Refrigeration, air-conditioning and cooling technology - 2007.pdf

PLH_KKK_U2_31.QXP 25.05.2007 11:02 Uhr Seite 22NOISES – AIRBORNE SOUND – STRUCTURE-BORNE SOUNDPipe support,Avoid pipeline forceson the inlet connectionLarge curvature radiusWhen the pipe diameter is reduced, suddencross-section changes are to be avoided.This is possible using conical adapters. If theformation of air pockets can be expected, eccentricadapters are preferable.Eccentric,conicaladapterMeasures against waterborne and structurebornesound propagation via pipelinesIntroducing waterborne and structure-bornenoise in pipelines can be prevented by specialdamping measures on the pump to the pipelines.A remarkable noise-reflecting effect from pipelinedirection changes is not expected with thewavelengths of the water-borne sound in homesystems and the dimensions of the pipelines.When sound-absorbing measures are taken, it isto be made sure that the operating safety of thepump isn't impaired, i.e. functionally reliabledamping elements must be selected. The followingexpansion joints come into question asabsorbing elements:5d min5d minFittings should not be installed in the pipelinedirectly after the pump connection, especiallynot on the entry side of the pump. Here, a minimumdistance of 5 · d also has a favourable effecton noise creation.Gate valve5d min• Expansion joints with length limitation withoutelastic elements (lateral expansion joints)• Expansion joints with length limitation withelastic elements as well as rubber metalflanges• Expansion joints without length limitationsFor expansion joints with length limitation withoutelastic elements, no additional pipelineforces act on the pump connection. But on theother hand, these expansion joints have only aslight absorbing effect. Expansion joints withoutlength limitations have the greatest absorbingeffect. With these, however, the largest additionalpipeline forces act at the same time. Thepipeline forces can theoretically reach 16 000 Nfor a pump with a nominal diameter of 100 andnominal pressure of 10. Practically speaking,however, due to the limited elasticity of the expansionjoints, only pipeline forces up to halfthis value can act. No generally valid statementscan be made at this time with regard to whatconnection forces are permissible.Pipe support22 Subject to change without prior notice 02/2007 WILO AG