Inserts
PREVENTION AND CARE IN THE TUBE BUNDLES
ONE OF THE MOST FREQUENT CORROSION PHENOMENON IN THE TUBE BUNDLES HEAT EXCHANGERS, IS THE FORM OF CORROSION EROSION, CALLED "IMPINGEMENT", THAT GENERALLY OCCURS AT THE TUBE INLET AREA OF WATER, MORE RARELY AT THE OUTLET AREA.
THE PHENOMENON IS DUE TO THE ROUGH VARIATION OF HYDRO-DYNAMIC CONDITIONS THAT OCCURS WHEN THE FLUID IS COMPRESSED, ENTERING FROM THE WATER BOX OF THE EXCHANGER INSIDE THE TUBE BUNDLE OR WHEN THE FLUID SPREADS AT THE OUTLET OF THE CONDENSER TUBE.
THESE PARTICULAR FLUID-DYNAMIC CONDITIONS ENHANCE THE FLUID TURBULENCE AT THE INLET AREA OF THE TUBE AND CAN CAUSE CAVITATION PHENOMENA AT THE OUTLET AREA.
BECAUSE OF THIS MECHANISMS IN THE TUBE ENDS, IT CAN OCCUR THE CONTINUOUS REMOVAL OF THE PROTECTIVE FILM THAT PROTECTS THE METALLIC MATERIAL AND, AS A CONSEQUENCE, A GREAT INCREASE OF THE CORROSIVE ACTION.
ACCORDING TO FLUID-DYNAMICS, A BAD PLANNING OF THE WATER BOX AS WELL AS AN EXCESSIVE SPEED OF FLUID AND THE PRESENCE OF SAND OR OF DRAGGER, SOLID PARTICLES CONTRIBUTE TO ENHANCE THIS KIND OF CORROSION WHICH CAN MORE FREQUENTLY OCCUR WITH SALINE OR SEA WATER .IT MAY BE FOUND, HOWEVER, ALSO IN RIVER WATER.
C.M.TECH IS ABLE TO FULLFILL EVERY REQUIREMENT FROM THE PRODUCTION OF INSTALMENT OF INSERTS OF ANY DIMENSION AND MATERIALS. SINCE MANY YEARS, IN FACT, THE TECHNICAL STAFF EMPLOYED CAN BOAST A GREAT EXPERIENCE IN THIS KIND OF INTERVENTION ON EXCHANGERS.
THE METALLIC MATERIALS COMMONLY AFFECTED WITH THIS KIND OF CORROSION ARE CARBON STEELS AND SOME COPPER ALLOYS, IN PARTICULAR ALUMINIUM OR ADMIRALTY BRASSES.
THIS CORROSIVE ATTACK GENERALLY AFFECTS A VERY LIMITED AREA OF THE TUBE ( 10-20CM) NEXT TO THE TUBE PLATE.
THIS ALLOWS OPPOSING WITH CERTAIN EASE THIS PHENOMENON THROUGH THE INSTALLATION OF INSERTS REALISED IN METALLIC MATERIALS MORE RESISTANT TO CORROSION EROSION.
THE INSERTS, OF A LENGTH REQUIRED BY THE CLIENT (GENERALLY 30 CM), ARE INSERTED INSIDE THE TUBE AND EXPANDED BY HYDRAULIC ENLARGING SO TO HAVE A PERFECT ADHERENCE WITH THE EXCHANGER TUBE. THIS OPERATION CAN BE PERFORMED ON TUBE BUNDLES EITHER AS A MANTAINANCE INTERVENTION WHEN CORROSION PHENOMENA ARE ALREADY PRESENT, OR AS A PREVENTIVE INTERVENTION ON NEW EXCHANGER IN ORDER TO GRANT BETTER SERVICES AND TO REDUCE THE RISKOF IMPINGEMENT.
THE INSERTS CAN BE PREPARED IN DIFFERENT KINDS OF METALLIC MATERIALS. FOR COPPER ALLOY TUBES ARE GENERALLY EMPLOYED INSERTS IN CuNi 70/30 OR IN CuNi 66/30/2/2 (Fe AND Mo),THAT PRODUCE PROTECTIVE FILMS HARD AND STRONG AND, THEREFORE , MORE RESISTANT TO ABRASIVE ACTION.FOR CARBON STEEL TUBE ARE EMPLOYED INSERTS IN AISI 316. THE HIGH SPEED OF SEA WATER ALLOWS A GREATER AFFLUX OF OXYGEN ON THE METALLIC SURFACE AND THIS STRENGTHENS THE PASSIVATION FILM OF STAINLESS STEEL AND, ABOVE ALL, INCREASE ITS AUTO-CICATRISATION.
IF REQUIRED, CAN BE INSTALLED INSERTS IN OTHER, CORROSION RESISTANT MATERIALS IN ORDER TO FACE PARTICULAR AGGRESSIVE CONDITIONS FORESEEN FOR THE EXCHANGER.
THE USE OF INSERTS NORMALLY ALLOWS INCREASING THE EXCHANGER LIFE AND, ABOVE ALL, IT ALLOWS IN MANY CASES SUBSTITUTING THE OPERATION OF "RE-TUBING" A SEA-WATER EXCHANGER WITH AREALLY MORE CONVENIENT MAINTENANCE INTERVENTION BOTH IN TERMS OF EXPENSES AND OF TIME.