Yokogawa PH18 User Manual

Instruction Manual

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Model PH18 Differential pH sensor

Yokogawa Corporation of America 2 Dart Road, Newnan, Georgia U.S.A. 30265 Tel: 1-800-258-2552 Fax: 1-770-254-0928

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2nd Edition

TABLE OF CONTENTS

PREFACE ...................................................................................................................................................... 1

1 INTRODUCTION .......................................................................................................................................... 3

2 GENERAL SPECIFICATIONS ...................................................................................................................... 5

2.1 Model PH18 differential pH sensor ........................................................................................................5

2.2 Model WU18 cable for PH18 sensor .....................................................................................................6

2.2 Dimensions of the PH18SA .................................................................................................................... 7

3 THE TYPE 18 PH PROBE ............................................................................................................................ 8

3.1 Typical applications ................................................................................................................................ 8

3.2 Handling information for the glass lined pH probe................................................................................. 8

3.3 Storage and hydration ............................................................................................................................ 8

3.4 Installation .............................................................................................................................................. 8

3.5 PH18 Installation examples .................................................................................................................... 9

4 PH202/PH402 and FLXA21/PH450 Instrument........................................................................................ 10

4.1 Set-up ................................................................................................................................................... 10

5 CALIBRATION ............................................................................................................................................ 11

5.1 Calibration set-up ................................................................................................................................. 11

5.2 Isopotential pH value ............................................................................................................................ 11

5.3 SLOPE .................................................................................................................................................. 11

5.4 ASY ....................................................................................................................................................... 11

5-5 Process Temperature compensation ................................................................................................... 11

6 CLEANING/STERILIZATION ...................................................................................................................... 12

6.1 Acceptable CIP cleaning processes ..................................................................................................... 12

6.2 Sterilization methods ............................................................................................................................ 12

7 MAINTENANCE .......................................................................................................................................... 12

8 POSITION OF THE O-RINGS .................................................................................................................... 13

9 ACCESSORIES ........................................................................................................................................... 13

APPLICATION DATA SHEET PH DIFFERENTIAL PH SENSOR ...............................................................14

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Caution - Inappropriate handling can cause damage.

Striking or scratching the sensor against hard surfaces such as steel, stone, glass or ceramic, may cause damage to the enamel. Such damage may not affect the sensor performance immediately,

but after prolonged exposure to the process, aking

of the enamel may occur.

Note - Enable impedance checks in the PH202/FLXA21 or PH402/PH450 The sensor impedance checking can give early warning of damage to the enamel layers. If the transmitter signals an impedance failure of the PH18, the sensor should be removed from the process, as soon as possible (within 24 hours). The

loss of signicant amounts of enamel may

thus be avoided.

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PREFACE

The PH18 should only be used with equipment that meets the relevant IEC, American or Canadian standards. Yokogawa accepts no responsibility for the misuse of this unit. The PH18 is packed carefully with shock absorbing materials, nevertheless, it may be damaged or broken if subjected to strong shock, such as if the package is dropped. Handle with care. Although the PH18 has a weatherproof construction, the connections can be harmed if it becomes submerged in water or becomes excessively wet. Do not use an abrasive in cleaning the PH18.

Notice

Contents of this manual are subject to change without notice. Yokogawa is not responsible for damage to the sensor, poor performance, or losses resulting from such, if the problems are caused by:

1. Incorrect operation by this user.

2. Use of the sensor in the wrong applications.

3. Use of the sensor in an adverse environment or incorrect utility program

4. Repair or modication of the sensor by an engineer not authorized by Yokogawa.

Warranty and service

Yokogawa products and parts are guaranteed free from defects in workmanship and material under normal use and service for a period of (typically) 12 months from the date of shipment from the manufacturer. Individual sales organisations can deviate from the typical warranty period, and the conditions of sale relating to the original purchase order should be consulted. Damage caused by wear and tear, inadequate maintenance, corrosion, or by the effects of chemical processes are excluded from this warranty coverage. In the event of warranty claim, the defective goods should be sent ( freight paid) to the service department of the relative sales organisation for repair or replacement (at Yokogawa discretion).

The following information must be included in the letter accompanying the returned goods:

1. Part number, model code and serial number.

2. Original purchase order and date.

3. Length of time in service and a description of the process.

4. Description of the fault, and the circumstances of failure.

5. Process/environmental conditions that may be related to the installation failure of the device.

6. A statement whether warranty or nonwarranty service is requested.

7. Complete shipping and billing instructions for return of material , plus the name and phone number of a contact person who can be reached for further information. Returned goods that have been in contact with process

uids must be decontaminated/ disinfected before shipment. Goods should carry a certicate to this

effect, for the health and safety of our employees. Material safety data sheets should be included for all components of the processes to which the equipment has been exposed.

Unpacking and checking

Upon receipt of the goods, carefully inspect the shipping package for any evidence of damage. If the carton is damaged, notify the shipping agent and the sales organisation immediately. If the shipping package is not

damaged, remove the products and parts. Conrm

that all items shown on the packing list are available and that the package does not contain any parts or

accessories llers. Notify the sales organisation if items

are missing.

PH18 sensor

The box of the PH18 sensor contains the following items: Sensor complete, possible options (check part number for possible options), instruction manual, material

certicate and quality inspection certicate. The WU18

cable is packed separately.

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1. INTRODUCTION

The PH18 is not a conventional electrode. It relies on two dissimilar ion sensitive enamel membranes to generate the signal. The measuring element is like a pH electrode, and the reference like a Sodium ion electrode.

Therefore the PH18 can only be used in combination with pH meters that feature: 1 Dual high impedance inputs 2 Adjustable setting for Isothermal Point

3 Adjustable temperature coefcient

The Yokogawa models PH202 and PH402 satisfy these requirements.

In both cases the membrane enamels are bonded

directly to the metal substrate with no lling solution.

The response curves Fig. 1 (pH), Fig. 2 (reference) and Fig. 3 (application range) show the way in which the potential is generated at each element and combined in the output of the sensor.

Fig. 1 Above pH11 the effect of sodium on the pH membrane starts to cause non-linearity (Sodium error) Fig. 2 Below pH3 the high Hydrogen ion content causes a change in the reference response Fig. 3 A linear response to pH is obtained between 3 and 11 pH Fig. 4 A plot of reference voltage against Sodium content.

The revolutionary measuring principle has some big

advantages. The absence of lling solutions and

reference junctions virtually eliminates the problems caused by aging and pollution of the reference sensor. Regular cleaning of the sensor virtually eliminates drift,

and the sensor benets from a very long working life. It is vital, however, to t the sensor to the application

correctly. The special nature of the reference element dictates that there must be a certain Sodium level in the process.

Fig. 4 shows a plot of reference voltage against Sodium content.

Because of the exponential nature of the response, it is plain that above about 0.5 N Na+ (30 g NaCl/l) in the solution, the reference output remains virtually constant. Of course when the Sodium concentration remains constant in a process the reference voltage will also be constant at much lower levels of Sodium.

It is because of the need to evaluate the chemistry of the process, that it is necessary to have an Application Data Sheet (page 16) completed before approval for this sensor can be made.

The mechanical construction of the sensor also means that it may be used in processes involving both high

temperatures and pressures. By eliminating the lling

solutions, the sensor is truly robust and can even withstand severe thermal shocks that would ruin most systems.

The stainless steel mounting adapter forms the liquid earth (solution ground) connection needed to ensure best stability of measurement. EXA also uses this connection in the diagnostic circuit.

The PH18 is a differential pH sensor. It does not measure absolute pH except in limited applications. It does, however, measure a single control point accurately, repeatably and with minimum maintenance.

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