Flow control gates

The flow control gates are adjustable metal plates that control the amount of material flowing out of the hopper by changing the height of the opening at the hopper. 

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Flow-control gate outomoticalty actuated by level of pellets in hopper... 

The basic components of a tractor unit are the following hopper, push rollers, conveyor, flow control gates, side arms, augers and automations and control panel. 

The distillation column operates at a pressure of 500 mmHg (500 mm of mercury, absolute). The feed point to the column is 12 m above the base of the tank. The tank and column are connected by a 50 mm internal diameter commercial steel pipe, 200 m long. The pipe run from the tank to the column contains the following valves and fittings 20 standard radius 90° elbows two gate valves to isolate the pump (operated fully open) an orifice plate and a flow-control valve. 

Occasionally an incident occurs that results in a common mode failure. This is a single event that affects a number of pieces of hardware simultaneously. For example, consider several flow control loops similar to Figure 11-4. A common mode failure is the loss of electrical power or a loss of instrument air. A utility failure of this type can cause all the control loops to fail at the same time. The utility is connected to these systems via OR gates. This increases the failure rate substantially. When working with control systems, one needs to deliberately design the systems to minimize common cause failures. 

It is quite important not to operate a turbine-driven pump by throttling the steam flow to the turbine. Let s assume that the operators have set the turbine speed at 3500 rpm, by adjusting the steam inlet gate valve upstream of a malfunctioning governor. Suddenly, the discharge flow-control valve cuts back, and the pump s flow decreases from 2000 to 1200 GPM. The pump speed will then increase, because fewer pounds of liquid are being pumped, and less horsepower is required to spin the pump. 

FIGURE 3.15 Differential EOF pumping rates were achieved from different gate voltages applied to the field-effect flow control electrodes. This produced (a) positive pressure for flow down and (b) negative pressure for flow up the field-free microchannel (ft) [371]. Reprinted with permission from the American Chemical Society. 

Globe valves are used for gases, for flow control and whenever tight shutoff is required. Gate valves are for most other services. 

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