Spectacles Blinds & Spades (Wermac)

8/18/2019 Spectacles Blinds & Spades (Wermac)

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11/1/2014 Special Flanges - Spectacle Blinds, Spades and Ring- Spacer s -

http://www.wermac.org/flanges/flanges_special_spectacle-blinds_spades_ring-spacers_paddle-spacers.html#thicknesscalc 1/3

1. Spectacle blind 2. Flanges 3. Gaskets 4. Stud Bolts

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Definition and Details of Flanges - Blinds & Spades

Spectacle blindsSpectacle Blinds are generally applied to permanently

separating pipesystems, or just to connect with each other. A

Spectacle Blind is a steel plate cut into two discs of a certain

thickness.

The two discs are attached to each other by section of steel

similar to the nose piece of a pair of glasses. One of the discs

is a solid plate, and the other is a ring, whose inside diameter

is equal to that of a flange.

Spectacle Blinds be applied in systems, which regularly need

to be separated from other installations. Normally, a

Spectacle Blind is mounted in the "open" position so that flow

through the pipe is possible. If the Spectacle Blind in the

"close" position is rotated, the p ipe is blanked off and no flow

is possible.

Maintenance on a pipesystem can be a reason to rotate the spectacle in the "close" position. This run will take place

through the hole, that is drilled in the connection piece. By loosening of all bolts, and partial removal of their, the

Spectacle Blind can be rotated. After replacing the gaskets (new gaskets are to recommend), the bolts can be re-

assembled and tightened.

Spectacle blind in open position Spectacle blind in closed position


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Spades & Ring SpacersSpades

Spades and Ring Spacers are basically the same as Spectacle Blinds, except that both are not attached to each other.

Spades and Spacers be applied in systems where maintenance is often not necessary, or in applications with large pipe

sizes. Depending on the flange size and the Pressure Class, Spades can weigh hundreds of pounds. To prevent

unnecessary weight to a flange connections, usually will be chosen not for a Spectacle Blind, but for 2 separate parts.

Typical Spade Typical Ring Spacer

1. Spade 2. Flanges

3. Gaskets 4. Stud Bolts

1. Ring Spacer 2. Flanges

3. Gaskets 4. Stud Bolts

Ring Spacer

So as for the Spectacle Blind already described, maintenance on a pipesystem can be a reason to temporarily replace a

Ring Spacer for a Spade. By loosening of all bolts, and half of the bolts temporarily remove, the Spade or Spacer can

be placed. After replacing the gaskets (new gaskets are to recommend), the bolts can be re-assembled and t ightened.

A small problem is that we basically can not see, or a Spade or a Spacer mounted between the flanges. Therefore the

handles are often specially marked, or both have a different design; a customer often provides its own specification.

What should never lack is, that in the handle, the diameter and the Pressure Class of a Spade or Spacer is engraved;

this applies also for the Spectacle Blind.

Surfaces - Dimensions - MaterialThe sealing surfaces of a Spectacle Blind, Spade or Ring Spacer are usually conducted in accordance with the

Face Finish from the flange. The diameter always is slightly larger than the Raised Face of a flange; by a correct

assembly, the bolts are just not touched by the Blind or Spacer.

The diameter of them, is depending on the flange size, and the thickness from the Pressure Class of a flange.

Dimensions from Spectacle Blinds, Spades and Ring Spacers, you will find in the main Menu "Flanges"

ASME B16.48 covers pressure-temperature ratings, materials, dimensions, dimensional tolerances, marking, and

testing for operating line blanks in sizes NPS 1/2 - NPS 24 for installation between ASME B16.5 flanges in the 150,

300, 600, 900, 1500, and 2500 Pressure Classes.

Spectacle Blinds, Spades and Ring Spacers should be made from a plate or forging specification, approved for use by

ASME B31.3, of essentially the same chemical composition as the mating flanges and piping involved.

Remark(s) of the Author...

Is it necessary to use Spectacle Blinds ?I think not, because they are ineffective in many practice situations.

On paper it seems simple, remove some bolts, turning the spade and mount the flange back. In practice is


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certainly not...

I am in favor of two separate flanges (ring and solid p late)

What is the formula to calculate the thickness of a spacer ?Sometimes it is necessary to use a thinner spacer, because a spacer with a standard thickness often can not be

mounted between two flanges...Think of a pressure test in a "Life Plant" where a spacer should be installed

between two flanges.

As a rule of thumb the following formula can be used to calculate the thickness in millimeters:

Pressure (barg) multiply by diameter (inches) divided by 10

Pressure: the highest pressure that the system can achieve

Diameter: the size of the spacer in inches

Example: 8 x 12 / 10 - thickness of spacer = 9.6 mm

NOTE: always try to apply spacer thicknesses in accordance with ASME B16.5.

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Spectacles Blinds & Spades (Wermac)