Control valve liquid flow

The liquid flow rate from a vertical cylindrical tank, 10 feet in diameter, is flow-controlled. The liquid flow into the tank is manipulated to control liquid level in the tank. The control valve on the inQow stream has linear installed characteristics and can pass 1000 gpm when wide open. The level transmitter has a span of 6 feet of liquid. A proportional controller is uaed with a gain of 2. Liquid density is constant. 

A stepper motor having a resolution of 1/256 of a revolution is used as direct drive for a gate valve controlling a liquid flow. The mass rate of flow G kg/s is given by ... 

A plate type column may be operated in either a cross-flow or a counterflow method. Cross-flow plates are the most common types. Perry and Green and Wankat discuss the advantages of both type plates. " Cross-flow plates use a downcomer to transport the liquid from the upper plate to the lower plate. They offer greater mass transfer efficiency and operating range. The downcomer may be located to control the liquid flow pattern. Newer designs of cross-flow plates employ perforations, which may be simple round orifices or may contain movable valve-like vents that act like variable orifices. These type plates will be discussed in the following section. 

Trays with drilled holes in the base plate, which are covered by movable and adjustable load valves. Liquid flows in a controlled manner across the tray (e.g.. 

A liquid-level control system can be configured in either of two ways with a control valve manipulating flow of liquid into the holding tank (Fig. E8.5a), or with a control valve... 

Like liquid control valve, there is a flow capadty limitation for vapor control valve. The difference is that for vapor control valve, its flow capacity is limited by sonic flow. For sonic flow, X is caiculated by Hq. (15b), and Y equals to 0.667 per Bq. (14). The value ofY will never be less than 0.667. For subsonic flow, the value of Y is between 0.667 to 1.0. By comparing the value of X and Fk XT, we can tdl whether vapor flow at control valve is sonic or not. If X is greater or equal to Fk XT, sonic flow at control valve is reached. Increasing X (pressure drop across the control valve) will not cause flow increase through the control valve. Therefore, for sonic flow, X is set equal to Fk XT,... 

The key components in the fuel vapor control system include the fuel tank, vapor vent valves, vapor control valve, vapor tubing, the activated carbon canister, and the engine vapor management valve (VMV) [25,26], During normal vehicle operation, fuel tank vapor pressure is relieved through the use of vapor vent valves installed in the vapor dome of the fuel tank. The vent valves are designed to allow for the flow of fuel vapor from the tank, and to assure that liquid fuel does not pass through the valve. 

PM Control - An impingement-plate scrubber is a vertical chamber with plates mounted horizontally inside a hollow shell. Impingement-plate scrubbers operate as eountercurrent PM collection devices. The scrubbing liquid flows down the tower while the gas stream flows upward. Contact between the liquid and the particle-laden gas occurs on the plates. The plates are equipped with openings that allow the gas to pass through. Some plates are perforated or slotted, while more complex plates have valve-like openings. 

Choking, or expansion of gas from a high pressure to a lower pressure, is generally required for control of gas flow rates. Choking is achieved by the use of a choke or a control valve. The pressure drop causes a decrease in the gas temperature, thus hydrates can form at the choke or control valve. The best way to calculate the temperature drop is to use a simulation computer program. The program will perform a flash calculation, internally balancing enthalpy. It will calculate the temperature downstream of the choke, which assures that the enthalpy of the mixture of gas and liquid upstream of the choke equals the enthalpy of the new mixture of more gas and less liquid downstream of the choke. 

Whenever two-phase flow is encountered in facility piping it is usually in flowlines and interfield transfer lines. Some designers size liquid lines downstream of control valves as two-phase lines. The amount of gas involved in these lines is low and thus the lines are often sized as singlephase liquid lines. Oversizing two-phase lines can lead to increased slugging and thus as small a diameter as possible should be used consistent with pressure drop available and velocity constraints discussed in Volume 1. 

Test procedures for liquid product detonadon arresters, hydranlic flame arresters, high velocity vent valves, and flow controlled apertures (velocity flame stoppers) allow the rise of these kinds of flame arresters as an alternative to standard static fixed element dry type flame arresters. This corild be especially risefnl in high flow applica-... 

Valves have two main functions in a pipeline to control the amount of flow, or to stop the flow completely. There are many different types but the most commonly used are the gate valve and the globe valve. The gate valve contains a disk that slides at right angles to the flow direction. This type of valve is used primarily for on-off control of a liquid flow. Because small lateral adjustments of the disk cause e.xtreme changes in the flow cross-sectional area, this type of valve is not suitable for adjusting flow rates. 

In a typical closed-loop system, liquid from the separator is cooled in a heat exchanger then recirculated. Any excess liquid added by mist and vapor flows out through a level-control valve. ... 

Bends and tee-pieces in pipework often create locally turbulent flow. This enhances the corrosivity of the process liquid. These effects should be minimized by the use of flow straighteners, swept tees and gentle bends. Flow-induced corrosion downstream of control valves, orifice plates, etc. is sometimes so serious that pipework requires lining with resistant material for some twelve pipe diameters beyond the valve. 

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