A question was raised recently regarding the value (cost versus function) difference between copper and cupro-nickel heat exchangers/coolers. It has always been my experience that the additional cost for cupro-nickel over copper heat exchangers has been minimal, enough so that it has always been my recommendation to go with cupro-nickel. Since I have been out of the business for over five years, I thought I would pose the question to Bob at Orca Marine. My question to him was "What are the costs and life expectancy of copper heat exchangers versus cupro-nickel?" His response was so informative I thought I would share it with all of you here. What follows is his first response to which I asked for additional clarification and then his second response. Sorry for the length of this post but I felt that the information was worth sharing. ********************* With respect to the questions regarding Cu and Cu-Ni: 1. The cost question is the easiest. The cost of the Cu-Ni metal in 1/4 inch tubes is between two and three times the cost of copper. Generally manufacturers (including us) will use thinner wall tubes if made of Cu-Ni, to reduce the metal content per unit length of tube ( without, of course, making them so thin that the increased life is offset by the thinner wall) so that the cost addition for an equivalent surface area (the critical parameter for heat transfer) is less than the cost of the metal itself. Of course the cost of the heat transfer tubes in an exchanger is only a part of the total cost. In a typical 5 inch diameter heat exchanger, Cu-Ni tubes would add approximately 10 to 20% to the cost of the finished unit. 2. How long an exchanger will last is a little more difficult. Cu-Ni is universally accepted as lasting better than copper in a marine environment. We, however, have no data in house which would let us even estimate the increased life. Cu-Ni is better placed on the electrochemical corrosion chart, is harder and has higher tensile strength. As an aside, it is also less conductive, but across the wall conduction is not controlling the capacity of any conventional heat exchanger. I think one of the problems of doing an analysis of this is the fact that the life of the heat exchanger is determined by many things, only one of which is the corrosion rate in the internal tubing. If that were the only, or even the controlling factor we could just look at research results to find an answer. In practice, however, bundle life is probably more affected by other factors in operation; such as a) how well the unit, and its zinc has been maintained. b) how much plugging (e.g. grass, plastic, marine growth) there has been in the tubes (erosion corrosion is probably the biggest "normal" problem, and partial plugging will increase velocity in the open tubes - increasing erosion). Cu-Ni is harder and stronger than Cu, and can withstand erosion better. c) how clean the raw water has been - in particular whether the raw water has carried sand, mud, fragments of marine shells, etc. which would exacerbate the erosion. d) what kind of joint was used to seal the tubes to the tube sheet - a soldered joint will, in general, not last as well as a brazed joint and a leak in the joint may occur no matter what the material of the tubes e) to what kind of mechanical stress (e.g. vibration) the unit is subjected f) and so on. When asked, my response is that a well maintained copper heat exchanger should last 10 years or more. A Cu-Ni unit should last even longer. Obviously there are many heat exchangers out there much older than 10 years. That they will eventually corrode is evidenced by the fact (I am told) that there is not too much copper found on ancient marine wrecks, yet copper was in wide use for all kinds of things well before the first century. Presumably it has just dissolved in the sea over time. These kind of time frames are not of interest to most serious boaters, however. I would like to be able to say that we have only been in business for 30 years, and that's not long enough yet to know how long they last - but that would be misleading since we are not likely to know the reason for a replacement. For what it is worth, when I was cruising on Saudades (our DeFever 49) before I was in the heat exchanger business, I bought Cu-Ni tubes. The added cost was more than worth the peace of mind in knowing that I had done what I could to minimize the chance of getting water in my oil, or my fresh water circuit - which would have been disquieting in a distant port, not to mention somewhere out at sea in weather. I wish I could be more definitive. ******************************* I then asked for clarification as follows: "Just to clarify one thing, is it accurate to say that the cost difference to the customer between Cu and Cu-Ni heat exchangers/coolers is approximately 10% to 20%? Perhaps a price comparison between a 2 X 12 oil cooler is a fair way to look at the difference to the retail customer." **************************** His response was: Our pricing fits the 10 to 20% range that I mentioned. In particular, our 2 x 12 oil cooler wholesale and suggested retail price both show a 12% increase in price for using Cu-Ni tubes. Our larger heat exchangers are generally around the 20% figure. While I do not have a complete picture of our competition's pricing, they generally show a higher price difference between Cu and Cu-Ni in oil coolers. At least one is over 50%. I think there are two factors contributing to this: 1. Many of our competitors manufacture what I refer to as "disposable" oil coolers. They are fabricated with inexpensive ends and sometimes using soft solder instead of brazing. Some do not include a drain. This makes our competitors' copper oil coolers substantially less expensive than ours, so the same dollar cost increase for Cu-Ni would show as a greater percentage increase on their oil coolers than ours. We do not produce "disposable" oil coolers. 2. Additionally, some of our competitors appear to price the Cu-Ni difference at more than the proportionate cost difference (evidently what the market will bear). On the hypothetical 2 x 12 oil cooler I have seen one competitor price Cu-Ni adders at about the same level as we do (arriving at a 20% difference in price), and one at twice our adder (arriving at over 50% increase). I guess the bottom line on Cu-Ni is that it is always more expensive, but how much more you pay for it depends on the seller's pricing policy as much as the underlying cost difference. Oil coolers are particularly prone to wide swings, perhaps because they are more of a commodity. Hope this helps. Regards, Bob **************************** His logic mirrors mine. For the minor cost difference, the better quality is well worth the additional expense of cupro-nickel, IMHO. High quality heat exchangers are one of the best investments one can make for their boat. Good luck, Bob Lowe www.MV-Dreamer.com <http://www.MV-Dreamer.com> www.CruisingAndMaintainingYourBoat.com <http://www.CruisingAndMaintainingYourBoat.com> --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.602 / Virus Database: 383 - Release Date: 3/1/2004