Book - School of Science and Technology

Liquefied petroleum gas 311Table 11.9 Flow of natural gas in steel pipes (BS 1387: medium)Paper mrunLitre per second in pipes having stated nominal bore (mm)15 20 25 32 40 50 65 80 100 125 1500.5 0.07 0.24 0.47 1.02 1.6 3.0 6.1 9.5 20 35 571.0 0.14 0.37 0.71 1.54 2.4 4.5 9.1 14.1 29 52 841.5 0.21 0.48 0.90 1.96 3.0 5.7 11.5 17.9 37 65 1062.0 0.25 0.56 1.08 2.31 3.5 6.7 13.6 21.0 43 76 1242.5 0.29 0.64 1.23 2.64 4.0 7.6 15.4 23.9 49 86 1403.5 0.34 0.78 1.50 3.20 4.8 9.2 18.6 28.9 59 104 1695.0 0.43 0.96 1.83 3.92 5.9 11.2 22.7 35.1 72 127 2057.0 0.51 1.17 2.23 4.75 7.2 13.6 27.4 42.3 86 152 24610.0 0.64 1.44 2.72 5.81 8.8 16.6 33.4 51.5 105 185 29815.0 0.81 1.82 3.43 7.30 11.0 20.7 41.8 64.3 130 230 37020.0 0.95 2.14 4.04 8.57 12.9 24.3 48.9 75.3 152 269 43225.0 1.09 2.43 4.58 9.71 14.7 27.5 55.2 84.9 172 303 4870.5 0.5 1 1 1.5 2 2.5 3.5 5 7 8Note: single resistances.For approximate purposes, equivalent lengths may be taken as length in metres as listed in the bottom line of the table for each bend, tee, etc.Liquefied petroleum gasMany households in Great Britain are not connected to gas from a public `mains' supply.Liquefied petroleum gases (LPG) are convenient alternatives in circumstances where asupply of natural mains gas is not available. They may be used not only for the familiarportable heaters and other domestic appliances but for firing to static boilers, etc., also.Whereas natural gas is a mixture of various hydrocarbon compounds, liquefied petroleumgases are available as commercially pure butane and propane. Use of butane isnormally confined to the smaller applications. Table 11.10 lists the properties of bothgases and, for comparison, those of natural gas.Delivery and storageLPG is stored on site, as a liquid, in pressure vessels which are fitted by the gas suppliersand remain their property. They are refilled as may be necessary by delivery from a roadtanker. It is a general recommendation that vessels for larger installations be fittedin duplicate so that inspection and any maintenance may be carried out withoutinterrupting output. Dimensions and other leading particulars of storage vessels are givenin Table 11.11.Regulations exist as to the siting of storage vessels and these are set out in a varietyof publications, some by HMSO, some by British Standards and others (the mostuseful) by the distributors' Trade Association. A prime requirement is that vessels mustnot be installed within buildings and particularly in basements, LPG being heavier thanair. According to the capacity of a store, the distance by which it is separated fromsources of ignition (such as balanced flue boilers having low level terminals), siteboundaries and buildings is laid down, and varies from 3 m for a small domestic sizevessel to 15 m for the largest. Access by tanker must not be more than 30 m distantfrom the store.