The Onis (Spectacle-Plate) lineblind is a unique mechanical device accepted world-wide for its contribution to efficiency and productivity with an emphasis on improving safety in process/industrial plants.
The Onis (Spectacle-Plate) lineblind provides a one-man, manual means of blanking a line in a matter of minutes or in some cases seconds without tools, guaranteeing total safety and visual evidence of the open or closed condition of the line.
Extensively used in refineries and petrochemical plants, the Onis lineblind has been supplied in sizes ranging from 15mm to 120mm as standard with larger diameters available, and redesigned for pressure capabilities ranging from 20 BAR for 48" units to 160 BAR for ½" units, and temperatures ranges from as low as -104°C to as high as 760°C.
"Give me a place to stand, and I can move the world!"
The Onis lineblind utilises the laws of leverage to translate the modest energy of one person into a force sufficient to spread 48" pipework. Two flanges or welded body halves which are connected by a set of four 9(4) shafts, two (2) being eccentric, and linkage plates. This arrangement creates a tremendous mechanical advantage allowing one person to spread pipework quickly and with ease.
Pulling the lever in 120° the two (2) eccentric (CAM) shafts rotate simultaneously exerting a force on the flanges which separates the pipe about the Onis spectacle plate, parallel and in a controlled manner. As an example, the smaller Onis lineblinds, with only 10 Kg force exerted to the lever, actuating shaft eccentricity develops 137,000 Kg in the closed position, and in respect to the CAM, 8,000 Kg in the full open/separated position.
Once the lineblind system is fully separated , a clearance of a few millimetres (3.5mm total pipe movement) is provided on either side of the spectacle plate allowing it to move freely, and with the aid of roller guides it moves in one plane, clear of the Onis body seats, thus preventing wearing or gouging of the ‘o’rings.
The selection of open (full bore) or closed (blanked) position is made quickly & effectively with little or no effort. Pushing the spectacle plate manually into position guarantees your choice, leaving the redundant part (open or blank) of the spectacle plate exposed, enabling quick and positive confirmation of blanked / open status.
With the spectacle plate in its chosen position, the operator simply moves the lever back to its original position, which again rotates the eccentric shafts simultaneously drawing the pipe flanges together and exerting a uniform compression on the ‘o’rings (seals) on the spectacle plate in either open or blanked position.
The application / duty conditions naturally dictate the materials of construction. The most critical item is the sealing method, using ‘o’rings set in the spectacle plate. Elastomers range from neoprene rubber to silicone coated Viton(R)*. In high temperature special applications carbon graphite seals are used with proven success.
With the use of elastomeric ‘o’rings, Onis lineblinds are designed with special grooves machined in the spectacle plate to hold / locate the ‘o’ring in position. The shape of these grooves does away with conventional designs, where the groove takes the cross-sectional profile of the ‘o’ring or a square channel / groove often allowing the ‘o’ring to pop out when heavily compressed or under extreme pressure. The Onis lineblind sealing grooves are diamond shaped, truncated to allow the ‘o’ring to project above the spectacle plate. The groove overhang holds the ‘o’ring firmly in position, and the three expansion areas in the groove allow the ‘o’ring to be compressed without the risk of pop-out, held in place when under pressure.
The Onis lineblind requires virtually no maintenance with the exception of periodic replacement ‘o’rings. This procedure can be carried out whilst the lineblind is in situ and operating. The ‘o’rings are located on the spectacle plate and be pried out and replaced from the redundant side (full-bore / blanked) of the plate.
Onis lineblinds will separate and blank pipe quickly and effortlessly, thus eliminating the manual approach which is often labour intensive, and where worker safety is always in question in the presence of heavy piping. Should there be any residual chemicals in a line when blanking by the conventional method of un-doing nuts / bolts on flanges and inserting \ spade / blank, there is the risk of uncontrollable exposure to dangerous substances, and having to clear the area and re-entering with protective clothing. Blanking with an Onis lineblind on the other hand, allow one (1) man, upon detecting the presence of residual chemicals, to reverse the lever motion by sheer reflex sealing the line and making the area safe in seconds.
*Viton(R) is a registered trade mark of DuPont Dow Elastomers