MIDI

MIDI< ® Pipes5-layered full plastic composite pipes

MIDI< ®Pipes>MIDI< ®Pipes>> A >MIDI< ® pipe is a 5-layeredfull plastic composite pipe withdiffusion barrier properties accordingto DIN 4726.The basic pipe and outer layer aremade of PE-RT and thus enclose thesensitive EVOH layer. To guaranteea non-detachable bond of the materialsthey are firmly fused togetherby layers of adhesive polymer.Why must thediffusion barrierbe protected?PE-RTAdhesive-LayerEVOHAdhesive-LayerPE-RTThe incipient deposit corrosion onthe inside of the pipe caused bysurface scratches shows theexistential importance of an intactdiffusion barrier.>> Danger of incrustation anddeposit corrosionThe oxygen input into a systemthrough the pipes used was long regardedas negligible compared toother input possibilities.Our many years of experience, however,have shown that even theslightest damage to the diffusionbarrier layer can mean the start ofdeposit corrosion. The use of 5-layeredpipes with a reliably protectedoxygen barrier in closed systems isthus indispensable.>> The optimum solution:>MIDI< ® pipeThe 5-layer design of >MIDI< ® pipespermanently prevents the damagingeffects of ambient moisture onthe diffusion barrier layer. What'smore, the outer PE-RT layer offersprotection against possible damageto the EVOH layer during transportand installation.The 5-layer designguarantees permanentprotection forthe oxygen barrier(EVOH layer).>> The EVOH layer is highlyfunctional, but sensitiveContact with moisture, in particularat higher temperatures, permanentlydestroys the diffusion barrier layer.According to the latest standards,the outer diffusion barrier layer ofconventional 3-layered pipes maynot be calculated as part of the wallthickness.>>Long-term protection is endangeredIn a 95°C monitoring test the EVOHlayer is attacked by the hot waterafter several hundred hours. It swells,cracks and thus can no longer contributeto the stability of the pipe.This leads to the fear that even ambientmoisture (e.g. during installation)could damage the oxygenblocking layer in the long term oreven destroy it completely.The diffusion barrier layeris extremely sensitive tomoisture. Water contactleads to swelling andthus the destruction ofthe EVOH layer.Brittleness, cracking orflaking of the EVOH layer:Deposit corrosion andincrustation can occurafter years.>> Permanent protection againstoxygen inputThe oxygen permeability of >MIDI< ®pipes is around 0.02 g/m 3 d, and thusfar below the requirements of DIN4726 (0.1 g/m 3 d). The 5-layer designmeans that the barrier layer is reliablyprotected against moisture and damage.External sealing fittings can thusalso be used without hesitation.>> Increased resistance to pressureCreep-rupture tests have shown that>MIDI< ® pipes with the same wallthickness withstand a higher internalpressure than pipes without a diffusionbarrier layer (even at higher temperatures).EVOH is durable and has a meltingpoint of over 180 °C!>> Improved ageing behaviourAn important factor in the ageingof polymers is the constant attack byoxygen. >MIDI< ® pipes, however, allowpractically no oxygen exchangeand this condition is retained becausethe barrier layer is protected. The excellentfeatures of PE-RT are thus furtherimproved.>> Minimum shrinkageThe shrinkage behaviour of >MIDI< ®The advantagesat a glancepipes is outstanding: on account oftemperature influences, the shrinkageis only 0.3% to 0.7%. A further shrinkage,such as is known for examplewith PE-X pipes, does not occur with>MIDI< ® pipes.>> WeldabilityThanks to the external layer of PE-RT,>MIDI< ® pipes can be welded.HPG Heizrohr Produktions GmbHTypenpr_MIDI_022007E

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