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INTRODUCTION
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.OPERATIONAL ADVANTAGES
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.
STANDARD DUTY CONDITIONS
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.
MECHANICAL ADVANTAGE WITH ONIS
"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.
ONE-MAN SEPARATING THE PIPEWORK
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.
SPECTACLE PLATE GUIDANCE SYSTEM
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 orings.
SPECTACLE PLATE - POSITIVE POSITIONING
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.
LINEBLIND CLOSING AFTER SELECTION
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 orings
(seals) on the spectacle plate in either open or blanked position.
THE O RING
The application / duty conditions
naturally dictate the materials of construction. The most critical item is
the sealing method, using orings 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.
SPECIAL DESIGN FEATURE
With the use of elastomeric orings,
Onis lineblinds are designed with special grooves machined in the
spectacle plate to hold / locate the oring in position. The
shape of these grooves does away with conventional designs, where the
groove takes the cross-sectional profile of the oring or a
square channel / groove often allowing the oring to pop out
when heavily compressed or under extreme pressure. The Onis lineblind
sealing grooves are diamond shaped, truncated to allow the oring
to project above the spectacle plate. The groove overhang holds the oring
firmly in position, and the three expansion areas in the groove allow the
oring to be compressed without the risk of pop-out, held in
place when under pressure.
QUICK & SIMPLE MAINTENANCE
The Onis lineblind requires virtually
no maintenance with the exception of periodic replacement orings.
This procedure can be carried out whilst the lineblind is in situ and
operating. The orings are located on the spectacle plate and
be pried out and replaced from the redundant side (full-bore / blanked) of
the plate.
ONIS ADVANTAGES MEAN GREATER SAFETY
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
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