4. All sharpcorners must be ground to aminimum of 1/8 in.radius.
5. All outlets to be of flanged or pad type. Certain lining materials
require that nozzlesb en ot less than 2in. (55 mm) in diameter.
6. No protrusions arep ermitted inside of the vessel.
Once the lining has been installed, there should be no welding permitted
on the exterior of the vessel.
After the fabrication has been completed, the interior surfaceofthe vessel
mustbeprepared to acceptthe lining. Thisisavery critical step. Unless the
surfacei sp roperly prepared, proper bonding of the lining to the shell will
not be achieved. The basic requirement is that the surface be absolutely
clean.T oensure proper bonding, all surfaces to be lined should be abrasiveblasted to white metal in accordance with SSPC specification Tp5-63 or
NACE specification 1. Awhite metal surfacec onditioni sd efined as being
one where all rust, scales, paint, and the like have been removed and the
surfaceh as au niform gray–white appearance. Streaks or stains of rust or
othercontaminants are not allowed. Anear-white blast-cleaned finish equal
to SSPC SP-10 is allowedo no ccasion. This is am ore economical finish. In
any case, it is essential that the finish be as the liningcontractor has specified.
Some liningc ontractors will fabricate the vessel as well as preparet he
surface. When the total responsibility is placed on the liningc ontractor,
the problem is simplified, and usually,abetter quality product will be
the result.
When av essel shell is fabricated from ar einforced thermosettingp lastic
(RTP), several advantages are realized. The RTPs generally have aw ider
rangeo fc orrosion resistance,b ut relatively lowa llowable operating
temperatures. When afl uoropolymer-type liningi sa pplied to an RTP
shell, the temperature to which the backupRTP is exposed, has been reduced
in addition to preventing the RTPfrom becoming exposed to the chemicals
in the process system. An uppert emperature limit for using RTPd ual
laminates is 3508 F( 1778 C).
Thed ual-laminate constructionl essenst he problemo fp ermeation
through liners. If therei sp ermeation, it is believed to pass through the
RTPs tructure at ar ate equal to or greater than through the fluoropolymer
itself,r esulting in no potential forc ollectiono fp ermeatea tt he
thermoplastic-to-thermoset interface. If delamination doesn ot occur,
permeationisn ot ap roblem.
6.2C onsiderations in Liner Selection
Before al iningm aterial is selected,c arefulc onsiderations hould be given
to several broad categories, specifically materials beingh andled, operating
conditions, and conditions external to the vessel.
Corrosion of Linings and Coatings
288
CAT8247—CHAPTER 6—6/10/2006—12:28—SRIDHAR—XML MODEL B–pp. 287–402
5. All outlets to be of flanged or pad type. Certain lining materials
require that nozzlesb en ot less than 2in. (55 mm) in diameter.
6. No protrusions arep ermitted inside of the vessel.
Once the lining has been installed, there should be no welding permitted
on the exterior of the vessel.
After the fabrication has been completed, the interior surfaceofthe vessel
mustbeprepared to acceptthe lining. Thisisavery critical step. Unless the
surfacei sp roperly prepared, proper bonding of the lining to the shell will
not be achieved. The basic requirement is that the surface be absolutely
clean.T oensure proper bonding, all surfaces to be lined should be abrasiveblasted to white metal in accordance with SSPC specification Tp5-63 or
NACE specification 1. Awhite metal surfacec onditioni sd efined as being
one where all rust, scales, paint, and the like have been removed and the
surfaceh as au niform gray–white appearance. Streaks or stains of rust or
othercontaminants are not allowed. Anear-white blast-cleaned finish equal
to SSPC SP-10 is allowedo no ccasion. This is am ore economical finish. In
any case, it is essential that the finish be as the liningcontractor has specified.
Some liningc ontractors will fabricate the vessel as well as preparet he
surface. When the total responsibility is placed on the liningc ontractor,
the problem is simplified, and usually,abetter quality product will be
the result.
When av essel shell is fabricated from ar einforced thermosettingp lastic
(RTP), several advantages are realized. The RTPs generally have aw ider
rangeo fc orrosion resistance,b ut relatively lowa llowable operating
temperatures. When afl uoropolymer-type liningi sa pplied to an RTP
shell, the temperature to which the backupRTP is exposed, has been reduced
in addition to preventing the RTPfrom becoming exposed to the chemicals
in the process system. An uppert emperature limit for using RTPd ual
laminates is 3508 F( 1778 C).
Thed ual-laminate constructionl essenst he problemo fp ermeation
through liners. If therei sp ermeation, it is believed to pass through the
RTPs tructure at ar ate equal to or greater than through the fluoropolymer
itself,r esulting in no potential forc ollectiono fp ermeatea tt he
thermoplastic-to-thermoset interface. If delamination doesn ot occur,
permeationisn ot ap roblem.
6.2C onsiderations in Liner Selection
Before al iningm aterial is selected,c arefulc onsiderations hould be given
to several broad categories, specifically materials beingh andled, operating
conditions, and conditions external to the vessel.
Corrosion of Linings and Coatings
288
CAT8247—CHAPTER 6—6/10/2006—12:28—SRIDHAR—XML MODEL B–pp. 287–402