Valves fuel regulation using

The flow of air to a gas-fired boiler furnace is regulated by a minicomputer controller. The fuel gases used in the furnace are mixtures of methane (A), ethane (B), propane (C), n-butane (D), and isobutane (E). At periodic intervals the temperature, pressure, and volumetric flow rate of the fuel gas are measured, and voltage signals proportional to the values of these variables are transmitted to the computer. Whenever a new feed gas is used, a sample of the gas is analyzed and the mole fractions of each of the five components are determined and read into the computer. The desired percent excess air is then specified, and the computer calculates the required volumetric flow rate of air and transmits the appropriate signal to a flow control valve in the air line. 

Valve stand — A free-standing frame including several fluid flow runs that is used to physically control the fluid flow to a combustion process. A typical oxy/fuel combustion equipment valve stand will include an instrument airflow run, an oxygen flow run, and a fuel flow run. The equipment on the valve stand typically includes the on/off valves, pressure regulators, flow control valves, and associated instrumentation necessary to operate a combustion process. 

A cascade control system can be designed to handle fuel gas disturbance more effectively (Fig. 10.1). In this case, a secondary loop (also called the slave loop) is used to adjust the regulating valve and thus manipulate the fuel gas flow rate. The temperature controller (the master or primary controller) sends its signal, in terms of the desired flow rate, to the secondary flow control loop—in essence, the signal is the set point of the secondary flow controller (FC). 

If you are using the GPS system design in this book, open the regulator that is connected to the electrolyzer/storage system to allow hydrogen gas to flow to the fuel cell. If there is a gas exit valve on the fuel cell, be sure to open it for full gas exit. Then, you can diminish the gas flow in increments if you wish during testing. 

Oil applications are based on pressure atomization technology even if small power application solutions are available based on oil evaporation by heat. Electronic control of the fuel/air ratio previews an actuator to move a butterfly for controlling the air flow and an actuator to move the oil pressure regulator. For gas, two actuators control two butterflies, one for gas and one for air, even if fhe gas pneumatic valves (whose working principle is based on a pneumatic feedback) are widely used. More advanced burners control air flow changing the fan speed, reducing the pressure drop in the hydraulic pipes and valves. Despite this, a butterfly valve is often necessary to control startup operation, especially for high power applications. 

Pressure control of air/fuel ratio is usually an air primary system, and VFD can be used with it. (See fig. 6.17.) The input signal (usually furnace temperature or boiler pressure) operates an air flow control. A cross-connection impulse, an air pressure signal, moves a regulator s valve until its output pressure sensor stops the fuel valve movement to balance the fuel pressure to match or follow the controlled air pressure. 

Use of fuel gas — Before a regulator to cylinder valve is connected, the valve must be cracked... 

Provisions must be made to never crack a fuel gas cylinder valve near sources of ignition. Before a regulator is removed, the valve must be closed and gas must be released from the regulator. Red is used to identify the acetylene (and other fuel-gas) hose, green is for the oxygen hose, and black is for inert gas and the air hose. Pressure-reducing regulators are used only for gas and the pressures for which they are intended. 

Fuel gas shall not be used from cylinders through torches or other devices which are equipped with shutoff valves without reducing the pressure through a suitable regulator attached to the cylinder valve or manifold. 

If, when the valve on a fuel gas cylinder is opened, there is found to be a leak around the valve stem, the valve shall be closed and the gland nut tightened. If this action does not stop the leak, the use of the cylinder shall be discontinued, and it shall be properly tagged and removed from the work area. In the event that fuel gas should leak from the cylinder valve, rather than from the valve stem, and the gas cannot be shut off, the cylinder shall be properly tagged and removed from the work area. If a regulator attached to a cylinder valve will effectively stop a leak through the valve seat, the cylinder need not be removed from the work area. 

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