Terminology

Aggregate pipe coefficient (C)	The aggregate pipe coefficient (C) is a safety buffer (safety reserve) to allow for the additional loads that occur in pipe systems. It corresponds to the safety factor (SF). 1.25 for water and 2.0 for gas.
Bead formation in butt-welding	Visual inspection of the form in which the bead is created can provide an indication of weld quality. However, such evaluation requires sound, appropriate, practical and theoretical expertise about the welding process.
Bending radius	In bending pipe, certain bending radius should not be exceeded (See Specification Manual table 6.3)
Brackets	Brackets (See Specification Manual paragraph 6.7) have the task of transferring the effective loads on the pipe system to the building structure or infra structure.
Building connections	Connections of building can be exposed to settling, which can be compensated by creating deformable zones.
Burning behaviour	Plastics are organic compounds and therefore combustible by nature.
Butt-welding equipment	The principle pieces of butt-welding equipment are: plane (in pipe construction machines), hot plate, clamping tool and hydraulic unit. Construction site (portable, e.g. trench welding machines) and workshop machinery (stationary welding machines) may be used. Construction-site machines are increasingly being converted to CNC controlled machines (fully automatic), which enable the construction-site operation to ensure reproducibility of welding joints and the automatic production of reports
Compensation for length changes	The inclusion of elbows, expansion couplers or compensators can compensate for length changes.
Compensators	Compensators are used if other compensation options cannot or can only be partially applied. The design depends on operating pressure and temperature. Axial, lateral and angular compensators are used.
Concrete-encased pipe systems	Concrete-encased pipe systems function as a fixed restraint. Fittings behave in concrete as fixed points and are therefore also subject to the same stresses, which means that any heat stresses must be absorbed and compensated for in the pipe system.
Connection method	In plastic pipe construction, there are two types of connecting technologies: detachable and non-detachable.
Creep tensile test	The creep tensile test is used to determine the creep modulus.
Detachable connection technology	Detachable connections, like flange joints and unions can be easily disassembled and re-assembled without destroying the connection.
Elasticity modulus (Creep modulus)	The elasticity modulus is the ratio of stress to expansion.
Elastomers	Elastomers are better known as rubber. They are wide-meshed, spaciously interlinked synthetic or natural rubber compounds. Interlinking is enhanced by vulcanisation.
Elbow	Elbows (expansion bends) absorb length changes by moving laterally perpendicular to the expansion direction. Depending on structural and spatial conditions, they can be U, L or Z shaped.
Electrofusion	Electrofusion is a practice also known as electric "sleeve" or "saddle" welding. The joining of the welding mates is effected by an electrofusion coupling on the inside of which an integrated heating coil (electrical resistance coil) is charged with current during the welding process and is heated as a result of its electrical resistance. As a consequence, the surfaces of both the coupling and the pipe or fitting (i.e. the contact areas) are plastcised. The process creates a homogeneous jointing between electrofusion coupling and pipe/fitting.
European standards	prEN 15014 Pressure Drainage & Sewerage is the harmonised European standard for buried or aboveground pressure facilities for general purpose water, drainage, sewerage and irrigation, as well as for any other pressure applications involving other fluids. National standards have been revised in order to comply with European standards.
Evaluating welded joints	Visual inspection is a non-destructive method of evaluating welds frequently employed in practice. This evaluation is primarily concerned with appearance (e.g. welding bead of butt-welding). It is however a type of assessment requiring theoretical and practical knowledge, as well as appropriate tester experience. If more accurate indications of weld quality are needed, then a more expensive non-destructive (e.g. ultrasonic or X-ray test) or destructive testing method has to be adopted.
Expansion couplers	Expansion couplers are predominantly employed in pressureless systems as connection elements and compensation for length changes.
Extruder	An extruder (See Specification Manual paragraph 1.5.1) is responsible for plasticising raw materials. Used, for example, in the manufacture of pipes, profiles and plates. Continuous process.
Extrusion welding	Four different variants of extrusion welding (See Specification Manual paragraph 9.2.4) are used. The individual variants are different in terms of material supply, type of welding equipment (e.g. hand extruder) and pressure tool (e.g. plunger, welding shoe). An extrusion welding extruder generally has the following elements: plasticising unit, hot gas tool and device for applying the required welding pressure.
Fixed points	Fixed points in association with suitable bracket concepts prevent shifting or movement of pipe systems.
Flange connections	Can be fixed or backing ring connections. Backing ring connections consist of the components: stub flange, backing ring and gasket. A combination of stub flange, backing ring, blind flange and gasket can be used to seal pipes. At higher loads, backing ring connections are preferable to fixed flange connections.
General quality controls	In connection with general quality controls, relevant tests should be run to ensure the quality and functionality of the employed fittings as well as the factory-made or on-site manufactured pipe systems. Such tests are best served by non-destructive test procedures.
Gluing	Gluing is only very conditionally meaningful and possible as an appropriate jointing technology for polyolefin materials. A bond is produced only with special multi-component adhesives. These glued connections are not at all capable of withstanding mechanical loads.
Ground water	Areas having a high ground water table can load external overpressure on the pipe system. The same holds true for concrete-encased pipe systems, which are exposed to short-term heightened overpressures. Both cases require the calculation of dent resistance.
Guide brackets (Guide saddles)	They serve to absorb both vertical and horizontal forces. (See Specification Manual paragraph 6.7)
Hand welding	The welding tool in which the appropriate nozzle is mounted (in most cases a round nozzle) is moved in a fanning motion over the surfaces to be welded. In this way, the substrate and welding filler are heated until the material in the welding zone is placticised. The filler (mostly in the form of a rod) is perpendicularly pressed by hand into the welding zone. The necessary welding or jointing pressure is applied by pushing down the welding rod by hand during the welding process. Appropriate welder skills and abilities are therefore required.
Health assessment of PE	The health assessment of plastic is laid down in food legislation and differs from country to country, making it necessary for manufacturers to inquire further. In the Netherlands, regulations have been established to govern substance quantities that can be present in end products. Authorised Lists have been formulated containing the materials that meet imposed requirements. PE is found on these Authorised Lists.
Heat conductivity	Variable indicating the capacity of a material to conduct heat. Filling, reinforcements, auxiliary material and coloring affect heat conductivity.
Heat expansion coefficient	The heat expansion coefficient is an important parameter in plastics. A statement of this mechanical value is usually accompanied by an indication of the linear expansion coefficient () (in literature, this is mostly expressed as the mean linear longitudinal expansion coefficient ).
Heat resistance	This term designates the temperature limits of thermoplastics under the effects of heat. Testing procedures are Martens, Vicat and ISO/R 75. No conclusions about working temperatures are possible.
Heat transfer coefficient	This variable is used to calculate the heat transition coefficient. It depends on the separation plane, geometry and flow speed of the medium.
Heat transition coefficient	The heat transition coefficient (k) provides information about the insulating capacity of a material.
Hot gas welding technologies	Hot gas welding is distinguished into hand welding, speed welding and extrusion welding. The plasticisation of the welding zones occurs by heating the welding surfaces (and filler material) with hot air. For this purpose, hot air is forced through a nozzle shaped specifically to sufficiently heat and plasticise the joint surfaces.
Impact resistance	Impact resistance is determined by means of the impact flexural test and the notched impact flexural test (the latter involving defined notches in the sample). Most important test methods are the "Charpy" and "Izod" tests.
Injection moulding machine	Injection moulding involves a discontinuous manufacturing process. The screw performs both a rotational and an axial motion. Important parameters for injection moulding are: temperature, time and pressure. Process steps are: plasticisation, injection and cooling.
Internal overpressure	Internal overpressure can result in pipe expansion, especially under the effects of heat. Sudden changes in operation conditions can cause pressure surges.
Internal pressure creep test	Simulates the life expectancy of a plastic pipe under an internal pressure load. The associated reference stress (_ref) is a function of the internal pressure, mean pipe diameter and wall thickness. It is calculated using the boiler formula.
Internal pressure loads	Internal pressure loads create stresses in various directions. Radial stresses, axial stresses and tangential stresses can occur.
Internal underpressure / external overpressure	Exposed to internal underpressure or external overpressure, a pipe will tend to buckle, which means it deviates for its ideal form (circular cross section). The critical buckle pressure should be calculated with regard to stability.
Length change	The length change of a pipe system is caused by varying operating temperatures, varying ambient temperatures or internal pressure loads. Frequently, several of these influences are superposed.
Maximum operating pressure (MOP)	The internal pressure load capacity was formerly used to designate the nominal pressure "PN" of pipes and fit tings. In the European standards, the designation has been abandoned and replaced by (SDR) or (ISO-S).
Melt index	The melt index indicates the flow capacity of a plasticised plastic. Previously known as the MFI value, it is now referred to as the MFR value.
Minimum required strength (MRS)	The minimum required strength corresponds to the reference stress (_ref) of water at 20°C and a service life of 50 years.
Non-detachable connection technology	Disassembly usually involves destruction of at least one of the connecting elements. Examples are butt-welding and electrofusion.
Notch effect	The notch effect affects the strength of the component. Grooves, scratches, inhomogenities or a component's structural form can have adverse affects on the fittings.
Orientation	Alignment of the macromolecules by external forces (e.g. extraction speed).
PE welding	Welding is for plastic pipe systems and equipment construction a common jointing technology. PE pipe systems are prominently jointed by butt-welding and electrofusion method.
Permeation	Diffusion tendency of a material, which is the permeability of fluids or gaseous elements through the plastic.
Pipe bending	Pipe bending is usually caused by the dead weight of the pipe and/or additionally incorporated valves and pipe fill. The relevant bracket distances (support distances) must therefore be determined and the suitable pipe brackets incorporated.
Pipe series number (ISO-S)	The pipe series number (ISO-S) indicates the internal pressure load capacity of a pipe, while taking a safety factor into account.
Plastic	Plastic is divisible into three main groups: thermoplastics, thermosets and elastomers.
Plastic processing machines	Extruders, injection moulding machines and calendars (not discussed in the Akatherm Specification manual and website) are machines used to manufacture plastic semi-finished products.
Polyethylene	Polyethylene is abbreviated "PE". PE is a semi-crystalline thermoplastic belonging to the polyolefin group. Depending on the average molar mass, the compound produced may be PE-LD (low density PE), PE-LLD (linear low density PE), PE-MD (medium density PE) and PE-HD (high density PE).
Polyolefin	This compound belongs to the group of semi-crystalline thermoplastics. Its most important representatives are polyethylene (PE) and polypropylene (PP).
Pressure test	The pressure test is only used for pressure pipe systems. It verifies both internal pressure stability and the leak-tightness of the system. Pressure tests consist of two test stages: the pre-test and the main test. In exceptional cases, a short-term test can be urn on pipe systems in which d_e 50 mm and pipe length is a max. 100 m.
Protective measures for above ground pipe systems	They are used to improve the insulation properties of pipe systems. The use of concomitant heating is necessary in many cases. Protective measure may also be taken against UV radiation.
Push-fit and expansion sockets	These are simple detachable connections. However, they should only be used in pressureless (under and overpressure free) pipe systems. They are therefore appropriate for pressureless drainage and/or sewerage systems.
Push-fit socket end thrust bearing	Plug and socket type water jointing system with push fit joints. A tough thermoplastic 'grip' ring located in a tapered groove allows the joint to resist end-thrust. It is quick and easy to install. No anchors or thrust blocks required. Suitable for ground subsidence areas and to limited space installation. Immediately serviceable.
Railway traffic loads (railway crossings)	The national guidelines for installation under railways and railway facilities as well as for railway crossings need to be taken in account.
Residual after-pressure stress	Phenomenon in injection moulding components. Residual after-pressure stress can also occur in extrusion components when, for example, after pressure has to be used in manufacturing solid bars to prevent bubbles and cavities.
Residual crystallisation stress	This occurs in semi-crystalline plastics (e.g. PE) due to crystallite formation during the cooling phase.
Residual orientation stress	Dependent on cooling conditions. Increasing cooling speed raises the stress potential in pipes.
Residual stress	During an extrusion process, residual stresses build up in pipes as a result of cooling procedures at high extraction speeds, for example. These stresses can be reduced in pipes by adopting special temperature controls or heat treatments (tempering).
Retraction	Retraction designates a longitudinal contraction (negative length change) in the direction in which the macro molecules are oriented.
Safety factor (SF)	The safety factor (SF) corresponds to the aggregate pipe coefficient (C).
Seals	Seals are needed to seal connections between two connecting elements. In the flange connections used in plastic pipe construction, flat gaskets (with and without steel inlays) and O-rings are mostly used. The material of the seal is adaptable to the flow medium.
Short-term tensile test	The short-term tensile test involves stretching a sample bar to the breaking point. The result provides an indication of the mechanical values of the tested material. The most important mechanical values are: expansion, tensile strength, breaking strength and breaking strain.
Shrinkage	In contrast to retraction, shrinkage designates a volume contraction (negative volume change) as a result of cooling processes. In contrast to retraction, a volume change is discernible in every plastic component. These volume changes are seen in the fitting structure and in the die or mould structure.
Sliding and hanging brackets (sliding and hanging bracket sleeves)	They are only able to absorb vertical forces.
Soil load	The soil layer on top of the pipe loads weight on the pipe and can cause it to deform. This load therefore has a significant effect on the pipe structure and the service life of the pipe.
Speed welding	The heating of the substrate and filler occurs by means of the beak-shaped tip at the lower end of the speed-welding nozzle. The necessary welding pressure is applied by this nozzle.
Standard dimension ratio (SDR)	The Standard Dimension Ratio (SDR) indicates the relationship of the pipe outside diameter to wall thickness.
Surface hardness	Designates the resistance against the penetration of the test specimen. Most important procedures are Shore A, Shore D and ball indentation hardness.
Temperature loads	Temperature loads have a very large effect on the mechanical properties of plastic pipe. Attention is first of all to be paid to the relatively large thermal length change.
Tempering	Heat treatment to reduce or eliminate residual stress potentials.
Tensile and compressive stresses on the pipe wall	They are created during pipe manufacture due to differing cooling conditions. Compressive stresses arise in the outer wall of the pipe (usually the first surface to cool) and tensile stresses on the warmer inner wall of the pipe.
Testing welds	A distinction is made between destructive and non-destructive tests. Destructive test methods are chiefly used to evaluate cases involving damage claims.
Thermoplastics	Thermoplastics can be divided into amorphous and semi-crystalline thermoplastics.
Thermosets	Thermosets possess a close-meshed interlinked macromolecular structure. They are hard, brittle and no longer plasticisable (meltable).
Tools used in extrusion welding	Work performed in extrusion welding makes use of a hand or stationary extruder with swivel head and transfer hose.
Traffic loads	Traffic loads are additional external loads that can affect the pipe system. They require special protective measures. If the prescribed minimum soil layer over the pipe is not maintained, protective pipes may have to be installed
Trench form, pipe embedding and backfill	Pipe trench design substantially influences the bearing capacity and stability of a pipe system, and therefore has a large influence on the service life of the system.
Unions	Unions are quick connection devices. They are detachable connections and enable simple assembly, disassembly and re-assembly without special implements and tools.
Valve fixing	Valve fixings not only serve as support for valves but prevent the transfer of reaction forces.
Water absorption	Many plastics tend to absorb water (swelling). This means that the stability of the plastic is no longer assured. PE has hardly any tendency to absorb water.
Weld preparation	Weld preparation is extremely important in all welding procedures. It has a significant effect on the quality of the weld and should therefore be undertaken with utmost care.
Welding	Welding is one of the most commonly used jointing technologies in plastic pipe construction. Various plastic welding procedures are used to manufacture fittings from pipes and pipe segments, joints made of pieces of pipe, as well as plastic shafts, tanks and other special components. Welding processes are non-detachable connection technologies.
Welding property of PE100	Demonstrated by extensive research: no problems have been shown to arise in welding PE80 to PE100 pipe elements of identical SDR values. Welding can therefore be done without restriction.
Welding shoe / pressure tool	A welding shoe or pressure tool has an effect on the appearance, formal possibilities and quality of the weld. This equipment is manufactured and adjusted in accordance with the desired seam width and form. The welding shoe has the function of evenly distributing the molten material produced in extrusion into the joint and applying the appropriate welding pressure.

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