February 25, 2024

Blinds and spacers provide a reliable means to stop the flow to pipe systems to manage flows, avoid contamination, and make maintenance easier. In particular, when positive shutdown is essential, Spectacle Blinds combines these two well-liked components to produce a single solution for your routing and flow control needs. The right choice of a spectacle blind is necessary for dependable, long-term performance, just like with other pipe components. The factors listed below provide a good starting point for choosing the best choice for your requirements.

SPECTACLE BLIND: WHAT IS IT?

 It’s crucial to look at how spectacle blinds are created to comprehend the advantages they provide and some drawbacks. They are made of a paddle blank (also called a spade or slip blind) and a paddle spacer (sometimes called a spacer ring). While the second surface has a ring with the same inner diameter as the linked piping, the first surface completely seals the piping systems. Each round’s connection to the others is made by a little nose piece or tie bar, not a handle, web or tie bar. The component’s namesake, a pair of glasses, or a figure eight may be seen when finished. With this design, the Spectacle blind may be rotated as necessary to allow for total closure or full functioning of a pipe system.

INSTALLATION OF A SPECTACLE BLIND

 The majority of the time, spectacle blinders are mounted for long-term usage. Their easy use and robust construction guarantee a long service life with little upkeep.

The Spectacle blinds are installed between two sections of welded pipe to block fluid flow during maintenance. The blind is installed by passing one of the flange bolts through the hole on the central tie bar rather than securing it with bolts around the whole diameter of the pipe like you would with a pipe flange. Gaskets are placed between the flanges and Spectacle blind to further strengthen the connection.

Due to this, it is crucial to take spectacle blind implementation into account while designing your piping procedures. To provide a solid, long-lasting fit, the extra area between the pipe flanges will also require enlarged stud bolts. To accommodate practically any intended application, spectacle blinders are offered in a variety of face kinds, including:

Flat face blanks

Raised face blanks

Female ring-joint blanks

Male ring-joint blanks

Prior to installation, be careful to take into account how this may affect the requirements for the gasket and flange. The following areas are frequent ones for installing eyewear blinds:

  • at the rotary or static equipment’s inlets and outlets
  • at the inlets and outputs of containers used for storage and processing
  • within bypass lines

COMMON PURPOSE FOR SPECTACLE BLINDS

 During system operations and maintenance, spectacle blinders provide more flexibility. In the case of valve degeneration, failure, or operator error, they’re also a great choice for ensuring positive shutdown. It’s simple to adjust eyeglass blinds. Simply release the bolts surrounding the flange, leaving the bolt that runs through the Spectacle blind in place, rotate the chosen face into the area between the pipes, and tighten the flange bolts once more. In some piping systems, new gaskets will need to be inserted.

LIMITATIONS OF SPECTACLE BLINDNESS

Despite the ease that spectacle blinds provide over the freestanding slip and spacer blinds, there is one significant disadvantage: weight. This is particularly true for big or intricate pipe systems, where the weight of several shutters might easily create excessive strains on the entire structure. To assist in preventing unnecessary burdens in these situations, solo choices are often advised.

STANDARDS AND DESIGN CODE FOR THE SPECTACLE BLIND

Spectacle blind design is governed by ASME B16.48. This standard details the Spectacle blind’s measurements, pressure-temperature ratings, material choices, labelling requirements, dimensional tolerances, and testing specifications. In general, ASME B16.5 pipe flanges in the 150, 300, 600, 900, 1500, and 2500 Pressure Classes are fitted between blinds that range in size from NPS 1/2 to NPS 24. They are made from steel plates and come in forged material grades such as ASTM A105 (high-temperature carbon), A350 (low-temperature carbon), and ASTM A182 (alloy, stainless steel, duplex).

There are also larger size, custom-made sight blinders with a diameter of >24 NPS available. While alloy/stainless steel blinds can be made by welding multiple pieces of steel together, carbon steel spectacle blinds are typically made from a single piece of steel.

DEFINED TERMS ASSOCIATED WITH SPECTACLE BLIND

Paddle Blank or Paddle Spacer Spacer Blank or Paddle Spacer With the same thickness as the “single-blind” that it replaces, rings are constructed to fit the pipe ID. When installing spacers, the flange and related pipe must be brought together, and a “ring spacer” must be installed to close the opening. Usually, welding is used to join the handle to the blank.

BLANK, SPACER, FLANGE SPADE, SINGLE/LINE, BLIND, AND PADDLE BLIND

To stop the unintentional flow, single-blind positive shut-off devices are typically mounted beside valves. They often tuck inside the bolt circle of corresponding flanges. Cast iron, fibreglass, and plastic are bolted, however. Simple gaskets are used with single blinds. The handle of the blank is manufactured solid, whilst the spacer has a formed eye or drilled hole to distinguish it from the blind in the installed line.

DISPLAY BLIND

 As a spectacle blind, a single-blind combined with a ring spacer is employed. They are switched out as needed to accomplish the goal. A pair of paddle blanks and a paddle spacer are used instead of a single spectacle blind when it becomes too heavy.

TEST BLANK (HYDRO TEST, PNEUMATIC TEST, OR SERVICE TEST)

 Test blanks are used while testing for leaks. Test blanks are specially created blanks that are exclusively utilised during the testing process.

VAPOR BLIND

 Vapour Blinds are positive sealing tools that stop vapour leakage into a pipeline or vessel. They resemble “single-blinds” in appearance. In general, they are 1/8′′ to 5/16′′ (3-8mm) thick and less substantial than single-blind.

JACK SCREW FLANGE

Jack Screw Flange is necessary for blinds that are greater in size. Jackscrews are useful for flange widening, spacer/blind replacement, and changing spectacle blinds.

SEVERAL SIGNIFICANT CONSIDERATIONS FOR SPECTACLE BLINDS

 Spectacle blinds must be reachable from a level surface, a platform, a portable ladder, or temporary scaffolding if they are lower than 4500 mm. When close to the equipment nozzles, the suitable weight of the Spectacle blind must be taken into account during the pipe stress calculations.

DIFFERENCE BETWEEN SPADES, SPACERS, AND SPECTACLE BLIND

 Spectacle Blind is akin to Spade and Spacer being taken together. A spectacle blind is the result of combining the shapes of a spade and a spacer. The weight of the Spectacle blind is too much for bigger pipe diameters. Therefore, a spade or spacer may occasionally be employed as needed. To make it evident what is installed in the line, the words “SPADE” or “SPACER” are imprinted on the handle of the spade or spacer. The spade handles, and spacers are visible from the outside when they are mounted. Fig. 5 provides the common handle configurations.

CONCLUSION

Due to their capability to swiftly separate pipeline components during repair operations without shutting down the entire system, spectacle blind flanges are crucial components of many industrial piping systems. To achieve the greatest results from your setup, it’s crucial to consider variables like pressure rating and material compatibility when selecting a spectacle blind flange. Additionally, it’s important to use the right welding procedures while installing spectacle blinds to ensure they create an airtight seal that stops leaks from happening while they’re in use. You can ensure that your industrial pipe system operates smoothly and effectively over time by learning how these components function!

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