Paddle Blinds, Spectacle Flanges, Bleed Rings & Spectacle Blinds 1

[sy123]

Hello All,
This might be too naive a question to put before you all, even then, could anyone mind writing down few lines about the following ( both functional & physics point of view & some standards (or) references for design of these items)

a) PADDLE BLINDS

b) SPECTACLE BLINDS

c) BLEED RINGS

d) SPECTACLE FLANGES

Appreciate your time.

 

[dcasto]

Paddle blinds are used to temporarly isolate pipe at flanges. The flanges maybe at a valve, or a set of flanges in the line, or at a nozzle on a vessel or pieces of equipment. The thickness based on pressure differential is calculated bt B31.3 section 304.5.3. Some times a very thin skillet is used to keep the two sides from communicating, not always for full pressure rateing. Skillets are usually stored in a wharehouse and used as needed. The skillet name comes from the addition of a handle to the round flate piece of steel with an OD equal to the ID of the flange bolt circle. Hence it looks like a cooking skillet.

Specticle blinds are blind flanges, only mated with a skillet having an opening equal to the ID of the line. The handle between to soild and the "hollow" skillet is shared, hence it looks like a pair of eye glasses, one is solid and the other has an opening like a glass frame. The same equation works. These are installed where they are in use all the time where the process must be 100% isolated (no leaking valves allowed). Make sure your piping designer knows the thickness so you can leave space for in in the line.

Bleed rings are like the hollow side of the specticle blind. On the hollowed out plte, a hole has been tapped from the inside to the outside. so the user can thread in a nipple and valve. This is essentially a tap into the process. If placed between the flange on a valve and the flange on a reflief valve, one could closse the valve and bleed the pressure off between it and the relief valve.

Specticle flanges, would be two ordinary flanges with enough gap between them to accept the specticle blind of the properly designed thickness between them.