Equipment failures (eg: boiler tube failures) often provide a critical test of the water treatment suppliers ability to respond to a customer problem.
FAILURE ANALYSIS INVESTIGATIONS ANSWER TWO QUESTIONS.
- Why Did The Failure Occur?
- What Can Be Done To Prevent A Recurrence?
- Tube Failures
- Problems In Ancilliary Equipment (Fans;Electrostatic Precipitators;Air Preheaters Etc.)
- Problems In Pretreatment Equipment
- Fireside Failures
- Heat Exchanger Tube Failures
- Cooling Tower Structural Failures
- Problems In Ancilliary Equipment (Pumps;Filters;Transfer Piping Etc.)Equipment failures (boiler tube failures) often provide a critical test of the water treatment suppliers ability to respond to a customer problem.
The two questions, which generally need to be addressed are: Why did the failure occur? And what can be done to prevent a recurrence? A root cause failure analysis investigation can provide the answers to both questions. The following discussion reviews one approach, which can be utilized to conduct a successful failure analysis investigation.
The analysis of a failure of a component in a piece of heat transfer equipment (for example, a heat exchanger tube failure or boiler tube failure) is quite often a complex exercise involving the evaluation of many different factors. For example, boiler tube failures can result from thermal effects such as rapid overheating, long term overheating, thermal stress, waterside chemical effects such as stress cracking, caustic attack, phosphate corrosion, acid corrosion, oxygen corrosion, galvanic corrosion, under deposit corrosion, design effects such as crevice corrosion or process side/fireside effects such as high temperature ash corrosion or erosion or water side erosion corrosion mechanisms.
The identification of the cause of the failure generally requires more than an examination of the failed metal specimen, although such examination is an important component of the elucidation of the mechanism. In practice three areas should be researched in detail to obtain a successful conclusion.
- A thorough examination of the design of the piece of equipment in question.
- A thorough examination of the failed component with complete analysis of any deposits observed and a thorough metallographic analysis of both the area of failure and a section of tube well removed from the area of failure, showing no signs of damage or stress.
- A thorough examination of the operation of the piece of equipment including such parameters as temperature, heat transfer rate, water flow rate, pressure, firing rate, and load changes (for boilers): along with a detailed evaluation of the waterside and process side chemistry.