Safe Isolation of Passing Valves
Safe Isolation of Passing Valves
The DBB-SAVER is used to fully prevent any leakage through either a Double Block & Bleed valve configuration or through a Single Isolation valve (e.g., ball, gate or plug valve).
How it works
The working principle of the DBB-SAVER makes leakage to the safe working area physically impossible. It works by creating, maintaining, and monitoring of a vacuum in the bleed section in a classical Double Block & Bleed configuration but also can be deployed in most Single Valve Isolations.
The bleed volume can either be the section between:
- both block valves in a classical DB&B configuration, or
- both seats in the body of a single valve, e.g., most ball, plug or gate valves, or
- any other combination of isolating device, like balloons, mud plugs, control valves, etc.
We are not greasing or sealing and do not affect the condition or the performance of the valve whatsoever. It is a temporary solution only for the duration of the downstream maintenance works when the valves are locked closed.
The DBB-SAVER is completely failed safe. In case the in-line leakage exceeds the capacity of the DBB-SAVER, an alarm will be raised. The alarm will be audible and visible on the location of the leaking valve, but also via wireless remote data transfer on the safe workplace and on a separate alarm monitor in the control room.
Our method has been Shell approved, for worldwide use on all their assets. Also, other major Oil and Gas companies have approved our unique method. Interested? Please contact us for more information.
When to use the DBB-SAVER
The DBB-SAVER is used when maintenance work must be executed on a piece of equipment, whilst bordering installation parts remain pressurized and available for operations.
This piece of equipment must be isolated. This is done by valves. Sometimes, valves are only the initial isolation, which makes it possible to safely place blind flanges afterwards.
Either when working on the equipment directly behind the isolation valves or when placing a blind flange, the isolation valves should not have a leak rate beyond the companies pre-defined standards to ensure a safe working place. In case of explosive and/or toxic media the standard is often tight shut off (TSO), which means zero leakage.
The valves can be in a Double Block & Bleed configuration or in a Single Valve configuration (like the example in the picture). In practice, regrettably, the valves often leak beyond the company’s maximum standard. The appliance of a DBB-SAVER guarantees a safe workplace, even if the valve(s) are passing heavily. Without any modifications to the valves themselves, for the full duration of the job.
Besides mitigating the leakage for 100%, the DBB-SAVER will monitor the bleed section automatically every second, instead of an operator checking them every shift or so. The human factor and the subjective assessment of the leak rate is taken out of the equation, and the DBB-SAVER does all the work with regards to the periodical checks. So, even when the valves are not leaking, the appliance of a DBB-SAVER is beneficial to ensure a safe workplace for the workers on the downstream equipment without compromise!
After the maintenance is finished, the DBB-SAVER can be disconnected and easily stored in the warehouse. The size of the DBB-SAVER is 1200x800mm (euro pallet size) so fits in most racks. Deviating sizes available on request.
Please refer to the “how it works” section to learn more on the working principle…
The DBB-SAVER is used to 100% mitigate any leakage through either a Double Block & Bleed or Single Isolation valve configuration (e.g. ball, gate or plug valve). Thereby, despite leaking isolation valves, the DBB-SAVER is able to combine the two main objectives the industry is striving for:
When maintenance has to be performed on a part of the installation. The remaining plant remains pressurized and operational.
The to be maintained equipment has to be safely isolated from the remaining plant.
This is done by closing isolation valves, often Double Block & Bleed (DBB) or Single Valve (SV) configurations. In some occasions followed by the installation of a blind flange. But: often valves are leaking, which makes safe performance of the maintenance work (or safe installment of blind flanges) hazardous and therefore not allowed.
When valves are leaking beyond the acceptable leak rate, and repair is not practically possible, what are then your options?
Closing a valve upstream of the leaking valve and depressurize the part in between?
This will have commercial consequences, as there is often more equipment that is to be taken out of operation, sometimes even leading to a total plant shutdown.
Postponing the maintenance; This leads to high cost, reduced plant availability, cancelled maintenance crew reservations etc.
Injecting grease (if possible) In case there are grease or emergency sealant nipples, these can be used. However: grease will disappear and causes a sudden, non predictable gas blow-through. The tightness of the valve is usually monitored periodically (e.g., 2x per operator shift), so workers could be exposed to hazardous gas for a prolonged period. Besides, dirt is sticking to the grease on the sealing surfaces and will cause even more severe leakage in the future.
Inject sealant (if possible).
In case sealant, the valve is often not fit for purpose anymore afterwards and will have inline leakage when the valve is taken back in operation.
“Accept” the leakage, and take additional measures on the workplace to minimize the hazard
e.g., by gas detection, using explosion safe tools or workers wearing personal protection equipment. The problem of these measures is, that they all are last line of defence measures, and dependency on those should be avoided
None of the above options is ideal. There is constantly a trade off between safety and commercial objectives But, with the DBB-SAVER, you can combine both safety and commercial objectives.
With the DBB-SAVER, all above issues are solved:
The application of the DBB-SAVER surpasses the safety level of a conventional bleed by far. It is the best solution available to deal with your leaking valves.
The DBB-SAVER can be used for various types of media. Often, these media pose a hazzard, and may be explosive and/or toxic.
The physical state of the medium can either be:
There is no min. or max. limit on pressure class or line size diameter for which a DBB-SAVER can be applied.
Capacity can be specified by the customer, based on the occurring leak rates or experience.
Material selection is based on media and process and ambient temperature range.
Standard models can handle a wide ratio of leak rates and media, and available from stock for fast response and emergency services (please refer to the services pages for more details).
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