Monday, April 11, 2016

Heat Exchanger Series # 1: Common Flaws in Heat Exchangers

Heat Exchanger Series # 1: Common Flaws in Heat Exchangers

Heat exchangers are vital for industrial applications to heat or cool industrial process steams to optimise plant operations. Facilities that operate heat exchangers should take care to ensure they are properly inspected and monitored for damage and wear-and-tear. Non-destructive testing of heat exchanger tubes promotes efficiency in heat transfer as well as avoiding leaks and cross-contamination of process fluids in the unit.

Common H/E Tubing Flaws Russell Equipment Finds

  • Internal or external corrosion
  • Inlet end erosion (internal)
  • CO2 and/or oxygen pitting
  • Thermal fatigue cracking
  • Fatigue or creep cracks
  • Baffle-wear ("saddle wear")
  • Steam erosion (external)
  • Tube to tube erosion

What Causes These Issues?

  • Fluid temperature
  • Fluid velocity
  • Pressure
  • Vibration
  • Improper fluid or steam flow
  • Combustion by products (eg: ash)
  • Condensation accumulation (wet steam)

These flaws can occur at any point in carbon steel heat exchanger. CO2 (Carbon dioxide) flaws are common in Amine bundles (pictured), and they are usually found on the outside of the tubes. The corrosion has a distinctive "stepwise" appearance, and the signals from corroded areas can look like "pits within pits". It takes a skilled operator to analyse these complex signals, which can be short or have an overall length that exceeds the exciter-detector spacing of an RFT probe. A thorough inspection of the entire unit is necessary to diagnose the types of defects that are present in the unit which can determine the actions your organization should take to repair and prevent the damage in the future.

If you are encountering defects in your heat exchanger, and you need help to identify it accurately, call 1-800-661-0127 and ask for Ankit or Dave to discuss heat exchanger inspection technical support.

Come back for our next instalment to find out how Russell NDE selects the right technology and probes to reveal defects in heat exchangers.