Corrosion of Linings
193
lining material should be selected. Permeation can result in debonding resulting from corrosion products or fluids accumulating at the interface between
liner and substrate. In addition, corrosion of the substrate can result, leading
to leakage problems and eventual failure of the substrate.
6.2.5.5 Absorption
As with permeation, absorption of the corrodent by the liner material can
result in swelling of the liner, cracking, and eventual penetration to the substrate. This can lead to high stresses and debonding.
6.2.5.6 Welding Flaws
It is essential that qualified personnel perform the welding and that only
qualified, experienced contractors be used to install linings. A welding flaw
is a common cause of lining failure.
6.2.5.7 Debonding
Debonding can occur as a result of the use of the wrong bonding agent. Care
should be taken that the proper bonding agent is employed for the specific
lining being used.
6.2.5.8 Operation
Lined vessels should be properly identified when installed with the allowable characteristics of the liner posted to avoid damage to the liner during
clean-up or repair operations. Most failures from this cause result while vessels are being cleaned or repaired. If live steam is used to clean the vessel,
allowable operation temperatures may be exceeded. If the vessel is solvent
cleaned, then chemical attack may occur.
6.2.5.9 Environmental Stress Cracking
Stress cracks develop when a tough polymer is stressed for an extended
period of time under loads that are small relative to the polymer’s yield
point. Cracking will occur with little elongation of the material. The higher
the molecular weight of the polymer, the less likelihood of environmental
stress cracking, other things being equal. Molecular weight is a function of
the length of individual chains that make up the polymer. Longer chain molecules tend to crystallize less than polymers of lower molecular weight or
shorter chains, and they also have a greater load-bearing capacity.
Crystallinity is an important factor affecting stress corrosion cracking. The
less crystallization that takes place, the less the likelihood of stress crack-
193
lining material should be selected. Permeation can result in debonding resulting from corrosion products or fluids accumulating at the interface between
liner and substrate. In addition, corrosion of the substrate can result, leading
to leakage problems and eventual failure of the substrate.
6.2.5.5 Absorption
As with permeation, absorption of the corrodent by the liner material can
result in swelling of the liner, cracking, and eventual penetration to the substrate. This can lead to high stresses and debonding.
6.2.5.6 Welding Flaws
It is essential that qualified personnel perform the welding and that only
qualified, experienced contractors be used to install linings. A welding flaw
is a common cause of lining failure.
6.2.5.7 Debonding
Debonding can occur as a result of the use of the wrong bonding agent. Care
should be taken that the proper bonding agent is employed for the specific
lining being used.
6.2.5.8 Operation
Lined vessels should be properly identified when installed with the allowable characteristics of the liner posted to avoid damage to the liner during
clean-up or repair operations. Most failures from this cause result while vessels are being cleaned or repaired. If live steam is used to clean the vessel,
allowable operation temperatures may be exceeded. If the vessel is solvent
cleaned, then chemical attack may occur.
6.2.5.9 Environmental Stress Cracking
Stress cracks develop when a tough polymer is stressed for an extended
period of time under loads that are small relative to the polymer’s yield
point. Cracking will occur with little elongation of the material. The higher
the molecular weight of the polymer, the less likelihood of environmental
stress cracking, other things being equal. Molecular weight is a function of
the length of individual chains that make up the polymer. Longer chain molecules tend to crystallize less than polymers of lower molecular weight or
shorter chains, and they also have a greater load-bearing capacity.
Crystallinity is an important factor affecting stress corrosion cracking. The
less crystallization that takes place, the less the likelihood of stress crack-