4
Liquid-Applied Linings
Of the variouscoating applications, the mostcritical is that of atank lining.
The coating must be resistant to the corrodenta nd be free of pinholes
through which the corrosive could penetrate and reach the substrate.T he
severe attackt hat many corrosivesh ave on the bare tank emphasizes the
importance of usingthe correct procedureinlining atank to obtain aperfect
coating. It is also essential that the tank be designed and constructed in the
proper manner to permit ap erfect lining to be applied.
Liquid-applied linings or coatings may be troweled on or spray applied.In
alined tank there are usually fourareas of contactwiththe stored material.
Each area has the potential of developing adifferent form of corrosive attack.
These areas are the bottom of the tank (where moisture and other contaminants of greater density may settle),t he liquid phase (the area constantly
immersed), the interphase (thea rea where liquid phase meetst he vapor
phase), andthe vapor phase(the area above the liquid). Each of these areas
can be more severely attacked than the rest at one time or another.The type
of material contained, the nature of impurities that may be present, and the
amount of water and oxygen present are all factors affecting the attack.
In view of this, it is necessary to understandt he corrosion resistance of the
lining material undereach conditionand not onlythe immersed condition.
Other factors that have an effect on the performance of the liningmaterial
are vessel design, vessel preparation prior to lining, application techniques
of the coating, curing of the coating, inspection, operating instructions, and
temperature limitations. In general, the criteriafor tank liningsare given in
Table 4.1.
4.1D esigno ft he Vessel
All vessels to be lined internally should be of welded construction. Riveted
tanks will expand or contract, thus damaging the liningand causing leakage.
Butt welding is preferred, but lap welding can be used providing afi llet
CAT8247—CHAPTER 4—17/10/2006—14:32—SRIDHAR—XML MODEL B–pp. 69–174
69
Liquid-Applied Linings
Of the variouscoating applications, the mostcritical is that of atank lining.
The coating must be resistant to the corrodenta nd be free of pinholes
through which the corrosive could penetrate and reach the substrate.T he
severe attackt hat many corrosivesh ave on the bare tank emphasizes the
importance of usingthe correct procedureinlining atank to obtain aperfect
coating. It is also essential that the tank be designed and constructed in the
proper manner to permit ap erfect lining to be applied.
Liquid-applied linings or coatings may be troweled on or spray applied.In
alined tank there are usually fourareas of contactwiththe stored material.
Each area has the potential of developing adifferent form of corrosive attack.
These areas are the bottom of the tank (where moisture and other contaminants of greater density may settle),t he liquid phase (the area constantly
immersed), the interphase (thea rea where liquid phase meetst he vapor
phase), andthe vapor phase(the area above the liquid). Each of these areas
can be more severely attacked than the rest at one time or another.The type
of material contained, the nature of impurities that may be present, and the
amount of water and oxygen present are all factors affecting the attack.
In view of this, it is necessary to understandt he corrosion resistance of the
lining material undereach conditionand not onlythe immersed condition.
Other factors that have an effect on the performance of the liningmaterial
are vessel design, vessel preparation prior to lining, application techniques
of the coating, curing of the coating, inspection, operating instructions, and
temperature limitations. In general, the criteriafor tank liningsare given in
Table 4.1.
4.1D esigno ft he Vessel
All vessels to be lined internally should be of welded construction. Riveted
tanks will expand or contract, thus damaging the liningand causing leakage.
Butt welding is preferred, but lap welding can be used providing afi llet
CAT8247—CHAPTER 4—17/10/2006—14:32—SRIDHAR—XML MODEL B–pp. 69–174
69