Chemical apparatus and process disinfecting – deodorizing – preser – With safety feature
Patent
1997-01-06
1999-01-19
Bhat, Nina
Chemical apparatus and process disinfecting, deodorizing, preser
With safety feature
422118, G05B 900, G05B 905
Patent
active
058611266
DESCRIPTION:
BRIEF SUMMARY
This is a national stage application of PCT/FR96/0216.
The present invention relates to a safety device for an apparatus under gas or vapour pressure, such as a reactor, comprising at least one downstream valve connected to the pressurized apparatus by a tube having a burst disc dividing this tube into an upstream segment and a downstream segment.
Regulations currently in force require that apparatuses under gas or vapour pressure be protected by one or more safety valves. When there is a risk of these valves being clogged by products resulting from normal operation of these apparatuses, it is common practice to place a burst disc upstream of these valves, this disc being intended to open before the pressure initiating opening of the valves is reached.
However, the industrial use of these devices with a safety valve sometimes leads to premature opening of a valve, which has the drawback of leading to accidental pollution of the surroundings of the site. This opening is all the more problematic since it results from accidental rupture of the burst disc, even though the pressure in the pressurized apparatus is very much less than the pressure initiating opening of the valve or valves. For example, it has already been observed that a burst disc calibrated at 48 bar, rupturing accidentally under a pressure of 41 bar, causes a safety valve calibrated at 50 bar to open.
The object of the invention is to provide a safety device which makes it possible to prevent premature opening of a safety valve in the event of accidental rupture of a burst disc when the pressure in the pressurized working apparatus protected by the valve is markedly less than the pressure initiating opening of this valve.
To this end, the subject of the invention is a safety device for an apparatus under gas or vapour pressure, comprising at least one downstream valve connected to the pressurized apparatus by a tube having a burst disc dividing this tube into an upstream segment and a downstream segment, characterized in that the downstream segment includes protection means which are designed to minimize the maximum pressure of a shock wave created by the rupture of the burst disc and striking the closure member of the said at least one valve.
The safety device of a pressurized apparatus according to the invention may include one or more of the following characteristics: ratios .gamma. of the heat capacities at constant pressure and at constant volume which is contained in the downstream segment B; placed on the segment B and has a shape designed to reduce the shock wave formed by an incident shock wave and by a reflected shock wave, and acting on the closure member of the said at least one valve; ratios .gamma. of the heat capacities at constant pressure and at constant volume which is contained in a chamber arranged on the downstream segment B; independently connected to the chamber; strainer projecting into the chamber; and gas overpressure.
An example of the prior art and an illustrative embodiment of the device according to the invention will now be described with reference to the appended drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a device according to the prior art;
FIG. 2 is a graph of the characteristics of a shock wave created by the rupture of a burst disc of the device in FIG. 1;
FIG. 3 is a diagram of a safety device according to the invention;
FIG. 4 is a graph giving the characteristics of a shock wave generated by the rupture of a burst disc of the device in FIG. 3, and
FIG. 5 is a diagram of another embodiment of the invention.
The device represented in FIG. 1 is known and comprises an apparatus 2 under gas or vapour pressure, for example a reactor, a tube 3, a burst disc 4, two safety valves 5 and 6 and an outlet collection pipe 7.
The tube 3 connects the apparatus 2 to the two valves 5 and 6. It consists of a straight pipe 8, a first end of which is tapped upstream of the apparatus 2 and the second end of which splits into two horizontal branches 9, 10, each having a right-angled shape.
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M.A. Grolmes et al., "Large-Scale Experiments of Emergency Relief Systems," Chemical Engineering Progress, vol. 18, No. 8, Aug. 1985, New York, US, pp. 57-62.
Bhat Nina
Industrie Chimique Mulhouse Dornach
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