Quick action line blind reliable and
safe mechanical blinding solution

Quick Action Line Blind – QLB

The Quick Action Line Blind (QLB) is a blinding system that is used to isolate or “blind” equipment typically for maintenance or inspection purposes. The technology allows the full blinding operation to be performed in minutes and provides up to 95% reduction in downtime compared to conventional systems such as spectacle blinds. Achieve substantial process improvement using the QALB with the following key advantages:

Technical sheet

Onis quick action line blind on site

Why using a Quick Action Line Blind ?

In every industry, the protection of people, environment, assets, or production is of central importance. Product segregation and equipment isolation are the concern of operations and maintenance staff, HSE managers, site managers, and shareholders every day.
Pressurized pipes are made safe using a valve or simple shut-off system, for instance, a steel plate inserted between 2 flanges. This plate used during “blinding operation” is called, depending on the country, spectacle blinds, blanks, spades, figure 8 blinds, etc.


However, these isolation solutions, currently in use, have multiple disadvantages:

  • Valves: the quality of their sealing and the open/closed positions are not guaranteed – the valves cannot serve as a positive isolation solution
  • The traditional blinding operation: this traditional piping blanking operation is time-consuming and laborious, and requires significant technical resources without guaranteeing a correct tightness as it is dependent on workers’ skills and working conditions.

Leaks due to faulty isolation technics can lead to fugitive emissions and pollution, operating losses, and more importantly still, the production facility’s damages or destruction and even consequences for humans (injuries, poisoning, death).


ONIS Quick Action Line Blind (QLB) is a mechanical pipe blinding equipment with quick irreversible action enabling a single person, without any tools, to blind / deblind a pipe, even very large in dimension, while guaranteeing perfect sealing and positive isolation for your systems.

How it works

ONIS MECHANICAL LINE BLIND is a mechanical piping equipment that can guarantee absolute tightness between upstream and downstream pipes whoever is operating it while reducing risks and costs.


Simple and quick to use, this mechanized positive isolation system brings reliability to any positive isolation operation.
For all ONIS Quick-Action Line Blinds, The two forged half-bodies / seats spreading operation is performed by a lever or a hand-wheel connected to a gearbox.
This flange spreading movement, generated by efficient and reliable synchronized eccentric shafts, allows the displacement of a slide gate designed with a full-bore and a blind position.
Seats clamping movement is as simple as spreading operation. Just oppositely operate the lever or handwheel.


This quick-action clamping mechanism is self-locking and resistant to overpressure and vibration
4 gaskets are only on slide gate 2 per position of use, accessible for inspection or replacement without disassembly
This positive isolation equipment is set and tested in the factory, requiring no adjustment on-site after installation or operation, and enabling perfect tightness for any and every operator.
Note: As for the traditional blinding system, before the operation of the ONIS Line blind (QLB), the pipe must be depressurized before starting the blinding operation.

Onis Quick Action Line Blind -3D Half-view

Technical specifications

All Quick Action Line Blind are designed following these specifications:

  • Forged bodies up to 42”.
  • Spreading design with no internal mechanism and no internal gasket.
  • Only four gaskets are located on slide gate: 2 accessible for maintenance during production.
  • Perfect sealings whoever is operating the line blind.
  • Self-locking design.
  • 100 % full bore

Onis Quick Action Line Blind is a patented technology. Indeed, it was designed to guarantees a 100% positive isolation securing your operators, your equipment, and your profitability. Moreover, 100% of Onis Line Blinds are tested in our workshop.


  • DN 12 – 1250 / 1/2 ‘’ – 50’
  • PN 20 – PN 420 / 150# – 2500#
  • Up to 420 bars / Up to 6100 psi
  • -120°C to 650°C / -184°F to 1200°F
  • Manual or automated


Onis line blind small size PLB range

PLB Type 1/2” up to 8”

Orange line blind Onis PLR DN450 PN100

PLR Type 10” up to 42”

ONIS MPL range large diameter 42 inch

MPL more than 42”

For any others ratings or design conditions fill free to contact ONIS.


ONIS Hisafe

The Hi-Safe products are a specific product line designed to answer all levels of safety for critical process applications.

Interlocks controlled with keys are used to manage the correct operational sequence and function of the blind. The basic Hi-Safe system uses a single key lock to manage the authorization of line blind’s operation – B1K Blind with 1 Key.

The B1K also provides a second safety feature option comprised of a patented safety boss on the slide gate.

Safety Boss is a machined raised surface that prevents the bodies from being clamped and locked when the slide gate is not in the full blind or unblinded position.

A next-level higher control system is provided with an S2S, a Step-to-Step product line where the system is comprised of multiple keys that can only be used in a specific sequence to ensure safe operation of the blind throughout the operational procedure.

The D3B or “Double Block and Bleed” is the flagship of the Hi-Safe product line.

This system is comprised of an upstream valve, mechanical blind, and downstream valve that are all interlocked together. There are significant benefits achieved by this system where an operator cannot perform the blinding operation without the connected piping being first isolated from the system. For more information click here for the D3B page. Additional safety features include the D3B+ where the bleeder ports are also interlocked to ensure the blind connected piping is first drained and depressurized before the blind functions.

Mechanized / Automated

When design conditions, safety, or project are required the ONIS devices can be motorized to facilitate the handling of the ONIS equipment.

Pneumatic, hydraulic, or electrical actuators can be adapted on any ONIS device.
Automation can also be adapted with live reporting to the local or remote control room.
So, performing remote positive isolation, rupture disc change or filter replacement is available with ONIS technology.

Custom designs

For each device, design conditions and media are requested in order to check the compatibility or the design of ONIS devices.

Even if ASME Code is used for calculation and design, any project of customers’ specifications can be followed on-demand as :

  • Materials
  • Specific design for congested area
  • Welding overlay
  • Weight restriction
  • Explosion proof requirement
  • Specific limit switches
  • Motorization
  • Firesafe

And so, ONIS engineers team are available to define with the end user the specifications and performance objectives

pictures (2)
Onis device firesafe test bench

High performance services for multiple applications

Frequently Asked Questions

Can ONIS Quick Action Line blind replace a valve?

No, a mechanized line blind is not a valve. It is a mechanical device that replaces figure 8 or spectacle blind. A line blind is a real positive isolation device and a valve is not: when a valve leaks, the leak is going downstream into the pipe. With a line blind, it is impossible because upstream and downstream pipes are physically separated with a steel plate. More information on blog “Positive Isolation Level of piping”

How can I be sure that there is no risk when I operate an Onis?

Different levels of safety are available: from operator’s training to safety optional devices such as safety locks, pressure gauge, ONIS engineer can support you to choose the best solutions, to sum up within HiSafe range products line which is a specific line dedicated to reducing the human factors.

Do we need to depressurize the pipe before operating an ONIS device ?

As for a traditional blinding operation, safety requirements are the same. Only the way and the time requested to open the pipe to the atmosphere is very reduced. Please have a look at video “How to operate a line blind” on media center page

Can you provide a solution without opening to the atmosphere?

It is not the philosophy of ONIS products because it is no more positive isolation. Indeed, in case of failure of the slide gate’s sealing, the risk is to have a leak from upstream to downstream and so to have non-safe isolation. Please have a look at “The different level of isolation.”

What is a ONIS Line blind lifespan ?

It depends on the environment mainly but we can say that some ONIS have been installed in 1979 and are still in operation. The reliability of ONIS line blinds has been proved after more than 40 years.

Do the ONIS line blinds are fire safe design ?

Yes, a fire-safe design is available.
Even if API 607 does not apply strictly to ONIS line blinds, ONIS company is equipped with its fire test bench and all the tests have been followed by a third part SGS or DNV.

What makes ONIS technology unique ?

No appreciation by the operator: ONIS design is set in our workshop for all lifespan to guarantee the tightness