192
Fundamentals of Corrosion
6. When butt fusion joints are to be used inside the shell, the preparation for these welds should be inspected.
7. Hydrostatic and thermal cycling tests.
8. Halide tests.
9. Final spark testing of the seams prior to shipping.
Additional inspections may be required if the vessel has special features such
as internal support ledges or pipe supports that may require hand welding
of components.
When preparing for shipment, flange covers should be shipped in place.
Flanges or pads that do not have covers should be protected with temporary
covers securely fastened in place.
6.2.5 Causes of Lining Failure
Linings, if properly selected, installed, and maintained, and if the vessel has
been properly designed, fabricated, and prepared to accept the lining, promise many useful years of service. However, on occasion, there have been lining failures that can be attributed to one or more of the following causes.
6.2.5.1 Liner Selection
Selection is the first step. Essential to this step is a careful analysis of the
materials being handled, their concentrations, and operating conditions as
outlined in the beginning of this chapter. Consideration must also be given
to the physical and mechanical properties of the liner to ensure that it meets
the specified operating conditions. If there is any doubt, corrosion testing
should be undertaken to guarantee the resistance of the liner material.
6.2.5.2 Inadequate Surface Preparation
Surface preparation is extremely important. All specifications for surface
preparation must be followed. If not done properly, poor bonding can result
and/or mechanical damage to the liner is possible.
6.2.5.3 Thermal Stresses
If not properly designed for, thermal stresses produced during thermal
cycling can eventually result in bond failure.
6.2.5.4 Permeation
Certain lining materials are subject to permeation when in contact with
specific corrodents. When the possibility of permeation exists, an alternate
Fundamentals of Corrosion
6. When butt fusion joints are to be used inside the shell, the preparation for these welds should be inspected.
7. Hydrostatic and thermal cycling tests.
8. Halide tests.
9. Final spark testing of the seams prior to shipping.
Additional inspections may be required if the vessel has special features such
as internal support ledges or pipe supports that may require hand welding
of components.
When preparing for shipment, flange covers should be shipped in place.
Flanges or pads that do not have covers should be protected with temporary
covers securely fastened in place.
6.2.5 Causes of Lining Failure
Linings, if properly selected, installed, and maintained, and if the vessel has
been properly designed, fabricated, and prepared to accept the lining, promise many useful years of service. However, on occasion, there have been lining failures that can be attributed to one or more of the following causes.
6.2.5.1 Liner Selection
Selection is the first step. Essential to this step is a careful analysis of the
materials being handled, their concentrations, and operating conditions as
outlined in the beginning of this chapter. Consideration must also be given
to the physical and mechanical properties of the liner to ensure that it meets
the specified operating conditions. If there is any doubt, corrosion testing
should be undertaken to guarantee the resistance of the liner material.
6.2.5.2 Inadequate Surface Preparation
Surface preparation is extremely important. All specifications for surface
preparation must be followed. If not done properly, poor bonding can result
and/or mechanical damage to the liner is possible.
6.2.5.3 Thermal Stresses
If not properly designed for, thermal stresses produced during thermal
cycling can eventually result in bond failure.
6.2.5.4 Permeation
Certain lining materials are subject to permeation when in contact with
specific corrodents. When the possibility of permeation exists, an alternate