Spring tension, valves

On spring-operated valves the adjustable spring tension offsets the inlet pressure. The relief set pressure is usually specified at 10% above the normal operating pressure. To avoid the possibility of an unauthorized person changing this setting, the adjustable screw is covered with a threaded cap. 

Take a closer look at the discharge portion of the indicator card shown in Fig. 29.3. Note that the cylinder internal pressure rises well above the discharge-line pressure, before gas is pushed out of the cylinder and into the discharge line. This is a consequence on the spring tension of the discharge valves. 

In order to force these valves open, a certain amount of extra pressure in the cylinder is needed. The extra pressure overcomes the spring tension. Once the valve is open, gas flows out of the cylinder, into the discharge line, and the cylinder pressure falls. But, as shown on the indicator card, the discharge valve apparently opens and closes five times during one cycle. 

The position regulation of the proportional amplifier in conjunction with the position transducer see to it that the magnetic armature (pre-tensioned valve spring) goes to and remains in the pre-selected position. 

The face of the wear plate should be checked periodically and remachined if necessary. A whistling noise during operation is an indication the wear plate Is worn out or the valve spring requires tensioning. 

The fuel now contained within the barrel is moved by the force of the plunger stroke to the delivery valve. The delivery valve is held in a closed position by a high-tension spring. As the plunger stroke continues, the fuel hydraulic pressure increases. Once the hydraulic pressure exceeds the force exerted by the high-tension spring on the delivery valve, the valve opens. Fuel then flows at high-pressure... 

Check valves ensure flow in one direction only [31,32]. Their design consists of a spring which holds a piston, a disc, or a ball in place to open or close the connection at a predetermined pressure, set by the tension in the... 

A tension spring 319 normally urges the valve 310 ture 315 moves in response to the action of spring 319... 

The lever that maintains tension on the spring is called the trip. This trip is latched when the turbine is rotating. When the turbine is in trouble, a mechanism unlatches the trip and the spring immediately slams the trip-throttle valve shut. A problem arises when the trip-throttle valve sticks. Typically, solids in poor-quality steam build up, fouling the valve. When the trip unlatches, the throttle valve may not close. 

---