internal coatings,potable water tanks
internal coatings,potable water tanks
(OP)
good day, great site, I have been reading the postings for some time and finally have a query to post
I need to find a epoxy type coating for the inside of a stainless steel potable water tank 30US gallon capacity.
the tanks are welded, passivated and then flushed before being stored to air dry.
at this stage I need to apply the coating, unfortunatly access for spraying the caoting is extremly limited. There is only a "fill" hole approximatley 1.50 dia and two exit holes bothe 0.50 dia
thanks
I need to find a epoxy type coating for the inside of a stainless steel potable water tank 30US gallon capacity.
the tanks are welded, passivated and then flushed before being stored to air dry.
at this stage I need to apply the coating, unfortunatly access for spraying the caoting is extremly limited. There is only a "fill" hole approximatley 1.50 dia and two exit holes bothe 0.50 dia
thanks





RE: internal coatings,potable water tanks
A few questions to clarify the tank construction...
Was this tank made "per" a drawing with "spec requirements" [MIl, MS, AS, Etc]... or just a drawing [with notes]?
What alloy/temper is the tank construction??
What welding process was used?? What NDI process??
Please confirm that the finish-welded tank interior was passivated ... if so, per what spec??
Are the interior surfaces completely "smooth"... or are there "bits" of weld-thru [flash or other sharp edges] and/or possible "open" metal seams??? IE: inspection [by borescope] of interior show any significant roughness or fluid-traps???
Regards, Wil Taylor
RE: internal coatings,potable water tanks
The tank is welded in accordance with Learjet specs LES 1026 and LES 1014 to a specification control dwg.
The material is 304 stainless annealed per AMS 5513. The NDT tests are called in the welding process(s)
The tank is passivated per LES 1323 and ASTMA967 then cleaned in accordance with ASTM A380 using distilled water.
Upon completion of the cleaning there is a water purity test per ISO 14951-10.
The tank is then hot air dried and sealed "to prevent moisture buildup"
The interior is fairly smooth although Visual evaluation shows several areas of open seams where interior baffles meet the tank walls with welded areas (weld -thrus) at intervals along the baffle's length
regards
Britcan
RE: internal coatings,potable water tanks
___ <in
__ / __________ top of tank
\ | |
\J |
/ spray |
/ |
/____________|
Steven Fahey, CET
"Simplicate, and add more lightness" - Bill Stout
RE: internal coatings,potable water tanks
My input is this:
1. The most important aspect of any coating application is SURFACE PREPARATION. Your design, from the very start, hinders surface preparation and it is doubtful you'll get good performance from an epoxy in this application (for example, the small, mostly closed tank; a smooth passivated CRES surface, both work against good performance of coating systems).
2. Many epoxy paint companies have epoxy coatings the meet NSF requirements for potable water applications.
3. If the container is CRES 304, annealed and passivated, WHY PAINT IT?