Pipeline doors or “closures” are commonplace in the pipeline industry, providing access to the pipeline itself as well as to high-pressure equipment associated with the pipeline such as filters, separators, strainers, etc. Despite their prevalence, the importance of closures to the safe and efficient operation of a pipeline system is often overlooked. Recent changes in closure definitions and terminology warrant a review of the systems, applicable standards, designs and considerations related to choosing a closure for a desired purpose.
The industry defines what a closure is in a variety of ways. One definition, for example, is a pressure-containing component used to blank off an opening nozzle on a vessel or end of pipeline — which could mean a bolted blind flange, a T-bolt cap or a “quick-opening” closure. ASME B31.4 and ASME B31.8 defines a “quick-opening” closure as a pressure-containing component used for repeated access to the interior of a piping system. ASME VIII-1 UG-35.2 (a) (1) defines quick-actuating closures while UG-35.3 (a) (1) defines “quick-opening” closures, both of which permit substantially faster access to the contents space of a pressure vessel than would be expected with a standard bolted flange connection. There are several ways the current codes can be interpreted, but what does it all mean?
This paper will present a history of pipeline closures from the early development to recent innovations. The paper will address:
- The different type of closures available and pros and cons of each.
- Safety systems
- The importance of the sealing element, including material, where it is located, how it is energized, low pressures, rapid decompression issues, etc.
- Locking elements versus Holding elements.
- The importance of proper maintenance.
- The use of the appropriate materials.
- Horizontal versus vertical configuration.
- Offshore versus onshore operation.
Keywords: Pipeline, Closures, Quick-Opening, Quick-Actuating, ASME B31.4, ASME B31.8, ASME Section VIII.