ph Probe type ph Reiner

Transcription

1 Contents 1 Preface 2 General instructions 2.1 Operating range 2.2 Warnings contained in the operating instructions 2.3 Notes on deliveries 2.4 Transport and storage 2.5 Warranty notes 2.6 Notes on return deliveries 2.7 Glass Testing 3 Safety 3.1 Proper use 3.2 Qualified personnel 4 Technical description 4.1 Features and properties 4.2 Measuring principle 4.3 Construction and function 4.4 Electrolyte reservoir 4.5 Reference electrode 4.6 Electrolyte 4.7 Thread adapter 4.8 Installation adapter 4.9 Technical data 5 Technical characteristics of measurement 5.1 Slope of the measuring chain 5.2 Zero point of the measuring chain 5.3 Intersection of isotherms 5.4 Resistance of the measuring chain 5.5 Diaphragm resistance 5.6 Measuring variance 5.7 Alkali error 5.8 Time response to ph change 5.9 Time response to temperature changes 6 Application limits 6.1 Chemical resistance 6.2 Temperature 6.3 ph range 6.4 Pressure 6.5 Inappropriate products 7 Installation and electrical connection of the probe 7.1 Installation of the probe 7.2 Installing the electrolyte reservoir 7.3 Electrical connection of the probe 7.4 Equipotential bonding 7.5 ph Reiner connection cord 7.6 List of ph transmitters approved by Pfaudler 8 Start-up and calibration 8.1 Preliminary note 8.2 Reconditioning the probe 8.3 Disinfecting the electrolyte system 8.4 Filling the electrolyte reservoir and venting of the probe 8.5 Setting the ph transmitter parameters 8.6 What is meant by calibration? 8.7 Calibration methods 8.8 Calibration by data input at the ph transmitter 8.9 Two-point calibration 8.10 Single-point calibration 8.11 Automatic calibration 8.12 Compressed air setting 9 Operation and maintenance 9.1 Recalibration 9.2 Replacing the electrolyte bottle 9.3 Electrolyte consumption 9.4 Cleaning and sterilization of the probes 9.5 Troubleshooting 9.6 Spare parts list Annex A Installation adapter assembly TYPE EL AUGUST 2006 Operating Instructions e

2 1 Preface These operating instructions are designed to familiarize users with the equipment of the ph probe and its use. The operating instructions should be accessible to the operating and maintenance personnel in order to ensure that all necessary information is available for any assembly and maintenance work. By knowing these operating instructions, you can avoid damage to the measuring equipment and ensure trouble-free operation. The information contained in these operating instructions corresponds to the state of the art at the time it is printed and is provided to the best of our knowledge. We reserve the right to include any improvements, amendments and new developments in the operating instructions without prior notice. The actual design of products may differ from the information provided in the operating instructions if warranted by technical modifications resulting from product improvements. The proposal submitted by Pfaudler for a concrete application will be binding in this case. The latest edition will always supersede all previous ones. The present operating instructions are made available to our customers and interested parties free of charge. Reprints and copies as well as transformation into electronic forms, in whole or in part, shall require our written approval. All rights reserved. 2 General instructions 2.1 Operating range The glassteel ph Reiner probes are used to measure the ph value of a solution. The ph value is a measure of the strength of an acid or an alkali solution. The ph Reiner probe can be installed directly in a pipeline or a reactor. Please refer to our publications 206 and 615 for details concerning the resistance of glass. m Never operate this measuring device outside its permissible operating conditions. 2.2 Warnings contained in the operating instructions m In these operating instructions, the danger symbol is used to draw your attention to especially important safety instructions. Compliance with these instructions is mandatory, because adherence to the instructions can avoid severe damage to people and/or equipment. 2.3 Notes on deliveries The respective scope of delivery is specified on the shipping documents attached to the shipment and corresponds to the valid purchase agreement. Check that the items delivered are complete and intact. If possible, keep the packing material for re-use for possible return shipments. 2.4 Transport and storage The probe should only be transported and stored in its closed original packaging, if possible. Where this is not possible, the probe must be protected against shock and impacts. In order to guarantee an as-new condition of the probe, maintain the following storage conditions: dry and dust-free as well as steady temperature and ventilation. The probes do not need any preservatives, they are resistant to normal environmental influences. If it is to be stored for prolonged periods of time, the probe must be protected from drying out. For this purpose, the bigger protective cap provided must be filled with demineralized water and fitted to the probe tip. The small protective cap provided must be fitted to the hose connector at the probe tip. In the event of prolonged service interruptions, the probe may also remain inside the empty container or the empty pipeline. However, the electrolyte reservoir must remain connected and pressurized for this purpose. Dry storage basically does not affect the function of the probe. Its characteristics are maintained in any case. However, the zero point may be subject to slight change which may result in a measuring error of 0.2 ph max. This error can be corrected by reconditioning the probe (refer to Sect. 8.2). During operation of the probe, this error will also disappear after a few hours. If a probe is immersed in liquid (product), the ph transmitter must not be disconnected from mains for more than 1-2 days. Otherwise, polarization at the measuring electrode may result in a zero drift which may eventually be outside the setting range of the ph transmitter. Where longer disconnection from mains cannot be avoided, the measuring circuit must be interrupted. This can be achieved by unscrewing the connector from the probe or separating the connection at the transmitter. 2 Pfaudler Werke GmbH OI e

3 2.5 Warranty notes Any warranty claims shall not be extended or limited by the information contained in the present operating instructions. For the exact warranty conditions, please refer to the Terms of Sale of Pfaudler Werke GmbH as amended. 2.6 Notes on return deliveries Before sending used probes to Pfaudler Werke GmbH or third parties for repair or other purposes, all parts must be cleaned and decontaminated. To protect our staff and for insurance reasons, your return shipment must be accompanied by a clearance certificate on which you confirm that the probe was properly cleaned and decontaminated. You may obtain a form sheet for this purpose from us on request. 2.7 Glass Testing The customary high-voltage spark test of the glass lined surface is not permitted for the measuring probes! Before performing a high-voltage spark test on the reactor, the probe must be protected against damage by electrical or mechanical influences. The entire glass lining of the probes can be monitored using the Pfaudler glass testing equipment of the types Corrosion Detector (portable) or GlasSparker. When monitoring a reactor with one of these glass testers, the integrated probes are also monitored automatically. Depending on the conductivity of the product, the accuracy of the measurement is influenced by a glass tester. For this reason, it must be ensured that the measurement and glass testing functions do not operate at the same time. Glass monitoring must be switched off during measurement. 3 Safety 3.1 Proper use Any use of the probe for purposes other than described in the present operating instructions will adversely affect the safety and functioning of the measuring device and is therefore not allowed. It is important to note the valid safety regulations concerning electrical installations. m Do not practice any working methods which may endanger safety. 3.2 Qualified personnel The probe may only be installed, operated and serviced by authorized personnel with special skills in measuring technology and in strict compliance with these operating instructions as well as the valid provisions. The failure to observe these instructions no matter whether intentionally or negligently releases Pfaudler Werke GmbH from all liability and warranty claims. 4 Technical description 4.1 Features and properties The ph probe ph Reiner may be used within a broad range of industrial ph measurements. It has been specifically designed for applications in the pharmaceutical and food industry. These applications make high demands on the hygienic condition and sterilization capability of the measuring equipment used, as well as the accuracy and stability of the measured values. These requirements are satisfied by ph Reiner to a very high degree due to the following features and properties: n Those parts of ph Reiner that are in contact with product are glassed with PPG = Pfaudler PharmaGlas or are made of stainless steel. PPG is a glass type that has been optimized for applications in the pharmaceutical industry. For more details, please refer to publication 615. The O-rings used are made of EPDM and have been approved for food applications (FDA). n The ph Reiner probe is suitable for CIP (clean-in-place) and SIP (sterilize-inplace) processes. n The electrolyte used for ph Reiner is filled into infusion bottles under sterile conditions. The bottles are equipped with a septum (partition wall) which ensures the sterile use of the bottles. n The entire electrolyte system of ph Reiner can be easily cleaned and disinfected with a 70 percent ethanol solution. n The length and diameter of ph Reiner probes correspond to the dimensions of commercially available glass electrodes. As the probe is available with various thread or installation adapters, it can be easily attached to all conventional process ports. Pfaudler Werke GmbH OI e 3

4 n The sensor area of ph Reiner is approx. 10 cm 2 and thus much larger than the sensor area of glass electrodes. As a result, accurate and well reproducible ph measurements are obtained even if the probe is contaminated. n Due to the special ph glass, and in connection with the derivation method of the Pfaudler ph probes, the ph Reiner probe is characterized by high longterm stability. This ensures accurate reproducibility of the measured values without subsequent calibration even after CIP or SIP processes. n The diaphragm does not get contaminated due to the overpressure in the electrolyte system. This ensures accurate ph measurements and long-term stability. n Due to its robust construction and the metallic probe body, the probe can be installed in pipelines and reactors directly and without any disturbing, expensive protective reinforcement. A high flow velocity at the probe is desirable because it ensures self-cleaning of the probe. Based on the robust construction of the probe, it has a very long useful life. Similar ph probes made by Pfaudler often reach a useful life of several years, depending on their application. 4.2 Measuring principle The ph value is a measure of the hydrogen ion activity a H + in a solution. The ph value is defined as the negative logarithm of the hydrogen ion activity a H +. Of practical importance is the ph value in the range between ph 0 and ph 14. That is, ph 0 is a strong acid, ph 14 is a strong alkali, and ph 7 is neutral. The ph Reiner probes operate according to the principle of potentiometry, i.e. a ph-dependent potential is built up at the ph probe that is subject to the hydrogen ion activity in an aqueous solution. This potential is derived and evaluated by a ph transmitter. The actual sensor of the ph Reiner probes consists of ph-sensitive glass. At the phase limit between the ph glass and the measured solution, the so-called gel layer, an ion exchange (hydroxilation) takes place in the course of which alkali ions of the ph glass are replaced with hydrogen ions of the measured solution. The thickness of the gel layer is approx nm. The ph-dependent potential building up in the gel layer is transferred by a ionic conductor to a metal derivative layer located below the ph glass. The ph sensor is a phase boundary structure between two chemically distinct substances with a liquid phase and a solid phase. Such a phase boundary structure is referred to as a half-cell. The potential of a half-cell, which is also called phase boundary or Galvani potential, cannot be measured directly because a measuring instrument would constitute another phase boundary in the measuring loop whose potential in turn would be unknown. For this reason, the potential of a half-cell can only be determined by a series connection of a second half-cell. The liquid phases of the half-cells are connected via a diaphragm. The second half-cell, the so-called reference electrode, supplies a defined, constant potential due to its very construction. The series connection of the ph electrode and the reference electrode provides a measuring signal that consists of the sum of the variable ph potential and the constant reference potential. The measured signal is supplied to a ph transmitter for evaluation through appropriate connections Figure 1 1 Socket (Variopin) and cable 2 Connector (Variopin) 3 Probe head 4 Self-locking coupling and electrolyte hose 5 Self-locking hose connector 6 Reference electrode (integrated in probe head) 7 Venting plug 8 Venting outlet 9 Thread adapter 10 Probe tube, glasslined with PPG 11 Pt1000 (integrated in probe tube) 12 Rhodium electrode 13 ph sensor (ph glass) 14 Ground diaphragm ph Reiner MT0076_1E 4 Pfaudler Werke GmbH OI e

5 4.3 Construction and function The ph Reiner probe consists of two principal components: n Measuring probe n Reference system The measuring probe consists of a glasslined steel tube (10). The ph sensor (13) and the diaphragm (14) are fitted to one end of the tube. The probe head (3) and the installation adapter (9) are located at the other end of the tube. The ph sensor consists of ph-sensitive glass, which will also be referred to as ph glass in this manual, and which has been fused around the perimeter at the end of the tube. The sensor area is approx. 10 cm 2. The metallic derivative layer is located below the ph glass which ensures high-resistance insulation between the derivative layer and the probe tube. The combination of the ph glass and the metal derivative layer results in the ph-sensitive measuring electrode. The potential of the measuring electrode is transmitted to the connector at the probe head by a fused-in, insulated stainless steel tape Above the ph glass, there is a rhodium electrode (12) that serves as product ground. This electrode allows for symmetrical measurement, and thus for continuous impedance monitoring of the measuring and reference electrode. The diaphragm, which is also called a ground or split diaphragm, is located at the tip of the probe tube. It has the task of making a conductive connection between the reference system and the product while preventing the product and the electrolyte from mixing. The diaphragm consists of a ground ceramic puck and the probe tube end which is glass-coated and ground inside. The ceramic puck is shrinkfitted into the end of the probe tube. The contact area between the ceramic puck and the ground glass surface forms the diaphragm gap. As the diaphragm gap allows penetration of electrolyte and the outside of the diaphragm is in contact with product, the electrolyte line provides a conductive link between the reference system and the product. Inside the probe tube, the electrolyte is guided through an insulated supply line from the probe head to the diaphragm. The electrolyte line can be vented through a venting plug at the probe head. A 6-pole connector (2) located on the probe head provides for connection of the probe to the transmitter. Connection is made using the ph Reiner connection cord. The electrolyte hose is connected to a self-locking swivel connector (5) located at the side of the probe head. The venting plug (7) for venting the probe is located below this connector. A thread adapter (9) below the probe head is used to screw the probe into the process port. All metal parts are connected to a contact inside the connector at the probe head in order to ensure grounding of the probe. The probe is linked to the equipotential bonding system (grounded) via this contact and the ph Reiner connection cord, refer to Section 7.4. The reference system consists of the electrolyte reservoir and the reference electrode. The electrolyte reservoir comprises a pressure vessel made of stainless steel which holds an infusion bottle made of PE. This bottle contains the electrolyte. The electrolyte reservoir is installed separately next to the probe on location. The reservoir is linked to the probe head by a PTFE hose (electrolyte hose) included in the delivery. The electrolyte reservoir must be permanently pressurized with compressed air. This is to ensure that electrolyte can permanently reach the diaphragm and finally the product through the electrolyte line. The permanent electrolyte diffusion is designed to avoid contamination of the diaphragm. Furthermore, it prevents product from entering the electrolyte line through the diaphragm gap and contaminating the diaphragm. The reference electrode (6) is installed in the electrolyte line inside the probe head and is linked to the electrolyte reservoir through the PTFE connection hose. The combination of the measuring electrode and the reference electrode and their conductive connection through the electrolyte line, diaphragm and product forms the measuring chain When the probe is immersed in the product, the measuring chain supplies a highresistance, ph-dependent potential that is converted by a suitable ph transmitter into a standard signal (4-20 ma) in proportion to the ph value. The measured ph value is influenced by the product temperature because the slope of a measuring chain depends on the temperature according to Nernst s constant (refer to Sect. 5.1). The ph Reiner probe is equipped with a Pt1000 (11) that is used to measure the product temperature inside the transmitter. Therefore, the temperature-dependent slope change of the sensor can be automatically compensated by the transmitter. Pfaudler Werke GmbH OI e 5

6 4.4 Electrolyte reservoir The electrolyte reservoir operates according to the following principle: A PE bottle (infusion bottle) containing electrolyte is placed into a pressure vessel. When the bottle is installed, a hollow needle penetrates the septum (rubber plug) of the bottle. The pressure vessel is closed and pressurized with compressed air. The pressure inside the vessel squeezes the soft PE bottle together, and electrolyte is pressed out through the needle. The electrolyte reservoir of the ph Reiner probe basically consists of a 2-piece container made of stainless steel (1, 3) and a plastic insert (4). The upper and lower part of the container are held together by a clamp (2). The plastic insert is located in the lower part of the container where it is fixed in place with a union nut (13). Below the union nut, there is a threaded joint (14) which serves the following functions: n The hollow needle that is pushed into the electrolyte bottle (8) is fastened to this joint. In order to replace the needle (6), the joint must be removed before the old needle can be pulled out and the new needle can be inserted. n If the electrolyte bottle is to be replaced, first the pressure vessel must be de-pressurized. This is done by opening the threaded joint by approx. 2-3 turns. A self-locking coupling (7) is provided at the bottom of the plastic insert which serves for connecting the electrolyte hose. The following parts are also attached to the bottom part of the pressure vessel: n Straight male union made of PVDF DN 4/6, G 1 / 4 with O-ring (11), for compressed-air connection n Steel angle bar for installation at a wall or pipeline (9) including ground terminal (10) n Female union for level monitoring (option) (12) Figure Electrolyte reservoir, upper part 2 Clamp 3 Electrolyte reservoir, lower part 4 Plastic insert 5 Septum (rubber plug) 6 Hollow needle 7 Self-locking coupling 8 Electrolyte bottle 9 Mounting plate Electrolyte reservoir The electrolyte reservoir has been designed for easy replacement of the electrolyte bottle without affecting the sterile properties of the electrolyte system. 10 Compressed air connection with return valve for plastic hose 6mm (OD) 11 Electrolyte monitoring empty message using ultrasound (refer to spare parts list option) 12 Union nut for plastic insert 13 Threaded joint for hollow needle and venting 14 Self-locking connector with electrolyte hose MT0075_1E The electrolyte reservoir is approved for a max. internal pressure of 7 bar. Optional level monitoring is available for the electrolyte reservoir. 6 Pfaudler Werke GmbH OI e

7 4.5 Reference electrode A silver chloride electrode is used as reference electrode, letter symbol: AgAgCl. The measuring chain zero when using a silver chloride electrode is reached at approx ± 1 ph. The zero point of ph Reiner is not identical to the isotherm point which is found at 1.0±1 ph. Therefore, the transmitter selected should offer independent, free parameterization of the zero point and the isotherm point (refer to Sect. 5.2 and 5.3). The guaranteed life of the silver chloride electrode amounts to 24 months from the date of delivery. However, its actual life is much longer in most cases and usually equals that of the ph Reiner probe. The reference electrode is permanently installed in the probe head. The reference electrode may only be replaced by Pfaudler. 4.6 Electrolyte Potassium chloride, 3-mol KCl, ph4 with an inhibitor additive, is used as electrolyte for ph Reiner. The electrolyte is filled into 1 liter PE bottles (infusion bottles) under sterile conditions which are supplied by Pfaudler. These bottles are completely placed in the electrolyte reservoir. Only Pfaudler electrolyte may be used in order to guarantee the faultless function of the probes for a long period of time. If KCl should be inappropriate, e.g., if no chloride may enter the product or if KCl reacts with the product, it is also possible to use another electrolyte. In such a case, however, it is absolutely necessary to contact Pfaudler. 4.7 Thread adapter The thread adapter is located right below the probe head. Its purpose is to screw the ph Reiner probe into the local process port. The adapter consists of a rotatable stainless steel ring with an external thread. The following thread sizes are available: n M20 x 1.5 n PG13.5 n 3 / 4 n 1 Using these thread adapters, ph Reiner can be directly screwed into the corresponding process ports that are also customary for glass electrodes. The necessary gaskets between the probe and the process port must be ordered separately because they depend on the installation conditions on location. Thread adapters with other thread sizes are also available on request subject to technical coordination. 4.8 Installation adapter The thread adapters listed in Section 4.7 are not suitable for all process ports found in practice. Therefore, special installation adapters are available for the following process ports: n Pfaudler Aseptic welded nozzles DN 30 n Ingold welded nozzles DN 25 n Varivent adapters The connection thread of the thread adapter is always size M20 x 1.5. Figure 3 Inserting the bottle All necessary gaskets are supplied together with the installation adapter. Installation adapters in other designs are also available on request subject to technical coordination. For assembly, refer to Annex A. Pfaudler Werke GmbH OI e 7

8 4.9 Technical data Slope of the measuring chain: mv/ph at 25 C * Zero point of the measuring chain: 8.65±1 ph * Isotherm point of the measuring chain: 1,0±1 ph/440 mv * Potential of the measuring chain: +600 to 400 mv Internal resistance of the measuring chain: Ω at 25 C Diaphragm resistance: approx kω Insulation resistance: Ω Internal capacitance (with connection cord): 5 nf Internal inductance (with connection cord): negligible Allowable working temperature: C Allowable working pressure: 1/+6 bar Max. ambient temperature: 50 C Temperature measurement Pt1000 Thermal shock resistance: T = 120 C Resistance: refer to Fig. 6 * for exact values, refer to test report 5 Technical characteristics of measurement 5.1 Slope of the measuring chain The slope S of a ph probe is defined as follows: S = E/ ph E = change in potential of the ph probe ph = ph change of the measured solution The theoretical slope of a ph probe is approx mv/ph at 25 C. In practice, this value is not reached due to design and manufacturing restrictions. The slope of a ph Reiner probe is approx mv/ ph at 25 C. In order to compare the slope of the probe with that of other probes, the value is always specified with respect to the standard temperature of 25 C. Due to the physical properties of the measuring electrode (ph glass), the slope of the probe is temperature-dependent. The slope changes according to Nernst s constant at a rate of mv per 1 C and per 1 ph. This temperature influence can be compensated by the modern ph transmitters used today. For this purpose, the transmitter must measure the temperature of the measured solution (product) and the most important characteristics of the probe slope, zero point and isotherm point must be programmed into the transmitter (parameterization) (refer to Sect. 8.5). without installation adapter with installation adapter 46 Each probe is tested and measured prior to delivery. The measured slope is specified in the test report supplied together with the probe (nominal value). The nominal slope value must be input into the transmitter in the course of calibration in order to calculate and compensate the temperature-dependent ph value shift (temperature compensation). 12,3 [mm] MT0081_1 Figure 4 Installation sizes 8 Pfaudler Werke GmbH OI e

9 The slope is recalculated during each twopoint calibration process. The new value calculated will then be used by the transmitter for temperature compensation during the current ph measurement. The slope of glassed ph probes remains constant during the entire life of the probe, i.e. the probes are not subject to aging. Therefore, recalibrating the ph Reiner probe regularly is not necessary if the measuring loop is properly insulated. 5.2 Zero point of the measuring chain The measuring chain zero is the ph with a measuring chain voltage of zero (total potential). The total potential basically consists of the sum of the individual potentials of the measuring and reference electrode. The zero point is decisively influenced by the type of reference electrode, and thus the potential of the reference electrode. A silver chloride electrode is used as reference electrode for ph Reiner, refer to Section 4.5. The measuring chain zero when using a silver chloride electrode is reached at approx. ph 8.65 ±1 = ph 0. Each probe is tested and measured prior to delivery. The measured zero point is indicated in the test report supplied together with the probe (nominal value). The nominal zero point value must be input into the transmitter in the course of calibration in order to calculate and compensate the temperature-dependent ph value shift (temperature compensation). Figure 5 U [mv] Isotherm intersection ph Characteristics of 25 C silver chloride electrode (AgAgCI) 80 C 5.3 Intersection of isotherms If the total potential of a measuring chain is plotted as a function of the ph value of a measured solution (product) for a certain, constant temperature of the measured solution in a diagram, a straight line is obtained which is also referred to as isotherm. The slope of the isotherm is temperature-dependent (refer to Sect. 5.1). For this reason, two isotherms determined at two different product temperatures each have a different slope (ascending gradient), and therefore a common intersection. The intersection of two isotherms is referred to as the isotherm intersection, or isotherm point in this manual. The coordinates of the isotherm point are referred to as ph is and U is. Isotherm point U is = approx. 440 mv, ph is = approx ph Zero point ph 0 = approx ph MT0072_1E The isotherm point of the ph Reiner probes is reached at ph 1.0 ±1 = ph is. For the exact value applicable to the respective probe, please refer to the test report. This value remains constant during the whole life of the probe. The value of U is is approx. 440 mv when using a silver chloride electrode. For the exact value applicable to the respective probe, please refer to the test report. The isotherm point must be input into the transmitter in the course of calibration in order to calculate and compensate the temperature-dependent ph value shift (temperature compensation). Depending on the transmitter used, one of the two coordinates U is or ph is must be entered as isotherm point. Some transmitters also require the input of both values. The zero point is recalculated during each calibration process. The new value calculated will then be used by the transmitter for temperature compensation during the current ph measurement. Pfaudler Werke GmbH OI e 9

10 5.4 Resistance of the measuring chain Short response times depend on the lowest possible resistance of the measuring electrodes. The resistance of the measuring electrode must be lower than the insulation resistance between the conductor electrode and the probe body. This requirement is met by a relatively lowresistance ph glass in combination with a high-resistance protective glass layer. The glassteel probe body is grounded for dissipating electrical leakage fields. Resistance at 25 C Measuring electrode: Reference electrode: Insulation: Ω 5-10 kω Ω 5.5 Diaphragm resistance The resistance of the diaphragm is kω. The diaphragm has been ground to ensure the minimum permeability (leakage rate) of the electrolyte. Based on the overpressure in the electrolyte system, the danger of contaminating the diaphragm is very low, and the same applies to the risk of diffusion potentials building up at the diaphragm. In aqueous media, the influence of the diaphragm resistance on the total potential, and thus the ph value, is extremely small or even zero. 5.6 Measuring variance During final testing in the factory, the exact values of the isotherm point, U is and ph is, are measured and specified in the test report. If the exact values of the isotherm point are entered in the transmitter, the measuring variance does not exceed ±0.05 ph. This value is only achieved, however, if the allowable operating conditions are maintained. 5.7 Alkali error The allowable measuring range is in between the lowest ph value and ph 10. Above ph 10, the alkali error produces a deviation that increases with temperature and the Na + concentration. The alkali error does not occur if no Na + ions are present. With K + ions (e.g. ammonia), measurement can be performed up to ph Time response to ph change Electrochemical processes at the surface of the measuring electrode and the time constant of the measuring loop determine the time response of the probe to ph changes. Up to strong alkali values, the electrochemical equilibrium is reached very fast, so that the influence of the electrical components of the measuring loop on the response times is of greatest importance. The display s response to sudden changes of the ph value generally does not affect the measuring process. The final value is normally reached after a few seconds. Only above ph 8 it takes a little longer to reach the final value. This delay, which is also common with glass electrodes, is caused by ion exchange processes at the electrode surface. 5.9 Time response to temperature changes The potential of the ph probe should settle with the smallest possible hysteresis even in the case of product temperature changes during ph measurement. Due to its very design, the measuring chain responds faster to temperature variations than the Pt1000 in the probe. The resulting maximum deviation is less than 0.1 ph at a temperature change of 1 C/min or less. However, the exact isotherm point of the measuring chain must have been entered in the transmitter for this purpose. 10 Pfaudler Werke GmbH OI e

11 6 Application limits 6.1 Chemical resistance Glass is considered to be resistant if erosion is less than 0.1 mm per year. This is an average value which is determined in experiments to DIN-ISO and represented in so-called ISO corrosion curves (refer to Fig. 6). The resistance of our ph probes depends on the yellow ph-sensitive glass (ph glass) because the resistance of this glass is slightly lower than that of our Pfaudler PPG glass. Exact determinations concerning the resistance cannot be made unless the application is known and corrosion tests were made. For more details, please refer to our Publication 614, Pfaudler compound glassteel materials. 6.2 Temperature The allowable product temperature depends on the ph. The maximum admissible product temperature is 140 C. For the permissible temperature range, please refer to Fig. 7. At product temperatures above 100 C, the pressure inside the electrolyte system must be higher than the vapor pressure in order to avoid boiling of the electrolyte. Otherwise, vapor bubbles may occur which result in a failure of the probe. Due to the rising resistance of the measuring electrode with falling temperatures and the associated delayed display response, the lower temperature limit is 0 C. However, based on the composition of the electrolyte, the ph probes may remain inside the reactor down to a temperature of 5 C. On request, special electrolytes are available which enable the probes to remain inside the reactor or the pipe down to a temperature of 30 C. However, the ph can no longer be measured reliably at frost temperatures. C MT0016_3E Figure 6 C MT0017_1E Figure 7 resistant ISO corrosion curve of ph glass Application range with a measuring accuracy of: < ±0.1pH with 0.1 nna + Erosion 0.1 mm/year ph Application range of the ph probes ph The glassed ph probe is resistant to thermal shock up to a DT of max. 120 C (temperature difference between product and probe). Pfaudler Werke GmbH OI e 11

12 6.3 ph range For the permissible ph application range, please refer to Fig. 6. Limitations are base on the chemical resistance (refer to Section 6.1) and the alkali error (refer to Section 5.7). After having been used in the strong alkali range, the setting behavior of the probes is slowed down when returning to the neutral range. In ranges below ph 8, the probe regenerates very quickly. 6.4 Pressure Probes are suitable for an operating pressure of 1 to +6 bar. The electrolyte reservoir is approved for a max. internal pressure of 7 bar. During operation, the pressure inside the electrolyte system should be at least 0.5 bar above the maximum possible operating pressure or the temperature-dependent vapor pressure of the probe. This is to ensure that no product can enter the probe or contaminate the diaphragm. Furthermore, it is ensured that the diaphragm gap is always in contact with electrolyte. A pressure regulation system is not necessary. Once set to the highest process pressure, the internal pressure of the probe does not have to be readjusted. The differential pressure may be greater than 0.5 bar up to 6 bar max., this will cause increased electrolyte consumption. 6.5 Inappropriate products Reliable ph measurements are not possible in water-free products (water content < 1 %). All fluorine-containing products below ph 6 lead to strong corrosion. Strongly hygroscopic products and the application of dry nitrogen to an empty reactor or pipeline will drain the gel layer, leading to a loss of the slope, which can be corrected by reconditioning the ph probe (refer to Section 8.2). Examples of proper pressure settings: 1. Pressure inside the reactor: 4 bar max. Vapor pressure: 1 bar at an operating temperature of 100 C Minimum internal pressure: 4.5 bar 2. Pressure inside the reactor: 2 bar max. Vapor pressure: 4 bar at an operating temperature of 140 C Minimum internal pressure: 4.5 bar m If the probe is subject to process pressure inside the reactor or the pipeline, it must be ensured that the pressure inside the electrolyte system is permanently at least 0.5 bar above the process pressure. Otherwise, there is a risk of product entering the probe through the diaphragm gap and clogging or contaminating the electrolyte line. 12 Pfaudler Werke GmbH OI e

13 7 Installation and electrical connection of the probe 7.1 Installation of the probe The probe may be installed both in reactors and in pipelines. It is important to maintain sufficient clearance between the probe and any built-in parts as well as the reactor or pipeline wall. The probe is screwed into the existing process port using the proper thread or installation adapter (refer to Sect. 4.7 and 4.8). The probe is available in a single length only. The ph Reiner probe may be installed in any orientation because the overpressure in the electrolyte reservoir ensures that electrolyte may flow from the electrolyte reservoir to the probe, regardless of the orientation of the probe, at all times. 7.2 Installing the electrolyte reservoir The electrolyte reservoir is installed vertically and as close as possible to the probe, max. distance 5 m. 7.3 Electrical connection of the probe For the electrical connection of the probe to the transmitter, please refer to the circuit diagram and the operating instructions of the transmitter used. The circuit diagrams for the transmitters approved by Pfaudler may be obtained from us on request. Use the ph Reiner connection cord (refer to Sect. 7.5) for linking the connector at the probe head and the transmitter. 6 Connecting the cables: Properly position the socket of the connection cord on the connector of the probe head and press connectors together. Manually tighten the union nut on the socket. For the core assignment of the ph Reiner connection cord, please refer to Section 7.5. m In order to avoid any type of potential loss, please ensure that no moisture can enter the connector or the socket. If necessary, dry both parts using a hair dryer or hot-air fan. 1 Compressed air or nitrogen 2 ph Reiner connection cord 3 ph transmitter 4 Supply voltage 5 Signal output 6 Equipotential bonding 7 Compressed air regulator (not included in delivery) The electrolyte reservoir and the probe head are linked by a PTFE hose (electrolyte hose) included in the delivery (delivered length 5 m). One end of the hose is equipped with a self-locking coupling and the other end with a self-locking connector. Plug the coupling onto the probe head and the connector onto the electrolyte reservoir. The hose may be cut to the appropriate length Connect the electrolyte reservoir to the compressed air supply using a pressurereducing fitting. Connection to the pressure vessel is made using a threaded joint made of PVDF DN4/6 G 1 / 4. The pressure inside the pressure vessel must be at least 0.5 bar above the maximum process pressure. For more details concerning the proper pressure setting, please refer to Section MT0073_2E Figure 8 Connection diagram of ph Reiner Pfaudler Werke GmbH OI e 13

14 7.4 Equipotential bonding For equipotential bonding, a distinction must be made between two different types of installation. A Installation within a plant which basically consists of metallic parts reactor, pipeline and nozzles with a high conductivity. In such plants, separate equipotential bonding of the probe is not necessary. Equipotential bonding (grounding) of the probe body is ensured by the metallic link between the installation adapter and the installation nozzle. The gray wire contained in the connection cord (probe body) need not be connected to the transmitter. The cable shield (green/yellow wire) must be connected to the transmitter s equipotential bonding terminal. No general description of the exact location of the equipotential bonding terminal on the transmitter to which the green/yellow wire must be connected can be given at this point because this terminal may differ in design depending on the type of unit and its manufacturer. The circuit diagrams for the transmitters approved by Pfaudler (refer to Sect. 7.6) may be obtained from us on request. The electrolyte reservoir must be connected separately to the equipotential bonding system of the plant or grounded. B Installation within a plant whose principal elements reactor, pipeline and nozzles are made of plastic or other non-conductive materials, or have been coated with non-conductive materials, such as glassteel. In such plants, separate equipotential bonding of the probe must be provided. All metal parts of the probe (probe body) are connected to pin C inside the connector at the probe head. Equipotential bonding is achieved by connecting the gray wire of the connection cord (probe body) to the equipotential bonding terminal of the transmitter. The cable shield (green/yellow wire) must also be connected to the transmitter s equipotential bonding terminal. No general description of the exact location of the equipotential bonding terminal on the transmitter to which the gray and the green/yellow wires must be connected can be given at this point because this terminal may differ in design depending on the type of unit and its manufacturer. The circuit diagrams for the transmitters approved by Pfaudler (refer to Sect. 7.6) may be obtained from us on request. 7.5 ph Reiner connection cord The ph Reiner connection cord is a prefabricated cable that is used to transmit all electric signals and functions from the probe to the transmitter. The cable is specifically designed for transmission of very high-impedance signals. As a standard, the cable is available in lengths of 3 or 5 m. Cable lengths of more than 5 m may adversely affect the response behavior of the ph Reiner probe. A special socket is fitted to one cable end which fits into the connector on the probe head. The other cable end has been stripped of the insulation. Connect the individual wires to the transmitter terminals. For the pin assignment, please refer to Table 1. Below the heat-shrinkable tube, a 220 nf capacitor has been fitted to the stripped cable end which is connected in series with the wire designed for the cable shield (green/yellow wire). A 470 nf capacitor has been installed in the probe head which is connected in series with the terminal for the probe body (gray wire). The purpose of these capacitors is to inhibit low-frequency compensation currents which might be present if both cable ends are connected to the equipotential bonding system. The electrolyte reservoir must be connected separately to the equipotential bonding system of the plant or grounded. 14 Pfaudler Werke GmbH OI e

15 A B C D E F 7.6 List of ph transmitters approved by Pfaudler Only suitable equipment may be used as ph transmitters which must have the following features: n Symmetrical high-impedance inputs, Ri Ω n It must be possible to set the zero point and the isotherm point of the probe freely and independently. A 220 nf F For programming the transmitters, please refer to the manufacturers operating instructions. The following units have been approved: B C D E Knick: 71(X) ph with option 356* 73 ph with option 356* 74 ph with option 356* 76(X) ph with option 356* 77(X) ph with option 356* PROTOS 3400(X) with module ph 32 Siemens: Sipan 3 P Sipan 32 (X) Sipan 34 Yokogawa: EXA ph 200 EXA ph 202 EXA ph 400 EXA ph 402 EXA xt ph 150 EXA xt ph 450 Polymetron: Monec 9135 Emmerson**: Model 54 ph Model 3081 Figure 9 Connection diagram Table 1 Assignment of cores of the ph Reiner connection cord Connector pin Conductor color Function A black ph sensor B red Reference electrode (coaxial shield) C gray Probe body D blue Rhodium electrode E white Pt 1000 F green Pt 1000 S green/yellow Cable shield MT0079_2 m If a probe is immersed in the product, the ph transmitter must not be disconnected from mains for more than 1-2 days. Otherwise, polarization may result in a zero drift and the need for calibration. Where longer disconnection from mains cannot be avoided, the measuring circuit must be interrupted. This can be achieved by unscrewing the connector from the probe or separating the connection at the transmitter. * the nominal zero point and the nominal slope can be parameterized **Rosemount Pfaudler Werke GmbH OI e 15

16 8 Start-up and calibration 8.1 Preliminary note When the probe has been installed and connected as described in Section 7, start-up is carried out in several steps: t Reconditioning of the probe (refer to Sect. 8.2). t Cleaning and disinfection of the electrolyte system (refer to Sect. 8.3). This process is required for sterile applications only. t Filling the electrolyte reservoir and venting of the probe (refer to Sect. 8.4). t Parameterization of the transmitter (refer to Sect. 8.5). t Calibration of the probe (refer to Sect ). The individual steps will be explained in detail below. 8.2 Reconditioning the probe New probes as well as probes that have remained dry for prolonged periods of time may be subject to slight measured value deviations during start-up. This deviation may be corrected by reconditioning the probe. By reconditioning, a gel layer is built up on the surface of the ph glass. This gel layer is an important condition for accurate and stable ph measurements. Cleaning and sterilizing the reactor or the pipeline containing the probe prior to start-up will be sufficient to recondition the probe. Additional reconditioning is not necessary. There are two ways of reconditioning the probe: n Watering of the probe for hours. Or, if the reconditioning process is to be accelerated: n Immersing the probe into water at C for approx. 30 min or vapor treatment for min. The probe can be reconditioned inside or outside the reactor or the pipeline. 8.3 Disinfecting the electrolyte system For sterile applications, the entire electrolyte system can be disinfected prior to the actual start-up. This process is performed with a 70 % ethanol solution. Empty bottles with a septum (rubber plug) which can be inserted in the pressure vessel are available from Pfaudler. The probe user must fill the bottles with ethanol himself. The permitted ambient temperature of the electrolyte reservoir is 0 to +50 C. Disinfection process: t Open clamp on the electrolyte reservoir and take off the upper part. If the electrolyte reservoir was already pressurized, it must be depressurized beforehand (refer to step 7). t Place the bottle in the middle of the lower part of the electrolyte reservoir with the septum (rubber plug) pointing downward. The septum is penetrated by the hollow needle located at the bottom of the electrolyte reservoir. t Reinstall the upper part of the vessel and close the electrolyte reservoir tightly using the clamp. t Apply a pressure of 3 bar min. to the electrolyte reservoir. t Open the venting plug on the probe head by approx. one turn and leave it open until approx ml of ethanol have emerged. Then close the venting plug again manually. t Allow the ethanol to react for approx. 2-5 min. t Shut off the compressed air supply and de-pressurize the electrolyte reservoir. This is done by opening the threaded joint at the bottom of the plastic insert by approx. 2-3 turns counter-clockwise. When the electrolyte reservoir has been de-pressurized, immediately close the threaded joint again manually. t Open clamp on the electrolyte reservoir, take off the upper part and remove the ethanol bottle. m Caution! After disinfection, the probe should be filled with electrolyte as soon as possible (refer to Sect. 8.4)! m For sterile applications, those parts of the probe that are in contact with product must be sterilized by suitable methods. (refer to Sect. 9.4). As the ph Reiner probe is SIP-compatible, it is not necessary to remove the probe from the reactor/pipeline for sterilization. 8.4 Filling the electrolyte reservoir and venting of the probe The electrolyte line must be free from bubbles in order to ensure a faultless electrical connection between the reference electrode and the diaphragm. 3mol KCl, ph 4, with an inhibitor additive is used as electrolyte (refer to Sect. 4.6). The permitted ambient temperature of the electrolyte reservoir is 0 to +50 C. m Only Pfaudler electrolyte may be used in order to guarantee the faultless function of the probes for a long period of time and without damaging the ground diaphragm. Process of filling and venting t Open clamp on the electrolyte reservoir and take off the upper part. If the electrolyte reservoir was already pressurized, it must be depressurized beforehand (refer to Sect. 8.3, step 7). t Remove red cap from the electrolyte bottle. Place the bottle in the middle of the lower part of the electrolyte reservoir with the septum (rubber plug) pointing downward. The septum is penetrated by the hollow needle located at the bottom of the electrolyte reservoir. For sterile applications, the septum must be disinfected with ethanol beforehand. t Reinstall the upper part of the vessel and close the electrolyte reservoir tightly using the clamp. t Apply a pressure of 3 bar min. to the electrolyte reservoir. 16 Pfaudler Werke GmbH OI e

17 t Open the venting plug on the probe head by approx. one turn and leave it open until the electrolyte emerges without any bubbles. If the electrolyte line was disinfected before, approx ml of electrolyte must emerge, depending on the hose length. Then close the venting plug manually and clean the entire area carefully with water. t Set the necessary operating pressure at the electrolyte reservoir as described in Section Setting the ph transmitter parameters The probe-specific characteristics, such as slope, zero point and isotherm point, as well as the user-specific settings must be entered in the transmitter (parameterized) before calibration can be carried out. The characteristic values are indicated in the test report supplied together with the probe. Some of the parameters to be entered are summarized in the list below. This list does not claim to be complete. For the parameters to be entered, please refer to the operating instructions of the transmitter used and the user s requirements. The parameters may be entered in parameter input mode or in calibration mode, depending on the transmitter used. Table 2 Parameterization 8.6 What is meant by calibration? Calibration is defined as the adjustment of the transmitter to the characteristic of the ph probe. The measuring chain of the ph probe supplies a potential that depends on the ph value of the product. The transmitter measures this potential and calculates the current ph from the measured value. The potential of the measuring chain, and thus the ph, is influenced by various factors, such as the current potential of the reference electrode or inevitable specimen variance. These factors, some of which cannot be detected by their very nature, are largely eliminated by calibrating the probe. 8.7 Calibration methods The following calibration methods are used in ph measurement technology: n Calibration through data input at the transmitter (refer to Sect. 8.8). n Two-point calibration (calibration using 2 buffer solutions of identical temperatures, refer to Sect. 8.9). n Single-point or product calibration (calibration with product, refer to Sect. 8.10). n Automatic calibration (refer to Sect. 8.11). We recommend performing two-point calibration in the course of initial start-up and after prolonged service interruptions. The individual methods and their suitability for ph Reiner will be described in the following sections. 8.8 Calibration by data input at the ph transmitter This calibration method is used whenever a quick function test of the probe is to be performed and/or if no high measuring accuracy is required. Process of calibration through data input Depending on the transmitter used, the calibration and/or parameterization mode must be activated and the characteristic values of the probe indicated in the test report must be entered. When the calibration mode has been exited, the probe is ready for use. However, this calibration method does not guarantee faultless functioning or a defined accuracy of the probe. For this reason, we recommend performing a twopoint calibration as soon as possible after calibration by data input. Parameter Value setting Option selected Slope Enter value from test report Zero point Enter value from test report Isotherm point Enter value from test report Quantity to be displayed ph Temperature compensation automatic Temperature sensor Pt 1000 Current output 0-20 ma or 4-20 ma ph or mv Pfaudler Werke GmbH OI e 17

18 8.9 Two-point calibration Two-point calibration is the calibration method that is used most frequently with ph probes because the measuring accuracy achievable with this method is totally sufficient for most practical applications, and a good functional control of the ph measuring equipment is achieved. For a two-point calibration, the ph value of two different buffer solutions is measured one by one at the same temperature. The measuring chain potential measured each time is then assigned to the relevant ph. Based on the two potentials measured and taking into account the current temperature, the slope and zero point values will be recalculated by the transmitter. Then, automatic temperature compensation is performed by the transmitter using these new, calculated values. Some preparations have to be made before the actual calibration can be started. n A constant ph measurement requires a state of equilibrium at the diaphragm, i.e. an evenly moistened ground surface. For this purpose, the electrolyte reservoir must be pressurized approx. 1 hour prior to the beginning of the calibration. n In order to reach the highest possible accuracy in the adjustment to the measuring chain characteristic, the ph values of the two buffer solutions should differ by at least 3 ph. We recommend using buffer solutions ph 7 and ph 2 for two-point calibration of the ph Reiner probe. Calibration should preferably be started with the buffer solution ph 7. If a limited measuring range is sufficient, a buffer solution ph 3 or ph 4.01 may also be used for the second measuring point. n The probe should be removed from the reactor/pipeline for calibration. Place the probe in a suitable plastic basin. In order to ensure grounding of the probe, the probe must be immersed in the buffer solution down to the thread or installation adapter. Process of two-point calibration t Recondition the probe and rinse it with distilled water. t Fill the plastic basin with the first buffer solution ph 7 and immerse the probe into the buffer solution down to the adapter because the buffer solution is grounded via the adapter. t Activate the calibration mode at the transmitter. Then select the Two-point calibration mode and enter the ph of the first buffer solution. t Wait until the measured value displayed has stabilized and then start the calibration process. The measuring chain potential determined is now assigned to ph 7. t When the first calibration step has been completed, rinse the measuring probe and the plastic basin with distilled water and fill the basin with the second buffer solution. t Immerse the probe down to the installation adapter into the second buffer solution ph 2 (optionally also ph 3 or ph 4.01). The two buffer solutions should have the same temperature. If this is not the case, wait until the temperature display has settled at a stable value. t Enter the ph value of the second buffer in the transmitter. t Wait until the measured value displayed has stabilized and then start the calibration process. The measuring chain potential determined is now assigned to ph 2 (or 3 or 4.01, respectively). t Exit calibration mode. t Two-point calibration should be verified after 1-2 weeks by a single-point calibration using product Single-point calibration Single-point or product calibration is performed in order to verify a ph measurement or for quality assurance purposes. Process of single-point calibration Take a product sample from the process using a suitable device. Then determine the ph value of this sample with the required degree of accuracy using a manual tester or in the lab. Compare the reference value thus determined to the value displayed on the transmitter. The value displayed can be corrected as follows in the event of minor deviations: Activate the calibration mode at the transmitter. Then select the Single-point calibration mode and enter the reference value measured manually. When exiting calibration mode, the measuring chain potential is assigned to the last measured ph value. In the event of major deviations, we recommend performing a two-point calibration or checking the entire ph measuring equipment (refer to Sect. 8.9) Automatic calibration Various ph transmitters offer automatic calibration. In this mode, the transmitter will detect the ph value of the buffer solutions with a tolerance of ±0.5 ph. In order to enable the transmitter to detect the buffer solutions, depending on the probe type used, the zero point and slope values determined by the first automatic calibration process must be entered manually in the transmitter. Please refer to the operating instructions of the transmitter used for the input of the two characteristic values in the transmitter. 18 Pfaudler Werke GmbH OI e

19 8.12 Compressed air setting For details concerning the proper compressed air setting at the electrolyte reservoir, please refer to Section 6.4. m If the probe is subject to process pressure inside the reactor or the pipeline, it must be ensured that the pressure inside the electrolyte system is permanently at least 0.5 bar above the process pressure. Otherwise, there is a risk of product entering the probe through the diaphragm gap and clogging or contaminating the electrolyte line. Figure 10 Removing the electrolyte bottle 9 Operation and maintenance 9.1 Recalibration Since glasslined ph probes are not subject to aging, recalibration is actually necessary only if calibration intervals have been prescribed, if the potential of the reference electrode has changed, or if a measuring error is suspected. Nevertheless, we recommend verifying the calibration approx. every 6 months in normal operation. When recalibrating the probe, you reach a good reproducibility of the measured value if you perform a singlepoint calibration with the product to be measured. For a description of the singlepoint calibration process, please refer to Section Replacing the electrolyte bottle In order to ensure faultless operation of the measuring probe, the electrolyte line must always be filled with electrolyte. Therefore, the electrolyte bottle should be replaced before it is entirely empty. m Before opening the electrolyte vessel it must be vented by turning the lower plastic thread of the electrolyte connection. Please rotate counter clockwise. Only Pfaudler electrolyte may be used in order to guarantee the faultless function of the probes for a long period of time. It is recommended to activate the HOLD function of the transmitter before replacing the electrolyte bottle. This is designed to ensure that the last ph value measured is maintained while the bottle is being replaced until the HOLD function is deacti-vated. As a rule, the electrolyte bottle should only be replaced at a product temperature of less than 80 C and without process pres-sure. If this is not possible, it should be replaced as quickly as possible. Procedure t Shut off the compressed air supply and de-pressurize the electrolyte reservoir. This is done by opening the threaded joint at the bottom of the plastic insert by approx. 2-3 turns counter-clockwise. When the electrolyte reservoir has been de-pressur ized, immediately close the threaded joint again manually. t Open clamp on the electrolyte reservoir, take off the upper part and remove the empty electrolyte bottle. t Remove red cap from the full electrolyte bottle. Place the bottle in the middle of the lower part of the electrolyte reservoir with the septum (rubber plug) pointing downward. The septum is penetrated by the hollow needle located at the bottom of the electrolyte reservoir. For sterile applications, the hollow needle and the septum must be disinfected with ethanol beforehand. t Reinstall the upper part of the vessel and close the electrolyte reservoir tightly using the clamp. t Apply a pressure of 3 bar min. to the electrolyte reservoir. t Open the venting plug on the probe head by approx. one turn and leave it open until the electrolyte emerges without any bubbles. Then close the venting plug manually and clean the entire area carefully with water. t Set the necessary operating pressure at the electrolyte reservoir as described in Section Electrolyte consumption At a differential pressure of 0.5 bar, a consumption of 0.01 to 0.02 ml/h is to be expected. If a higher differential pressure is present, the consumption may rise to 0.2 ml/h. We recommend contacting our measuring technology department if a higher consumption is noticed. Pfaudler Werke GmbH OI e 19

20 9.4 Cleaning and sterilization of the probes Glass is largely insensitive to contamination. It will be sufficient to check the ph glass and the area of the diaphragm 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. When cleaning the probes manually, a 5-20 % acid, such as HCl may be used to remove deposits or product films, if this cleaning process is carried out at ambient temperature. Do not use any fluorine-containing acids because they strongly attack glass. m When handling acids, please make sure to observe the accident prevention regulations applicable to hazardous substances and their use. CIP processes The probe may also be cleaned inside the reactor or the pipeline by the so-called CIP method (clean-in-place). The following media are permitted for cleaning the probe: n % alkaline solution, max. 85 C, max. 1 h n 1.5 % acid (HNO 3 ), 60 C, max. 15 min. n Steam 134 C, max. 2 h. The plant operator will define the type and procedure of the CIP process. By cleaning with alkali media, the gel layer on the surface of the ph glass is damaged. This will result in a zero point drift which will cause a short-term measuring variance of up to 0.5 ph. The zero point drift can be corrected by reconditioning the probe. Reconditioning (regeneration) is performed by a subsequent CIP process using water or steam. Figure 11 shows the behavior of the regeneration time and the measuring variance with respect to various cleaning agents. Alkali cleaning is performed using 2 percent NaOH at 85 C. The ph Reiner probe is resistant to thermal shock up to a DT of max. 120 C (temperature difference between product and probe). If the probe had not been sufficiently reconditioned, a slight zero point drift may occur after the first cleaning process because no stable gel layer had been built up at the surface of the ph glass prior to cleaning. This zero point drift must be corrected by subsequent single-point calibration in the transmitter. D ph 0,1 0 0,1 0,2 0,3 SIP processes The probe may also be sterilized inside the reactor or the pipeline by the so-called SIP method (sterilize-in-place). The following media are permitted for sterilizing the probe: n Product n Water vapor n Alcohol solutions n Aseptic solutions The plant operator will define the type and procedure of the SIP process. The ph Reiner probe is resistant to thermal shock up to a DT of max. 120 C (temperature difference between product and probe). If the probe had not been sufficiently reconditioned, a slight zero point drift may occur after the first sterilization process because no stable gel layer had been built up at the surface of the ph glass prior to sterilization. This zero point drift must be corrected by subsequent single-point calibration in the transmitter. For CIP processes it must be ensured that the admissible alkali and acid concentrations as well as the maximum temperature or cleaning time are not exceeded. Otherwise, the ph glass would be subject to increased corrosion. Corrosion doubles with every 10 C of a temperature increase when using alkalis for cleaning. 0,4 0, C Steam 95 C Water 80 C Water 25 C Water Regeneration time (min) after 30 min CIP using 2 percent NaOH at 85 C MT0078_1E Figure 11 Reconditioning the ph Reiner probe after cleaning with alkali 20 Pfaudler Werke GmbH OI e

21 9.5 Troubleshooting Malfunction Cause Remedy Display oscillates when touching the electrolyte hose a Insufficiently vented Venting Identical display with different buffer solutions Zero drift Zero point no longer in permitted range Zero drifts when venting the probe a Pore in the ph glass (product is in contact with the derivative layer) b Cable or transmitter input defective a Reference electrode exhausted or defective b Defective cable or insulation fault caused by moisture Repair by Pfaudler Replacement Have Pfaudler replace reference electrode Check cable, replace if necessary, Remove moisture with hot air blower Slope too low or very slow response a Lime or other deposits Determine potential at ph 3 and ph 7 Slope 55 mv/ph at 25 C Keep probe for 30 min in 10 % HCl solution, rinse in water and measure again b If acid treatment is not successful Inspection by Pfaudler c Insulation fault due to moisture Check cable and replace if necessary, remove moisture with hot air blower Pfaudler Werke GmbH OI e 21

22 9.6 Spare parts list Spare parts for the probe Part no. Thread adapter M20 made of Thread adapter PG 13.5 made of Thread adapter 3 / 4 made of Thread adapter 1 made of Spare parts for Ingold adapter Installation adapter DN25/M Spacer tube 16 x 1.5, length 69 mm, made of Support ring for spacer tube made of PTFE Union nut G 1 1 / 4 made of O-ring 10.0 x 2.5 mm made of EPDM K O-ring 20.0 x 2.5 mm made of silicon D Spare parts for Pfaudler aseptic adapter Installation adapter DN30/M Spacer tube 16 x 1.5, length 69 mm, made of Support ring for spacer tube made of PTFE Union nut G 1 1 / 4 made of O-ring 10.0 x 2.5 mm made of EPDM K O-ring x 3.53 mm made of EPDM D Spare parts for the electrolyte reservoir Part no. Electrolyte reservoir, complete, without level monitoring Electrolyte reservoir, complete, with level monitoring Plastic insert made of POM, complete Clamp gasket DN 100 made of Perbunan (NBR) O-ring 28.0 x 4.0 mm made of silicon, blue K Hollow needle made of stainless steel O-ring 8.0 x 1.5 mm made of silicon, transparent K Electrolyte hose 4.0 x 1.5, length 5 m, made of PTFE, prefabricated, including connector and coupling Electrolyte hose 4.0 x 1.5, length 5 m, made of PTFE, without connector and coupling Connector, self-locking, made of EPDM Coupling, self-locking, made of EPDM Straight male union with O-ring DN 4/6, G 1 / 4, made of PVDF Closing plug M12 x 1 mm made of PVDF O-ring 10.0 x 2.0 mm made of Viton D other spare parts Part no. Electrolyte 3mol KCl, sterile, 1 liter plastic bottle liter plastic bottle, empty, to be filled with ethanol Demineralized water, sterile, 1 liter plastic bottle ph Reiner connection cord, 3m, with Variopin coupling, black K ph Reiner connection cord, 5m, with Variopin coupling, black K Pfaudler Werke GmbH OI e

23 TYPE EL AUGUST 2006 Pfaudler Werke GmbH OI e 23

24 Annex A Installation adapter assembly The ph probe can be fitted to various installation adapters m When handling the probe, please avoid hitting the sensor with steel or stone because the glass may get damaged. Procedure: t ph-reiner without adapter screw. 1 The adapter screw M20 part no must be pushed onto the sensor head and fastened to the probe head using four M3 headless setscrews in the groove on the probe head. 2 t 2 pce PTFE support rings, part no t Push the 1 st PTFE support ring onto the probe. 4 t Push the spacer tube onto the probe. 5 t Fit both parts to the adapter screw. 6 t Push the second support ring to the screw and press it into the spacer tube. 7 t Place the O-ring 10x2.5 in position and roll it to its position. 8 t If necessary, push a suitable union nut for fastening the installation adapter onto the assembly. 9 t Carefully push the installation adapter onto the probe. The assembly of the installation adapters always follows the same procedure, regardless of the type of adapter. 10 t Hold down the adapter screw and firmly tighten the installation adapter clockwise If the O-ring has been sufficiently prestressed, the gap will be closed Figure 12 Installation adapter assembly 24 Pfaudler Werke GmbH OI e

25 Annex A Installation adapter assembly 12 7 Figure Pfaudler Werke GmbH OI e 25