Spectacle blinds

Routing of Flare Header through Process Areas - Flare headers in process areas should be routed to avoid locations of particularly high fire risk, such as over pumps, near furnaces, etc. The headers and subheaders should also be laid out and provided with isolating CSO valves and spectacle blinds, unless prohibited by local codes, such that it is not necessary for flare lines to remain in service in units which are shut down separately. Blowdown and water disengaging drums should be spaced from process areas. 

There is no automatic control on the flowrate of the gas inlet stream or weak-acid condensate stream, since both of these flows are predetermined by feed flowrates earlier in the process. Isolation valves and provision for spectacle blinds are included to enable the column to be isolated during shutdown periods. 

Blanking and blinding— The absolute closure of a pipe, line, or duct by the fastening of a solid plate (such as a spectacle blind or a skillet blind) that completely covers the bore and that is capable of withstanding the maximum pressure of the pipe, line, or duct with no leakage beyond the plate. 

Tags should be used to identify locations where equipment has been altered for lockout, including valves, flanges, skillets, spectacle blinds, switches, and blocking devices. The tag should identify the person who applied it, the reason the tag was applied, and the date the tag was applied. 

If a flange is to be routinely blinded, a spectacle blind (also known as a Figure 8, disk-and-donut, or spec blinds) can be installed. This type of blind looks like a pair of spectacles or the number 8, with one section closed and the other open. When the flange is broken and the line cleared, the blind can be rotated around the one bolt that is left in the flange. It is simple to ensure that the blind has been installed because the open part of the blind will be sticking out from the flange face. 

If spectacle blinds in horizontal pipes are insulated, the blind should point downwards at an angle of 45° to avoid water leaking into the insulation. 

Figure 8 plates are friendlier than slip plates (blinds) as their position is apparent at a glance. If slip plates are used, their projecting tags should be readily visible, even when the line is insulated. In addition, spectacle plates are easier to fit than slip plates, if the piping is rigid, and are always available on the job. It is not necessary to search for one, as with slip plates. 

Most blinds are either of the line or spectacle type. 

Location and installation of Vents, drains, drip legs, drip rings, utility station connections, steam traps, filten, strainers line blinds, spectacle plates, by-passcs, insinimeni lapping points for pre.ssure, temperature and flow, plugs and rodding out points ... 

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