A flow control valve is an essential component of any hydraulic system, since it manages the flow rate of fluid throughout the system, which in turn controls the performance of the machinery in question. Various elements contribute to this flow rate, and further contribute to the overall hydraulic flow control.
What is Hydraulic Flow?
Hydraulic flow rate is a very important figure to know, so that it is possible to determine volumetric flux, as well as the power necessary to pump any fluid through a pipe. The rate of flow itself is understood as the volume of any substance which flows through a surface area during a predetermined period of time. In order to calculate the rate of flow, it is necessary to know the flow velocity, the angle of flow, and the area of the pipe, or these elements must be derivable from a problem statement.
Basic geometry can be used to determine the cross-section area of any pipe, depending on what its shape might be. Then it will be necessary to multiply that area by the flow velocity, which is generally expressed in units of length divided by the unit of time squared. When the pipe cross-section and flow velocity are actually perpendicular, the flow rate angle will be 0°.
The final step necessary in calculating flow rate is to multiply the value obtained from the previous calculation by the cosine of theta, in which theta is the flow angle between any area and the direction of flow. It is only necessary to use theta when you can’t calculate a precise perpendicular cross-section area from the first calculation.
What is a Hydraulic Flow Control Valve?
A hydraulic flow control valve is responsible for regulating the flow rate of gases or liquids as they navigate through a pipeline. Valves are used for achieving optimal performance in a system like this, which means it’s necessary to use the appropriate flow control valve for any given application. In a hydraulic system, flow control valves are used to regulate the flow between motors and cylinders, which in turn manages the speed of those components.
Since they also control the rate of energy transfer at any specified pressure, control valves also have a tremendous influence over the total amount of work being done. The actuator speed will influence the rate of energy transfer so that speed becomes a function of the flow rate. Directional valves are used for slightly different reasons, due to the fact that they cause energy to be transferred to a specific location at a specified time. In some cases, directional valves are used to manage pressure and flow rates for the purpose of effectively throttling the flow of fluid.
How Does a Hydraulic Control Valve Work?
There are a number of different flow control valve designs, because there are just as many kinds of applications they are used for. This makes it important to select the right kind of flow control valve for the right application. There are only a few different kinds of flow control valves, these being a ball, a diaphragm, a needle, butterfly, and a plug valve.
A basic flow control valve will have a hole that opens or closes for the purpose of increasing or decreasing the flow rate. Probably the simplest operation for a flow control valve is that of the ball valve, which consists of a ball that gets attached to a handle. There is a hole through the center of the ball and when the handle gets turned, the hole can be aligned with openings in the valve so as to allow flow to take place. To shut down that flow, the handle would then be used to align the hole, such that it’s perpendicular to the valve openings, and this would then restrict any flow.
Most other kinds of valve types operate in a similar way, having some kind of mechanism which either blocks flow or allows flow. A butterfly valve for example, is equipped with an internal metal plate that is attached to a mechanism which turns. That plate can be opened or closed as the mechanism is turned. Needle valves include an adjustable needle, along with a valve stem that allows or restricts the flow of any liquid. With these being one of the most precise valve types, a needle valve can be adjusted so that it allows free flowing of liquids, partial flow of liquids, or a complete blockage of fluid flow.
When dealing with hydraulic circuits there are a number of ways that flow can be managed, and these can either make use of very simple methods or they can be fairly sophisticated. The most common methods used for flow control are the following: proportional flow-logic valves, flow dividers, priority valves, pressure-compensated variable flow valves, orifices, flow regulators, proportional flow-control valves, rotary flow dividers, deceleration valves, pressure-compensated variable flow valves, bypass flow regulators, demand-compensated flow controls, and simple flow regulators.
Of these, the simplest by far are orifices, and in actual operation, an orifice would be placed in series with a pump. All you have to do is obstruct the orifice to cause a decrease in flow, or a complete blockage. The more sophisticated options would be able to sense any changes in pressure and react accordingly, and they can also monitor flow rate, and even make some kind of response when flow rate goes above or drops below a predefined threshold. Pressure-compensated valves have a compensatory mechanism which automatically makes adjustments to inlet pressures and load pressures, so as to maintain a consistent flow rate.
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