Figure 8 Blanks 1

[Tuga29]

Could you please give some advice on Figure 8 Blanks CS protective coating. Is there any requirement. Contractor says it can't be painted and we don't agree with that.

 

[LittleInch]

I wouldn't be painting anything which relies on surface contact as the sealing mechanism like a line blind or spacer.

If you want to protect it, just use some sort or removable sealing like grease or oil based preservative which can be cleaned off when you need to swing the blind.

Each location will determine whether you need to provide some sort of anti corrosion protection or not. If it's a highly corrosive atmosphere ( say sea water spray) I would use a blind paddle and a spacer as two separate items instead of a spectacle or figure of 8. No "requirement" per se.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Tuga29]

We are in a C5-M corrosive environment and the design define just figure 8 blank. In normal production the blind face will corrode fast.

 

[LittleInch]

Sorry C5-M ?? Please explain.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[KevinNZ]

C5-M given in BS EN ISO 12944-2[1] and BS EN ISO 9223[2],

C1
very low ≤ 1.3 - Heated buildings with clean atmospheres, e.g. offices, shops, schools, hotels
C2
low > 1.3 to 25 Atmospheres with low level of pollution
Mostly rural areas Unheated buildings where condensation may occur, e.g. depots, sports halls
C3
medium > 25 to 50 Urban and industrial atmospheres,
moderate sulphur dioxide pollution
Coastal area with low salinity Production rooms with high humidity and some air pollution e.g. food-processing plants, laundries, breweries, dairies
C4
high > 50 to 80 Industrial areas and coastal areas with moderate salinity Chemical plants, swimming pools, coastal, ship and boatyards
C5-I
very high
(industrial) > 80 to 200 Industrial areas with high humidity and aggressive atmosphere Buildings or areas with almost permanent condensation and high pollution
C5-M
very high
(marine) > 80 to 200 Coastal and offshore areas with high salinity Buildings or areas with almost permanent condensation and high pollution

 

[racookpe1978]

So, change your material to a stainless, non-corrosive. The "paint" (primer plus two or coats to cover) will not yield a smooth enough surface to seal the joint when the figure 8 is flipped.

 

[LittleInch]

Kevin,

Thanks, I hadn't come across that description of atmospheres before - very useful.

Anyway - you can't paint these things. Clearly the designer hasn't given this any/enough thought given its location, especially as it was probably the process engineer who drew it in the first place.

So to avoid this thing become useless my recommendation remains the same - get a deviation / change / site instruction whatever to replace it with a spacer and keep the blind in the maintenance shed or make it out of Duplex.



Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[GD2]

Any thought about putting dissimilar material for galvanic corrosion? LittleInch’s recommendation for greasing looks the best option to me.

Ganga D. Deka, P. Eng
Canada

 

[zdas04]

I would do it LittleInch's way, but I would drill a hole in the handle on the spacer in the direction of flow and a hole in the blind across flow. I'm not sure that this will always prevent misunderstanding, but at least it is visual like a spectacle blind is visual.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist