Pex Tubing
Pex tubing is a thin, flexible plastic that is used in plumbing and heating applications. Pex tubing can be handled easily, and doesn't droop or sag like metal or rigid plastic piping does.
Pex is made from polyethylene which makes it resistant to chemicals, moisture, hydrocarbons, oxygen, and radiation.
The difference between Pex and other types of pipe is that if you break a piece of Pex tubing off (either accidentally or by accidently puncturing it) the broken end will harden into a brittle piece while the coil remains as flexible as ever.
Pex tubing is used in commercial applications ranging from the residential and industrial to large utility corporations such as gas, electric, water and telecommunications. The tubing is used for plumbing applications including hot and cold water lines, drainage lines, sewer systems, radiant flooring installations, heating for floor coverings (such as tile), fire sprinkler systems (water) and gas piping.
Pex insulated electrical cable covers are also used in electrical wiring to provide additional protection from the elements or during installation of the cable. The tubing is also used in HVAC systems as an insulation sleeve.
The use of Pex tubing is expanding in the commercial market to include fire sprinkler systems, as an insulation sleeve for HVAC air handling ducts, and as an inner seal for hot water lines. It has been used as a ducting material for air conditioning (RID) applications and in the process of designing air handlers (RIM).
Pex tubing is used in commercial settings where the temperature of the fluid being transported must remain constant, such as oil and gas pipelines and oil/water separator tanks. It is also used in industrial applications where continuous heat transfer is required, such as furnaces, chiller boilers, machine rooms, and heat exchangers.
This type of tubing comes in a variety of sizes and materials which can range from copper to steel. It has multi-layered walls that are designed to resist deformation without affecting the flow characteristics or strength properties of the material. Tubes are available with Pex joints (butt welds) which allow quick installation with cold or hot water supply lines.
Compared to other pipe materials, Pex is more flexible and easier to install. It is also easier and quicker to repair if it should become damaged. However, Pex is not as long-lived as other types of piping materials, so it must be replaced sooner than the typical 10–15-year life span.
Pex tubing can be formed and cut at room temperature, unlike high-temperature cutting machines which have several steps of heating and cooling in order to create a cutting edge on end of the tube (usually a thin metal blade). Pex tubing can also be melted and molded into complex shapes for plumbing applications.
Pex tubing consists of a series of individual tubes and is formed by cutting the ends, heating the tube, and pulling it through a machine. Pex tubing has a range of installation tolerances depending on the application, but typically has very tight tolerance for water-jacketed lines (pipe with a water jacket surrounding its circumference) while having typical tolerances for other applications. The initial installation process typically involves slipping Pex onto metal fittings, pushing the ends together and crimping them. However, if an industry standard to form Pex tubing is to be used then much less care must be taken during this step, as there are many tools for forming Pex in place.
Pex tubing can be used in nearly any type of installation, especially plumbing. Clutch applications are common for Pex tubing being used with a coupling. Pex comes in a range of colors and styles which allows it to blend in with its surroundings and is fire-resistant so it may be installed in areas where there is potential for fire exposure. It can also be recycled if damaged.
Although the use of PEX pipe is very efficient, durability is still an issue. This was discovered from different experiments that were conducted by using same types of pipes over a 12-month period at the same time on an average flow rate (70 kg/hr). The results showed that PEX pipes can be used for at least eight years, and copper pipes can be used for at least five years. However, if high flow rate is expectable then PEX can be used for only three years and copper pipes cannot be used so easily. These problems are caused due to the different types of chemical reactions that are taking place in these materials over time.
As it ages, PEX tubing may lose its flexibility and elasticity causing it to lose its ability to bend with ease. This can cause serious issues if the tubing is exposed to extreme temperatures, as well as being affected by chemicals.
PEX tubing is commonly made of polyethylene, and can be used to transport gas and liquids at temperatures ranging from -40 to 140 degrees Fahrenheit. It is not recommended that PEX be used for applications where the fluid type, temperature or pressure will vary greatly. Pex piping is crushed, but only slightly. When it gets brittle when cold water is run through it that is a sign of problems with the material.
Pex pipes are susceptible to chemical corrosion, resulting in the development of acidic byproducts. Acidic water can cause the deterioration of this pipe's physical structure. Corrosion is not limited to the top layer of the pipe, but also attacks the polyethylene in the middle layers of the pipe (due to high temperatures, changing pressures, or moving and twisting).
PEX tubing was intended for potable water service. However, many American water utilities have switched from chlorinated water systems which makes PEX tubing incompatible with most municipal drinking water systems. Additionally, PEX does not have an FDA approved food contact rating. The U.S. Department of Transportation (USDOT) requires that PEX be used in a controlled environment in order to ensure that it will not contaminate hydraulic fluids passing through it.
As with any pipe installation, proper planning is the key to a successful project. The pipes are not normally installed in the finished product, but rather in an area where there is easy access to all sides of the pipe for both inspection and maintenance. Pipes can be installed either on-site or off-site in a controlled environment.
A variety of fittings allow PEX tubing to be used in nearly any application. These fittings range from simple unions or couplings that join two pieces of tubing together into a complete assembly where multiple pieces are joined together and have end caps attached to them.
Conclusion:
PEX is a versatile material used in many plumbing applications.
It is not recommended that PEX be used in areas where the fluid type, temperature or pressure will vary greatly.
If using PEX, it should be installed in an area that can be readily accessed for inspection and maintenance.
1. Leveen JW, Mertz RG. Corrosion of polyethylene (PE) pipes for potable water distribution systems. CEN-CENELEC Technical Committee 76 WG 2 -2001 . Brussels: CEN; 2001 . Chapter 1: 3–24 .
2. Ball A, et al.. Potable water applications of crosslinked polyethylene (PEX).
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Pex Tubing