Eddy Current Tube Analysis
Heat Exchanger Failure: Myth or Fact?
Heat exchange systems have practically no risk of failure when they’re new. In fact, some components have such nominal exposure that they are not apt to fail for years, if ever. After all, they have no moving parts. Is it a myth, then, that these vessels can fail catastrophically, resulting in extended downtime and loss of revenue for their owners? Unfortunately, catastrophic failure is a very real possibility.
Tubes within these vessels rest on steel supports, or sheets, about 1/4” or 1/2” thick, spaced along the length of the vessel. As the tubes expand and contract from temperature change, erosion occurs. However, the most damage is caused by tubes vibrating against their steel supports as fluid flows through them at high velocity (up to 1400 feet per minute or more).
As heat exchanger technology has advanced, and manufacturers look for ways to provide more efficient machines, the tubes have become thinner to facilitate better heat transfer. Where 16 gauge tubing was once the standard, modern devices have tubes with 22-24 gauge wall thickness. Internal rifling can make tube walls even thinner.
Every new Centrifugal, Reciprocating, Screw and absorption chiller manufactured in the last 15 years, has .028” wall tubes in them or thinner. Many new Chillers manufactured in the U.S. , Canada, Asia and Europe today, have .022” wall copper condenser and evaporator tubes in them.
Vibration wear, ongoing erosion damage, and thinner tube walls can combine to make the risk of failure dangerously high after a heat exchanger has been in service for just a few years. Galvanic corrosion, impingement, deposit and waterline attacks, crevice corrosion, Ant Nest corrosion, fatigue, stress cracking, and other forms of wear take their toll, as well. Unquestionably, heat exchanger vessels will deteriorate and fail if left unchecked.
An Eddy Test Can Prevent Future Problems
Another myth persists, as well: the common belief that you have to wait for tubes to fail before you know which ones to replace. In other words, catastrophe is unavoidable unless you replace all tubes, good or bad, before they fail.
Condenser & Chiller Services’ eddy current tube analysis technicians, can identify damaged tubes before they fail, as well as good tubes that don’t need to be replaced. This process is an easy, effective way to prevent heat exchanger failure and save you valuable time and money.
The eddy test has been employed in various fields on non-destructive evaluation (NDE) for years. In heat exchanger testing, a specialized impedance bridge device that generates a magnetic field is maneuvered through the tubes, causing eddy currents to flow. By analyzing the magnitude and depth of these currents, we can spot all manner of tube defects. We can see which tubes need to be replaced, and can provide retubing service to selectively remove and replace them with new tubes.
In-Service & Factory Eddy Test Services
Condenser & Chiller Services offers inline testing of in-service heat exchanger equipment. If your heat exchanger has been in use for more than three years, it should be tested for potential tube damage, and all heat exchangers should have eddy current tube analysis performed at least every three years.
For OEMs, we can eddy test your heat exchangers at the factory prior to shipping. Our baseline testing will ensure that your products are free of manufacturing defects and will perform at their peak.
Our Eddy Current Inspection analysts are highly experienced and can evaluate 1,200 to 1,600 tubes a day, depending on their length. This can be done on-site at your location for fast, efficient service with minimal equipment downtime. We have been providing this quality service for over 30 years. Our technicians are all ASNT-TC-1A certified to level II and Level III capacity. Since we are an ASME code shop with “U” and “R” repair certifications, we are also certified and inspected by Hartford Steam Boiler. No other Independent Eddy Current Company has this type of experience, background or certifications. We are independently certified by an outside NDT training company. As a licensed Contractor in several states, all of our technicians also have to train in the field and in our shop for the repair, maintenance and retubing of condensers, evaporators and heat exchangers on Carrier, Trane, York, McQuay, Smardt, Artic Chill, Chill-Con, Henry Technologies, Bell & Gosset, Dunham Busch, Ketema, Standard, Sanyo, Broad and Thermax chillers. This gives us the experience needed to properly diagnose and test your equipment.