Overview
This is the model of a Lever Safety Valve. Lever Safety valves were used to release some of the steam from a stationery boiler when the pressure rose above the safe limit.
Details of the assembly (see Drawings): VALVE-SEAT (2) is screwed in the valve BODY (1). The SPINDLE (6) and TOGGLE (7) together keeps the VALVE (3) pressed against the VALVE-SEAT (2). The top of the valve BODY (1) is closed with a COVER (4) with the help of six bolts (14). A COVER-BUSH (5) is used to prevent the leakage through the central hole of the COVER (4). A LEVER-GUIDE (9) is screwed to the COVER (4) in order to restrict the LEVER (10) movement. The WEIGHT (12) is attached to the LEVER (10) by means of LEVER-PIN (13). The TOGGLE (7) is held in position by means of TOGGLE-PIN (8). FULCRUM-PIN (11) is used to connect the LEVER (10) and the COVER (4), to act as the fulcrum.
Some Mathematical Details
The WHEIGHT component has got a mass of 86888.633 g that is 86.889 kg. Its weight force is equal to
F1 = m x g = 86.889 x 9.81 = 852.381 Newton
The force F2 over the TOGGLE component, thus over the VALVE component, is equal to:
F2 = (F1 x l1) / l2
Where:
l1 is the distance Fulcrum - Weight = 468 mm = 0.468 m
l2 is the distance Fulcrum - Toggle = 100 mm = 0.1 m
F2 = (852.381 x 0.468) / 0.1 = 3989.143 Newton
The area of the aperture of the valve seat is: A = Pi x R^2
A = Pi x 50 ^ 2 = 7853.98 mm2 = 0.00785398 m2
When the pressure of the steam grows over Pmax the valve opens: Pmax = F2 / A
Pmax = 3989.143 / 7.85398 E -3 = 507.914 E +3 Pascal = 507.914 KPa = 5.013 atm = 5.079 bar
If you want a higher Pmax, you have to rise l1, the distance between the fulcrum and the weight.
Contents
There are two videos of the assembly in this page, followed by the link to a page containing the drawings of every single components.
The videos can be seen at full screen (double click on video, click to play and stop) or as picture in picture, using controls in video's bottom right side.