The vacuum drainage system is divided into indoor vacuum system and outdoor vacuum drainage system according to the scope of action. The vacuum drainage system has the characteristics of stability and reliability, which can be used as a sewage transmission scheme for sewage collection and transmission in special conditions, complex terrain, subway engineering, general industrial areas, commercial areas and residential areas, so that the drainage system has great flexibility.
Composition and working principle of outdoor vacuum drainage system
The outdoor vacuum drainage system is composed of sewage collection well, vacuum contact startup device, vacuum drainage pipe network, vacuum station, vacuum monitoring system, etc. the system work is controlled by the automatic opening and closing of vacuum contact startup device of each sewage collection well. Under the action of vacuum negative pressure, sewage can be vertically lifted to the main sewage pipe or sewage treatment plant.
As the start-up facility of vacuum drainage system, sewage collection well is generally set near each single building. According to the specific situation, each building can be set with one or more. First, the sewage is discharged to the outdoor inspection well according to the indoor gravity, and the last sewage inspection well in each gravity sewage pipe network is used as the single sewage collection well. As an integral part of the vacuum drainage system, the vacuum contact startup device is located in the sewage collection well and controls the work of the system. The company adopts the special vacuum contact valve as the starting device, and its working steps are as follows:
The vacuum contact valve is equipped with an air pressure sensing tube. When the water level of sewage in the sewage collection well rises, the air in the sensing pipe will be compressed with the rise of the sewage level, so that the air pressure in the sensing pipe will rise.
Air pressure is transmitted through the intake pipe to the pressure sensor at the top of the contact valve. When the air pressure in the induction pipe rises to a certain rated value, the pressure switch is opened and the vacuum drainage system starts to work. At this time, under the action of vacuum pressure difference, collect the atmospheric pressure on the sewage level in the well, and send the sewage into the vacuum pipe behind the contact valve.
As the air carried by the sewage in the water collecting well enters, the air in the sewage escapes, and the water level in the well falls back, causing the air pressure in the air inlet pipe to drop. When the air pressure in the air inlet pipe drops to a certain value, the pressure switch automatically closes the valve body, and the system enters the next cycle after one working cycle. The vacuum contact opening and closing device can also adopt other control forms, such as PLC electromagnetic vacuum valve.
Vacuum drainage pipeline includes vacuum drainage main pipe and sewage branch pipe. Two 45 degree elbows are used for connection to form downstream conditions and reduce the interference of tributaries to the main stream. Due to the influence of vacuum pressure difference, sewage flows in a pressure flow state in the drainage pipe, from the branch pipe to the main pipe. When the vacuum contact valve is just opened, the average flow of sewage in the drainage branch pipe is 4 μ M / s, and the maximum flow is 5-6 μ M / s. With the air in the collection well and the air escaping from the sewage entering, the vacuum degree in the pipeline gradually decreases, and the pressure difference also decreases. The flow rate inside and outside the pipe is gradually reduced, and the flow rate is also gradually reduced. When the pressure inside and outside the pipe tends to balance, the vacuum contact valve is closed, the sewage in the pipe is in the state of gravity flow, and the sewage is collected to the lowest point at the end of the pipe network. Therefore, the vacuum drain pipe should be laid in waves or zigzags in sections to collect part of the sewage as the water seal needed to generate vacuum. Therefore, the waste water is transported by the vacuum pipeline with section relay intermittent operation instead of reaching the discharge point at one time.
Vacuum station is the core of the whole vacuum drainage system. The vacuum tank is maintained in a vacuum state by suction of a vacuum pump. The vacuum tank forms the vacuum pressure difference between the vacuum drainage pipe and the water collecting well, and the vacuum pressure difference enables the sewage to be transported through the pipe.
The function of vacuum contact valve monitoring system is to find out the vacuum fault point in the pipe network accurately and timely, so as to maintain the normal operation of the system. In the process of pipe network operation, the vacuum failure point is usually caused by the contact valve can not be closed normally. By monitoring the opening and closing status of the vacuum contact valve, the monitoring system can scan the contact valve which can not be closed normally and find out the vacuum fault point. Its working principle is to install a sensor on the valve body of the vacuum contact valve. The other end of the sensor is connected with the monitoring system through the signal cable, and the opening and closing status signal of the contact valve is fed back to the display of the monitoring system (usually located in the vacuum station). When the contact valve is opened for a long time, the indicator light on the display will be on and its code will be displayed at the same time. In this way, it can quickly find the vacuum valve that can not be closed normally, shorten the time for maintenance personnel to check the pipe network, and ensure that the vacuum drainage system can be put into normal operation as soon as possible