Positive isolation explain
Many applications in the piping industry are required to shutoff part of the production process in order to carry out maintenance operations on one or several pieces of equipment. During a maintenance operation, it is crucially important to isolate the downstream from the upstream of the lines. So to avoid any risk of human and material damages.
Positive isolation is the action of fully isolating a unit or a part of the plant from the active process. It is usually achieved by physically disconnecting a portion of pipe from the next one. This approach is mainly used in critical applications which require high safety levels like steam crackers units, gas transportation, manifolds, tank farms, oil production and many other petrochemical process.
How does it work?
To ensure a complete positive isolation, the traditional way consists to unbolt and spread the flanges to insert a metal plate in between. Depending on the country, this metal plate is called spectacle blind, slip blind, blind flange, paddle blind, blanking flange, figure-8, …
As opposed to a valve, which doesn’t provide a completely sealed physical barrier as it will inevitably leak. Only the insertion of a metal plate between the flanges can guarantee a physical disconnection and thus a positive isolation. This is most commonly called blinding or blanking operation. Nevertheless, for several industries the insertion of a spectacle blind, especially in very large units, is neither practical nor cost-effective. It requires specialized and expensive tools and is a time-consuming operation, plus, in congested areas, it is much more difficult to perform. It would be interesting, then, to find a more efficient and less expensive solution.
Another way of implementing positive isolation is the use of Быстродействующее Механизированное Стационарное Отсечное Устройство. To understand this technology, one needs to understand how it works and how it differs from the usual way. A quick action line blind is a mechanical system which provides positive isolation in minutes, without any tool. Moreover, it can be handled by a single operator. This method is widely used in the oil & gas industries and it has been adapted to many others.
Depending on your process, positive isolation could be mandatory, that’s why it is very important to determine what isolation levels you require.