Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual

Transcription

1 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual Rev 1 4/01 Sensing and Control

2 Copyright, Notices, and Trademarks Printed in U.S.A. Copyright 2001 by Honeywell Revision 1 April 2, 2001 Warranty/Remedy Honeywell warrants goods of its manufacture as being free of defective materials and faulty workmanship. Contact your local sales office for warranty information. If warranted goods are returned to Honeywell during the period of coverage, Honeywell will repair or replace without charge those items it finds defective. The foregoing is Buyer s sole remedy and is in lieu of all other warranties, expressed or implied, including those of merchantability and fitness for a particular purpose. Specifications may change without notice. The information we supply is believed to be accurate and reliable as of this printing. However, we assume no responsibility for its use. While we provide application assistance personally, through our literature and the Honeywell web site, it is up to the customer to determine the suitability of the product in the application. Sensing and Control Honeywell 11 West Spring Street Freeport, IL Meredian is a U.S. registered trademark of Honeywell DirectLine is a trademark of Honeywell Other brands or product names are trademarks of their respective owners ii Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

3 About This Document Abstract This document provides the operation and maintenance information for the Meredian II Combination Industrial Electrodes for ph and ORP. Contacts World Wide Web The following lists Honeywell s World Wide Web sites that will be of interest to our customers. Honeywell Organization WWW Address (URL) Corporate Sensing and Control International Telephone Contact us by telephone at the numbers listed below. Organization Phone Number United States and Canada Honeywell (215) Tech. Support Asia Pacific Honeywell Asia Pacific Hong Kong Q&A Faxback (TACFACS) Service (852) Europe Honeywell PACE, Brussels, Belgium [32-2] Latin America Honeywell, Sunrise, Florida U.S.A. (954) /01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual iii

4 Contents 1. INTRODUCTION General Specifications INSTALLATION Unpacking Electrode Preparation Calibration MAINTENANCE Shelf Life and Storage Resistance Check for Clogged Reference Junction Servicing a Clogged or Dried Out Reference Junction Troubleshooting Cleaning ORP Reference Solutions Protective Tips Accessories and Replacement Parts Tables Table 1-1 Meredian II Electrode Specifications... 3 Table 3-1 Troubleshooting Chart Table 3-2 Buffer Solution Redox Potential Table 3-3 Accessory and Replacement Parts Figures Figure 1-1 Meredian II ph Electrode with Slotted Top... 2 Figure 2-1 Cable for All ph Electrodes and ORP Electrodes Used with Instruments Other Than DirectLine... 9 Figure 2-2 Cable for ORP Electrodes Used with DirectLine... 9 Figure 3-1 Meredian II Combination Electrode Tips iv Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

5 Introduction 1. Introduction 1.1 General This manual covers the Meredian II Combination ph with the following part numbers: Instrument Compatibility Part Number 9782, APT2000, APT4000, 7082, DirectLine DL and the Meredian II ORP Electrodes with the following part numbers: Instrument Compatibility Part Number 9782, APT2000, APT4000, 7082, DirectLine DL The Meredian II Combination ph Electrode (Figure 1-1) is a dual element system designed for use primarily in aqueous solutions. It is comprised of a glass ph measuring element which is completely sealed with a non-permeable ph sensitive and a diffusion-type, silver-silver chloride, reference element housed in a Ryton body. The measured electrical potential of the Meredian II ph Electrode is the difference between the potential of the glass element and the potential of the outer reference element when the electrode is immersed in a process solution. The Meredian II ph Electrode must be positioned so that the process solution is in constant contact with both the (measuring electrode) and the reference electrode. The Meredian II Electrode for ORP measurements is a dual-element device comprising a noble-metal redox element and a diffusion-type, silver-silver chloride (with saturated KCI gel) reference element housed in a 4/01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 1

6 Introduction Ryton body. The measured electrical potential of the Meredian II Electrode is the difference between the potential on the inert noble-metal element and the potential of the outer reference element when the electrode is immersed in a process solution. ph Glass Membrane Reference Junction O-Ring Tip O-Ring Slotted Tip Electrode Body Reference Junction Figure 1-1 Meredian II ph Electrode with Slotted Top a/n Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

7 Introduction 1.2 Specifications Specifications for each Meredian II Electrode part number are listed in Table 1-1. Specifications applicable to all electrodes are as follows: Pressure Limit: C; C ( F; F) Table 1-1 Meredian II Electrode Specifications Electrode Part No. Function Operating Temp. Range C Auto Temp. Comp. Construction ¾ NPT Mounting Lead Termination Used on Electrode Mtg Notes , ph (1-13) 20 to 110 Yes Ryton body, slotted tip, Cable end, for immersion only 12 tinned X X 1, 2, ph (1-13) 20 to 110 Yes Ryton body, slotted tip, Cable end, for immersion only 20 tinned X X , ph (1-13) 0 to 80 Yes Ryton body, slotted tip, Cable end, for immersion only 12 tinned X X 1, ph (1-13) 0 to 80 Yes Ryton body, slotted tip, Cable end, for immersion only 20 tinned X X ph (1-13) 20 to 110 Yes Ryton body, slotted tip, Cable end, for immersion only 12 quick disconnect X X 1, 2, ph (1-13) 0 to 80 Yes Ryton body, slotted tip, Cable end, for immersion only 12 quick disconnect X X 1, ph (1-13) 20 to 110 Yes Ryton body, Both ends, for in line 8 quick disconnect X 1, 2, 3, ph (1-13) 0 to 80 Yes Ryton body, Both ends for in line 8 quick disconnect X 1, 2, ph (1-13) 20 to 110 Yes Ryton body, Both ends for in line 12 quick disconnect X 1, 2, 3, ph (1-13) 0 to 80 Yes Ryton body, Both ends for in line 12 quick disconnect X 1, 2, 3 4/01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 3

8 Introduction Electrode Part No. Function Operating Temp. Range C Auto Temp. Comp. Construction ¾ NPT Mounting Lead Termination Used on Electrode Mtg Notes ph (1-13) 0 to 80 Yes Ryton body, ph (1-13) 20 to 110 Yes Ryton body, ph (1-13) 0 to 80 Yes Ryton body, ph (1-13) 20 to 110 Yes Ryton body, 12 tinned X 12 tinned X 20 tinned X 20 tinned X ph (1-13) 0 to 80 Yes Ryton body, None (connector for integral DirectLine mounting) X ph (1-13) 20 to 110 Yes Ryton body, None (connector for integral DirectLine mounting) X , Redox (Oxidation Reduction) potential 5 to 100 None Ryton body, slotted tip, glass, gold electrode Cable end, for immersion only 12 tinned X X , Redox (Oxidation Reduction) potential 5 to 110 None Ryton body, slotted tip, glass, platinum electrode. Cable end, for immersion only 12 tinned X X ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, slotted tip, platinum electrode Cable end, for immersion only 20' tinned X X ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, slotted tip, gold electrode Cable end, for immersion only 20' tinned X X ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, platinum electrode None (connector for integral DirectLine mounting) X 4 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

9 Introduction Electrode Part No. Function Operating Temp. Range C Auto Temp. Comp. Construction ¾ NPT Mounting Lead Termination Used on Electrode Mtg Notes ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, gold electrode None (connector for integral DirectLine mounting) X ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, platinum electrode 12' tinned X ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, gold electrode 12' tinned X ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, platinum electrode 20' tinned ORP (Oxidation Reduction Potential) 5 to 100 None Ryton body, gold electrode 20'tinned X NOTES: 1. Temperature range indicated for optimum performance. 2. Reduced life above 9 ph and 60 C. 3. Electrode can be installed directly into 3/4 NPT opening; however, see Automatic Temperature Compensation Considerations (page 7). 4. While electrode bodies are rated at 110 C, cables are rated at 105 C maximum. 4/01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 5

10 Introduction 6 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

11 Installation 2. Installation 2.1 Unpacking Remove the electrode from the box and carefully remove the vinyl tape and plastic cap from the sensing end. If excess salt crystals are present, remove by placing the electrode under a running tap of warm water until dissolved. Keep termination and leadwires dry. Protect quick disconnects from damage or dirt on electrodes so equipped. When the Meredian II electrode is equipped with a quick-disconnect cable, it is important to avoid contamination of the internal area of the coaxial cable connector. Avoid touching the center contact of the quick disconnect connector. For electrodes without quick disconnect cables, avoid touching the insulation of the inner conductor of the coaxial cable. Contamination, such as oils and salts form bare hands can form a leakage path which could affect the necessary high resistance required between the center conductor and all other conductors. CAUTION Always protect the fragile ph sensitive membrane whenever handling electrodes and during any testing when the electrode is removed from the process. The cap contains an electrode conditioning solution of 4 ph buffer saturated with potassium chloride. For best performance and longer life, always replace the cap when the electrode is not in use. If conditioning solution is not available, use buffers of 4.01 or 6.86 or tap water. CAUTION For integral DirectLine ph and ORP electrodes, be careful not to contaminate the PWB connector on the electrode. 2.2 Electrode Preparation Automatic Temperature Compensation Considerations - ph ONLY The temperature sensor is positioned approximately 2 above the glass ph membrane. The electrode body should be immersed at least 4 into the process to achieve best temperature response. When large or abrupt changes in temperature occur in process, a small temporary error in ph value may result from temperature lag. In flow applications it is good practice to enclose the electrode and pipe tee in insulation to assure good process temperature sensing. Special Precautions Electrodes are fragile devices and should be protected and handled with care. The of the ph electrodes are attacked by hydrofluoric acid, even in low concentrations. In general, s have reduced service life above approximately 9 ph in hot solutions. The rate of attack increases as the ph and/or temperature increases. As ph and temperature increase above 80 C and above 10 ph, it may be impractical to attempt to use a ph electrode because of glass corrosion. Do not install where temperatures may approach 10 C (+12 F) when the process is shut down or freeze damage may result. 4/01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 7

12 Installation Connections Electrical connections depend upon the electrode and measuring system used. These connections are described in the appropriate electrode mounting or instrument manual. The center conductor in the coaxial cable is the measuring element lead; the orange conductor of the cable is the reference element lead. The pair of white conductors are the temperature sensor leads. Electrodes without connectors may have a third white conductor which is a shield and connects to the SC terminal in the direct ph measuring instrument. ORP Applications Cables Note that in some applications (including the cyanide to cyanate reaction) the ORP measuring element is negative at the start and becomes positive as the reaction goes to completion. In other measurements (including the chrome-reduction reaction), the measuring element starts positive and becomes less positive as the reaction goes to completion. For all cyanide-oxidizing and chrome-reduction reactions, the control point and point of interest is the positive region of the measurement. Therefore, in both these applications, connect the measuring element lead (inner coax conductor) to the + (or R) terminal. Connect the reference element lead (orange conductor) to the negative terminal (or high impedance cable). Other applications may require reversal of these connections. Refer to the instructions furnished with the electrode mounting or instrument for detailed connection information. DirectLine ph Electrodes Integral mount electrodes ( , -002) do not have cables but employ a connector to mount the DirectLine Sensor Module directly on the electrode. Remote mount electrodes ( , -002, -003, -004, and , -002, -003, -004) have an integral cable. The cable is a combination coax with three separate tinned leads. The center of the coax is the measuring lead, the orange lead is the reference lead, the white/black lead coming off the coax is the shield, and the two white leads are the temperature sensor leads. See Error! Reference source not found.. DirectLine ORP Electrodes Integral mount electrodes ( , -002) do not have cables but employ a connector to mount the DirectLine Sensor Module directly on the electrodes. Remote mount electrodes ( , -002, -003, -004, and , -002, -003, -004) have an integral cable. The cable is a twisted pair cable with a shield. The red lead is the measuring lead, the black lead is the reference lead, and the bare wire is the shield. ORP electrodes have NO temperature sensor leads. See Error! Reference source not found.. Non-DirectLine ph Electrodes ph electrodes used with instruments other than the DirectLine Sensor Module (e.g., APT2000/4000, 9782, 7082) have integral cables that terminate either with a connector or with tinned leads. Connector type electrodes ( , , , , , and ) are used to connect to external glass preamplifiers. Tinned lead type electrodes ( and ) are used to connect to terminals of an instrument's internal preamplifier. The cable is a combination coax with three separate tinned leads. The center of the coax is the measuring lead, the orange lead is the reference lead, the white/black lead coming off the coax is the shield, and the two white leads are the temperature sensor leads. See Error! Reference source not found.. 8 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

13 Installation Non-DirectLine ORP Electrodes ORP electrodes used with instruments other than the DirectLine Sensor Module (e.g., APT2000, 4000, 9782, 7082) have integral cables that terminate with tinned leads. The cable is a combination coax with a separate tinned lead. The center of the coax is the measuring lead and the orange lead is the reference lead. ORP electrodes have NO temperature sensor leads. See Error! Reference source not found.. Shield Lead Orange Ref White Temp White Temp NOTE: ORP does not have Temp Leads. Skin and Tin Leads Figure 2-1 Cable for All ph Electrodes and ORP Electrodes Used with Instruments Other Than DirectLine Red Measuring Black Ref. Shield Figure 2-2 Cable for ORP Electrodes Used with DirectLine 4/01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 9

14 Installation 2.3 Calibration The exact potential from electrode systems varies from electrode to electrode and can change slightly over a period of time. For calibration procedures refer to the instructions for the instrument with which the electrode is used. 10 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

15 Maintenance 3. Maintenance 3.1 Shelf Life and Storage Electrode stock should be rotated or checked once a year. Prolonged storage on the shelf can cause the reference electrode to dry out. To avoid this, a routine maintenance should be done as follows: 1. Remove the electrode from its storage box and remove the cap. 2. Rinse away any excess crystals. 3. Refill the cap with electrode storage solution. (See the CAUTION note in Section 2.1.) 4. Replace the cap on the electrode. 5. Wrap vinyl tape around the joint of the cap edge with the electrode body. 6. Replace the electrode in its storage box and mark the date on the box. The electrode filling materials will freeze at 10 C (+12 F). Avoid storage at or below this temperature, or above 50 C (122 F). 3.2 Resistance Check for Clogged Reference Junction A resistance check across the reference junction can be used to verify a clogged junction. The resistance measurement is made between the reference lead of the electrode and a stainless steel wire immersed in a beaker of concentrated KCI solution. Use an AC bridge to make the measurement in order to avoid polarization. If the measured resistance is 5000 ohms or greater, the electrode junction may be clogged. If an AC measurement cannot be made, a crude approximation can be made by using a DC ohmmeter with care. Proceed quickly to avoid polarizing the elements. Reverse the meter polarity to obtain two resistance readings. If the highest reading is 10,000 ohms or greater, the electrode junction may be clogged. If the electrode elements become dc polarized, accurate measurements are not possible for about one-half hour. 3.3 Servicing a Clogged or Dried Out Reference Junction When the electrode s porous reference junction has been determined to be clogged or dried out, immerse the end of the electrode for one hour in water at approximately 90 C. Remove the storage cap but do not remove the protective tip (see Figure 1-1) during the cleaning operation. Recheck the junction per Section 3.2. If still clogged, transfer the electrode to a beaker of saturated KCI solution and heat to boiling. Remove the heat and allow the electrode to soak in this solution while it cools to room temperature. 4/01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 11

16 Maintenance 3.4 Troubleshooting For possible problems and corrective actions refer to Table 3-1. Table 3-1 Troubleshooting Chart Symptom Possible Cause Correction Random drifting and extremely sensitive to body capacitance. Poor electrical connection. Electrode operating below its temperature range. Quick disconnect not making contact. Check wiring for poor connections to spade lug, terminal screw or for broken wire. Select an electrode rated for the operating temperature range. Check and correct connectors. Dried reference. Service (See Section 3.3.) Sluggish response. Coating. Clean (See Section 3.5.) No ph response (measurement doesn t change with a change in ph.) Process environment has attacked the ph glass membrane. Cracked or broken membrane. Electrode improperly wired. Rejuvenate the membrane by etching in a 5 % ammonium bifluoride solution for 1 to 2 minutes. CAUTION: Frequent etching will destroy the electrode. Always try other cleaning methods first. Replace electrode. Check and correct wiring and insulation. 3.5 Cleaning ph Electrodes Some processes have materials that tend to adhere to the glass of the electrode. Frequency of cleaning is determined from experience, the effect on the measurement and the tendency of adherence. Loose or lodged debris can usually be removed by placing the electrode under a flowing spigot or the jet of a wash bottle. Use care when handling the electrode. The glass can be wiped gently with a soft wet cloth or a paper tissue. Remove oil deposits with a detergent or any solvent. Excellent results can be obtained with laboratory detergents such as Micro or Sparkleen. Most household detergents such as Joy or Windex are also effective. If necessary, use dilute hydrochloric acid or other dilute acid to clean the glass. The plastic can be cleaned with almost any cleaning agent. Do not leave the electrode in a concentrated base or acid for more than 5 minutes. Always wash the electrode thoroughly after cleaning; then rinse in distilled water. Keep the electrode s protective tip in place during cleaning or rinsing. This is important in order to avoid contaminating or diluting the reference gel electyrolyte. Before using, allow the electrode to soak for an hour in a neutral buffer such as 6.86, part number ORP Electrodes Clean the electrode periodically at intervals dependent upon conditions of the application. The precipitation of metal hydroxides, in some applications, can result in impurities coating the electrode surface and this could lead to a lack of response. The metal electrode surface may be wiped clean with a soft, wet cloth. Oily deposits may be removed with detergent. Avoid the use of harsh abrasives. If it is difficult to remove other deposits, dilute acids or bases may be used. 12 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

17 Maintenance 3.6 ORP Reference Solutions Although the exact value of the ORP potential measured is not needed for the usual empirical-type application, a means of checking the electrodes and measuring instrument as a maintenance procedure may be desired. ORP measuring systems may be checked by measuring a solution having a known oxidationreduction potential. To prepare such a solution, dissolve 0.1 gram (0.5 cc or 0.1 teaspoon by volume) of quinhydrone powder in 5 cc of acetone or methyl alcohol (methanol). Add this to not more than 500 cc of a standard ph reference solution (buffer). The ORP potential of this solution is indicated in Table 3-2 for several temperatures. The polarity sign shown is that of the measuring element with respect to the reference element. Table 3-2 Buffer Solution Redox Potential ph Reference Solution (Buffer) Saturated With Quinhydrone ORP Potential* Solution Temperature 20 C 25 C 30 C 25 C - Pint Liquid, Part mv 263 mv 259 mv 25 C - Pint Liquid, Part mv 94 mv 88 mv 25 C - Pint Liquid, Part mv 43 mv 49 mv *The ORP potential values have a tolerance of ±50 mv under industrial conditions. 3.7 Electrode Tips The Meredian II Electrodes are supplied with either a slotted protective tip or a smooth tip as noted in the Specifications. Figure 3-1 shows these tips. CAUTION When replacing a tip, note that two O-rings are used to form seals at the electrode body and at the ceramic reference junction. Assure that these O-rings are in place before installing a tip on an electrode. The O- ring part numbers are listed in Section 3.8, Accessories and Replacement Parts. Before replacing a tip, clean the housing threads and the two O-rings with a damp cotton swab. The tip is properly seated on the electrode housing when it is hand tightened so that the large O-ring is compressed into the housing body. Do not apply any sideways force to the assembly while changing tips. Slotted Tip Used for Submersion Applications Smooth Tip Used for In-Line Threaded Applications Figure 3-1 Meredian II Combination Electrode Tips 4/01 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 13

18 Maintenance 3.8 Accessories and Replacement Parts Accessory and replacement parts are listed in Table 3-3. Table 3-3 Accessory and Replacement Parts Description Part No. Storage Cap Standard Buffer Reference Solution, 1 Pint 4.01 ph 6.86 ph 9.18 ph O-Ring for protective tip O-Ring for ceramic reference junction Protective Tips (Figure 3-1) Slotted Tip, Ryton* Smooth Tip, Ryton O-Ring for DirectLine Integral Electrode *Supplied with the electrode, 7774 Assemblies 14 Meredian II Combination Industrial Electrodes for ph and ORP Instruction Manual 4/01

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20 Sensing and Control Honeywell 11 West Spring Street Freeport, IL Printed in USA