PIETRO FIORENTINI NORVAL, Инструкция по установке, пусконаладке и обслуживанию

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TECHNICAL MANUAL MT044
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The slam-shut mechanism consists of:
• a mobile obturator A with sealing gaskets subject to the load of the closing spring G;
• a lever assembly L whose rotation causes the movement of the obturator A;
• a pressure switch device I-N whose internal motion determines the open or closed position of the obturator A.
The pressure switch device (fig. 8) comprises a control head 11 in which the pressure to control Pa acts on the
diaphragm 21 which is integral with the shaft with cams 18.
The load of the pressure Pa on the diaphragm is contrasted by the springs 14 and 15, which respectively determine
intervention for a pressure increase or decrease.
The slam-shut device is set by adjusting the rings 12 and 13.
The intervention value is increased by turning the rings clockwise and vice versa when turned anticlockwise.
In the case of intervention for pressure increase, when the Pa exceeds the set-point, the load on the diaphragm
21 of the control head B increases until it overcomes the resistance of the spring 14 .
This provokes the downward displacement of the shaft 18 which shifts the feeler 19 and releases the lever
mechanism 20 by means of the cam 23.
Intervention for a pressure decrease takes place as follows.
As long as the value of Pa stays above the set load of the spring 15, the spring support 17 rests on support 16.
If the pressure Pa drops below the set-point, the support of spring 16 stops its stroke on the beat of the body 5
and the spring 15 displaces the support 17 upwards and the shaft 18 as a result. The cam 24 then shifts the feeler
19 and causes the release of the lever mechanism 20.
Intervention of the slam-shut device can also be provoked manually by means of the release button 22. The
connection between the control head 11 and the Pa control point can be made with the interposition of a device
(Push) fig. 14 which makes it easy to control the operation of the pressure control device.
Fig. 8a Fig. 8b