Level measuring instrument
The level measuring instruments are generally arranged as follows:
1. The position of the instrument connection head (nozzle) of the level measuring instrument should avoid the impact of entering various logistics.
2. The observation surface of the instrument should face the operating channel, and there should be no objects around that obstruct the maintenance of the instrument. The level measuring instrument should be installed at one end of the platform or widen the platform.
3. If the instrument connector (nozzle) of the level measuring instrument is located at the bottom of the equipment, it should extend 100mm into the equipment.
4. When measuring the boundary position, the upper instrument connector (nozzle) of the level measuring instrument must be located within the liquid phase layer.
5. When multiple level gauges are used in combination, it is advisable to use a connected pipe installation type.
The installation requirements for glass plate (tube) level gauges are as follows:
1. When measuring the same liquid with a glass plate (tube) level gauge and a float (float) level gauge, the measurement range of the glass plate (tube) level gauge should include the measurement range of the float (float) level gauge.
2. When multiple level gauges are used in combination, adjacent level gauges should overlap by 150-250mm in the vertical direction, and the horizontal spacing should be 200mm.
3. When multiple liquid level gauges are used in combination, it is advisable to use an external connecting pipe for installation. Cut off valves should be installed at both ends of the connecting pipe, and the glass plate (pipe) liquid level gauge can be installed on this pipe without additional cut-off valves.
The installation requirements for the external float level gauge are as follows:
1. Cut off valves should be installed at both ends of the liquid level gauge.
2. The middle position of the measuring range of the liquid level gauge.
3. The distance between the upper and lower instrument connectors (nozzles) of the top and bottom flange level gauge should be at least 500mm more than the measurement range.
The installation requirements for the internal float level gauge are as follows:
1. The normal liquid level should be in the middle position of the float.
2. When the liquid level fluctuates greatly, a surge tube should be added.
The installation requirements for the internal float level gauge are as follows:
1. The horizontal centerline of the flange for installing the level gauge should be consistent with the normal liquid level.
2. There should be no obstacles within the range of the floating ball, and anti-collision plates should be added in situations with significant logistics impact.
The installation requirements for magnetostrictive level gauges are as follows:
1. Magnetostrictive level gauges should be installed at the top of the container or at the top of the connecting pipe leading out from the side of the container.
2. The magnetostrictive level gauge installed on the top of the dome shaped tank or spherical tank should be installed with a flange, and the inner diameter of the flange type instrument connector (nozzle) should be larger than the diameter of the float.
3. When installed on the connecting pipe outside the container, the inner diameter of the connecting pipe should be greater than the outer diameter of the float, and the connecting pipe should be made of non-magnetic materials (such as stainless steel, aluminum, or alloy).
The installation requirements for ultrasonic and microwave (radar) liquid (material) level gauges are as follows:
1. When measuring liquid level, it is advisable to install it vertically downwards for detection.
2. When measuring the material level, the ultrasonic or microwave beam should be directed towards the discharge port at the bottom of the silo.
3. The distance between the center of the ultrasonic or microwave beam and the container wall should be greater than the beam radius at the lowest liquid (material) level calculated from the beam angle and measurement range.
4. The beam path of ultrasound or microwave should avoid the spraying range of the container feed stream.
5. The beam path of ultrasound or microwave should avoid agitators and other obstacles.
6. The installation of ultrasonic or microwave level gauges should also comply with the requirements of the manufacturer.
The installation of guided wave radar and capacitive level gauge should meet the following requirements:
1. The liquid level gauge should be installed at the top of the storage tank to avoid collision with movable parts inside the equipment; When the medium inside the device fluctuates violently, a through-hole protective tube should be added to fix the waveguide rod (probe).
2. When installing the level gauge on the external connecting pipe of the equipment, the following regulations should be followed:
a) The length of the waveguide rod (probe) should include the upper and lower measurement dead zones, and its end should be at least 50mm lower than the center of the lower connecting port of the connecting pipe;
b) A guided wave radar liquid level meter using a dual rod probe, with a connecting pipe diameter of not less than 80mm; A guided wave radar liquid level meter using a single rod probe, with a connecting pipe diameter of not less than 50mm. 3. When using a cable probe guided wave radar level gauge to measure large liquid levels, the cable probe should be straightened and fixed at the bottom of the equipment. In cases of severe liquid level fluctuations, a through-hole protective tube should be added for fixation.
3. When using a cable probe guided wave radar level gauge to measure large liquid levels, the cable probe should be straightened and fixed at the bottom of the equipment. In cases of severe liquid level fluctuations, a through-hole protective tube should be added for fixation.
4. When the temperature of the measured medium is high, it is advisable to install the transmitter separately.
5. The installation of guided wave radar and capacitive level gauge should also comply with the requirements of the manufacturer.
The installation of static pressure liquid level measuring instruments shall comply with the following regulations:
1. The instrument connection head (nozzle) of the single flange level gauge should be at least 300mm away from the bottom of the tank and located in an easy to maintain position.
2. The installation height of the double flange remote differential pressure level gauge should not be higher than the lower pressure flange on the container, and the zero point and negative migration should be accurately calculated. The conducting capillary tube should be fixed with angle steel or steel pipe, and insulation measures should be taken in places with large environmental temperature changes.
3. The installation of using differential pressure transmitters to measure liquid levels should meet the following requirements:
a) The distance between the connection heads (nozzles) of the upper and lower pressure gauges should be greater than the required measurement range; The distance between the connection head (nozzle) of the lower pressure gauge and the bottom of the tank should not be less than 200mm, and should avoid the liquid extraction port. The connection head (nozzle) of the upper pressure gauge should avoid the gas phase spray inlet, and if it cannot be avoided, anti flushing measures should be taken;
b) When measuring the liquid level of volatile or condensable media, an isolation tank should be added on the negative pressure side (gas phase) or on both positive and negative pressure sides, and the zero point and negative migration should be accurately calculated;
c) When measuring the liquid level of the steam drum in a steam boiler, a temperature self compensating balance vessel should be installed, and the pressure pipe should be heat traced and insulated.
4. When using the plug-in blowback method to measure liquid level, the end of the pressure tube inserted should be at least 200mm away from the bottom of the tank and cut into a slope shape.
Installation of radioactive level instruments
The installation of radioactive level instruments should strictly follow the requirements of the manufacturer and comply with the relevant health and safety protection regulations of the People's Republic of China.
Installation of steel strip level gauge and float level gauge
The installation of steel strip level gauges and float level gauges should comply with the requirements of the manufacturer.
Regulating valve
The installation position of the regulating valve is specified as follows:
1. The installation position of the regulating valve should meet the process requirements and be easy to install, maintain, and operate.
2. Regulating valves should not be installed on pipe trenches or pipe racks. If it must be installed at a high place, a platform should be added.
3. When the regulating valve is equipped with auxiliary devices such as accident gas source tank, handwheel, and locking valve, there should be space for installation and operation.
4. The regulating valve should be located near the relevant local indicator instruments.
The installation size requirements for regulating valves are as follows:
1. The distance between the bottom of the regulating valve and the ground or platform surface should be greater than 250mm. For single and double seat regulating valves with reverse valve cores, it is advisable to leave space below the valve body for extracting the valve core.
2. The clearance distance between the top and the bypass pipeline should be greater than 200mm. The upper and lower positions of the regulating valve and the bypass valve should be staggered.
The piping requirements for regulating valves are as follows:
1. Set up shut-off valves and bypass valves for regulating valves according to process requirements and special instrument needs.
2.Those who meet one of the following conditions do not need to install shut-off valves and bypass valves:
a) Operating conditions are not harsh (clean medium with temperature not exceeding 225 ℃ and pressure not exceeding 0.1MPa), control non critical parameters, and a regulating valve with a diameter greater than or equal to 100mm and a handwheel;
b) Sequential control regulating valve;
c) Emergency stop interlock valve;
d) Butterfly shaped regulating valve with a diameter greater than 350mm;
e) Three way regulating valve; f) Steam regulating valve for steam turbine pump driven by backup motor;
g) Places where it is necessary to reduce the leakage of hazardous media such as hydrofluoric acid, phenol, etc.
3. For regulating valves with a diameter less than 25mm, they can be installed above the bypass.
The piping requirements for the actuator are as follows:
1. A regulating valve that relies on venting to quickly activate a pneumatic actuator A solenoid valve with a minimum operating pressure difference of zero should be configured.
2. When the signal is interrupted or the gas source (or other power source) is interrupted, the actuator should keep the valve in a process safe position; An accident gas source tank should be installed for double acting cylinder actuators without self resetting capability.
3. Pneumatic power amplifiers and fast exhaust valves should be installed in the control signal air circuit of large-diameter or pneumatic diaphragm regulating butterfly valves or regulating valves that require rapid action.
4. The pneumatic control valve air source piping shall comply with the following regulations:
a) In places where the installation of regulating valves is concentrated, the air source can be filtered and depressurized in a centralized manner;
b) In places where the installation positions of regulating valves are scattered, the gas sources to each valve should be filtered and depressurized separately;
c) The air source of the cylinder gate valve should be filtered and depressurized separately, and equipped with an oil mist device.
5. The power oil piping of hydraulic cylinder actuators shall comply with the following regulations:
a) The power oil system should be equipped with two sets of filters that are mutually backup;
b) The highest point of the hydraulic system should be equipped with a relief valve;
c) The hydraulic system should be equipped with energy storage devices and backup automatic pressurization equipment.
Industrial Process Analysis Instruments:
The determination of the sampling point location should meet the following requirements:
1. The sample at this point can timely and accurately reflect the changes in the measured parameters of the process fluid, making it a measurable process fluid.
2. The process lag time between this point and the process calibration point (usually a regulating valve, heating or cooling device) is short.
3. Can provide clean and dry samples.
4. Can obtain appropriate sample pressure and temperature.
5. Easy to access and maintain.
6. The head of the sampler should be extended to the center of the pipeline, and the sampling port should be facing away from the sample flow direction. 7. The sampling point should be taken at the top or side of the process pipeline, not at the bottom of the process pipeline.
The position of analytical instruments should meet the following requirements:
1. Try to be as close as possible to the sampling point for easy access and maintenance.
2. Try to avoid the following situations:
a) the influence of hot equipment or pipelines;
b) The impact or vibration;
c) In situations where mechanical damage may occur;
d) In situations with strong electromagnetic interference.
The installation requirements for the sampling system are as follows:
1. The material of the sampling system should comply with the following regulations:
a) Not reacting with the sample;
b) Do not extract components from the sample;
c) Impurities shall not be allowed to enter the sample or substances leached out of the sampling system components shall not be allowed to enter the sample through infiltration or diffusion.
2. The pipeline design of the sampling system should comply with the following regulations:
a) The pipelines and fittings of the sampling system should be degreased, degreased, and cleaned to ensure no mechanical damage or leakage;
b) On the premise of ensuring the required sample flow rate of the analyzer, the capacity of each component and tube of the sampling system should be minimized;
c) Under the premise of allowable pressure drop in the pipeline, the sample flow rate in the sampling system should be kept as high as possible;
d)Insulation, heat tracing or cooling measures should be taken to ensure that the sample does not undergo phase transition or reaction in the sampling system;
e) When the process system operates under negative pressure, the pumping method should be used for sampling;
f) When there are particles or powder catalysts in the process logistics, the sampling pipeline should have dust removal, filtration, and blowback measures.
3. The sampling system should be equipped with a fast sampling circuit, except for the following situations:
a) The analyzer is directly installed at or near the sampling point;
b) Analytical instruments for gases that can be directly released (such as air, flue gas, etc.);
c) Analyze water analysis instruments that can be directly discharged into the sewage system.
4. The rapid sampling circuit should send the sample taken from the process material back to the process system. The driving force for sample flow in the rapid sampling circuit should be as follows:
a) The differential pressure between the sampling point and the return point on the process pipeline;
b) Sampling and sample return mechanical pump (or gas/steam jet pump).
5. The treatment of analyzed waste samples that cannot be economically returned to the process system should comply with the following regulations:
a) It is not allowed to discharge hydrocarbons and chemical liquids on site, and a dedicated sample recovery system should be established;
b) Water samples that meet sanitary discharge standards can be discharged into the underground rainwater drainage system;
c) Gases that meet hygiene emission standards can be vented on-site;
d) A small amount of light hydrocarbon gas or hydrogen can be discharged into the atmosphere at a high altitude, causing it to rapidly diffuse to a concentration below the lower limit of explosive gas mixtures;
e) Toxic gases should be discharged to a safe location and should not be directly released into the atmosphere on site.
The sample processing system should have some or all of the following functions:
1. Reduce or increase the pressure of the sample to the inlet pressure required by the analyzer.
2. Reduce or increase the temperature of the sample to the inlet temperature required by the analyzer.
3. Raise the sample temperature so that the gas is at least 10 ℃ above its dew point to prevent condensation of high boiling point sample components; Raise the liquid sample at least 20 ℃ above its freezing point to prevent crystallization.
4. Heat and vaporize the liquid phase sample into the gaseous sample required by the gas phase analyzer.
5. Use separators, collectors, or dryers to remove non sample moisture.
6. Filter out impurities and solid particles in the sample.
The installation of the analyzer should meet the following requirements:
1. The remote sampling analyzer should be installed relatively centrally in the on-site analyzer cabinet, analyzer shed, or automatic analyzer room.
2. The automatic analyzer room should have the following functions:
a) It should have heating and insulation facilities in cold regions;
b) Cooling facilities should be available in hot areas;
c) Good ventilation or mandatory ventilation facilities;
d) The structural materials of the automatic analyzer room should not produce factors that affect the stable operation of the analyzer or factors that affect safety;
e) The automatic analyzer room should have water supply and sewage measures;
f) Easy for operators to enter and maintain;
g) Equipped with standard sample steel cylinder installation facilities;
h) The indoor power supply, air supply, and steam supply of the automatic analyzer should be well-designed and have good lighting conditions.
3. When combustible or toxic gas samples are introduced into the automatic analyzer room, combustible or toxic gas detection and alarm instruments should be installed.
4. The exit position of the automatic analyzer room should be such that personnel can safely evacuate in case of emergency in the device area.
5. The automatic analyzer room should be manufactured and installed internally by a professional manufacturer.
6. The installation location of the automatic analyzer room should meet the following requirements:
a) It should be placed in non explosive hazardous areas. If it is located in Zone 1 or Zone 2 explosive areas, corresponding explosion-proof measures must be taken;
b) The automatic analyzer room should be located near the pipe gallery. Try to shorten the distance between sampling points and public works as much as possible;
c) The automatic analyzer should avoid causing indoor vibration amplitudes greater than 0 If the frequency of the seismic source exceeds 25Hz, vibration reduction measures should be taken;
d) The automatic analyzer room should not be located in a place that causes continuous strong magnetic field interference to the analyzer;
e) The location inside the automatic analyzer room should be convenient for inspection, operation, maintenance, and repair.
Design of Electrical Wiring for Analyzer
The design of the electrical wiring for the analyzer should comply with relevant explosion-proof regulations and take measures to avoid electromagnetic interference and interference from power sources on signals.
Instrument valves and fittings
The type regulations for valves on instrument pressure pipes are as follows:
1. Generally, socket welded valves are recommended, but other types of valves can also be used.
2. If there is liquid in the pressure pipe, a shut-off valve should be used as a vent valve at the highest point of the pipeline.
3. Use gate valves, ball valves, or globe valves as drain valves at the lowest point of the pressure pipe.
4. The valve material should be carbon steel or stainless steel, and other materials can also be selected according to the process conditions.
The selection regulations for fittings on instrument pressure pipes are as follows:
1. Bend, straight, tee or four-way joints should be connected by socket welding.
2. The number of detachable joints on the pressure pipeline should not exceed 3, and detachable joints should be connected using threads or high-quality card sleeves.
3. The material of the pipe fittings should be equal to or better than that of the pressure pipe.
Pneumatic signal pipeline and gas source pipeline:
1. The gas supply pipe should be led out from the upper or side of the main (branch) pipe and equipped with a shut-off valve. The shut-off valve of the gas supply pipe should be a threaded connection gate valve or ball valve.
2. A gas source valve should be installed when the gas supply pipe is led to the instrument.
3. Valves on gas supply pipelines should be made of metal, brass can be used indoors, and carbon steel or stainless steel valves are suitable for outdoor and harsh environmental conditions; The fittings and valves on the pneumatic signal pipeline should be made of stainless steel material.
4. Each local pneumatic instrument should be equipped with a small filter pressure reducing valve.
5. The fittings and valves on the gas source pipeline should be connected with threads.
6. The fittings on the pneumatic signal pipe should be connected with clamps.
Backblowing and flushing system for instruments
The requirements for the instrument pressure pipeline blowback system are as follows:
1. The anti blowing system is mainly used for liquid level measurement by blowing method and measurement of fluidized bed pressure and differential pressure. It is advisable to use purified compressed air, nitrogen, or desulfurized dry gas as blowback air.
2. The blowing point should be as close as possible to the shut-off valve, and the backflow blowing volume should be limited by a limiting orifice plate or a rotor flowmeter and a shut-off valve.
a) The reverse blowing pressure (absolute) should be at least twice the pressure of the measured medium (absolute);
b) The amount of back blowing gas should be determined based on the blowing speed. The pressure and differential pressure of the fluidized bed should be measured at a blowing speed of 1m/s. For general flow rate, liquid level, and pressure measurements, the blowing speed should be 0 2~0. 3m/s.
3. To prevent gas source blockage, the following measures should be taken:
a) Install common or individual filters;
b) Check valves should be installed on the blowing pipeline. Depending on the specific piping situation, several blowing points can share one check valve, or one check valve can be installed on a single platform;
c) The blowback system of fluidized beds (such as reactors and regenerators in catalytic cracking units) should be separated from the instrument gas supply system, and the blowback pipe should have a vertical pipe above the blowing point, blowing air from top to bottom.
The requirements for the flushing system are as follows:
1. The flushing liquid system is mainly used for measuring media with high viscosity, easy solidification, easy coking, and solid impurities The flushing solution should not affect the quality of the measured medium and corrode the instrument. The flushing solution can be selected from the medium with a certain pressure in the process itself (such as top reflux, solvent)
An independent flushing system can also be set up. The flushing liquid main pipe should be equipped with filters and low pressure alarm devices, and the flushing liquid tank should have liquid level control and high/low liquid level alarms.
2. The pressure of the flushing fluid should be stable and greater than the maximum operating pressure of the measured medium.
3. On the flushing liquid pipeline of each measuring instrument, shut-off valves, check valves, and shut-off valves should be installed to adjust the flushing liquid volume, and a rotor flowmeter should be installed to indicate the flushing liquid flow rate.
4. In a continuous flushing system, estimation of flushing fluid usage and selection of pipe diameter:
a) The flow rate of the flushing liquid should be 0.06m/s. During continuous flushing, the flushing liquid consumption for the sharp orifice flow meter (pressure hole 2X Φ 8) is 2 X 0 015m3/h; The pressure gauge (pressure hole Φ 12) is 0.025m3/h; The differential pressure level instrument (pressure tap 2X Φ 12) has a capacity of 2 X 0.025m3/h;
b) The circulation volume of the flushing solution should not be less than 3-5 times the calculated consumption;
c) The diameter of the flushing solution can be selected according to Table 1.
Table 1 Diameter of flushing solution
Note: Calculated based on a flushing point consumption of 0.03m3/h.
