2-Wire Dual Channel Transmitter/Analyzer FLXA202/21

The FLEXA™ series analyzers are modular-designed analyzers used for continuous online measurements in industrial installations. They offer single or dual sensor measurement, making them the most flexible 2-wire analyzer available.

With the FLXA202, there is no need for multiple analyzers, since it is easily scalable at the site location by swapping the internal measurement module to what is needed, giving you more flexibility and optimizing your OPEX.

Support of Up to Two Sensors

Through the installation of up to two sensors, FLXA202 realizes interruption-free measurement even during maintenance. For dual sensor measurement, the sensor modules must be the same parameter – pH/ORP and pH/ORP, SC and SC, and DO and DO. Dual sensor measurement offers additional functionalities including a variety of calculated data from the two measuring parameters, as well as, the option to program the analyzer as a redundant system.

Advanced Functions

With the FLXA202, one analyzer can accept any of four types of measurements: pH/ORP, Contacting Conductivity (SC), Inductive Conductivity (ISC) and Dissolved Oxygen (DO)Sensors with self-diagnostics capabilities. Additional functions include:

  • Continuous measurement of sensor impedance, asymmetric potential, and slope, and continuous monitoring for electrode contamination/damage, burnout, and decline in measurement liquid level (ex. pH Analyzer)
  • Online Sensor Wellness checking for predictive maintenance

Clear Touch Panel Display for Improved Operability

The FLEXA series analyzer provides improved operability with intuitive touchscreen operation, featuring a clear display and user-friendly indication with 12 languages. A quick setup menu for immediate measurement and a display of sensor status and estimated maintenance time improve efficiency. The interactive screen is housed in a robust aluminum die-cast housing (FLXA202) or a plastic construction (FLXA21).

Modular Design for Increased Scalability

The FLEXA™ series analyzer features a modular design with replaceable sensor modules, enabling the construction of a variety of systems. Users can opt to do without a display and can also select the case material (plastic or stainless steel).

Model Code
FLXA202

FLXA21
Area Classification General Purpose
Class I Div II (without the use of IS Barrier)
Class I Div I (with the use of IS Barrier)
General Purpose
Class I Div II (without the use of IS Barrier)
Class I Div I (with the use of IS Barrier)
Enclosure Material Aluminum alloy die cast with epoxy coating (Standard offering
Aluminum alloy die cast with urethane or high anti-corrosion coating (available upon request)
Plastic (Polycarbonate)
Housing Rating IP66 (except Canada), Type 4X (except Canada), Type 3S/4X (Canada) IP66/ NEMA 4A/ CSA 3S
Power Supply 2-wire 24VDC Loop Powered 2-wire 24VDC Loop Powered
Output Signal Bi-directional HART digital communication, superimposed on mA (4-20mA) signal Bi-directional HART digital communication, superimposed on mA (4-20mA) signal
Optional FF (FOUNDATION Fieldbus) and PF (Profibus) communication

Extension Terminal Junction Box BA10/WTB10

Between measuring plant and control rooms, especially when the distance between these places is greater than the length of the standard appropriate electrode cables, the connecting equipment can be an expedient method for connecting sensor cables to a measuring instrument.

Overview:

One of the primary applications for high purity water is for boiler feed water. The measurement of pure water pH can be one of the quickest indicators of process contamination in the production or distribution of pure water. Effective chemical treatment of the feed water is vital in maintaining the useful operating life and minimizing maintenance costs of the boiler.

Industry:Power, Pharmaceutical, Common

Industrias:
Aplicacione
Overview:

The level of dissolved oxygen is critical to the quality and consistency of any brew. Too little dissolved oxygen results in the fermentation step of the process will lead to: off flavors (e.g. poor removal of diacetyl and acetaldehyde), poor yeast crop in terms of quantity and vitality, and low ester and alcohol production. 

Overview:

El control de los recursos de agua del mundo es sin duda uno de los temas más importantes. La demanda de agua desde los usuarios industriales hasta domésticos prevé un aumento en todo el mundo industrializado. Yokogawa ha estado aplicando sistemas de medición de mantenimiento mínimos.

Overview:

Wet scrubbers are used in utilities, paper mills, and chemical plants to remove sulfur dioxide (SO2) and other pollutants from gas streams. Undesirable pollutants are removed by contacting the gases with an aqueous solution or slurry containing a sorbent. The most common sorbents are lime, Ca(OH)2, and limestone, CaCO3

Industrias:
Overview:

For control of batch neutralization, a pH measurement coupled with a timer-controlled chemical feed scheme provides very satisfactory results.

This system can be adapted for either acid waste or alkaline waste neutralization.

Aplicacione
Overview:

The term "cooling tower" is used to describe both direct (open circuit) and indirect (closed circuit) heat rejection equipment. Cooling towers are heat-transfer units, used to remove heat from any water-cooled system. The cooled water is then re-circulated (and thus, recycled) back into the system. Since the process water is re-circulated, the mineral concentration increases as a result of the evaporation.

Industry:Refining, Food and Beverage, Power, Oil and Gas, Pulp and Paper, Chemical

Industrias:
Overview:

The proliferation of microorganisms and the resultant formation of slime is a problem which commonly occurs in aqueous systems. Problematic slime producing microbes may include bacteria, fungi and/or algae. Slime deposits typically occur in many industrial aqueous systems including cooling water systems, pulp and paper mill systems, petroleum operations, clay and pigment slurries, recreational water systems, air washer systems, decorative fountains, food, beverage, and industrial process pasteurizers, sweetwater systems, gas scrubber systems, latex systems, industrial lubricants, cutting fluids, etc.

Industry:Refining, Food and beverage, Power, Oil and Gas, Pulp and Paper, Chemical

Industrias:
Overview:

There are a number of suppliers of oil and fat products used for edible purposes. These products include, but are not limited to olive oil, peanut oil, soybean oil, sunflower oil, lard, shortening, butter, and margarine. The raw materials for these products include animal by-products, fleshy fruits (palm and olive), and oilseeds. 

Industry:Food and Beverage

Aplicacione
Overview:

The kraft process (also known as kraft pulping or sulfate process) describes a technology for conversion of wood into wood pulp consisting of almost pure cellulose fibers. Wood chips are by harsh chemicals (white liquor) to produce pulp and spent liquor (black liquor).

Overview:

La sosa cáustica y ácido clorhídrico, producida en las plantas electrolizadoras, son materiales fundamentales utilizados en varias industrias; químicas, farmacéuticas, petroquímicas, pulpa y papeles, etc. El beneficio es el resultado de la producción efectiva con costos de explotación/mantenimiento mínimos. El control adecuado del proceso genera estabilizado productos de calidad estables con una gran ganancia operativa.

Overview:

Process liquid analyzers such as pH meters, conductivity meters, ORP meters, and density meters play an important role at electrolysis plants in the control of concentrations of various process solutions. This requires both precision and stability under harsh conditions that include highly corrosive substances, high temperatures, and many impurities.

Overview:

Control of sodium chloride (NaCl) concentration at a salt dissolver where solid salt is dissolved in water, is highly important because of the electrolysis efficiency. A conventional way of measuring the concentration of supersaturated NaCl solution had been performed by using non-contact type sensors (e.g., γ-ray density meter) since NaCl, impurities, and precipitates are in the solution.

Overview:

Most zinc are produced at hydrometallurgically, where a high-grade zinc product can be obtained and valuable metals mixed in the raw material can be recovered. In the hydrometallurgy, the raw material of zinc concentrate is roasted and then dissolved in sulfuric acid to remove impurities. The process called leaching and pH control of the leachate is important.

Industry:Chemical, Power

Industrias:
Overview:

In a semiconductor plant, a variety of chemicals are used in various manufacturing processes. The chemicals used for specific purposes are produced by diluting raw liquid with demineralized water using in diluting equipment, and the control of the concentration at this point is performed by conductivity measurement. 

Overview:

In the manufacturing process of Pharmaceutical, Chemical and Food & Beverage industries, the cleaning and sterilization of tanks and piping are done with various cleaning solutions, fresh or hot water and steam after manufacturing products. Clean-In-Place (CIP) is the system designed for automatic cleaning and disinfecting.

Overview:

Cyanide-bearing wastewater from mining and electroplating facilities and certain types of chemical plants is toxic and must be treated by oxidation with chlorine or chloride to bring the cyanide concentration within regulatory limits.

Industry:Electrical and Electronics

Overview:

Introduction

In Bioscience company's pH is used at various places including glass lined reactor for product efficiency. One of such measurement of pH in reactor as explained below.

Application Information

Typical example of process is:

Reactor used is GLASS LINED REACTOR and length is 1950mm; and flange size 100mm split flange with 8 holes

PCB (fixing hole center to center) 190mm; flange outer to outer 225mm; flange extension pipe (Nozzle) ID 95mm.

Nature of fluid: Aqueous media
Operating temp & pressure: 30°C temp & atmosphere pressure
Area classification - Example Zone 1 / Zone 2
Nozzle ID: 95mm.

glass1

Product Recommendation

Measurement System

Process Liquid Analyzer: 

  • 2-wire FLEXA pH/ORP Analyzer
Features
  • Dual sensor measurement on 2-wire type analyser
  • Indication of sensor wellness

 

  • 4-wire PH450G pH/ORP Analyzer

Features

  • Easy touchscreen operation
  • Trending display up to 2 weeks
  • Advanced Process Temperature Compensation

Sensor Selection:

Hamilton® POLILYTE HTVP

Features:

  • Best measurement accuracy both in high-alkali processes and in samples with very low conductivity.
  • Sterilizable and autoclavable
  • SINGLE PORE‘s for clog-free contact of electrolyte with measurement medium
  • HAMILTON “H” pH glass
  • Serialized with batch number

Sensor Accessories

5mtrs Cable, Model No.: WU10-V-S-05 ,

Immersion sensor fitting (Customised): 1900mm Length, 4" Flange Connection with 8 holes PCB (fixing hole centre to centre) 190mm;  flange outer to outer 225mm; pipe (Nozzle) ID95mm. MOC : PTFE.

Tangible benefit

More reliable and accurate analysis of pH which helps to improve end product quality.

Note: For additional information on this application contact the local Yokogawa Process Liquid Analyzer Department

Overview:

The detectors used to perform dissolved oxygen (DO) measurement in oxidation ditch type sewage treatment plants tend to become dirty quickly and require frequent cleaning. It has been d ifficult to remedy this problem inexpensively. One solution that significantly reduces the sensor maintenance workload is the use of float holders.

Industrias:
Overview:

Continuous technology improvement is ongoing in the pulp & paper industry to obtain the best possible performance. Problems at the wet end (stock preparation) can rarely be corrected downstream. That is why monitoring and controlling pH in pulp stock is critical to the paper making process. Essentially, at every stage in the manufacture of paper, correct pH values play a vital role.

Overview:

Reverse osmosis (RO) is a separation process that uses pressure to force a solution through a membrane that retains the solute on one side and allows the pure solvent to pass to the other side. More formally, it is the process of forcing a solvent from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in excess of the osmotic pressure.

Overview:

La mejora continua de la tecnología en curso en la industria de pulpa y papel sirve para obtener el mejor rendimiento posible. El desempeño mejorado de la planta se traduce en la mejora de la calidad y menor costo, al mismo tiempo una operación de la planta amigable con el medio ambiente.

Industrias:
Overview:

Wastewater from electroplating facilities and certain types of chemical plants contains toxic forms of hexavalent chromium such as chromate and dichromate. The hexavalent chromium in this wastewater must be reduced before the water can be discharged. This requires a two-step process: hexavalent chromium (CR6) is reduced to trivalent chromium (CR3); and CR3 is precipitated as chromium hydroxide.

Industry:Electrical and Electronics

Overview:

Many Ethanol plants running today are using a combination style pH electrode with a non-flowing reference to measure pH in the Mash Slurry transfer line from the Mash slurry mix tank to cook. The Mash is being pumped out of the Mash Slurry tank is at approximately 180 °F and 40 to 60 psig.

Overview:

Removal of free oil and grease from a wastewater stream reduces the potential for equipment problems to occur further downstream. There are three forms of oil encountered in wastewater treatment at a refinery. 

Industrias:
Overview:

Sour Water is the wastewater that is produced from atmospheric and vacuum crude columns at refineries. Hydrogen sulfide and ammonia are typical components in sour water that need to be removed before the water can be reused elsewhere in the plant. Removal of these components is done by sending the sour water from the process to a stripping tower where heat, in the form of steam, is applied.

Overview:

Power plant boiler houses designed to burn coal or high sulfur oil are required by Federal and State pollution regulations to "scrub" (remove) sulfur dioxide from flue gasses to meet emission limits. SO2 in flue gasses is known to be harmful to the environment, as it is one contributor to the formation of acid rain. pH control is critical for the proper functioning of the scrubber system.

Industrias:
Overview:

Introduction

The United States Pharmacopoeia (USP) and European Pharmacopoeia (EP) regulations require total organic carbon (TOC) to be monitored in pharmaceutical waters. Implementing these guidelines is required for companies that bring drugs to the US market. These guidelines are contained in the USP monograph (article). 

Among other functions, the USP states qualifications for sterility and packaging methods that delineate between the various specific types of water. However, there are two basic types of water preparation, Water for Injection and Purified Water. The analytical standards for these two types of water are very similar, differing in the fact that Water for Injection has stricter bacterial count standards and must also pass the bacterial endotoxin test. Preparation methods are very similar to a point, however, Water for Injection preparation must incorporate distillation or double pass reverse osmosis. Discussion of the various methodologies used in preparation of USP water applies equally to Purified Water (PW) and Water for Injection (WFI). 

There are two main types of water, purified water (PW) and water for injection (WFI). Purified Water is water obtained by distillation, ion-exchange treatment, reverse osmosis, or other suitable process. It is prepared from water complying with the regulations of the U.S. Environmental Protection Agency (EPA) with respect to drinking water. It contains no added substances. And, Water for Injection (WFI) is water purified by distillation or reverse osmosis. 

These waters are used as ingredients in either dose form or bulk pharmaceuticals, so purity is critical. WFI is the purest grade of bulk water monographed by the USP, and is found in the manufacture of parenteral (injected), ophthalmic (eye drops), and inhalation products. The Fundamental objectives of the USP are:

I. To maintain or improve the existing water quality
II. Improvement of the reliability of the measured values by means of modern analytic instruments
III. Reduction of the number of samples
IV. Authorization of the in-line measuring method

USP 23 and 24

Before 1996, the quality of these waters was determined by a number of off-line, “antiquated” laboratory tests. The USP monograph 23 (and currently 24) replaced these tests with an on-line conductivity measurement as the initial marker. While PW only needs to meet a TOC limit, the WFI has to meet bacterial tests in addition to the TOC and conductivity limits. In this application note we will concentrate on the USP requirements for conductivity only. This change to an on-line conductivity measurement was precipitated by many desires including improving the reliability of the testing by using modern instrumentation, providing immediate alarms and options for quality control, eliminating sample collection and handling errors, and reducing the cost of testing. 

The conductivity requirements mandated by USP are tiered in three stages:

Stage One: Use In-line or grab sample methods to measure the conductivity and water temperature. This conductivity reading must not be temperature compensated. Compare these readings to the Stage I graph shown, or the values in table I. If the conductivity is below the limit stated for that temperature, the water meets the requirements. If the conductivity is above the limit, proceed to Stage Two. Advantages to In-Line measurement are:

I. Real-time information for conductivity and temperature
II. Immediate limit value alarm
III. Data output for recording and documentation of the water quality
IV. Simple and reasonably-priced measurement
V. Avoiding errors due to sampling, handling and transport

Stage Two: Take a grab sample and measure the conductivity after equalization with atmosphere and temperature normalization to 25ºC. If the water conductivity is below 2.1 μS then Stage Three is needed. 

Stage Three: If Stage Two is exceeded, measure the pH of the grab sample and check conductivity against the results in table I of conductivity vs. pH. If the sample is within the limits, it passes. If it does not, the water is deemed unacceptable for PW or WFI use. 

Solution

Yokogawa’s conductivity transmitters and converters possess USP functions that make this seemingly complex and troublesome requirement pain free, and automatic. The FLEXA two-wire conductivity transmitter has the USP23/24 Stage One table pre-programmed in its software. When enabled, the transmitter will send a FAIL signal when the water exceeds the USP limit. It also can display and transmit the uncompensated conductivity that USP mandates for compliance recording.

The SC450 and DC402 four-wire conductivity converters have additional USP features. These units have the ability to display and transmit the uncompensated conductivity for USP compliance, as well as the NaCltemperature compensated measurement, valuable for process control. The USP23/24 Stage One table is pre-programmed into these instruments, and a FAIL alarm will be given if the conductivity limits are exceeded. Alarms on these units can be dedicated as USP “warning” alarms with user defined safety margins. These “warning” alarms will inform the operator that his/ or her water is trending towards the USP limit, and will allow him/or her to take preemptive corrective action.

Overview:

In maintaining and managing industrial plants, monitoring waste water pH/ORP is both a legal obligation and an unavoidable necessity for protecting the environment. Monitoring without an attentive eye can lead to severe consequences.

Overview:

Application Description

Many Ethanol plants running today are using a combination style pH electrode with a non-flowing reference to measure pH in the Mash Slurry transfer line from the Mash slurry mix tank to cook.  The Mash is being pumped out of the Mash Slurry tank is at approximately 82 °C and  2 to 4 bar (180 °F and 40 to 60 psig).

The original pH electrode systems that were installed during plant construction are online retractable assemblies and are mounted in orientations from completely horizontal to completely vertical and everywhere in between.

The Problem

The combination probe that is being used will typically drift out of calibration very quickly.  Also, the probe is damaged sometimes from excessive removal from the process.  The reason this probe drifts out of calibration is due to the fact that the non-flowing reference system plugs and becomes fouled by the mash passing by it.  pH measurements are only as good as the reference required to make this measurement.  If the reference is not doing its job, the measurement electrode will drift.

Process Overview

Product Recommendations

Yokogawa manufactures a multi-probe holder called the FF20 – flow through fitting or the FS20, which is pH chamber assembly with ½” NPT process connections.  With these holders we use a combination electrode, part number:  SC21C-AGC55 for measurement and reference and a separate temperature sensor part number: SM60-T1.  The Yokogawa electrode system works due to the fact that the SC21C-AGC55 combination probe uses a pressurized reference system.  By using plant air regulated to a KCl reservoir, the SC21C-AGC55 utilizes a positive flowing reference that does not foul. 

Plants using this system typically check the pH measurement against a grab sample and only make adjustments if the sample and the online measured values are more than 0.2 pH difference from one another.  Typically, the system will not need daily or weekly calibrations.  Most plants will pull the electrodes once a month for cleaning and calibration in a standard 4 and 7 buffer solutions.

Installation Considerations

The Yokogawa pH system is not retractable from the process.  It is usually best to put the Yokogawa pH electrodes in a by-pass or recirculation line that you can add isolation valves for isolating the probes from the process for maintenance and calibration.  The probe assembly should be mounted downstream of the Slurry Tank transfer pump.  Ideally it will be in a recirculation line going back into the tank or into the suction side of the slurry pump.

The picture below shows an installation that is actually flowing from left to right.  The arrows indicate the direction of the mash flow through the recirculation line and back into the suction side of the pump.  You will get an idea of the installation of the Yokogawa probes and the pressurized reference KCl reservoir from this picture.  The reservoir pressure is typically set 1 to 2 psig above the slurry line pressure.  The KCl reservoir will require refilling every 2-3 months for most applications

Note: For additional information on this application contact the local Yokogawa Process Liquid Analyzer Department

Overview:

Introduction 

A process and apparatus for removing SO2 from a gas stream having the steps of scrubbing the SO2 with an ammonia scrubbing solution and removing any aerosols generated by the scrubbing in a wet electrostatic precipitator. The scrubbing solution is maintained at a pH between 6 and 8 to increase the speed of absorption of SO2, to Increase the ratio of sulfite to bisulfite which also facilitates the oxidation of SO2, and to avoid the need to use exotic, corrosion resistant alloys. Ammonium sulfate, a valuable fertilizer, can be withdrawn from the scrubbing solution.

Process background 

Fossil fuels are burned in many industrial processes. Electric power producers, for example, burn large quantities of coal, oil, and natural gas. Sulfur dioxide (“SO2”) is one of the unwanted byproducts of burning any type of fossil fuel. It is known to cause acid rain, and to have serious negative health effects on people, animals, and plants. A great deal of research has been done to find a way to economically remove SO2 from flue gas streams before it enters the atmosphere.

The pH of the ammonium sulfate solution should be kept between about four and six. This range is the result of a compromise between competing factors. On one hand, ammonium sulfate solution is capable of absorbing SO2 more rapidly when its pH is higher. The ability to absorb SO2 better implies that the size of the scrubbing tower can be smaller, thus saving capital costs. In addition, the liquid to gas (“L/G”) ratio can be smaller, meaning less liquid will be required and operating costs will be lower.

On the other hand, higher pH levels are also associated with the release of free ammonia from solution, often termed “ammonia slip.” In addition to incurring an economic loss because of lost ammonia, free ammonia in the scrubbed flue gas reacts with uncaptured sulfur dioxide and trioxide to create an ammonium sulfate/bisulfite aerosol that is visible as a blue or white plume in the stack discharge, leading to secondary pollution problems. Controlling the amount of free ammonia in the desulfurization process is in part a function of the ammonia vapor pressure, which results from a combination of pH and levels of unoxidized ammonium sulfite that remain in the absence of sufficient oxygen. Therefore, high pH values and high levels of unoxidized ammonium sulfite promote ammonia slip.

Typical Process Example 

  • Name of Application / Process: Ammonia Scrubbing
  • Location of Sensor mounting (location name): Tail Gas Scrubber Complex
  • Operating Temp / Max.Temp: 75 to 80 deg C
  • Operating Press / Max. Press: 2 to 2.5 Kg/cm2
  • Type of Installation: On Pipe ( Direct mounting ) / Flow through Chamber (By pass mounting ) /
  • Process Composition: Liquid - Scrub Acid,
    • P2O5:105 ppm,
    • AN (Ammonical Nitrogen):1326 ppm,
    • UN(Urea Nitrogen):22 ppm,
    • TN(Total Nitrogen):1348 ppm,
    • Florine:116 ppm.

Typical problems

  • Frequent cleaning, glass can be eaten away as the temperature and chemical attack glass

Remedies

  • Use of high temperature special sensor

Product Recommendation

Measurement System

Process Liquid Analyzer: 

  • 2-wire FLEXA pH/ORP Analyzer

 

Features

  • Dual sensor measurement on 2-wire type analyser
  • Indication of sensor wellness

 

  • 4-wire PH450G pH/ORP Analyzer

Features

  • Easy touchscreen operation
  • Trending display up to 2 weeks
  • Advanced Process Temperature Compensation

Sensor Selection:

SC25 sensor from Yokogawa is the perfect sensor for this application. High temperature sensor SC25 because of its design can serve purpose.

 

 

Features SC25V

  • External titanium Liquid Earth
  • Pt1000 integration in pH compartment giving highly accurate temperature compensation
  • CIP and Steam cleaning possible
  • Large internal KCl volume giving the sensor a longer life time
  • SC25V-ALP25 for chemically harsh applications and high temperatures

Cable:

  • WU10-V-S series

Retractable fitting:

  • PR10 series

On-line measurements always present extra challenges compared to at-line measurements, for example, when maintenance needs to be done. Applications like this where the sensors have to be removed without interruptions or shut-downs the PR10 is especially suitable. Without any special tools the PR10 can be retracted safely from the process up to 5 bar.

For ease of use optional flush ports are available. In the retracted position the sensor can be kept moist, cleaned or even calibrated. This can all be done without process interruption or disassembly of the armature.

Tangible benefit

Better life of sensor, improve end product quality.

Note: For additional information on this application contact the local Yokogawa Process Liquid Analyzer Department

 

 

Overview:

Sodium chlorate is an inorganic compound with the chemical formula NaClO3. It is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 300 °C to release oxygen and leave sodium chloride. Several hundred million tons are produced annually, mainly for applications in bleaching paper.

Aplicacione
Overview:

Introduction

The Combined Effects of pH and Percent Methanol on the HPLC Separation of Benzoic Acid and Phenol:

Many mobile-phase variables can affect an HPLC (High Performance Liquid Chromatograph) separation. Among these are pH and the percent and type of organic modifier. The pKa of a weak acid is the pH at which the acid is equally distributed between its protonated (uncharged) and unprotonated (charged) forms. This is illustrated by the Henderson–Hasselbalch equation:

pH = pKa + log ([A_]/[HA]

where [A_] is the concentration of the weak acid in its unprotonated form
and [HA] is the concentration of the weak acid in its protonated form.
 

If the weak acid is equally distributed between its two forms, ([A_]/[HA]) = 1, log ([A_]/[HA]) = 0, and pH = pKa. If the weak acid is not equally distributed between its two forms, then the pH will be either less or greater than the pKa of the weak acid.

For example, if [A_] < [HA], ([A_]/[HA]) < 1, log ([A_]/[HA]) < 0, and pH < pKa. Thus, a weak acid exists primarily in its protonated form at a pH below the pKa and therefore has a greater affinity for the nonpolar stationary phase. If [A_] > [HA], ([A_]/[HA]) > 1, log ([A_]/[HA]) > 0, and pH > pKa. Thus, a weak acid exists primarily in its unprotonated form at a pH above the pKa and therefore has a greater affinity for the polar mobile phase.

Fig 1 - full-factorial experimental design

Fig. 1 - A three-level, two-factor
full-factorial experimental design

Organic modifiers also have an effect on the retention of solutes in HPLC. In the reversed-phase mode (polar mobile phase, nonpolar stationary phase), the most polar solute component will elute first. This is because the most polar component interacts least with the nonpolar stationary phase.

As the polarity of the mobile phase is increased, those solute components that were previously highly retained (nonpolar components) will be retained even more.

Two species that are of public interest because of their classification as moderate environmental and health hazards are benzoic acid (pKa = 4.202) and phenol (pKa = 9.98). The purpose of this study is to investigate the combined effects of pH and percent methanol on the reversed-phase HPLC separation of these compounds.

A three-level, two-factor fullfactorial experimental design will be used to specify nine mobile phases for consideration in this study. The levels of pH were chosen to bracket the pKa value of benzoic acid (below, near,
and above 4.202). It was not possible to study a mobile phase with a pH > 7.5 owing to the pH range limit of the column. A methanol/water mobile phase was selected for this study because methanol is readily available in most undergraduate labs and relatively inexpensive. In addition, both solutes elute in a relatively short time, making completion of this lab during one or two lab periods possible.

Table 1. Mobile Phases Specified by the Experimental Design
 
Phase No. Methanol % pH
1 25 3.0
2 25 4.5
3 25 6.0
4 50 3.0
5 50 4.5
6 50 6.0
7 75 3.0
8 75 4.5
9 75 6.0

Major Observation

At low mobile-phase methanol concentration (25%), as pH increases, the retention time of phenol appears to be unaffected, whereas the retention time of benzoic acid decreases significantly. Over the pH range investigated, the mobile-phase pH is below the pKa of phenol. Thus, phenol will remain in its protonated form and should be unaffected by these mobile-phase changes. However, as pH increases, benzoic acid shifts from its protonated to its unprotonated form, decreasing its affinity for the nonpolar stationary phase and decreasing its retention time.

At intermediate (50%) and high (75%) mobile-phase methanol concentrations, as pH increases, the retention time of phenol remains unaffected by increases in pH while the retention time of benzoic acid decreases. This is consistent with the behaviour at low methanol concentration.

At pH 3.0, as percent methanol increases, the retention times of both phenol and benzoic acid decrease significantly. Because both solutes are polar, increasing mobile-phase polarity causes both to be retained less tightly. At pH 4.5 (slightly above the pKa of benzoic acid) and pH 6.0 (well above the pKa of benzoic acid) as percent methanol increases, the retention times of phenol and benzoic acid decrease. This is consistent with the retention behaviour at pH 3.0.

Typical Process Details

  • Customer plant: Bulk drug plant
  • Application: This is 4 cycle application. There will 
be a pipe connected to inlet which allows process to flow through the column and the same will be sent out from another pipe at outlet.
  • pH measurement is typically required at both the inlet and outlet. Temp: 30-40°C. pH range shall be 7 to 7.5. Between this range the customer can take necessary action to control his process.
  • Conductivity max. 300 micro siemens/cm.
  • Cycle 1: Process contains 95% liquid methanol, 
2% liquid ammonia, 3% water.
  • Cycle 2: Process contains 30% liquid methanol, 
70% water.
  • Cycle 3: Process contains 90% liquid methanol, 
5% liquid ammonia, 3% water, 2% sugar content.
  • Cycle 4: The column will be cleaned by flushing 
with DM water.
Overview:

In flue gas desulfurization systems that use magnesium hydroxide (Mg(OH)2) slurry, the consumption of the desulfurization agent (Mg(OH)2) is controlled by using online pH analyzers. A great concern in the pH measurement is heavy staining of the pH electrodes by the Mg(OH)2 slurry. To ensure accurate measurement, frequent cleaning of the electrodes with an acid is required, adding to both maintenance workload and cost.

Industry:Chemical, Power

Aplicacione
Overview:

To defray energy costs, many industrial plants have their own boilers to generate steam to produce a portion of their energy needs. In addition to generating power, the steam may also be used directly in plant processes or indirectly via heat exchangers or steam jacketed vessels. 

Industrias:
Overview:

The contacting and inductive sensors can both be measured using the FLXA202 analyzer but they require a different input module.  The input module required varies based on the model number of the FLXA21/202.   Look at the data plate on your analyzer and find the 2 letter code for “TYPE”:

Then find that code in the top line of the table below:

The part number for the Input Module you need to order is on the Module (in this example ISC) line below your Type Code.

The Input Modules Snap into place inside the FLXA202. There may be a black rubber locking adapter behind the tabs on the side of the input module. Remove this lock and then push the tabs out on both sides at the same time to remove the Input Module.

See below for the tabs (1) and Locking adapter (2):

Here is the Locking adapter partially removed:

You can order the Input Module from one of our Sales Representatives for your area. Locate your sales rep here.

Overview:

To test the conductivity input do the following: 

  1. Write down the cell constant and change it to 1.00 (this is not mandatory, it makes the math easier) 
  2. Place a jumper wire between 13 to 14 and another one on 15 to 16 (not necessary on the DC400/402) 
  3. Place a resistance between the 13/14 and 15/16 connection. If the unit is set in resistivity it should match the resistance. If it is displaying conductivity it should read Y where Y = (cell constant)/(input resistance) and the units are Siemens. So if the result is 0.005 Siemens this equals 5 milliSiemens.and 0.000005 Siemens equals 5 microSiemens. 

Remember to set the cell constant back to the original value if you changed it.

Overview:

Yes, the input module can be changed in the Converter. 

 

See the FAQ:

Which Input Module do I order for my FLXA21/202 analyzer?

Overview:

Yokogawa's pH and conductivity sensors include a temperature sensor to allow for temperature compensation. The pH and conductivity sensors have a relatively large temperature mass and respond slowly to the changes in the process temperature. This is fine for temperature compensation or diagnostic uses but not for process control of the temperature. Process temperature sensors have a much lower mass and respond much quicker to temperature changes. Use those for process control, not the temperature sensor built into the pH or Conductivity sensor. 

Overview:

In a dual input FLXA202 or FLXA21 analyzer you can use a HART Splitter to convert the HART® dynamic variables into current outputs or contact outputs. The model number is "1W-KFD2-HLC-EX1.D" and the description is "P+F HART Splitter." In the FLXA menu you can select which dynamic variables you like as "SV" "TV" and "FV."

Go to Commissioning>Advanced Setup>Communication>HART> then use the down arrow to select the SV, TV, and FV fields.

Overview:

Yes, the SENCOM Module in these sensors allows a Modbus Master to
connect using Modbus RTU protocol and access the following data:

  • pH
  • Temperature compensated pH
  • ORP
  • pH compensated ORP
  • rH
  • Temperature
  • Junction resistance value
  • Sensor details (Model, Serial Number, production date)
  • Sensor calibration data (zero, slope, temperature offset)
  • Sensor status signals (e.g. Glass impedance detection)

As shown in the diagram above, our pH is calculated by subtracting value B from value A. To do this the B value is stored inside the sensor and can be displayed independently at any time. Since ORP is simply the value of B, we can easily display both pH (A-B) and ORP (B) without any issues.

Yokogawa Technical Report
Overview:

Yokogawa has been offering the EXA200 series two- wire liquid analyzer for processes since 1990. This analyzer has been used in various fields including the quality control of raw materials in process plants in the electric power and petrochemical industries, reaction management of products, quality control in waste water facilities, and quality monitoring of river water and tap water.

Catálogos
Manuales
Especificaciones Generales
Software
Información Técnica
Certificados
Dibujos
MSDS/SDS

¿En busca de información adicional sobre Yokogawa Iberia, tecnología y soluciones?


Contáctenos
Top