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A-8

Appendix A

Model 752 and 752A Differential Pressure Transmitters

DPU Below Tank with Reference Leg: Hot or Cool Liquids

The use of a reference leg cancels out the "dead leg" (piping from the tank

bottom to center line of meter body). Seal fluid in the reference leg must not

volatilize. Process media can be used as a reference leg seal fluid if it will

condense in the reference leg under all conditions. Otherwise, special, immis

cible seal fluid must be used. Differences in densities of process media and

seal fluid must be considered when computing the differential pressure range

of a DPU.
1.

Partially fill the reference leg by opening the bottom block valve, both

shutoff valves, and the bypass valve.

2. Crack the drain valves on the DPU housing and vent the DPU. Close

when clear, bubble-free liquid flows.

3. Close the bypass and shutoff valve on the reference leg.

4. Remove the plug from the top port in the 2-inch pipe cross connection,

and fill the reference leg manually.

Open the reference leg shutoff valve and crack the vent valve until

bubbles are expelled. Leave the reference leg full.

6. Replace the plug in the pipe cross and close the vent valve.

7. Slowly open the upper block valve.

HIGH-PRESSURE

SHUT-OFF

VALVE

REFERENCE

LEG

2" CROSS

BYPASS

VALVE

VENT

VALVE

BLOCK

VALVE

BLOCK

VALVE

DPU

SHUT-OFF

VALVE

DRAIN VALVE

Figure A.7—DPU Below Tank with Reference Leg

Содержание Barton 752

Страница 1: ...heory of Operation 9 Basic Components 9 Differential Pressure Unit DPU 9 Electronic Transmitter 11 Basic Operation 11 Surge Voltage Protection Circuit 11 Reverse Polarity Protection 11 Regulator 11 Strain Gage Bridge Network 12 Signal Amplifier 12 Current Amplifier 12 Temperature Compensation 12 Section 3 Installation Startup and Shutdown 13 Overview 13 Unpacking Inspection 13 Initial Calibration ...

Страница 2: ...tenance 19 General Field and Periodic Maintenance 19 Electronic Transmitter 19 Differential Pressure Unit DPU 19 Calibration 19 Electrical Connections for Calibration 20 Calibration Checkpoints 21 Calibration Procedure 21 DPU Inspection and Cleaning 22 Troubleshooting 23 Section 5 Assembly Drawing and Parts List 27 Section 6 Dimensional Drawings 31 Appendix A A 1 Safety Precautions A 1 Flow Applic...

Страница 3: ...p ment The instrument utilizes miniaturized hybrid electronic circuits and a molecular bonded strain gage sensing cantilever beam actuated directly by the bellows travel within the DPU In many applications the electrical con nections are contained within a junction box as shown in Figure 3 1 page 15 However the junction box is optional Differential Pressure Unit The mechanical actuating device for...

Страница 4: ...wer supply specified at 50 VDC 1 volt must be considered a 49 VDC source to insure the minimum required voltage at the transmitter Use the actual value when available Otherwise use the worst case value For power supply wiring instructions refer to the electrical connections shown in Figures 3 1 and 3 2 page 15 Zero and Span Control The transmitter has two 10 turn potentiometers one for zero adjust...

Страница 5: ...ange 0 30 inches water column to 0 500 psid Consult factory for other ranges Output 4 20 mA or 10 50 mA direct or reverse acting Reference Accuracy 0 5 of factory calibrated span including effects of non linearity hysteresis and repeatability 0 25 accuracy optional Zero Span Adjustments Combined zero span field adjustments are limited to 5 of factory calibrated span See Zero Suppres sion and Custo...

Страница 6: ... 200 500 psid range 1 0 of factory calibrated span per 1000 psig Overpressure Effects 1 30 psid range 0 5 of factory calibrated span per 1000 psig 30 200 psid range 1 5 of factory calibrated span per 1000 psig 200 500 psig range 3 0 of factory calibrated span per 1000 psig Overpressure limit Up to 3000 psig on either side of DPU without damage to unit Process Connections 1 4 and 1 2 NPT female on ...

Страница 7: ...alification The Model 752 and 752A transmitters have been subjected to IEEE 344 qualification testing that demonstrates that the unit will not lose its pressure boundary or structural integrity when subjected to loadings associated with seismic accelerations up to 12 Gs ...

Страница 8: ...8 Section 1 Model 752 and 752A Differential Pressure Transmitters ...

Страница 9: ... beam which is actuated directly by the valve stem connect ing the two bellows If the bellows are subjected to a pressure greater than the differential pressure range of the DPU they will move through their normal range of travel plus a small additional amount of overtravel until the valve on the stem shaft seals against its valve seat As the valve closes on the seat it traps the fill liquid in th...

Страница 10: ...s steel sheets The diaphragms are assembled and seam welded to form the bellows Strain Gage Assembly The strain gage assembly Figure 2 2 consists of a strain gage beam and a glass to metal seal feed through assembly Strain gages are bonded to opposite sides of the strain gage beam The end of the strain gage beam is installed directly into a cutout in the valve stem con necting the two bellows of t...

Страница 11: ...ries The current from the power supply enters the transmitter passes through the reverse polarity protecting diode then divides into two separate paths The main current flows through the current amplifier stage and returns to the loop The remainder of the current passes through the electronic regulator where it divides into two paths through the bridge circuit and the voltage amplifier The current...

Страница 12: ... integrated circuit operational amplifier which pro vides amplification of the strain gage bridge network output voltage Current Amplifier The current amplifier circuit converts the signal amplifier output voltage to current The amount of current is precisely regulated with the feedback net work to make it proportional to the bridge output Temperature Compensation The Model 752 and 752A are temper...

Страница 13: ...nitial Calibration Check The Model 752 and 752A transmitters are factory calibrated However to ensure that the calibration is intact following shipping a calibration check is recommended prior to operating the instrument See Calibration page 19 for step by step instructions Record the as found values and recalibrate if necessary Mounting Mount the transmitter so that the pressure housings are in a...

Страница 14: ...eet of uninsulated piping between the transmitter and the primary metering device for each 100 degrees in excess of 135ºF 4 Install a suitable pulsation dampening device upstream of the transmitter Where severe pulsation is present the accuracy of the flow measurement will be affected 5 For ease of operation and maintenance install manifolds to allow sensing lines to be shut off while removing the...

Страница 15: ...all a load resistor sized for the application WARNING Failure to properly calculate power supply DC output voltage may result in inaccurate transmitter readings possibly leading to safety system performance degradation during design basis events To avoid equipment inaccuracy hazards follow the examples and tables in this section for determining the proper power supply DC output voltage GND Receive...

Страница 16: ...t be exercised when calculating the power supply output voltage A power supply specified as 50Vdc 1 volt must be considered a 49Vdc source to ensure the minimum required voltage at the transmitter Use the actual value when available otherwise use worst case value Use Figure 3 3 as a reference to determine if the maximum calculated value of RT RLine RLoad RExt is correct Loop Resistance Calculation...

Страница 17: ...nal An optional EMI RFI filter is available upon request Contact the factory for information The following precautions are recommended to limit EMI RFI interference 1 Run signal wires in solid conduit or use high quality shielded cable to connect the transmitter to the power equipment 2 House the transmitter leads in solid conduit up to the junction box where the shielded cable is connected to the...

Страница 18: ...justment of the zero and or span is necessary perform all 12 steps described in the Calibration Procedure page 21 6 Check the manifold and piping for leaks as follows a Open the bypass valve s then open one shutoff valve to pressurize the instrument b Close the shutoff valve and the bypass valve c Any leakage will be indicated by a change increase or decrease in the transmitter output NOTE Be care...

Страница 19: ...i bration check is recommended upon receipt and again before the transmitter is operated for the first time If as found values are not within the specified range a full calibration should be performed The transmitter should be recalibrated at periodic intervals determined primarily by the usage of the transmitter historical performance the desired accuracy of the output signal or indications that ...

Страница 20: ... is secure before applying power to instrument when used in hazardous areas Failure to do this may result in personal injury or property damage GND Precision DC Voltmeter Power Supply Load Resistor 500 ohms 4 20 mA systems 200 ohms 10 50 mA systems Model 752 752A Milliammeter optional Figure 4 1 Electrical connections for calibration Flexible cable is recommended for electrical connections to the ...

Страница 21: ...put 4 20 mA Transmitter 10 50 mA Transmitter Current 0 08 mA Voltage 0 04 Vdc Current 0 2 mA Voltage 0 04 Vdc 0 4 mA 2 Vdc 10 mA 2 Vdc 25 8 mA 4 Vdc 20 mA 4 Vdc 50 12 mA 6 Vdc 30 mA 6 Vdc 75 16 mA 8 Vdc 40 mA 8 Vdc 100 20 mA 10 Vdc 50 mA 10 Vdc This value includes the effects of conformance non linearity deadband hysteresis and repeatability This value was obtained using a 500 ohms load resistor T...

Страница 22: ...ometer as required to produce the recommended output level 9 Repeat steps 7 and 8 until no further refinements can be made 10 Apply the calibration pressures referred to in Table 4 2 page 21 starting from 0 to 100 and record the applied pressures and the output levels at each measurement 11 Repeat the calibration checks in descending order from 75 to 0 and record the applied pressures and the outp...

Страница 23: ...he transmitter should be returned to the factory for repair or replacement Table 4 3 DPU Troubleshooting Problem Possible Source Probable Cause Corrective Action Low or No Output Primary Element or DP Source Orifice installed backwards or oversized Flow blocked upstream from run Density changes in process media or ref leg Replace orifice Clean out run or open valve Refill reference leg with same d...

Страница 24: ...e spring broken or body tampered with Vent housing Replace gasket Return unit for repair Erratic or Intermittent Operation Primary Element Flow pulsating Install dampening device upstream of meter run Piping from Primary Element to Transmitter Liquid trapped in gas piping or gas bubble in liquid piping Vapor generator installed wrong Reference leg gassy or liquid vaporizing Remove trapped liquid o...

Страница 25: ...tter zeros but cannot get full output Power Source Low voltage Repair power source Load Resistance Resistance too high Replace load resis tance or repair as required Transmission Cable Resistance or length of cable in excess of specifications Measure cable loop resistance and bring within specifications Electronic Module Amplifier Loss of gain Return to factory for repair Out of Calibration Electr...

Страница 26: ...26 Section 4 Model 752 and 752A Differential Pressure Transmitters ...

Страница 27: ...27 Model 752 and 752A Differential Pressure Transmitters Section 5 Section 5 Assembly Drawing and Parts List Figure 5 1 Model 752 and 752A front view ...

Страница 28: ...52 circuit board assembly 4 to 20 mA replacements no longer available 9A C0752 1056B 1 Model 752 circuit board assembly 10 to 50 mA replacements no longer available 9A C0752 1070B Model 752A circuit board assembly 4 to 20 mA 9A C0752 1269B Model 752A circuit board assembly 10 to 50 mA 9A C0752 1270B 4 Shaft and spring assembly 9A C0752 1100B 2 6 O ring EPT E740 75 3 8 x 1 2 9A C0001 1051R 2 7 Moun...

Страница 29: ...ng EPT E740 75 11 16 x 13 16 9A C0001 1130R 2 31 Terminal bracket 9A C0752 1112C 1 32 Pan head screw 8 32 x 1 4 SST 9A C0119 0006J 2 33 Marker strip 9A C0752 1113C 1 34 Terminal block 9A C0038 1170T 1 35 Pan head screw 8 32 x 1 2 SST 9A C0119 0005J 2 36 Conduit hub 9A C0024 1006T 2 37 Drain plug 9A C0186 0001T 1 38 Wire assembly black 9A C0752 1120B 1 39 Wire assembly red 9A C0752 1119B 1 40 Port ...

Страница 30: ...30 Section 5 Model 752 and 752A Differential Pressure Transmitters ...

Страница 31: ...2A Differential Pressure Transmitters Section 6 Section 6 Dimensional Drawings Figure 6 1 Model 752 and 752A transmitters with junction box front view Figure 6 2 Model 752 and 752A transmitters with junction box side view ...

Страница 32: ...32 Section 6 Model 752 and 752A Differential Pressure Transmitters Figure 6 3 Model 752 and 752A transmitters rear view ...

Страница 33: ...ted to the upstream tap of the primary device Note To prevent overheating the DPU during blowdown monitor the tem perature by placing your hands on the pipe between the DPU and the manifold pipe containing the vent valves Liquid Level Applications The process media may be used as a reference leg seal fluid when it is of a type that will condense in the reference leg under all conditions If the pro...

Страница 34: ...ck valve to pressurize DPU then close the block valve 3 Close one bypass valve and check the system for leaks If output travels upscale check for low pressure piping leaks If output travels downscale check for high pressure piping leaks 4 Repair piping if necessary and repeat steps 1 through 3 until output remains stable at zero 5 Close both shutoff valves and open the bypass valve s 6 Open both b...

Страница 35: ... output travels upscale check for low pressure piping leaks If output travels downscale check for high pressure piping leaks 4 Repair piping if necessary and repeat steps 1 through 3 until output remains stable at zero 5 Close both shutoff valves and open the bypass valve s 6 Open both block valves and slowly open both shutoff valves 7 Close the bypass valves and if two bypass valves are used open...

Страница 36: ... and one block valve to pressurize the DPU then close the block valve 3 Close one bypass valve and check the system for leaks If output travels upscale check for low pressure piping leaks If output travels down scale check for high pressure piping leaks 4 Repair piping if necessary and repeat steps 1 through 3 until output remains stable at zero 5 Close the bypass valves If two bypass valves are u...

Страница 37: ...s until the piping and the DPU housings are filled Piping and housing chambers shall be free of bubbles The pointer should rest at zero or output will be 4 mA or 10 mA as applicable when the instrument and piping are completely filled 4 Install the side and fill plugs in the reservoirs 5 Close the shutoff valves and open the block valves 6 Slowly open both shutoff valves simultaneously and check f...

Страница 38: ...d close the shutoff valves alternately until liquid is free of bubbles and spills out of both upper DPU body ports 4 Close the vent valves or tighten the plugs Close the block valves and open the shutoff valves 5 The pointer should rest at zero or output will be 4 mA or 10 mA as ap plicable If it does not and no leaks are detected the housing and or pip ing are not completely filled with liquid Re...

Страница 39: ...n the shutoff valves 5 The pointer should rest at zero or output will be 4 mA or 10 mA as ap plicable If it does not and no leaks are detected the housing and or pip ing are not completely filled with liquid Repeat steps 1 through 4 until the output is stable at the lowest value 6 Slowly open both bl ock valves and close the bypass valve 7 For service with hot or gassy liquids fill both sides of t...

Страница 40: ...of a DPU 1 Partially fill the reference leg by opening the bottom block valve both shutoff valves and the bypass valve 2 Crack the drain valves on the DPU housing and vent the DPU Close when clear bubble free liquid flows 3 Close the bypass and shutoff valve on the reference leg 4 Remove the plug from the top port in the 2 inch pipe cross connection and fill the reference leg manually 5 Open the r...

Страница 41: ...utoff valves 2 Crack open the DPU low pressure drain valve and close it when liquid stops flowing from it 3 Crack open the DPU high pressure vent valve and close it when bubble free liquid flows from it DRAIN VALVE BLOCK VALVE HIGH PRESSURE DPU BLOCK VALVE SHUT OFF VALVE VENT VALVE SHUT OFF VALVE Figure A 8 Cool Non Condensing Liquid DPU Level with Tank Bottom ...

Страница 42: ...es and shutoff valves 2 Crack open the DPU low pressure drain valve and close it when liquid stops flowing from it 3 Crack open the DPU high pressure drain valve and close it when bubble free liquid flows from it HIGH PRESSURE SHUT OFF VALVE BLOCK VALVE DRAIN VALVE DPU SHUT OFF VALVE BLOCK VALVE Figure A 9 Cool Non Condensing Liquid DPU Below Tank ...

Страница 43: ...FOREGOING WARRANTY IS IN LIEU OF AND EXCLUDES ALL OTHER EXPRESSED OR IMPLIED WARRANTIES OF MERCHANTABILITY OR FIT NESS FOR A PARTICULAR PURPOSE OR OTHERWISE 2 Components manufactured by any supplier other than Cameron shall bear only the warranty made by the manufacturer of that product and Cameron assumes no respon sibility for the performance or reliability of the unit as a whole 3 In no event s...

Страница 44: ...2 7700 ms me c a m com LATIN AMERICA 55 21 2172 9714 ms latinamerica c a m com ASIA PACIFIC 603 7954 0145 ms kl c a m com INDIA 91 982 2431686 ms ind c a m com HEADQUARTERS HOUSTON TX 1 281 582 9500 EUROPE CASPIAN RUSSIA S AFRICA 44 1892 518000 ms uk c a m com UNITED STATES 1 800 654 3760 ms us c a m com ...

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