1. Overview Gas purification is a process in which the raw gas sent from the coke oven is washed, stripped of ammonia, dechlorinated, etc. into a relatively pure refined gas, which is then sent to the gas station or end user.
The refined gas after purification contains various components such as CO, O2, N2, and H2. The content of each component is related to the control of the process, and the process systems are not the same. Flowmeters are usually measured in volume flow and mass flow. Masteel Coking Company selected the ST98 mass flowmeter from FLUIDCOMPONENTSINTL (FCI) of the United States for the measurement of the factory gas, and adopted the metric KG/HR as the measurement unit. The collected data was sent to the central control room of the DCS system for centralized management. This article summarizes some installation techniques of the ST98 mass flowmeter on high-altitude and large-diameter pipelines and some issues needing attention in the debugging process for your reference.
2. Equipment Structure and Measurement Principles The ST98 mass flow meter is a thermal diffusion mass flow meter for various gas measurements. It consists of a flow element, a flow transmitter, and a package. For small-diameter process lines, on-line flow elements are generally used; for large-diameter process lines larger than 40 mm, plug-in flow elements are generally used. The process connection of the flow element, the input power of the flow transmitter, the calibration of the output signal, and the packaging and installation methods all have multiple options for the user to choose. According to the requirements of the on-site environment (I zone explosion-proof), Masteel chose the ST98 mass flow meter with flow transmitter and flow element integrated in the local package and plug-in threaded connection.
The measurement principle is: A low power heater creates a temperature difference between two RTDs by heating a resistive temperature detector (RTD). The flow of fluid will carry away the heat on the heated RTD, causing a proportional change in the temperature difference between the two RTDs. The flow transmitter converts the temperature difference between RTDs into a scaled output signal to DCS and an optional display value to the field digital display. Figure 1 shows the ST98 flow element.
3. Installation 1) Confirm the installation position of the flow element The factory gas pipe is erected on the top of the corridor frame, the elevation is +7500mm, the outside diameter of the pipe is 1220mm, and the material of the pipe is Q235 carbon steel. ST98 requires at least 20 times the diameter of the pipe (process line) in the upstream of the flow element and 10 times the diameter of the straight pipe in the downstream. The flow element is inserted into the process line, over the centerline 0.5 inch (12.7 mm), and in line with the pipeline cross section in the same plane. FCI recommends that the flow element be mounted vertically or horizontally in the process line.
Considering that the process gas may contain moisture or even a small amount of tar and other liquids accumulate on the RTD and drop into beads, taking away some heat affects the temperature difference between the two RTDs, thereby affecting the measurement accuracy. We used to install the flow element at an angle of 45° diagonally between the process line and the horizontal line (as shown in Figure 2). When liquid stays on the RTD, it rapidly spreads out along the RTD so that it does not collect in droplets and take away heat.
2) The process connector installation process is a 304 stainless steel connector with a circular column (see Figure 3). It must be ensured that the bottom surface S of the process connection head is parallel to the axis of the process line and the plane of L1, so as to ensure that the flow element crosses the center of the cross-section after the process connection head is inserted into the process pipeline, and is parallel to the cross-section.
First, according to the requirements of the installation location, mark a point O on the process pipeline. At both sides of the O point, use a line hammer to determine the tangential points A and A' of the vertical direction and the process pipeline (eg, flat view 4). Connect AA. ', A and A' for the AA' vertical line, from A and A' along its vertical downward marked 1/4 of the process pipeline perimeter position B and B', over O point for OO '⊥BB' at the point O', then O' point is the exact installation position of the flow element.
The OO' line is extended, and two points C and C' of equal distance are marked on the OO' and its extension lines from the O' point (as shown in FIG. 4). Open the hole at point O' and spot weld the process joint to point O'. With the aid of a square, the process connection head is adjusted so that its upper base surface S is parallel to the process line axis in the BB' direction. On the S surface, make L2 ⊥ BB' and the outer edge of the ring intersect at D, D' (see Figure 3). Adjust the process connector so that the length of the CD connection and C'D' connection is equal, and then solder the process connector. In this way, it is ensured that after the flow element is inserted into the process connection head, the cross section of the process pipeline is parallel and the cross-section of the cross-section is located at the center of the circle.
3) Installation of the flow element I. Calculate the 1/2 of the outside diameter of the pipe, plus 0.5 inch. Mark this length on the probe of the flow element (from the end of the RTD).
II. Insert the flow element fasteners into the process joints and tighten according to ANSI B16.5 torque specifications and use the appropriate sealant. The measuring process joints and the tightened fasteners are overall higher than the size of the pipe, and this length is marked on the first mark.
III. Insert the flow element and adjust its position so that the second mark is located on the flat surface of the fastener so that the flow element exceeds the centerline of the pipe by 0.5 inch; and the facet of the flow arrow is parallel to the flow direction of the process medium (±1 °), and point the arrows to the flow direction of the process media.
IV, confirm the above 3 steps are correct (because the metal collar is screwed into the flow element probe after tightening, the flow element can not make any adjustment), use a wrench to clamp the fastener, tighten the fastener bolts Twist 1.25 more turns so that the flow element is sealed and fixed in place.
4. Connections I, ST98 Mass Flow Meter User Manual The device description and wiring diagram indicate that the power supply is available for 24VDC or 220VAC, providing a connection terminal. Can be opened after the transmitter package found: ACONLY next to the terminal, so the input power can only use 220VAC.
II. ESD Warning Flow Transmitters contain Electrostatic Discharge (ESD) sensitive devices that require the use of standard ESD when opening packages or handling electronic circuit board devices WARNING: Use a megohm resistor with a ground, or a wrist strap, or knee Belts that keep high static electricity, such as non-ESD permitted plastics, tapes, and packaging plastics away from the equipment.
III. Grounding and Shielding For safety reasons, ST98 specifically requires 220 VAC power supply to use a three-wire system. One of the grounding wires must be connected to the ground terminal of the terminal block of the flow transmitter.
Due to the traditional 4 ~ 20mA I / O products are more sensitive to high-frequency noise generated by variable frequency drive equipment, and the site of high-frequency electrical noise pollution is more serious. To avoid interference to the signal transmission loop of the instrument, use shielded cables for the output signal cables. The shield layer is grounded near the transmitter. The DCS cabinet is wrapped and protected at one end. (In addition, the AC power grounding, DC power supply grounding, and cable The shield grounding and cabinet grounding are separated from each other in the cabinet, and the grounding net is independent of the factory lightning protection grounding net, etc.).
5. Commissioning Using an RJ-12 communication serial port provided by ST98 flow transmitter, it can communicate with FCI's FC88 communicator and PC's DB-9 or DB-25 interface for parameter setting of flow transmitter. Or modify, need to pay attention to the following several error-prone problems during debugging.
I. The flowmeter output data and the data measurement unit displayed by the DCS operation station should be unified, such as SCFM or NCMH, LB/HR or KG/HR.
II, flowmeter output data calibration and DCS control system to be consistent with the data calibration, such as 4 ~ 20mA, 0 ~ 20mA, 1 ~ 5VDC, 0 ~ 5VDC or 0 ~ 10CDC.
III. The electronic part of the flow meter uses a constant as a fitting curve parameter to display the flow value. This constant consists of 4 sections and is calculated based on the relevant parameters such as the percentage of various components (such as CO, O2, N2, and H2 in the refined gas) provided by the user in the process medium. Flowmeter manufacturers generally fix this constant in EEPROM before the equipment is shipped, and users cannot modify it. The user-supplied parameters are derived from the design theory values ​​of the design unit, and therefore have certain deviations from the actual site parameters. Therefore, the flowmeter will have a large error in practical applications. Therefore, such flowmeters of Masteel Coking Co., Ltd. have experienced serious deviations.
6. Concluding remarks Through on-site analysis and debugging of multi-technical personnel such as Wuye Automation Branch, equipment manufacturer and owner supervision, we highly appraised the details and the use of skills in the installation process, especially for flow components. The choice of orientation when inserting the process pipeline was fully affirmed by FCI. In fact, when the ST98 thermal insert-mount mass flow meter is used in a process gas that may contain moisture, etc., that can condense into liquid impurities, the flow element mounting orientation has been used with a 45° upward direction below the midline of the process line. FCI's user manual does not consider the medium containing impurities in the installation orientation of the equipment. Therefore, the original recommended installation method has not been corrected. FCI technical personnel has verbally recommended and supported the installation method used in this paper.
During the operation of the equipment, the error still exists seriously. After detailed analysis, it is considered that: The percentage content of various gases in the process medium previously provided by the owner is inaccurate. After sampling the gas, these parameters are sent to SANMARCOSFCI headquarters and the constants are recalculated. After the manufacturer's technical support personnel were newly set up, the measurement accuracy of the two ST98 mass flowmeters in the second gas purification plant of Masteel Coking Co. was controlled within ±1%, thereby avoiding the economy caused by inaccurate metering of the manufactured gas. loss.
This article uses a lot of space to explain the ST98 flow element on-site installation of some of the tips, especially the ESD warning and shielding grounding in the construction of the small details easily overlooked and debugging problems in the tuning process is easy to produce several aspects. I hope that when I install and debug similar instruments in the future, I can provide my colleagues with some experiences and lessons that we can learn from.
The refined gas after purification contains various components such as CO, O2, N2, and H2. The content of each component is related to the control of the process, and the process systems are not the same. Flowmeters are usually measured in volume flow and mass flow. Masteel Coking Company selected the ST98 mass flowmeter from FLUIDCOMPONENTSINTL (FCI) of the United States for the measurement of the factory gas, and adopted the metric KG/HR as the measurement unit. The collected data was sent to the central control room of the DCS system for centralized management. This article summarizes some installation techniques of the ST98 mass flowmeter on high-altitude and large-diameter pipelines and some issues needing attention in the debugging process for your reference.
2. Equipment Structure and Measurement Principles The ST98 mass flow meter is a thermal diffusion mass flow meter for various gas measurements. It consists of a flow element, a flow transmitter, and a package. For small-diameter process lines, on-line flow elements are generally used; for large-diameter process lines larger than 40 mm, plug-in flow elements are generally used. The process connection of the flow element, the input power of the flow transmitter, the calibration of the output signal, and the packaging and installation methods all have multiple options for the user to choose. According to the requirements of the on-site environment (I zone explosion-proof), Masteel chose the ST98 mass flow meter with flow transmitter and flow element integrated in the local package and plug-in threaded connection.
The measurement principle is: A low power heater creates a temperature difference between two RTDs by heating a resistive temperature detector (RTD). The flow of fluid will carry away the heat on the heated RTD, causing a proportional change in the temperature difference between the two RTDs. The flow transmitter converts the temperature difference between RTDs into a scaled output signal to DCS and an optional display value to the field digital display. Figure 1 shows the ST98 flow element.
3. Installation 1) Confirm the installation position of the flow element The factory gas pipe is erected on the top of the corridor frame, the elevation is +7500mm, the outside diameter of the pipe is 1220mm, and the material of the pipe is Q235 carbon steel. ST98 requires at least 20 times the diameter of the pipe (process line) in the upstream of the flow element and 10 times the diameter of the straight pipe in the downstream. The flow element is inserted into the process line, over the centerline 0.5 inch (12.7 mm), and in line with the pipeline cross section in the same plane. FCI recommends that the flow element be mounted vertically or horizontally in the process line.
Considering that the process gas may contain moisture or even a small amount of tar and other liquids accumulate on the RTD and drop into beads, taking away some heat affects the temperature difference between the two RTDs, thereby affecting the measurement accuracy. We used to install the flow element at an angle of 45° diagonally between the process line and the horizontal line (as shown in Figure 2). When liquid stays on the RTD, it rapidly spreads out along the RTD so that it does not collect in droplets and take away heat.
2) The process connector installation process is a 304 stainless steel connector with a circular column (see Figure 3). It must be ensured that the bottom surface S of the process connection head is parallel to the axis of the process line and the plane of L1, so as to ensure that the flow element crosses the center of the cross-section after the process connection head is inserted into the process pipeline, and is parallel to the cross-section.
First, according to the requirements of the installation location, mark a point O on the process pipeline. At both sides of the O point, use a line hammer to determine the tangential points A and A' of the vertical direction and the process pipeline (eg, flat view 4). Connect AA. ', A and A' for the AA' vertical line, from A and A' along its vertical downward marked 1/4 of the process pipeline perimeter position B and B', over O point for OO '⊥BB' at the point O', then O' point is the exact installation position of the flow element.
The OO' line is extended, and two points C and C' of equal distance are marked on the OO' and its extension lines from the O' point (as shown in FIG. 4). Open the hole at point O' and spot weld the process joint to point O'. With the aid of a square, the process connection head is adjusted so that its upper base surface S is parallel to the process line axis in the BB' direction. On the S surface, make L2 ⊥ BB' and the outer edge of the ring intersect at D, D' (see Figure 3). Adjust the process connector so that the length of the CD connection and C'D' connection is equal, and then solder the process connector. In this way, it is ensured that after the flow element is inserted into the process connection head, the cross section of the process pipeline is parallel and the cross-section of the cross-section is located at the center of the circle.
3) Installation of the flow element I. Calculate the 1/2 of the outside diameter of the pipe, plus 0.5 inch. Mark this length on the probe of the flow element (from the end of the RTD).
II. Insert the flow element fasteners into the process joints and tighten according to ANSI B16.5 torque specifications and use the appropriate sealant. The measuring process joints and the tightened fasteners are overall higher than the size of the pipe, and this length is marked on the first mark.
III. Insert the flow element and adjust its position so that the second mark is located on the flat surface of the fastener so that the flow element exceeds the centerline of the pipe by 0.5 inch; and the facet of the flow arrow is parallel to the flow direction of the process medium (±1 °), and point the arrows to the flow direction of the process media.
IV, confirm the above 3 steps are correct (because the metal collar is screwed into the flow element probe after tightening, the flow element can not make any adjustment), use a wrench to clamp the fastener, tighten the fastener bolts Twist 1.25 more turns so that the flow element is sealed and fixed in place.
4. Connections I, ST98 Mass Flow Meter User Manual The device description and wiring diagram indicate that the power supply is available for 24VDC or 220VAC, providing a connection terminal. Can be opened after the transmitter package found: ACONLY next to the terminal, so the input power can only use 220VAC.
II. ESD Warning Flow Transmitters contain Electrostatic Discharge (ESD) sensitive devices that require the use of standard ESD when opening packages or handling electronic circuit board devices WARNING: Use a megohm resistor with a ground, or a wrist strap, or knee Belts that keep high static electricity, such as non-ESD permitted plastics, tapes, and packaging plastics away from the equipment.
III. Grounding and Shielding For safety reasons, ST98 specifically requires 220 VAC power supply to use a three-wire system. One of the grounding wires must be connected to the ground terminal of the terminal block of the flow transmitter.
Due to the traditional 4 ~ 20mA I / O products are more sensitive to high-frequency noise generated by variable frequency drive equipment, and the site of high-frequency electrical noise pollution is more serious. To avoid interference to the signal transmission loop of the instrument, use shielded cables for the output signal cables. The shield layer is grounded near the transmitter. The DCS cabinet is wrapped and protected at one end. (In addition, the AC power grounding, DC power supply grounding, and cable The shield grounding and cabinet grounding are separated from each other in the cabinet, and the grounding net is independent of the factory lightning protection grounding net, etc.).
5. Commissioning Using an RJ-12 communication serial port provided by ST98 flow transmitter, it can communicate with FCI's FC88 communicator and PC's DB-9 or DB-25 interface for parameter setting of flow transmitter. Or modify, need to pay attention to the following several error-prone problems during debugging.
I. The flowmeter output data and the data measurement unit displayed by the DCS operation station should be unified, such as SCFM or NCMH, LB/HR or KG/HR.
II, flowmeter output data calibration and DCS control system to be consistent with the data calibration, such as 4 ~ 20mA, 0 ~ 20mA, 1 ~ 5VDC, 0 ~ 5VDC or 0 ~ 10CDC.
III. The electronic part of the flow meter uses a constant as a fitting curve parameter to display the flow value. This constant consists of 4 sections and is calculated based on the relevant parameters such as the percentage of various components (such as CO, O2, N2, and H2 in the refined gas) provided by the user in the process medium. Flowmeter manufacturers generally fix this constant in EEPROM before the equipment is shipped, and users cannot modify it. The user-supplied parameters are derived from the design theory values ​​of the design unit, and therefore have certain deviations from the actual site parameters. Therefore, the flowmeter will have a large error in practical applications. Therefore, such flowmeters of Masteel Coking Co., Ltd. have experienced serious deviations.
6. Concluding remarks Through on-site analysis and debugging of multi-technical personnel such as Wuye Automation Branch, equipment manufacturer and owner supervision, we highly appraised the details and the use of skills in the installation process, especially for flow components. The choice of orientation when inserting the process pipeline was fully affirmed by FCI. In fact, when the ST98 thermal insert-mount mass flow meter is used in a process gas that may contain moisture, etc., that can condense into liquid impurities, the flow element mounting orientation has been used with a 45° upward direction below the midline of the process line. FCI's user manual does not consider the medium containing impurities in the installation orientation of the equipment. Therefore, the original recommended installation method has not been corrected. FCI technical personnel has verbally recommended and supported the installation method used in this paper.
During the operation of the equipment, the error still exists seriously. After detailed analysis, it is considered that: The percentage content of various gases in the process medium previously provided by the owner is inaccurate. After sampling the gas, these parameters are sent to SANMARCOSFCI headquarters and the constants are recalculated. After the manufacturer's technical support personnel were newly set up, the measurement accuracy of the two ST98 mass flowmeters in the second gas purification plant of Masteel Coking Co. was controlled within ±1%, thereby avoiding the economy caused by inaccurate metering of the manufactured gas. loss.
This article uses a lot of space to explain the ST98 flow element on-site installation of some of the tips, especially the ESD warning and shielding grounding in the construction of the small details easily overlooked and debugging problems in the tuning process is easy to produce several aspects. I hope that when I install and debug similar instruments in the future, I can provide my colleagues with some experiences and lessons that we can learn from.
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