Copper alloys condenser tubes

B 169 Aluminum Bronze Plate, Sheet, Strip, and Rolled Bar B 171 Copper-Alloy Condenser Tube Plates... 

Behavior of copper alloys condenser tubes under velocity conditions. 24... 

The erosion resistance of copper alloy condenser tubes can be related directly to velocity. The velocity limits for common copper base alloys are shown in Figure 1.18. The velocity limit is roughly proportional to the strength of the alloy (i.e., copper is the weakest material and displays the poorest erosion resistance) copper-30% nickel is one of the strongest alloys and displays the best erosion resistance. 

Figure 1.18 Behavior of copper alloy condenser tubes under velocity conditions.13...

Table 9>4. Corbosion of Copper Alloy Condenser Tubes ...

Mitchell, N. W., A Study of the Corrosion of Copper Alloy Condenser Tubes. Trana. ASMS, 1946. 

Parker, J. G. and Roscow J. A., Method for the Assessment of the Quality of Surface Films Formed on the Cooling Water Side of Copper-Based Alloy Condenser Tubes , Br. Corros. J., 16, 2, 107-110(1981)... 

Phosphorized deoxidized arsenical copper (alloy 142 (23)) is used for heat exchangers and condenser tubes. Copper-arsenical leaded Muntz metal (alloy 366), Admiralty brass (alloy 443), naval brass (alloy 465), and aluminum brass (alloy 687), all find use in condensers, evaporators, ferrules, and heat exchanger and distillation tubes. The composition of these alloys is Hsted in Table 5. 

Iron is added in small (usually 0.5—1.0 wt %) amounts to increase strength. More importantly, iron additions also enhance corrosion resistance, especially when precautions are taken to retain the iron in solution. Precipitation of the iron—nickel-rich phase does not result in strengthening and can cause degradation of corrosion resistance (47). A small (up to 1.0 wt %) amount of manganese is usually added to both react with sulfur and deoxidi2e the melt. These copper alloys are most commonly applied where corrosion resistance is paramount, as in condenser tube or heat exchangers. 

Many shell-and-tube condensers use copper alloy tubes, such as admiralty brasses (those containing small concentrations of arsenic, phosphorus, or antimony are called inhibited grades), aluminum brasses, and cupronickel austenitic stainless steel and titanium are also often used. Utility surface condensers have used and continue to use these alloys routinely. Titanium is gaining wider acceptance for use in sea water and severe service environments but often is rejected based on perceived economic disadvantages. 

Irregular grooving can occur, especially on copper alloys after acid cleaning. Tubes can be only partially filled with cleaning solution. Condensation and running of the fluid down the tube interior cuts tortuous channels (Fig. 7.9). 

Six iron anodes are required for corrosion protection of each condenser, each weighing 13 kg. Every outflow chamber contains 14 titanium rod anodes, with a platinum coating 5 /tm thick and weighing 0.73 g. The mass loss rate for the anodes is 10 kg A a for Fe (see Table 7-1) and 10 mg A a for Pt (see Table 7-3). A protection current density of 0.1 A m is assumed for the coated condenser surfaces and 1 A m for the copper alloy tubes. This corresponds to a protection current of 27 A. An automatic potential-control transformer-rectifier with a capacity of 125 A/10 V is installed for each main condenser. Potential control and monitoring are provided by fixed zinc reference electrodes. Figure 21-2 shows the anode arrangement in the inlet chamber [9]. 

Copper alloys Seawater Condenser tubing. Piping. Pump impellers. 

Other gases which are occasionally present usually arise from pollution. Ammonia, which in various forms may be present in waste waters, attacks copper and copper alloys its presence in estuarine waters is one of the main causes of condenser-tube corrosion. 

Copper and copper alloy pipes and tubes are used in large quantities both for conveying fresh and salt waters and in condensers and heat exchangers where fresh or salt waters are used for cooling. Pumps, screens, valves and other ancillary equipment may also be largely constructed of copper alloys. Large tonnages of these materials are therefore used in power stations, on... 

Fresh waters are, in general, less corrosive towards copper than is sea-water, and copper is widely and satisfactorily used for distributing cold and hot waters in domestic and industrial installations . Copper and copper alloys are used for pipes, hot-water cylinders, fire-back boilers, ball floats, ball valves, taps, fittings, heater sheaths, etc. In condensers and heat exchangers using fresh water for cooling, tubes of 70/30 brass or Admiralty brass are usually used, and corrosion is rarely a problem. 

As an example of the effects of a scale deposit, assume a copper-alloy tubed condenser operating at 70 °F inlet temperature, 2 in Hg back-pressure and in a clean condition ... 

In the table of recommended water characteristics for nonfired water tube boilers, BSI proposes that plants containing copper alloys in either the feed or condensate system should have a FW pH limited to 8.5 to 9.2. If the feed system is completely ferrous, the pH should be limited to 9.2 to 9.5. For plants utilizing the FW for spray attemperation or desuperheating, the pH should be controlled with volatile alkalis only. 

Copper alloys are used extensively in power plant condensers, and as a result, copper can usually go into a corrosion product film or directly into solution as an ion or as a precipitate in the initial stages of condensation by tube corrosion. As corrosion products form and increase in thickness, the corrosion rate decreases until a steady state is achieved. Studies indicate that copper release is a function of flow rate more so than of the salt content of the makeup water. 

Copper-Base Alloys. There is a wide range of copper-base alloys that have given good service in sea water. Admiralty brass, 70 Cu-29 Zn-1 Sn, plus an inhibitor such as arsenic, has found wide use as condenser tubes in marine-based plants using sea water for cooling. While it is not so resistant as the cupro-nickels, it often seems to be preferred because of the lower initial cost. 

It will also be possible by relatively minor piping changes to convert the forward-feed evaporator to backward feed, which might be more favorable if the calcium sulfate scale problem can be solved. Except for tubes, pump shaft sleeves, impellers, etc., the plant will be built exclusively of steel and cast iron. Tube materials will be evaluated by tubing different evaporator effects and heat exchangers with steel, admiralty metal, aluminum brass, and 90/10 cupronickel. The copper alloy tubes will be used exclusively in the final condenser and in the few heat exchangers that are in contact with nondeaerated sea water. 

High velocities of aqueous solutions impinging on copper and brass tubes produce impingement on the metal or alloy. The aluminum brass and cupronickel alloys have great resistance to flow-induced attack up to a well-defined maximum for the flow rate, beyond which the film on the metal surface will be disrupted. Admiralty brass and aluminum brass have lower values for maximum velocity of flow than cupronickels. Admiralty brass and aluminum brass are preferred to cupronickels for use in media containing sulfide species. Coatings have been developed for cupronickel and aluminum brass condenser tubes for land-based and marine systems. 

Muntz metal. An alloy containing approximately 60% copper and 40% zinc a low percentage of lead is sometimes added for free-cutting. It is classified as a brass and used primarily for condenser tube plates and other electrical applications. It is formed by hot-working and is not amenable to coldworking. 

Copper-nickels contain up to 30% nickel and have moderate strength and better corrosion resistance than other copper alloys. They are used for condenser tubing, tube sheets, salt water piping and ferrules. 

Aluminum alloys can also be attacked by microorganisms. For example, there have been MIC problems with aluminum fuel tanks and transfer lines. In this case, microorganisms grow in the water layer under the fuel to produce volcano-shaped tubercles, frequently evolving gas. Pitting occurs under the tubercles. MIC attack on copper alloys is usually insignificant. However, corrosion of copper condenser tubes by microbially produced ammonia has been reported. In addition, sulfuric acid has been produced by microbial activity by corrosion of underground copper pipes. 

In the case of the steam condensers, the probes, installed on the cooling water side, controlled the behaviour of the tube bundle materials. The most interesting applications regarded the procedures for the passivation of copper alloys even in polluted water conditions, and the cleaning of tube bundles. 

Cupronickels contain from 15 to 20 per cent of nickel, the remainder being copper. They can be cold-worked for example they can be cold-rolled from I inch down to 0-05 inch without annealing being necessary. They have been extensively used for bullet jackets. The 2 5 Ni, 75 Cu alloy used in coinage has already been mentioned. A 30 Ni, 70 Cu alloy is used for condenser tubes. Another useful alloy, sometimes known as constantan, has 40 Ni and 60 Cu. Owing to its high electrical resistance and low resistance temperature coefficient it is used for standard electrical resistances. 

E6.2. Predict whether or not galvanic corrosion will cause the following alloys to be subjected to leaching (i) carbon and carbon steel alloys in an oxidizing atmosphere, (ii) steel rivets in aluminum drain gutters, (iii) copper-nickel alloy in refinery condenser tubes, (iii) graphite fiber-reinforced aluminum composites, (iv) brass in water, (v) iron-chromium alloys, and (vi) carbon steel pipe in contact with the weld to stainless steel pipe. 

Condenser Tube Alloys Including Copper-Nickel Alloys... 

Aluminum brass resists high-velocity waters (impingement attack) better than does admiralty metal. Cupro-nickel alloys are especially resistant to high-velocity seawater when they contain small amounts of iron and sometimes manganese as well. For the 10% Ni cupro-nickel alloy, the optimum iron content is about 1.0-1.75%, with 0.75% Mn maximum for the analogous 30% Ni composition, the amount of alloyed iron is usually less (e.g., 0.40-0.70% Fe accompanied by 1.0% Mn maximum) [46]. It is found that supplementary protective films are formed on condenser tube surfaces when iron is contained in water as a result of corrosion products upstream or when added intentionally as ferrous salts. Accordingly, the beneficial effect of iron alloyed with copper-nickel alloys is considered to result from similar availability of iron in the formation of protective films. 

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