Slow close check valve with centrifugal pump safety operation
Pump is the core of the industrial fluid equipment, its effect is like the heart of the human body, for fluid power within the device of the system, and ensure the normal working of the technological process.
Commonly used pumps, according to the categories of score positive displacement pump, vane pump, special purpose pumps, etc.
Among them, the vane pump centrifugal pump in the most widely used.
In the process of the centrifugal pump running need to avoid two problems: stop the pump water hammer and lower than the minimum flow.
Solve problems, the two methods is more, but the basic idea is how to a suitable system around the centrifugal pump configuration.
Valve door in these system plays a very important role, and with the two types of problem understanding deepens, the birth of many special valve gate.
Stop pump water hammer protection and the valve door is water hammer in the pressure pipeline due to the severe changes of medium velocity alternating series of sharp pressure lifting water hammer phenomenon.
The harm of water hammer is very big, can destroy a pump, pipe and other equipment.
Water hammer in the pressure pipeline there are many causes, such as pump valve door down quickly, abnormal shutdown, etc.
Stop pump water hammer mechanism when due to abnormal reasons, such as power, pump suddenly stopped working: the initial stage, piping within the medium depends on inertia to move on, but the speed is gradually reduced to zero;
At this point, if the piping layout is fall of on any account, medium under the action of gravity will go back to the pump;
When backflow medium reaches a certain speed, the pump outlet check valve will shut down quickly, so, arrive here a large number of medium speed suddenly become zero, cause a tremendous rise of pressure medium here & ndash;
Stop the pump water hammer.
A large number of literature points out, stop the pump water hammer is the main water pump outlet check valve shut down suddenly.
But studies have found that, although in some cases, the pump outlet non-return valves can be canceled, but in most cases, to prevent the backflow medium into the centrifugal pump, the pump outlet of backflow prevention setting is required.
Stop pump water hammer countermeasures to avoid the measures to prevent water hammer pump is going to have a lot of, such as installation of water hammer eliminator, pressure relief valves, pressure regulating tank, etc. , the only introduction two application more common valve door related measures.
1, set up slow close check valve slow close check valve is a kind of achieved by increasing the actuators, damper slow close check valve.
Above to install a slow close check valve of the centrifugal pump stopped pumping water hammer protection system diagram, the slow close check valve need to cooperate with gate valve gate (
When the medium under the action of gravity flow back, slow close check valve, effectively avoid the because of the ordinary check valve closed suddenly water hammer.
Its shortcomings as part because closing speed is slow, medium inevitably flow back into the centrifugal pump, pump so can lead to mechanical failure.
2, set up slowly-closing check butterfly valve door this is a application is common in large water conservancy system, the effect is good method.
Slowly-closing check butterfly valve door performed by the butterfly valve door, structure and the hydraulic control system.
Above for installing slowly-closing check butterfly valve gate of centrifugal pump stopped pumping water hammer protection system diagram.
The system only need to install slowly-closing check butterfly valve door, can play the role of the check valve and can play the role of switch valve.
When open centrifugal pump, according to the first slow, quick steps to open, ensure the pump low load open;
When the pump stop working suddenly, its closed after the first fast slow steps, which can avoid the generation of water hammer, and can avoid the excessive medium backflow through the pump, causing the mechanical failure of the pump.
Avoid the minimum flow condition and minimum flow valve door refers to guarantee the normal work of the pump can flow.
If the pump is lower than the minimum flow under the condition of work, will cause the noise and vibration of the pump performance will become unstable, even can cause abnormal cavitation of pump, reduce the service life of pump.
So measures must be taken to avoid work in centrifugal pump minimum flow conditions, the common approach is to feed the centrifugal pump sets minimum flow loop.
But from the pump itself value, only for the big flow, high lift, high power of centrifugal pump set minimum flow circuit is reasonable.
Centrifugal pump to allow the minimum flow of value be determined by the pump manufacturer calculation or experiment.
The simplest minimum flow loop only need to install a shut-off valve in the circuit, such as gate valve gate, when think open when the pump is in working condition of minimum flow valve door, turn on the minimum flow loop, avoid pump work at the minimum flow condition.
Summary introduce the basic structure of the valve gate valve with general door, but because according to the working condition of application of the corresponding improvement, makes the valve door dedicated to solve the problem of the two types of gate valve.