Class location

The classification of a particular location is carried out by taking an area bounded by a certain length along a pipeline route and certain distances either side of the pipeline with the pipeline in the centre line. This gives a number of blocks along the pipeline. The number of dwellings or the number of people normally resident within that block is then counted by observation and use of a suitably detailed and up to date map. This provides an objective assessment with which to base the location classification.

The size of individual areas is fixed for ASME B31.8 as 1 mile (1.6 km) long and 0.25 miles (400m) wide, regardless of the pipeline diameter, design pressure or fluid being transported. Classification is made by counting buildings designed for human habitation.

The size of the area for BS 8010 is a fixed length, 1.5 km, but a variable width based on design pressure, pipeline diameter and fluid being transported. The classification determination is based on the number of people normally occupying buildings within this area. For factories & offices an allowance can be made for the time when the premises are not occupied and a reduction in the number of persons normally present made for the purposes of the classification. The number of persons is then divided by the area of the box to obtain the number of persons per hectare (10,000 m²). This allows for a small concentration of people within the overall area being considered to be spread out and avoids anomalous results.

CSA class locations are determined by dwelling density and other location development, such as industrial installations, within the area extending 200 m perpendicularly to either side of the centre line of a pipeline. Pipeline operators monitor for changes in class location in these areas, along existing pipelines, in accordance with CSA Z662.

ASME B31.8: Requires regular reclassification of the pipeline route after construction to take account of new buildings and expansion of towns. A table and design rules exist to indicate whether a change in design factor, MAOP or other considerations are required if the area classification is affected.

BS 8010:  Requires future development to be taken into consideration when allocating location classification, but does not require further re-classifications once the pipeline is constructed.

CSA Z662: The construction of new housing developments or commercial and industrial centers, can lead to areas which had originally been designated as Class 1, being reclassified as Class 2 or Class 3 if the level of additional development exceeds that which is allowed for by the original design.

 

ASME B31.8			BS 8010		CSA Z662
CLASS	DESCRIPTION	DEFINITION (buildings)	CLASS	DEFINITION (persons per ha)	DESCRIPTION	CLASS
1	Wastelands, deserts, farmland, sparsely populated areas	10 or less	1	<2.5	None	1
					10 or fewer dwelling units	1
2	Fringes of towns and cities, farms, etc.	>10, < 46			One or more of the following: Class 2 a) 11 to 45 dwelling units; b) a building occupied by 20 or more persons during normal use; c) a small, well-defined outside area occupied by 20 or more persons during normal use, such as a playground, recreation area, outdoor theatre, or other place of public assembly; or d) An industrial installation, such as a chemical plant or a hazardous substance storage area, where release of the service fluid from the pipeline could cause the industrial installation to produce a dangerous or environmentally hazardous condition.	2
3	Suburban housing and shopping areas, light industry and offices	>45	2	= or >2.5	46 or more dwellings	3
4	City centers and areas of multi-storey buildings and dense traffic	subjective	3	Subjective	A prevalence of buildings intended for human occupancy with 4 or more stories above ground	4