibit benefits for both the user and the system builder. These systems reduce the possibility of danger where hazardous media are conveyed within the plant in addition to cutting down on potential downtime in production.
The use of cyanide in gold mining operations is an example of an application where a double containment system would be beneficial. Double containment piping systems comply with the international cyanide management code, where standards of practice outline the requirement of implementing measures to protect the environment and persons through the prevention or containment of spillage.
When properly installed, double containment piping systems meet the legal requirements and help to lower insurance premiums. After calculating the cost of penalties and the costs of cleaning up spills and leaks, it becomes obvious that the industry has a legal and financial responsibility to protect the environment.
In the case of damage, an integrated leak detection system makes it possible to locate the leakage point rapidly. Investing in a safe double containment piping system is beneficial as the costs of renovation and subsequent precautionary measures (e.g. a special fire brigade for chemical spills) can be reduced or eliminated.