A193-B8M bolt

• Feb 26, 2018

• #2

Guest

Syahar1975 said:

floro carbon

Click to expand...

Suggests a Teflon coating. Why this would be considered necessary on a 316SS fastener I cannot guess.
I am generally skeptical of non-metallic protective coatings on fasteners.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

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• Feb 26, 2018

• #3

Screwman1

Mechanical

May 4, 2012

281

US

We see a lot of B8M bolts with Fluorocarbon coating for special chemical use in railcar construction. It adheres fine with the proper surface prep. Make sure to have one of the folks that do a lot of fastener work do the application, it's not the same as a fitting plate.

 

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• Feb 27, 2018

• #4

XL83NL

Mechanical

Mar 3, 2011

3,120

NL

We have coated our B8M studs in the past as well with PTFE, partly due to customer requirement, partly since we generally PTFE (i.e. Xylan) coat all or studs and nuts to reduce friction, when design temperatures allow so.

 

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• Feb 27, 2018

• #5

MJCronin

Mechanical

Apr 9, 2001

5,102

US

A little footnote here ..... in favor of fluoro coating fasteners.

When a fastener is coated, the identification etched on the item is typically lost. Having various coating colors available can be an advantage.

(i.e stainless - yellow, low carbon steel - blue, carbon alloy - green..... etc.

In well organized and planned operations, many clients require different colors for stud/nut/bolt material combinations. This help prevent mix-ups and substitutions that can be expensive and dangerous. Inspection and maintenance is made simpler....throughout the life of the plant.

I have been to many plant sites where management does not pay any attention to bolt management and simply gives up and specifies that only the strongest (and most expensive) bolts are used on site. This is an expensive and often lame brained solution

Of course, you can still have uncoated bolts for special cases.

https://www.metcoat.com/assets/files/Fluorokote1Brochure.pdf

MJCronin
Sr. Process Engineer

 

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• Feb 27, 2018

• #6

XL83NL

Mechanical

Mar 3, 2011

3,120

NL

Here's a snap of what we have in our bolt spec, to identify colours

 

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• Feb 27, 2018

• #7

Guest

Screwman1,
I guess I am skeptical because I have only seen such fasteners after the coating has failed and the barrier breached.
I have trouble wrapping my head around the idea that any plastic coating can survive the necessary torqueing.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

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• Feb 27, 2018

• #8

XL83NL

Mechanical

Mar 3, 2011

3,120

NL

it will not survive repetitive torqueing; a few 'open and closes' will easily take away the coating. But the added cost vs the advantages, even if it were for a single use, is what makes us keep on using the PTFE coating. We usually dont go beyond bolt sizes 1" or larger.

 

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• Feb 27, 2018

• #9

EdStainless

Materials

May 20, 2004

16,367

Waukesha WI USA

I personally like fluorocarbon coatings on SS fasteners, it is easier than assuring that the correct anti-seize compound is used every time. And when the coating begins to fail mechanics are willing to use new fasteners.
I have found the cost of coating to less than machining out a seized stud or bolt.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

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• Mar 2, 2018

• Thread starter
• #10

Syahar1975

Mechanical

Feb 3, 2011

224

ID

XL83NL,

Is there any standard color for florocarbon bolt and nut ?

I look at again the drawings and found the bolt specs is A193B7 with note :florocarbon. The supplier gave us bolt not green color bolts and nuts.

Looking to your snapshot green is A193L7.

Syah

 

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• Mar 2, 2018

• #11

david339933

Industrial

Jun 15, 2011

1,204

CA

No Standard....If you don't specify they will give you anything. The B7's I receive are blue on request.

 

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• Mar 2, 2018

• #12

XL83NL

Mechanical

Mar 3, 2011

3,120

NL

david339933 said:

The B7's I receive are blue on request.

Click to expand...

Same here. Based on that, we made up our own standard and include the colour in our purchase order. L7 doesnt need to be green, it can be anything you want. I just picked the most obvious colours (to visually differentiate from) for the most commonly used grades.

 

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