Double-walled pipe
Encyclopedia
A double-walled pipe is a secondary contained piping
system. It is a pipe
within a pipe, or encased in an outer covering, with an annulus
(interstitial space) between the two diameters. The inner pipe is the primary or carrier pipe and the outer pipe is called the secondary or containment pipe. The great majority of double-walled piping applications involve wastewater
, groundwater
, and process safety
.
U.S. Environmental Protection Agency (EPA) standards, published in 40 CFR
Parts 280 and 281, mandate double-walled piping for many below-ground transport systems in wastewater treatment plants and at sanitary or hazardous-waste landfills or remediation sites. These and other regulations affect below-grade transport of hazardous materials in fuel storage systems, tank farm
s, drainage or runoff from process plants, and some food-processing and related applications. Double-walled containment systems are also used for certain classes of toxic or corrosive chemicals, mostly gases, used in semiconductor fabrication
. Double-walled pipes may also be used where a waste water pipe traverses a drinking water catchment
area.
Double-walled pipe system may use plastic pressure pipe systems materials of high-density polyethylene (HDPE), polyvinyl chloride
(PVC), chlorinated polyvinyl chloride
(CPVC), polypropylene
(PP), polyvinylidene fluoride
(PVDF), and ethylene chlorotrifluoroethylene copolymer (ECTFE). Dual-wall stainless steel
tubing is most commonly used in semiconductor plants for the containment of highly toxic gases.
A leak detection
system in the containment pipe indicates if the carrier pipe is leaking. Double wall pipes are usually hydrostatically tested
, or tested to hold and maintain a target gas pressure before the first use.
A different special application of a double-walled pipe is a jacketed pipe, which is used to make high viscosity
liquids flow at elevated temperature through the carrier pipe. The outer pipe circulates hot fluids that heat up the interior carrier pipe and its contents in turn.
Piping
Within industry, piping is a system of pipes used to convey fluids from one location to another. The engineering discipline of piping design studies the efficient transport of fluid....
system. It is a pipe
Pipe (material)
A pipe is a tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases , slurries, powders, masses of small solids...
within a pipe, or encased in an outer covering, with an annulus
Annulus (mathematics)
In mathematics, an annulus is a ring-shaped geometric figure, or more generally, a term used to name a ring-shaped object. Or, it is the area between two concentric circles...
(interstitial space) between the two diameters. The inner pipe is the primary or carrier pipe and the outer pipe is called the secondary or containment pipe. The great majority of double-walled piping applications involve wastewater
Wastewater
Wastewater is any water that has been adversely affected in quality by anthropogenic influence. It comprises liquid waste discharged by domestic residences, commercial properties, industry, and/or agriculture and can encompass a wide range of potential contaminants and concentrations...
, groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
, and process safety
Process safety
Process safety focuses on preventing fires, explosions and accidental chemical releases in chemical process facilities or other facilities dealing with hazardous materials such as refineries, and oil and gas production installations.Occupational safety and health primarily covers the management of...
.
U.S. Environmental Protection Agency (EPA) standards, published in 40 CFR
CFR
CFR can refer to:* Code of Federal Regulations of the United States* Council on Foreign Relations, U.S. foreign policy think tank* Campaign finance reform in the United States* Cost and Freight, word used in international commerce...
Parts 280 and 281, mandate double-walled piping for many below-ground transport systems in wastewater treatment plants and at sanitary or hazardous-waste landfills or remediation sites. These and other regulations affect below-grade transport of hazardous materials in fuel storage systems, tank farm
Tank farm
Tank farm may refer to the:*Alternate name for an oil depot, a facility for storage of liquid petroleum products or petrochemicals*Tank Farm, also known as 'Tuff Crater', a volcanic crater in the Auckland Volcanic Field, New Zealand...
s, drainage or runoff from process plants, and some food-processing and related applications. Double-walled containment systems are also used for certain classes of toxic or corrosive chemicals, mostly gases, used in semiconductor fabrication
Semiconductor fabrication
Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. It is a multiple-step sequence of photolithographic and chemical processing steps during which electronic circuits are gradually created on a wafer...
. Double-walled pipes may also be used where a waste water pipe traverses a drinking water catchment
Water well
A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump...
area.
Double-walled pipe system may use plastic pressure pipe systems materials of high-density polyethylene (HDPE), polyvinyl chloride
Polyvinyl chloride
Polyvinyl chloride, commonly abbreviated PVC, is a thermoplastic polymer. It is a vinyl polymer constructed of repeating vinyl groups having one hydrogen replaced by chloride. Polyvinyl chloride is the third most widely produced plastic, after polyethylene and polypropylene. PVC is widely used in...
(PVC), chlorinated polyvinyl chloride
Chlorinated polyvinyl chloride
Chlorinated Polyvinyl chlorideDensity1.56 g/cm3Young's modulus 2.9-3.4 GPaTensile strength50-80 MPaElongation @ break20-40%Notch test2-5 kJ/m2Glass temperature 106 - 115 °CMelting point212 °CVicat B106 to 115 °C...
(CPVC), polypropylene
Polypropylene
Polypropylene , also known as polypropene, is a thermoplastic polymer used in a wide variety of applications including packaging, textiles , stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers, automotive components, and polymer banknotes...
(PP), polyvinylidene fluoride
Polyvinylidene fluoride
Polyvinylidene fluoride, or PVDF is a highly non-reactive and pure thermoplastic fluoropolymer.PVDF is a specialty plastic material in the fluoropolymer family; it is used generally in applications requiring the highest purity, strength, and resistance to solvents, acids, bases and heat and low...
(PVDF), and ethylene chlorotrifluoroethylene copolymer (ECTFE). Dual-wall stainless steel
Stainless steel
In metallurgy, stainless steel, also known as inox steel or inox from French "inoxydable", is defined as a steel alloy with a minimum of 10.5 or 11% chromium content by mass....
tubing is most commonly used in semiconductor plants for the containment of highly toxic gases.
A leak detection
Leak Detection
Pipeline networks are the most economic and safest pipeline transport for mineral oil, gases and other fluid products. As a means of long-distance transport, pipelines have to fulfill high demands of safety, reliability and efficiency. Most pipelines, regardless of what they transport, are designed...
system in the containment pipe indicates if the carrier pipe is leaking. Double wall pipes are usually hydrostatically tested
Hydrostatic test
A hydrostatic test is a way in which leaks can be found in pressure vessels such as pipelines and plumbing. The test involves placing water, which is often dyed for visibility, in the pipe or vessel at the required pressure to ensure that it will not leak or be damaged. It is the most common method...
, or tested to hold and maintain a target gas pressure before the first use.
A different special application of a double-walled pipe is a jacketed pipe, which is used to make high viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
liquids flow at elevated temperature through the carrier pipe. The outer pipe circulates hot fluids that heat up the interior carrier pipe and its contents in turn.