| 摘要 |
<p>A safety guard or lockout device (22) for a dual chamber orifice fitting device (1) having a removable orifice plate (4). In a normal position when the upper and lower chambers (8, 9) are equal in pressure, the guard (50) of the safety guard device (22) is in a retracted position relative to the square end (36) of a valve gear shaft (18) as shown in Figure 3 to permit connection of a manual tool, such as a wrench, to square end (36) of valve gear shaft (18) for actuation of isolation valve member (16). When changing the orifice plate (4), the pressure in the upper chamber (8) is reduced to atmospheric conditions and provides a fluid pressure differential between chambers (8) and (9). The fluid pressure differential moves fluid responsive member (30) and guard (50) to an extended position covering the square end (36) of valve gear shaft (18) to prevent access of a manual tool to the shaft (18) thereby preventing operation of the isolation valve (16) separating the upper chamber (8) from the lower chamber (9).</p> |
