36C26220Q0742-0001002.doc

INTERNAL INSPECTIONS OF FEEDWATER DEAERATORS

NON-DESTRUCTIVE TESTING (NDT)

VHA Boiler Plants

Introduction:

Feedwater deaerators in boiler plants are large welded steel pressure vessel (tank) assemblies that contain hot water and steam under pressure. They are nearly always located on a mezzanine above the boiler room operating floor. Since the mid-1980’s there has been a program in the industry to provide remedies for a problem of cracked and sometimes completely failed welds in feedwater deaerator pressure vessels. Such a failure could endanger life and property from the sudden release of hot water and steam. A major remedy is regular inspection of the welds by visual means and by non-destructive testing.

Testing Requirements:

The VHA Directive 2003-050, “Boiler Plant Operations”, requires that the welds of feedwater deaerator pressure vessels be inspected by the wet magnetic particle method every 6 years. This inspection is performed on welds accessible from the interiors of the pressure vessels. If problems are found on a unit, it may be necessary to inspect and test more frequently after repairs are made. Annual visual inspections of the welds are also required.

This requirement is based on recommendations of NACE International, the corrosion engineering society.

VHA has had this inspection program for many years, and this program has discovered cracked welds in VHA feedwater deaerators.

Non-Destructive Testing Method:

As the name implies, the welds are tested in a way that does not damage, harm or change the material being tested.

The full name of the required test is the Wet Fluorescent Magnetic Particle Technique (WFMT). This is a method of finding surface and slightly subsurface discontinuities in magnetic materials. Small magnetic particles are suspended in a liquid which is then coated on the weld to be tested. When the weld is magnetized, the arrangement of the particles shows any weld discontinuities, such as cracks. Surface preparation, such as cleaning and wire brushing is necessary prior to the test.

The tests must be conducted under the overall supervision of Qualified Professional Inspectors (QPE) by qualified Level II non-destructive examination technicians. Prior to the WFMT test, the welds must be visually inspected by the QPE.

Contracting Documents:

A ”Statement of Work, Inspection of Boilers and Feedwater Deaerators” is on the CEOSH website. vaww.ceosh.med.va.gov Click on Administrative Library, Search using “bps” for “boiler plant safety”.

VHA (183A)

1/19/06