| 摘要 |
<p>A system for delivering fluid, e.g. liquefied petroleum gas or 'LPG', through a delivery path (10) under pressure. A delivery control valve (16) is selectably operable to close and open the delivery path (10) and monitors a parameter of the fluid, e.g. dielectric constant, and to sense the presence of vapour or gas phase in the fluid. A control means (30) responsive to the indicating signal from the sensing means (20) causes the delivery control valve (16) to close the delivery path upon sensing the presence of a significant proportion of vapour or gas phase in the fluid. A gas introduction point (35) upstream of the sensing means (20) enables gas to be introduced so as to knowingly expose the sensing means (20) to fluid containing gas phase and thereby enable controlled testing of the correct functioning of the sensing means (20). In the case of the fluid being liquefied gas, pumping means (45) upstream of the sensing means (20) can continue operation after closure of the delivery control valve (16) so that the gas or vapour phase will undergo compression and as a result will liquify and the control means (30) will then cause re-opening of the delivery control valve (16). The closure of the delivery control valve (16) prevents liquefied gas having a significant proportion of gas or vapour phase passing through a metering means (15) downstream of the sensing means (20).</p> |
