A major manufacturer of safety relief valves requested sealingsystems developer, Busak+Shamban, to design a more effectivesolution for sealing valves employed within refrigerated transportunits and compressors. Primarily, a component was required thatstandardised on a single elastomer compound suitable for use withany of the wide range of chemically aggressive refrigeration mediaencountered along with the various lubricants employed.
With its almost universal chemical compatibility, Isolast®, theadvanced perfluoroelastomer from Busak+Shamban was identified asthe ideal sealing material. However, due to the relatively largeamount of elastomer used within the original valve seat assembly,including custom-moulded ‘L’ section seals, fixed in place byassembling mating parts, the cost criteria for the whole assemblycould not be achieved.
Busak+Shamban engineers, utilising advanced FEA (Finite ElementAnalysis), converted the existing three-piece design to a singlepiece metal plunger with the Isolast‚ part bonded in place. Thisprovided significant material cost savings and furthermore, thesolution lowered assembly costs, by reducing the number of parts tobe handled, increasing speed of assembly and dramatically cuttingthe overall parts inventory.
Traditionally, sealing integrity is compromised whenperfluoroelastomers, bonded with conventional adhesive, encounterelevated temperatures and aggressive media. However, Busak+Shambanhave proven methods in bonding Isolast® to a wide range of surfacesincluding stainless and mild steel, aluminium, brass and variousplastics (see photograph).
Busak+Shamban has developed an Isolast® sealing solutionwith almost universal chemical compatibility for use within safetyrelease valves for refrigeration applications, includingrefrigerated trucks.
Bonding achieved with the Isolast® materials does not affect thephysical performance properties nor the general chemical resistanceof the perfluoroelastomer itself. In addition, immersion tests in arange of chemicals, including acetic acid, Methyl Ether Ketone(MEK) and sulphuric acid, show the bond to be resistant to chemicalattack, even at high temperatures. In fact, bond strength proved tobe equally as high, following immersion in the media, as it wasbefore the soak tests began.
Busak+Shamban engineers were confident of their proposal and thesamples submitted complied with all the customer’s rigoroustesting. A competitor’s seal solution of a similar sealconfiguration, failed the same tests when the elastomer separatedfrom the valve plunger.
Since introducing this design of seal into their safety reliefvalves, the customer has supplied several thousands for largevolume OEM projects throughout Europe, with no quality orperformance problems.