APPENDIX B
Product description
1.
This appendix draws upon the World LP Gas Association website, the LPGA’s Codes
of Practice, suppliers’ literature and documentation from the British Standards
Institute.
What is LPG
2.
LPG is the abbreviation used to describe liquefied petroleum gas, a group of
hydrocarbon gases typically containing three or four carbon atoms per molecule and
often referred to as C3 or C4.
3.
The normal constituents of LPG are: propane (chemical formula C3H8), propylene
(C3H6), Butane (C4H10) and butylenes (C4H8). Commercial-quality products marketed
as butane and propane in the UK are not pure chemical hydrocarbons and contain
trace quantities of other similar gases.
4.
In the UK, quality specifications for LPGs are defined by BS 4250 Specifications for
Commercial Propane and Commercial Butane, the typical properties of which are
given in Table 1.
TABLE 1 Limiting requirements for properties of commercial butane and propane
Property
Commercial
butane
Commercial
propane
Gauge vapour pressure, at 40°C (measured or
calculated) (kPa), max
505
1,550
Total sulphur content (mg/kg), max
200
200
Mercaptan sulphur content (mg/kg), max
50
50
Hydrogen sulphide content (mg/m3), max
0.75
0.75
Ammonia content (mg/m3 in the vapour phase),
max
2.3
2.3
Copper corrosion, 1h at 40°C
Class 1
Class 1
Tendency to freeze in valves
-
Pass
Dienes content, mole percent max
0.5
0.5
Ethylene content, mole percent, max
-
1.0
Alkynes content, mole percent, max
0.5
0.5
C4 and higher hydrocarbons content, mole per cent,
max
-
10.0
C5 and higher hydrocarbons content, mole per cent
max
2.0
2.0
R number
10 max.
10 max.
O number
33 max
33 max
Source: BS 4250:1997.
Key characteristics
5.
LPG exists in gaseous form under normal atmospheric pressure and temperature.
Unlike natural gas (methane—CH4), which can only be liquefied by refrigeration, LPG
is easily liquefied by moderate compression at ambient temperat