| 摘要 |
A two-stage servo valve (5) through which flow does not pass operates a main pressure-relief valve (7) which has a considerably greater capacity. Flow control elements (35, 36, 38, 39) allocated to a control element of the first stage ensure positive valve operation. In one preferred embodiment, the main valve is mounted directly on a container which must be relieved of pressure at a predetermined excess pressure. The servo valve is preferably arranged close to the main valve and is connected thereto in flow terms. A flow damper (100) having a self-cleaning orifice is arranged between a head space (68) of the main valve and a pressure-relief connection (11) of the servo valve, in order to improve the operating reliability of the overall valve arrangement. A changeover device (15, 16, 24, 76), operating like a ball valve, allows a test-pressure source to be connected in order to test and adjust the response and closing behaviour of the servo valve, on its own or in combination with the main valve. In another embodiment, a single-stage proportional servo valve (131) operates a main valve (7) for pressure relief which is proportional to the respective excess pressure (Fig. 16). A shut-off element (142) which is under partial pressure-equalisation and has a large diameter, together with seals (145b) having a small diameter, ensures an improved sensitivity to excess pressures, an improved response behaviour and improved stability. A changeover device (154, 158) operating like a ball valve is used to save a test-pressure medium. <IMAGE>
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