Vacuum System Design
When the vacuum components, such as valves, traps, dust collectors and vacuum pumps are connected to each other, the exhaust pipeline should be as short as possible, the flow conductance of the pipeline should be large, and the diameter of the pipeline should not be smaller than the diameter of the pump diameter. This is an important principle for vacuum system design. But at the same time, it is necessary to consider the convenience of installation and maintenance. Sometimes in order to prevent vibration and reduce noise, the mechanical pump is to be located in the pump room close to the vacuum chamber.
The mechanical pump (including the roots pump) has vibration. To prevent the vibration from affecting the entire system, usually use a hose to reduce the vibration. There are two kinds of hoses: metal and non-metal. No matter which kind of hose is used, it must be ensured that it will not be crushed under the action of atmospheric pressure.
After the vacuum system is completed, it should be easy to measure and detect leaks. The actual production tells us that the vacuum system is often prone to air leakage during the working process, which affects the production. In order to quickly find the leak, it is necessary to perform segmented leak detection, so each interval closed with a valve must have at least one measurement point for measurement and leak detection.
The valves and pipes configured in the vacuum system should make the pumping time of the system short, easy to use, safe and reliable.
Generally, in a system with a vapor flow pump as the main suction pump (diffusion pump or oil booster pump) and a mechanical pump as the backing pump, in addition to the backing pipeline (the pipeline of the vapor flow pump in series with the mechanical pump), also there should be a pre-vacuum line (the line from the vacuum chamber to the mechanical pump).
Secondly, there is a high vacuum valve (also called the main valve) between the vacuum chamber and the main pump, a fore-stage pipeline valve (also called a low-vacuum valve) is set on the fore-stage pipeline, a pre-vacuum pipeline valve is set on the pre-vacuum pipeline (called low vacuum valve).
The high vacuum valve on the main suction pump usually cannot be in a vacuum state under the valve cover, and the valve cover is opened under the atmospheric pressure state, which must be ensured by electrical interlocking. The foreline valve and the pre-vacuum line valve should take into account that the valve itself can open at atmospheric pressure.
For a vacuum system with a vapor flow pump as the main pump, the main valve should be covered with the main pump, the front-stage pipeline valve should also be covered with the main pump, and the pre-vacuum pipeline valve should be covered with the vacuum chamber.
On the inlet pipe of the mechanical pump, an air bleed valve should be provided. When the mechanical pump stops working, the valve can be opened immediately, so that the inlet of the mechanical pump can be vented to the atmosphere to prevent the mechanical pump oil from flowing back into the pipeline, so the valve should be electrically interlocked with the mechanical pump.
A vent valve should also be set on the vacuum chamber for charging and reclaiming. The position of the valve should take into account that when the gas is deflated, the gas impulse is large, so as to prevent the weak components in the vacuum chamber from being damaged due to the excessive impulse. The size of the air release valve is related to the volume of the vacuum chamber. It should be considered that the air release time should not be too long, which will affect the work.
The design of the vacuum system should ensure stable and reliable exhaust, easy installation, disassembly and maintenance, convenient operation, and interchangeability of connections between components.
In order to achieve stable exhaust during operation, the performance of the main pump is required to be stable, the operation of each valve is flexible, the sealing is reliable, the joints of each component in the system are airtight, and the sealing performance of the vacuum chamber is good.
In the design of vacuum system, in principle, each closed pipe size should have an adjustable size. This adjustable size has been solved by hoses in the past design, and most of the systems are now designed without hoses.
The dimensional accuracy of vacuum components is improved and the sealing rubber ring on the connecting flange is used to solve the installation error, which can improve the strength and rigidity of the system, reduce the brackets used on the system, and be more beautiful.
New technology should be adopted in the design of vacuum system to achieve automatic control and interlock protection. With the development of vacuum technology, it is required to be able to perform automatic operation during the entire pumping process, such as using a vacuum relay to control the roots pump to start work at a pressure of 1333Pa.
The water pressure relay is used to control the water pressure of the steam flow pump at a certain pressure. When the water pressure is insufficient or the water is cut off, the power will be cut off immediately and an alarm will be issued to prevent the pump from burning out.
For complex vacuum systems and equipment with strict technological process and parameter requirements, microcomputer program control should be adopted, which is safer and more reliable.
In the design of vacuum system, it is required to save energy, reduce costs, and be convenient and reliable to use. It makes great economic sense to do this, it can make the designed vacuum application equipment have a wide market sales.
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