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In order to ensure the quality of the operation of the dcs system, the instrumentation signals of the input system must be accurate. For this reason, it must be installed in strict accordance with GBJ93-96 "self-control installation map" and instrument manual. The requirements for the installation and use of the instrument are as follows:
First, the pressure transmitter
1. The pressure and negative pressure pressure-receiving device shall not be installed in the straight-line pipe of the stream, and shall not be installed in the place where the pipe bends, corners, dead angles and vortices are sufficient to make the static head distortion.
2. When installing pressure or negative pressure pressure device, the pressure tube should not protrude into the inner part of the fluid pipeline or equipment because it is perpendicular to the flow beam. The pressure tap should have a smooth outer edge instead of sharp edges. Exist, continuous conduits and fittings should be cut neatly and the burrs removed.
3. Install the pressure tube on the horizontal and inclined pipes at the upper part of the pipe when the fluid is gas.
When the fluid is a liquid, the lower half of the pipe is in the range of 0-450 in the horizontal centerline or on the pipe centerline.
When the fluid is steam, the upper half of the pipe is in the range of 0-450 in the horizontal centerline or on the pipe centerline.
4. All pressure-receiving devices must be equipped with a single door, and the primary door should be close to the pressure-receiving device.
5. The horizontal section connecting the impulse pulse pipeline should maintain a certain slope, and the direction of the slope should ensure the discharge of air or condensed water. The slope of the pipeline requires that the pressure pulse line be no less than 1:100. The pressure pulse line should be equipped with a drain valve at the pressure gauge to flush the line and remove air.
6. The impulse pulse pipeline should be purged before installation to ensure that the pipe is clean and unblocked. The valve on the pipeline should be tested for tightness before installation. After the pipeline is laid, the tightness test is carried out again. The pumping pulse line should be filled with water before driving (note that it is extremely impermissible to inject air bubbles during irrigation to affect the measurement).
7. For the installation of the smart transmitter, please refer to the instruction manual for the installation of the random transmitter.
Second, the temperature transmitter
1. The temperature sensing element should be placed in a place that can represent the temperature of the measured medium. The temperature sensing element should not be placed near the dead angle of the valve, elbow and equipment. The temperature sensing element should be placed obliquely, and the direction of inclination should be such that the temperature sensing end greets the fluid.
2. When installing a heat-sensitive element on a pipe with a diameter of 76 mm or less, a method of expanding the pipe should be used.
3. For easy disassembly and to prevent dirt from falling into the thermometer, when installing a platinum resistance thermometer on a horizontal pipe, it is generally installed horizontally or slightly downward.
4. The temperature sensing part of the platinum resistance thermometer should be installed at the center of the pipe, and the temperature end exceeds the center of the pipe by 50-70mm.
Third, electromagnetic flowmeter
1. The environmental conditions (temperature, humidity, electromagnetic field, etc.) at the installation location must meet the requirements of the instructions.
2. Straight pipe length. According to the condition of the pipeline where the flowmeter is located, the necessary straight pipe length must be ensured. Generally, the upstream pipeline maintains a straight pipe section of 10D or more, and the downstream maintains 3D-4D. D is the pipe diameter.
3. The addition of chemical additives will affect the conductivity of the liquid and should not be injected upstream of the meter. If it must be injected upstream, it must maintain a sufficient volume of reactor or straight pipe section so that the liquid conductivity flowing through the flowmeter is already stable.
4. Installation method: No matter whether it is installed horizontally, vertically or obliquely, it must be ensured that the measuring tube is always filled with liquid and no air bubbles exist (see the instrument manual). For vertical installations containing solid particles or slurries, the flow direction is from bottom to top. The plane where the electrodes are located must be parallel to the ground.
5. Grounding
A. The working ground of the flow sensor is to ensure that the reference potential is the same as the measured body, and the liquid potential should be the same as the ground potential. The electromagnetic flowmeter is equipped with a grounding ring, which acts to establish a liquid grounding by contacting the liquid. According to the material of the pipe where the flowmeter is located, the grounding connection method is correctly adopted. The working grounding should adhere to the principle of “single point grounding”. (See “Chemical Automation and Instrumentation”, 1998, Issue 4, 48-49, “Grounding Measures for Electromagnetic Flowmeters”. The grounding resistance should be ≤100 ohms.
B. Shield grounding. The signal cable that is output from the flow converter to the secondary instrument DCS system is grounded on the side of the control room and grounded through the ground bus.
6. Reasonable process procedures and correct operation. Prevents bubbles generated during production from flowing through the electromagnetic flowmeter.
Fourth, vortex flowmeter
1. Pipe bracket: If there is vibration in the pipeline, support should be added.
2. Installation: If the pipeline is filled with liquid, the Reynolds number is greater than 2×104, then the pipeline can be installed vertically or at an oblique angle.
3. Valve position and straight pipe length
A. In general, install the flow meter upstream of the valve. The length of the straight pipe before and after the flow is >20D and >5D, respectively.
B. Install the valve upstream of the flowmeter: for the use of piston or or Roots blower, air duct of the compressor or use of piston, plunger pump morning high pressure liquid pipe (about greater than 1Mpa) may generate liquid vibration . In these cases, the valve can be installed upstream of the flow meter. At this time, the length of the straight pipe between the flowmeter and the valve should be greater than 20D, and the length of the straight pipe downstream of the flowmeter should be greater than 5D.
4. Length of elbow and straight pipe section: 20D straight pipe length should be guaranteed upstream of the flow. If a gate valve is installed upstream of the flowmeter, the upstream length of the straight pipe of at least 20-40D should be guaranteed.
5. Length of shrinkage and expansion pipe and straight pipe: The upstream of the flowmeter should ensure the length of the straight pipe of 10D, and the length of the straight pipe of 5D should be guaranteed downstream.
6. Pressure measuring point: Take the pressure measuring point between 2-7D on the downstream side of the flowmeter.
7. Temperature measurement point: Take the temperature measurement point between the 1-2D distance on the downstream side of the temperature measurement point.
Five, power concentration transmitter (a), the installation of the transmitter
Position
A. The transmitter should be installed in a location that avoids mechanical damage and vibration. The electronic unit should be installed in a cool, ventilated place and protected against mud. It is recommended to install a waterproof baffle on it.
B. The transmitter should be installed as close as possible to the measuring point of the dilution water connection to ensure the shortest time lag.
C. The transmitter can be mounted on a vertical, horizontal slurry tube. The vertical position transmitter should be perpendicular to the axis of the pump and the horizontal position should be mounted on the side of the slurry tube. It is recommended to install in a vertical position as much as possible.
Distance
A. The installation position of the transmitter should consider the minimum stable distances L1 and L2 of the slurry tube before and after. In general, L1 = 10D, L2 = 5D, D - pipe diameter. It is also possible to estimate the length of L1 based on the actual flow rate and concentration using the drawing of the instrument manual, L2 = L1 x 0.3 + 0.3.
B. This estimation method is applicable to chemical pulp and long fiber pulp. In the case of waste paper pulp, ground wood pulp and short fiber pulp. The result of the above estimation is multiplied by 1.25.
3. When connecting the short tube to install the transmitter to connect the short tube, special attention should be paid to the distance from the short tube method blue port to the inner wall of the slurry tube. H=20-22mm. If the short tube is processed according to the adhesive paper supplied with the equipment, it should be The short tube is added to the slurry tube, but the inner wall of the slurry tube is ensured to be welded without being raised.
4. Slurry tube: If the material of the slurry tube is carbon steel and other materials, welding is more difficult. It is recommended to install a 1m long stainless steel tube to install the transmitter, and connect the short tube to the center position.
5. Transmitter sensing components
A. Do not allow the machine to collide with the blade. Do not use a manual blade or force the transmitter.
B. Blade installation should be parallel to the slurry tube and consistent with the direction of the slurry flow.
6. Transmitter wiring
A. All signal cables connected to the junction box must be 1.3-1.5mm2 multi-core shielded cable.
B. All cables should be protected by galvanized steel pipes or cable sleeves. Power and signal cables must be protected by pipe.
(2) Installation of sampling valve and dilution water valve
1. Sampling valve: The installation position can be selected below the transmitter, which is convenient for operation.
2. Dilution water pipe
A. The installation position of the dilution water valve should be installed as close as possible to the dilution point.
B. The dilution water pipe should be inserted vertically into the suction side of the slurry pump by 15-50mm. The water pipe is located between the slurry tank and the slurry pump, 1/3 away from the slurry pump.
C. The dilution water pipe should be capable of producing a flow rate of approximately 5 m/s at the junction.
D. The dilution water pressure should be stable. It is recommended to install a pressure gauge on the water pipe.
Six-flange level transmitter
1. The transmitter should be installed at the bottom of the pool and need to measure the liquid level at another position (not suitable for access to the exhaust port)
2. The transmitter should be installed where the liquid is relatively stable, avoiding and moving away from the spoiler (eg agitator, slurry pump, etc.)
Seven recommendations on the prevention and control of electromechanical interference
1. Power and measurement wires should be installed in completely separate, metal-made wire trays that should be connected together and grounded approximately every 100m. At least 2m distance between the two different types of wire bridges is required.
2. Force the switchgear to be as far away as possible from the instrumentation system, using at least a separate stand.
3. For the shielding of instrumentation, the principle of “Faraday closure” should be applied: there should be a complete, connected shield around the conductor. The electrical shield should be heavy-duty woven (covering 80%). The electrical enclosure or shield can only be grounded at one end (usually connected to the power supply) and continually connected through a grounding box or cabinet.
Eight-quantity cutting
a) Quantitative cutting diameter 50-250mm can be installed on vertical, horizontal and inclined pipes. 300mm-350mm should be installed on the horizontal slurry pipe and adjust the mechanical upwards.
b) Clean the slurry pipe before installing the cutting door to ensure that there is no debris on the pulp line, prevent mechanical damage and quantitative cutting and sealing ring, and the direction of the cutting arrow is consistent with the direction of the slurry flow.
The electronic unit can be installed near the quantitative cutting or control room, should avoid mechanical damage and vibration, and be waterproof and anti-slurry, the ambient temperature does not exceed 40 ° C
Nine, input type liquid level transmitter
1. When installing in stationary water, such as deep wells and pools, the method of inserting steel pipes is generally used. The inner diameter of the steel pipe is about Ñ„ 45 mm, and the steel pipe has several small holes at different heights so that the water can smoothly enter the pipe.
2. When installing in flowing water, such as waterways or non-stop agitation water, insert steel pipes with an inner diameter of about 45 mm, and make small holes at different heights on the opposite side of the water flow direction to allow the running water to enter the pipe.
3. The installation direction of the transmitter is vertical downward installation, and the transmitter should be placed away from the liquid inlet and outlet and the agitator.
4. If necessary, wrap the wire around the transmitter and use the wire to vibrate up and down to avoid breaking the cable.
10. Before installing the L-type three-way valve, carefully confirm the valve type, specification, and flow path switching, and install the valve strictly according to the valve instructions. Prevent the failure of the pass after the takeover, the continuous phenomenon of the break.