Sizing for Sealing a Flange with Flangeseal

 How do I Know What Size to Order: FS-Flangeseal and AQW-FPK (Flange Protection Kit)

An installed Covalence FS (Flangeseal)

     Coating a flange can be tricky.  You've typically got a significant size difference between the outside diameter of the flange - and the diameter of the pipeline.  You've also got a number of bolts that could have sharp edges.  You've got a gasket of some kind that you'd likely don't want to covered in anything permanently (that would prevent you from re-entering that flange if it was necessary.  You've also likely got some amount of uncoated pipe where the flange is welded in.  There are a lot of important data points there.  Let's try and break it down so it is a bit simpler.

     Typical flangeseal nomenclature will be something like this (I'll give a few examples):  

FS 24000-24 -- this is for a flange with an ACTUAL OD of 24.0".  This FS is supplied 24" wide (we'll get more into that below).

FS 36000-36 -- an FS for a 36" OD Flange that is supplied at 36" wide.  

FS 12750-24 -- an FS for a 12.75" OD Flange that is supplied at 24" wide.

     So, the first number is VERY important!  That tells us how to make the Flangeseal so that is long enough to wrap all the way around the flange and meet back up with itself.  An FS 12750 would never work on a 24" OD flange --- it would be like someone with a 36" waist trying to button up jeans that are made for a 22" waist.  

     The second number is the width of the flange as supplied.  That is slightly trickier to figure out.  Let's say you are working with a 24" OD Flange and a 12.75" OD Pipe.  In addition, let's say that flange is 4 inches wide itself and there are 4 inches of uncoated pipe where the pipe and flange connect.

     First thing I look at:  24" OD flange down to a 12.75" OD pipe.  Picture the sleeve installed.  The sleeve is going to 'step down' from the peak of the flange down to the pipe surface and nearly 6" of the sleeve "width" is going to be lost on that vertical of the sleeve shrinking.  Does that make sense?  Simplify it by picturing yourself cutting a strip of duct tape that spans from your kitchen island down to the floor and across to the wall.  You would have to measure - the number of inches you want it to be attached to your kitchen island -- and the distance from island to floor -- and the distance across floor to wall.  In this paragraph - the step down from outermost flange to pipe is like the distance from the kitchen island to the floor.  

     So right there - with this 24" to 12.75" dimension we know we are going to lose 6" of our sleeve width TWO TIMES (have to figure this step down will happen on both sides of the flange.  So that is 12" of our width "used" already.  In addition - the flange is 4" across (which includes where the bolts are, etc).  We've now used 16" of our sleeve width (12+4).

     Now let's add in that there are 3" of bare steel adjacent to the flange on both sides.  That is 6" of bare steel (total - we have to add them together) AND we still need to overlap onto good pipe coating by at least 3" per side (another 6").

     That leaves us (in terms of sleeve width) with:

• 12" of width used to bridge the gap between flange and pipe
• 4" of width used to cover the flange itself
• 6" of width used to cover bare steel
• 6" of width used to overlap onto good coating

12 + 4 + 6 + 6 = 28"

     The minimum FS width that could work on this configuration is 28".  Our standards are 24" and 35.5" --- so the only option here is to use a 36" wide Flangeseal (24" would not properly seal).  

Flange Protection

Heat Shrinkable Corrosion Protection for Flanges

     Flangeseals are a niche product that we manufacture and sell.  Though the volume isn't yet tremendous, this is a fantastic product with a long, successful use history.  Flange Protection is a fairly common need out in the world.  There can be plenty of confusion as well though, as flange protection sleeves very often are specified on different criteria than we see field joint coatings specified.  Coincidentally, I've recently been in a position to have a few different discussions about our specific flange protection solution.

     Being that these are separate projects, there is an interesting opportunity here to evaluate our product (Flange Seal) from a couple of different angles:  Technically and cost.  

     First let's look at coating thickness:

Flangeseal is supplied with a backing thickness of 51 mils.  It is supplied with an adhesive thickness of 47 mils.  So we have a total supplied thickness of 98 mils.  This is a product that will shrink 67% if allowed to shrink that much (unrestricted by a pipe diameter, etc).  In such a case where there was going to be a full unrestricted recovery, this product backing thickness would be 127 mils.  Just like the backing, the adhesive thickness will increase during the shrink process (volume of the adhesive does not change, while the area of sleeve backing is reduced, resulting in a thicker adhesive even with the consideration that some small amount of adhesive will flow at the edges of the sleeve by design to form a seal.

That would mean a total, full unrestricted recovery of something in the neighborhood of 180 mils.  This may answer the question as many spec writers would see a number like this on a data sheet - and would copy it over to a spec - not realizing that they may have made a mistake.  If they meant to include the "full unrestricted recovery" dimensions (which are certainly are directly tied to the installed dimensions) then they have succeeded.  If, on the other hand, they have included a number which is the 'full unrestricted recovery' dimension but what they really want is the installed thickness - they may have inadvertently caused themselves an issue. 

Determining installed thickness can very often be a difficult task (as evidenced by the fact that no shrink sleeve manufacturer anywhere in the world reports an installed thickness).  Why is it difficult?  Because there are a number of very important factors.  How much 'slack' was in the shrink sleeve prior to shrinking?  What was the exact temperature of the preheated steel?  How much longitudinal shrink occurred during the shrink process?  What were weather, humidity and wind conditions during the shrink process?  What was the exact thickness of the adhesive during the manufacturing process (this can vary a great deal for mastic products, though the plant is always certain to guarantee a minimum thickness). 

Looking at this through my own 15 years of experience, exclusively with this product line, here are my opinions.

This product would be ~180 mils with a full recovery.

This product is 98 mils supplied. 

I believe it is reasonable to assume that the shrink sleeve thickness at the pipe will reach the 130+ mil thickness. 

This raises another difficult aspect of trying to define 'installed thickness' (which your client may not have even intended to do).  Because the sleeve will shrink a great deal when it bonds to the pipe surface; while not shrinking nearly as much as it bonds to the Flange surface (which is much larger) - the installed sleeve will be thicker at the pipe surface than it is at the flange surface; because shrink sleeve recovery has such a significant bearing on installed product thickness.

I'm sorry I could answer that one with fewer words.  I'm sure that is more than you ever wanted to know about installed shrink sleeve thicknesses.

 Now, when considering specifically my product (FlangeSeal) against a competitors heat shrinkable option:

Competitors product: 

Backing thickness supplied:  31 mils

Backing fully recovered:  not reported

Flangeseal:

Backing thickness supplied: 51 mils

Backing thickness fully recovered:  128 mils

So right there - we are looking at ~62% thicker backing as supplied.  I expect there will be a similar disparity with fully recovered dimensions.  So 62% thicker backing.  That is pretty significant when considering the weight these sleeves will bear on larger flanges. 

An important note:  our backing is comprised of three layers:

1 layer of radiation cross linked polyolefin

1 layer of a fiber mesh material specifically designed to improve penetration resistance and abrasion resistance (critical for sealing a flange in my opinion)

a 2nd layer of radiation cross linked polyolefin

From all I can see - my competitors product is comprised of a single layer of polyethylene.

Looking at adhesive thicknesses (which aren't as important in my opinion) - Competitor is at 44 mils and our Flangeseal is at 47 mils. 

I really think the fiber mesh laminated in the backing of our product is the most important difference though.  Truly, I think it is the difference between a product that works...and a product that doesn't.