Level measuring instrument
In the production process, the surface position of the liquid stored in the container is called the liquid level; The surface position of the solid pile at a certain height is called the material level; The position at which two incompatible substances with different densities meet is called the boundary or interface. Liquid, material level and interface are collectively called level. The instrument for level detection is called the level detection instrument. At present, the liquid level instruments are mainly used in Qingshen Gas field, which mainly include float level controller, magnetic flap level meter and radar level meter. 4.1 Float level controller
The float liquid level controller is suitable for liquid level control in various containers. When the liquid level reaches the switching value of up and down, the controller contact sends an on-off switch signal. At present, the instrument used in Qingshen gas field is mainly installed on each separator, and is used with flash alarm to make hard alarm on the upper and lower levels of liquid level set in the container. 4.1.1 Main structure
It is composed of two parts, the float ball assembly and the contact assembly, which are isolated from each other. 4.1.2 Working Principles
The change of the liquid level is felt by the external float ball, and the instrument contact is driven by the magnetic shaft to realize the alarm and control of the liquid level. When the measured liquid level rises or falls, the float ball rises and falls, so that the magnetic steel at its end swings up and down, and the magnetic steel installed in the same magnetic pole in the shell swings up and down through the magnetic repulsion, and the contact at the other end makes the static contact connected or disconnected, and controls the flashing signal alarm to issue an audible and visual alarm, or other control functions. When the float level controller is rising and falling with the liquid level, only when it is in the upper and lower two largest positions of the operating range, the moving contact will make the static contact connected or disconnected, sending a on-off signal, and in the process of the lifting action, the static contact is always in the disconnected state, so as to prevent false alarm and continuous alarm. 4.1.3 Troubleshooting
Float level controller plays a switch role in the production process, usually used in conjunction with the flashing signal alarm or other chain equipment, so the fault is to lose the switch function, according to the actual maintenance experience, the fault mainly has the following aspects: (1) Float card neck, for the high alarm float level controller, float card neck is mostly due to the oil and impurities floating on the surface of the liquid level, and this situation occurs in winter, when the liquid level in the container drops, a small part of the oil and impurities above the float card neck due to cold weather, resulting in the float can not work normally. For the low level alarm, it is mostly due to too much sludge in the container. The phenomenon caused by these two cases may make the flashing signal alarm light in the duty room steady on or reach the alarm limit. In the first case, the liquid level in the container can be raised beyond the float, and the oil and impurities can be equalized with the liquid temperature in the container. In the second case, you can only clean the tank and remove the sludge in the container. (2) Float turn, due to long-term use, float level controller float connection is corroded, resulting in float turn. (3) Magnetic steel demagnetization, due to long-term application, the float level controller float end of the magnetic steel loses magnetism, and when it moves up and down, there is no magnetic repulsion installed in the shell of the same magnetic pole of the magnetic steel swings up and down, the other end of the contact is connected or disconnected with the static contact, it can not play the role of contact switch. In this case, the container can only be stopped and a new float level controller can be replaced. Figure 4-1 Object and working principle of the float liquid level controller 4.1.4 Precautions
(1) The diameter of the opening of the installation container should be greater than the diameter of the float, and the action range of the float should reach the two largest positions of the upper and lower, otherwise it cannot be installed or the float cannot work normally. (2) Can not be installed near the inlet and outlet, otherwise the liquid level fluctuation is large, easy to cause false alarm. 4.2 Magnetic flap level gauge
The magnetic flap liquid level meter can be used for the medium liquid level detection of various equipment such as towers, tanks, tanks, ball containers and boilers. This series of level gauges can achieve high sealing, leak proof and suitable for high temperature, high pressure, corrosion resistance. It makes up for the defects such as poor clarity and easy rupture of the glass plate (tube) liquid level gauge, and there is no blind area in the whole process measurement, with clear display and large measurement range. At present, the instrument used in Qingshen Gas field is mainly installed on the separator and the sewage tank, which is used to continuously monitor the change of the liquid level in each container. The liquid level meter of the separator is used with the automatic drainage system to realize the automatic discharge of sewage. 4.2.1 Working Principle
The magnetic flip plate liquid level meter is a new type of instrument which indicates the liquid level by turning the two-color magnetic flip plate driven by the magnetic steel in the float. The magnetic float in the cavity floats up and down with the liquid surface, and in the floating process, the magnetic coupling drives the magnetic flap to turn over and make it red, so as to intuitively indicate the liquid level value and keep it at the same height as the liquid level in the container. At the same time, through magnetic coupling, a certain magnetic sensor on the corresponding liquid surface is activated and converted into the corresponding (4-20) mA current output by the converter. Figure 4-2 Physical object and working principle of the magnetic rotating column liquid level gauge 4.2.2 Troubleshooting
Table 4-1 Common faults of a magnetic flap liquid level gauge Fault Cause Troubleshooting The liquid level rises or falls or the instrument has no indication. The float is damaged. Replace the float. The float loses magnetism. The float is stuck or cannot be lifted or lifted Clean the liquid level gauge chamber and float flip plate lose magnetism. The magnetic flip plate does not work. The magnetic flip plate indicates an abnormal magnetic flip plate
4.2.3 Precautions
(1) The installation of the liquid level gauge must be vertical to ensure that the float assembly moves freely up and down the main tube. (2) No magnetic permeator is allowed around the body of the liquid level gauge, otherwise it will directly affect the normal operation of the liquid level gauge. (3) The laying of the electric tropical zone can not be close to the magnetic flap to prevent the magnetic flap from deformation due to heat. 4.3 Radar level gauge
The instrument used in Qingshen Gas field is mainly installed on the separator, methanol tank and sewage tank, which is used to continuously monitor the change of liquid level in the container. 4.3.1 Structure
Radar level meter is mainly composed of radar detector and radar display instrument. The radar detector mainly consists of three parts: main body, connecting flange and antenna. 4.3.2 Working Principle
Transmitting - reflecting - receiving is the basic working principle of radar level meter. A high-frequency oscillator is used as a microwave generator, and the microwave generated by the generator is directed to the radiation antenna by a waveguide, and is shot down. When the microwave encounters the obstacle liquid level, some of it is absorbed and some of it is reflected back. By measuring the transmitted wave and reflected wave liquid level to achieve some parameters of the relationship between liquid level measurement. Figure 4-3 Radar liquid level gauge and working principle 4.3.3 Troubleshooting
Table 4-2 Common faults of radar liquid level gauge Fault Cause Troubleshooting Common Display Full tank antenna condensation Strengthen antenna heat preservation Incorrect display Parameter Settings Reset the machine itself Troubleshooting 4.3.4 Precautions
(1) Antenna insulation should be strengthened to avoid antenna condensation. (2) The height of the liquid level is obtained through calculation, therefore, the parameters entered by the computer must be correct.