Contents 1. Starting up 1.1 Scope of delivery: 1.2 Reconditioning 1.3 Installing the ph probe 1.4 Installing the switch cabinet 1.5 Filling the electrolyte reservoir 1.6 Installing the reference electrode 1.7 Connecting the ph probe and the electrolyte reservoir 1.8 Connecting the compressed air 1.9 Venting the probe 1.10 Electrical connection 2. Operation and maintenance 2.1 Cleaning 2.2 Replenishing electrolyte 2.3 Electrolyte consumption 2.4 Impedance monitoring 2.5 Service interruptions 2.6 Recalibration 2.7 Single-point calibration 2.8 Two-point calibration 2.9 Replacing the electrolyte hose kit 2.10 Troubleshooting 2.11 Spare parts list Start-up and maintenance manual 920-2 e
Start-up and maintenance manual for a ph measuring system of Pfaudler Werke GmbH For more information concerning the construction, functioning, technical data and characteristic values, please refer to Operating Instructions 307. The present Operating Instructions are available in English, French and German language. 1.3 Installing the ph probe The ph probe must be installed in the relevant nozzle DN 50 together with a PTFE gasket DN 50. This gasket is included in the scope of delivery. The four M16 screws should be tightened cross-wise with a maximum torque of 30 Nm. If a glass lined ph probe is installed in a stainless steel tube with a welding neck fl ange, the internal edge of the fl ange must be chamfered in order to avoid damages to the glass at the probe fl ange when the gasket is pressed together (refer to Fig. 1). 1. Starting up 1.1 Scope of delivery: A ph measuring system made by Pfaudler normally consists of the following components: ph probe type 03/N, switch cabinet with built-in electrolyte reservoir and ph transmitter various accessories The ph transmitter will be programmed by Pfaudler with all necessary parameters and probe data. When the ph probe has been installed and supplied with electrolyte, compressed air and voltage, the ph measuring system is immediately ready for operation. 1.2 Reconditioning If the probe was left dry for a prolonged period of time (>4 weeks) prior to start-up, a measuring error of approx. 0.2pH may occur after start up which may be eliminated by reconditioning the probe. In order to recondition the probe, immerse the measuring electrode (yellow ph glass) for 5-10 h in puffer solution or slightly acidifi ed water. The protective cap should be used in order to recondition the probe. By reconditioning, a gel layer is built up on the surface of the measuring electrode. This gel layer is an important condition for stable and reproducible ph measurements. ATTENTION: If a glass lined ph probe is installed in a stainless steel tube with a welding neck fl ange, the internal edge of the fl ange must be chamfered in order to avoid damages to the glass at the probe fl ange when the gasket is pressed together. Pipe with fl ange ph-probe Chamfer Fig. 1: Assembly 2 Pfaudler GmbH
During installation or removal of the probe, please be careful not to hit the steel material as the glass would be damaged. 1.4 Installing the switch cabinet The switch cabinet should be installed vertically at the closest possible distance from the ph probe. The maximum distance from the probe is limited by the length of the ph connecting cable. 1.5 Filling the electrolyte reservoir Remove the front plug from the cover plate on the upper side of the elec-trolyte reservoir. The delivery in-cludes 3 PE bottles containing 1 liter of KCl electrolyte each. A draw tube closure is provided for draining the bottles. Fill the electrolyte reservoir with electrolyte by pressing the PE bottle with the draw tube closure fi tted; note max. fi lling level. After fi lling, turn plug back in and tighten it manually. Only Pfaudler electrolyte may be used in order to guarantee the faultless function of the probes for a long period of time and to avoid irreversible damages. Reason: Inhibitors are added to the Pfaudler electrolyte that reliably prevent glass corrosion. 1.6 Installing the reference electrode The reference electrode is supplied in a light- and water-tight protective sleeve fi lled with electrolyte. This sleeve is held by a clip in the switch cabinet. Remove the yellow plug from the cover plate on top of the electrolyte reservoir and turn the reference electrode into this threaded hole. Plug the connector on the ref-erence electrode cable that is in-stalled inside the switch cabinet onto the head of the reference elec-trode. 1.7 Connecting the ph probe and the electrolyte reservoir A 10 m hose made of synthetic material 6 x 1 mm is included in the delivery. Cut this hose to the desired length and guide it through the cable gland located below the electrolyte reservoir into the switch cabinet. Attach the hose ends to the threaded hose couplings of the probe head and the ball valve in the lower part of the electrolyte reservoir. If possible, do not use any tools for this work in order to avoid damages. 1.8 Connecting the compressed air and adjusting the air pressure A bulkhead stuffi ng box has been provided in the lower left part of the switch cabinet. The compressed air supply must be connected to this box using a 6 x 1 mm hose. Adjust the necessary operating pressure at the pressure reducer in the upper left part of the switch cabinet. The pressure must exceed the maximum process pressure occurring by 1 bar. A rotary handle and a pressure gauge on the pressure reducer are used to set the pressure. The maximum permissible pressure in the electrolyte reservoir is 10 bar. 1.9 Venting the ph probe Apply compressed air to the electrolyte reservoir and open the ball valve on the electrolyte reservoir in order to let electrolyte fl ow into the ph probe. There is a venting plug with a hose nipple on the probe head. Connect a hose to the nipple and turn the venting plug open until electrolyte emerges without bubbles. Collect any spilt electrolyte in order to prevent the formation of conductive earth links. In the event that electrolyte was spilt over the probe head, the probe head must be cleaned with water. 1.10 Electrical connection An intrinsically safe ph transmitter in two-conductor design is included in the switch cabinet. This transmitter must be connected to an intrinsically safe isolation amplifi er to be installed in the explosion-free area. The cable is introduced to the switch cabinet through a cable gland and directly connected inside the transmitter. For a detailed wiring diagram, please refer to the document set. Please observe the relevant installation and safety instructions with respect to the connection of the transmitter. The blue ph connection cord was connected to the ph transmitter and routed out of the switch cabinet prior to delivery. Plug the male connector of the ph connection cord into the female connector in the terminal box of the ph probe. In order to protect the plug connection against moisture and mechanical damage, it is important to push the protective sleeve over the plug and tighten the spiral screw connection. Connect the ground lug on the fl ange with the equipotential bonding system of the plant; minimum cross-section 6 sqmm. 2. Operation and maintenance 2.1 Cleaning Glass is largely insensitive to contamination. Depending on the product properties, it will be suffi cient to check the measuring electrode (yellow ph glass) and the glass puck for product traces at certain time intervals. When you observe measuring errors or a slow setting behavior, the probe must be cleaned. In most cases, contaminated areas can be cleaned with water, a solvent or a liquid, non-abrasive detergent for stainless steel products. Do not use any metallic or abrasive materials. A 5-10 % acid such as HCl may be used to remove deposits or product fi lms, if the probe is previously removed from its place of installation Pfaudler GmbH 3
and cleaning is carried out at ambient temperature. Do not use any fl uorinecontaining acids because they strongly attack glass. When handling acids, please make sure to observe the accident prevention regulations applicable to hazardous substances and their use. 2.2 Replenishing electrolyte In order to ensure faultless operation of the measuring probe, the electrolyte reservoir must always be fi lled with a suffi cient quantity of electrolyte. The end of the reference electrode must always be immersed in the electrolyte, otherwise, the measuring loop will be interrupted. Close the electrolyte valve at the bottom of the electrolyte reservoir Switch off the air supply. Carefully turn out the fi lling plug on top of the electrolyte reservoir because the reservoir is still pressurized, and the excess pressure fi rst has to escape. Fill the electrolyte reservoir with electrolyte through the fi lling hole up to the level mark (maximum level 1.7 liters) (refer to 1.5). To restart the unit, proceed in reverse order. Only Pfaudler electrolyte may be used in order to guarantee the faultless function of the probes for a long period of time and to avoid irreversible damages. Reason: Inhibitors were added to the Pfaudler electrolyte that reliably prevent glass corrosion. 2.3 Electrolyte consumption If a difference of 1 bar is maintained between the process pressure and the pressure inside the electrolyte reservoir, electrolyte is consumed at a rate of approx. 0.05 to 0.1 ml/h. If a higher differential pressure is present, the consumption may rise to 5 ml/h. We recommend contacting our measuring technology department if a higher consumption is noticed. 2.4 Impedance monitoring Impedance monitoring of the measuring electrode (yellow ph glass) has been set to the following values in the ph transmitter: R min 10 MΩ R max 500 MΩ If one of the two limit values is reached, an alarm is output by the ph transmitter. The way in which the alarm is signaled depends on the type of equipment and the individual confi guration. 2.5 Service interruptions If a probe is immersed in a fl uid to be measured, the ph transmitter must not be disconnected from mains for more than 5-10 hours. Otherwise, polarization on the measuring electrode may result in a zero drift and the need for calibration. Where longer disconnection is necessary, it is important to disconnect the measuring circuit at the probe either by removing the plug from the reference electrode or at the probe s terminal box. In the event of long service interruptions, the ph probe may remain inside the system. Dry storage basically does not affect the function of the probe. Its characteristics are maintained in any case. However, the zero point and slope may be subject to slight change which may result in a measuring error of 0.2 ph max in the event of longer service interruptions. This error can be corrected by reconditioning the probe (refer to Sect. 1.1). If the probe is used again for 1-2 hours, the error will also disappear. 2.6 Recalibration Since glass lined ph probes are not subject to aging, recalibration is actually necessary only if a measuring error is suspected or if calibration intervals have been prescribed. However, we recommend checking the condition and measuring accuracy of the probe after approx. 6 months through single-point calibration. It is entirely suffi cient and most practical to perform single-point calibration inside the product because the probe need not be removed for this purpose. Single-point calibration inside the product is also referred to as product or sample calibration. The general process of single-point calibration is described in the next section. 2.7 Single-point calibration For single-point or product calibration, the ph value of a product sample is measured using an external ph measuring device. This external ph value is entered into the ph transmitter and compared to the internal value stored there. A possible deviation must be balanced by zero adjustment. Single-point calibration is performed while the probe is installed. Calibration process Activate the Single-point calibration mode on the ph transmitter (depending on the transmitter model, this mode is also referred to as product or sample calibration). Store the current ph value (this is done automatically or manually, depending on the type of equipment). Now take a sample from the process as soon as possible and measure the ph value of the sample using a 4 Pfaudler GmbH
manual device or in the lab (= sample ph). Please note that the sample ph is temperature-dependent and/or may be infl uenced by the evaporation of volatile substances. Therefore, the sample ph should be measured as soon as possible. Then enter the sample ph into the ph transmitter and exit the singlepoint calibration mode. When exiting this mode, the sample ph is compared to the value stored in the beginning of the process, and possible deviations are compensated by zero adjustment. For details concerning the operation of the relevant ph transmitter, please refer to the manufacturer s operating instructions. 2.8 Two-point calibration Two-point calibration is performed if a measuring error is suspected, or if the accuracy of the measurement is to be optimized. For a two-point calibration, the ph probe must be removed from the application and immersed into two different buffer solutions one by one. The voltage measured by the ph transmitter must be allocated to the ph value of the individual buffer solutions. Based on the two voltages, the slope and zero point values will be recalculated by the transmitter. Afterwards, ph measurements are performed by the transmitter using the updated values thus obtained. We recommend using buffer solutions ph 3 and ph 7 for two-point calibration. The fi rst measurement should be carried out using the buffer solution with the lower ph value. The black protective cap included in the delivery may be used as calibration cup that holds the buffer solution (without the rubber inserts). At minimum of 250 ml are required of each buffer solution. In order to avoid disturbances caused by static charges and to detect possible insulation faults, the buffer solution must be grounded. The buffer solution is grounded by connecting a wire between the solution and the equipotential bonding system. Calibration process Remove the ph probe, clean and rinse it with distilled water. Immerse the ph probe in the calibration cup holding buffer solution ph 3. The yellow ph glass must be fully immersed; remove possible bubbles on the diaphragm by shaking the cup shortly. Connect the buffer solution to ground potential. Prior to the actual two-point calibration, you fi rst have to verify whether or not an insulation fault exists in the measuring circuit using the following method: The ph value must not change by more than + 0.1 ph when the ground wire is removed from the buffer solution. In the event of greater deviations, an insulation fault may be present in the measuring circuit, and the ph probe or the entire ph measuring system must be checked for insulation faults. Activate the Two-point calibration mode on the ph transmitter. (depending on the type of equipment, this mode may also have a different name). Enter the ph value of the fi rst buffer solution, ph 3.0, in the ph transmitter. When the measured value displayed has become stable, fi nish the 1 st calibration step (this is done automatically or manually, depending on the type of equipment). Then rinse the ph probe and the calibration cup with distilled water. Immerse the ph probe in the calibration cup holding buffer solution ph 7. The yellow ph glass must be fully immersed; remove possible bubbles on the diaphragm by shaking the cup shortly. Connect the buffer solution to ground potential. Enter the ph value of the second buffer solution, ph 7.0, in the ph transmitter. When the measured value displayed has become stable, fi nish the 2 nd calibration step (this is done automatically or manually, depending on the type of equipment). Terminate the two-point calibration mode. The measuring chain zero and slope values have been updated. For details concerning the operation of the relevant ph transmitter, please refer to the manufacturer s operating instructions. 2.9 Replacing the electrolyte hose kit We recommend replacing the electrolyte hose kit approx. once per year in order to prevent clogging of the electrolyte system. The electrolyte hose kit consists of a thin PTFE hose with a special integrated thread and an external sealing sleeve with O-rings. The hose can be replaced while the probe is installed. However, no process pressure may be present because otherwise product could enter the diaphragm gap and contaminate the diaphragm. Pfaudler GmbH 5
Assembly instructions 1 Close the ball valve at the electrolyte reservoir. 2 3 Carefully open the venting plug on the probe head to relieve the internal pressure; then close the venting plug. Remove the 4 probe head screws and take off the pressure fl ange. It is not necessary to remove the connecting hose. 5 6 Cut new PTFE hose diagonally to the proper length Make sure to cut the hose from 2 sides in order not to cut the internal thread. Use the old hose to determine the right length. The diagonal cut, the right length and a longer thread are important in order to ensure continuous fl ow in the electrolyte system. 4 Pull the electrolyte hose kit from the gasket seat using pointed pliers. If necessary, clean the pressure fl ange and probe head from electrolyte residues using demineralized water and dry parts afterwards. 6 Pfaudler GmbH
7 8 9 Grease sealing elements and gasket seat in the probe head with silicon or Vaseline. Push the electrolyte hose kit into the probe. Press gaskets into the gasket seat. Open the ball valve at the electrolyte reservoir. Vent probe. Connect a hose to the nipple at the venting plug and open venting plug until electrolyte emerges without bubbles. Collect any spilt electrolyte in order to prevent the formation of conductive earth links. In the event that electrolyte was spilt over the probe head, the probe head must be cleaned with water. The ph probe is now ready for use. 10 Place the pressure fl ange on the probe head, turn in the screws and tighten them crosswise. Pfaudler GmbH 7
2.10 Troubleshooting Malfunction Cause Remedy Display oscillates Air bubbles in electrolyte line Vent probe, refer to Sect. 1.8 Display remains at 0 or full scale Electrolyte hose clogged Replace electrolyte hose kit, refer to Sect. 2.9 Deposits inside the diaphragm Measuring circuit interrupted Reference electrode not immersed in electrolyte Increase pressure to max. 10 bar and rinse the electrolyte system by venting the probe, refer to Sect. 1.8 Cable in terminal box or ph cable broken Connector not connected to reference electrode Replenish electrolyte, refer to Sect. 2.2 Display drifts Deposits on measuring electrode Clean probe, refer to Sect. 2.1 Moisture in measuring circuit Dry terminal box and ph cable using hot air blower or in hot cabinet at max. 60 C. Replace the electrolyte hose kit 8 Pfaudler GmbH
2.11 Spare parts list Spare parts for rod probe type 03/04 ph pressure fl ange, complete (only for type N) Straight male union with O ring DN 6/8, G 1/4, made of PVDF, natural ph probe head, complete Venting plug on probe head M24 made of PVDF, white O-ring for venting plug 12 x 3 mm made of Viton A Part no. 591 362-025 142-591 270-591 122-024 163D Terminal box (< DN100) made of aluminum 591 014- Rubber gasket for terminal box 591 015D Connection adapter, complete 595 610- Cover for terminal box made of aluminum 029 442- Rubber gasket for cover 591 082D Explosion-proof ground terminal M5 029 422- Electrolyte hose kit for probe length 300 mm 591 8931 Electrolyte hose kit for probe length 450 950 mm 591 8932 Protective cap, complete, for probe diameter 38 mm, made of PE black 591 076- Spare parts for electrolyte reservoir type N Part no. Electrolyte reservoir type N, 1.7 liters, complete, without isolation amplifi er 255 294- Connector and cable for reference electrode 591 368- Venting plug M10, length 45 mm, made of POM, black 591 885- O-ring for venting plug 9 x 2 mm made of Viton A 024 268D Shut-off valve with non-return valve, G1/4, M8, made of PVDF, white 595 719- O-ring for venting plug 6 x 3 mm made of Viton A 024 381D Cup P4-25 made of PC, transparent yellow 029 133- Connection cover 591 891- O-ring for connection cover 120 x 4 mm made of Viton A 024 123- Hose 6 x 1 mm, length 10 m, made of PA11, transparent Ball valve, consisting of: Connection nipple G1/4 made of PVDF, white O-ring for connection nipple 12 x 2 mm made of Silicone O-ring 10 x 2 mm made of Viton A PTFE disk 2-port directional control ball valve, complete, DN 4, G1/4, made of PVDF, natural Straight male union with O ring DN 6/8, G 1/4, made of PVDF, natural 029 359D 254 952-029 729-024 105D 595 870-029 137-025 142- Pfaudler GmbH 9
Connection cable for Pfaudler probes
The information provided in this documentation corresponds to the state of the art at the time of printing. It is published in good faith. However, we will accept no warranty claims based on the information provided in this documentation. We reserve the right to include improvements, amendments and new findings in this documentation without prior notice. The actual design of products may deviate from the information contained in the calatoge if technical alterations and product improvements so require. The proposal made by Pfaudler for a concrete application will be binding in such cases. The present documentation is made available free of charge to our customers and other interested parties. The right to print or copy this documentation, or any parts there of, or to convert the same into electronic form shall be subject to our written permission. All rights reserved by us. Pfaudler GmbH P.O. Box 1780 D-68721 Schwetzingen Pfaudlerstraße D-68723 Schwetzingen Phone +49 6202 85-233 Telefax +49 6202 85-273 E-mail info@pfaudler-instrumentation.com www.pfaudler-instrumentation.com