INSPECTION/TESTING AND CERTIFICATION OF BOILERS AND PRESSURE VESSELS
Above ground tank inspection  
Heat exchanger inspection
Boiler/HRSG inspection
Pipe inspection
Condenser inspection 
Pressure vessel inspection

BOILER INSPECTIONS
The siren goes off. The lights flash, the boilers shut down and you lose fortune in downtime and repairs that can take weeks to complete. Thus, the price of emergency shutdown – THAT IS THE REASON FOR AZU INSPECTION: To eliminate such failure.                                                    

 BACKGROUND
The very high temperatures found inside steam boilers (in excess of 1500 degrees Fahrenheit or 800 degrees Celsius) can cause the formation of a specific type of hard, brittle iron oxide called magnetite on the inside and outside surfaces of steel boiler tubing. At very high temperatures, water vapor will react with the iron in the steel to form magnetite and hydrogen according to the formula:


3 Fe + 4 H 20 = Fe 3O 4 + 4 H 2

The speed of this reaction increases with temperature. Oxygen atoms will diffuse inward through the magnetite layer, and iron atoms will diffuse outward, so the scale continues to grow even after the tube surface is completely covered.

Magnetite scale acts as thermal insulation on the pipe, since the thermal conductivity of scale is only about 5% that of steel. When heat can no longer transfer efficiently from the flame through the tube into the steam inside, the tube wall will heat up to temperatures beyond the intended operating range. Long term exposure to overly high temperatures, combined with the very high pressure inside the tube, leads to inter-granular micro-cracking in the metal and to creep deformation (a slow swelling or bulging of the metal), which in turn eventually leads to tube failure by bursting.

A secondary issue is oxide exfoliation, in which pieces of oxide scale break off (usually due to thermal stresses during boiler startup or shutdown). These hard pieces will be carried by the steam flow into the turbine, where over time they will cause erosion damage.

The growth of magnetite scale and the associated metal damage are primary limiting factors with respect to boiler tube service life. The process begins slowly and then accelerates, for as the scale grows thicker the tube wall becomes hotter, and that in turn increases the rate of both scale growth and metal damage. Studies in the power generation industry have indicated that the effect of scale is relatively insignificant up to thicknesses of approximately 0.012" or 0.3 mm, but that beyond that thickness the negative effects of scale increase rapidly. Periodic measurement of scale thickness allows a plant operator to estimate remaining tube service life and to identify and replace tubes that are approaching the failure point. Ultrasonic testing provides a quick and nondestructive method for measuring scale. Our Hand-held, portable instruments Model 38DL and thickness gage or the EPOCH series flaw detectors can measure internal oxide layers down to a minimum thickness of approximately 0.125 mm or 0.005 inch.

 

Storage Tank Inspection
Azu Inspection provides comprehensive Storage Tank Inspections utilizing floor scanning, ultrasonics and MPI techniques.

Tubular Heat Exchangers
Azu Inspection provides inspection services for all types of  tubular heat exchanger using RFET, ECT & RVI methods.

Piping Inspection
Azu Inspection provides services for piping that is above ground and or partially buried.

Isometric drawings can be made for easy interpretation. Additional services include a full assessment and recommendations by our API certified staff.

Condenser Tube Inspection
Within the Power Generation Industry, Azu offers an Ultra High Speed Condenser Tube Inspection Service.

This system inspects an average of 8 tubes per minute with one inception system.

Pressure Vessel Testing
Various types of pressure vessels can be scanned using the Azu Inspection Low Frequency Electromagnetic Technique (LFET).

The plates can be tested from the inside or outside of the vessel.

Stack Column and Tower Inspections
Azu Inspection has conducted numerous inspections of Stacks, Columns and Towers in various types of process facilities.

These can be inspected with LFET and Ultrasonic Crawlers. Some inspections have been performed at high temperature.

 

 

Copyright © 2003-2012 Azu Services Limited . All Rights Reserved.