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Refex pH & ORP Electrodes

South Fork Industries is a proud supplier of Refex pH and ORP electrodes, some of the finest quality sensors widely used in commercial applications. These sensors are manufactured in a variety of different styles, and are suitable for use in many industrial processes where they can be applied to both to extremely harsh or general-purpose applications.

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Refex's electrodes provide stable, accurate readings in the most taxing environments.

At the heart of every Refex electrode is a unique nonporous reference system that delivers high quality performance, stable readings and accurate pH/ORP measurements. Refex sensors last many times longer than conventional electrodes with porous junction reference cells, require minimal maintenance, and exhibit minimal drift.

Refex sensors are available in many industry standard sizes, and can easily be retrofitted for existing systems and housings. For highly specific applications, South Fork Industries will work with you to design a measurement solution that meetings your specifications.

What are pH and ORP electrodes?

Electrodes are electrochemical sensors used to measure pH or ORP (oxidation reduction potential) in industrial process applications. From clean water to sewage sludge, from biopharmaceuticals to petroleum, they can be put to work everywhere.

It’s most likely that the type of electrode you’ve come across in your work is a glass electrode, as these are the most common. Don’t be deceived by the simple design of this humble electrode—there’s a lot going on inside.

Learn more about pH electrodes and how to care for them.

What does an electrode look like? Expand

Example of a combination sensorThe traditional pH electrode features a glass tube with a small bulb at one end and an electrical wire or connection at the other. The tube may be a single tube (measurement electrode only) or may be a tube within a tube (combination sensor with both measurement and reference electrodes). The inside of the tube is filled with an electrolyte, usually a buffered chloride solution. The pH of the solution inside is usually neutral (a pH of roughly 7) but can vary depending upon the measurement application.

The pictured example is a combination sensor. That tube with the bulb at the end of it is the measurement electrode and has a length of silver wire coated in silver chloride that runs down the length of the tube to the bulb. The outer tube contains a reference electrode similar in makeup to the measurement electrode, with the key difference that it is electrically connected to the solution being measured. Here’s the important thing—the bulb at the end is thin and made of a special pH-sensitive glass. It’s this element of its construction that allows the sensor to take a measurement.

How do electrodes work? Expand

pH sensors measure pH by measuring the voltage or potential difference of the solution in which it is immersed. If the solution is acidic, the concentration of hydrogen ions in it will be higher that the concentration of hydrogen ions in the sensor buffer solution and the sensor will see a positive potential difference in the measured solution when compared to the measurement. Alkaline solutions are the opposite. There are fewer hydrogen ions in an alkaline solution and therefore a negative potential difference. The greater the difference of hydrogen ions in either direction, the greater the potential difference.

How do you calibrate an electrode? Expand

Before you even get started, make sure your electrode sensor is calibrated. Don’t know how to do it? Round up a few buffer solutions of known pH. Dip your pH sensor into them and calibrate accordingly. It’s really that simple. But the importance of understanding your equipment inside and out can’t be underestimated. Don’t start your work with a sensor that’s off. And if you’re not sure whether a sensor is properly calibrated, then calibrate it.

What applications are electrodes typically used for? Expand

Electrochemical sensors are found in a myriad of jobs and applications. Doctors, engineers, water treatment facilities, food industries, and pharmaceuticals are just a few examples of where sensors can be found.

What is the lifespan of an electrode? Expand

Refex electrodes are extremely durable compared to competing brands of pH and ORP probes. In typical real-world applications, they have been found to operate five times longer than other electrodes, without maintenance. In some cases, Refex electrodes have operated for more than a year in conditions where traditional electrodes lasted only days.

But no matter the quality of the electrode, at some point cleaning will be necessary. But glass electrodes can be very sensitive, and must be handled with care during cleaning. Bear in mind, pH electrodes are not made to last forever, nor should they be expected to. Electrodes have a typical operating lifespan of one to three years, no matter your dedication to regular cleaning and maintenance. Eventually, they need to be replaced.

But proper care and maintenance are an essential part of getting the most out of your pH/ORP sensors and keeping your readings accurate. Frequent manual cleaning or the use of an automated cleaning system will enable you to get the longest possible life out of each electrode.

What cleaning solution should be used to clean electrodes? Expand

The cleaning solution you use will depend upon your particular process and the residues you are trying to remove. There is a wide range of pre-mixed cleaning solutions available online, or you can make your own. Make sure you take care when handling any cleaning solution. Some can be hazardous, so make sure you follow all safety instructions and wear appropriate protective equipment!

General Contamination: Immerse the electrode in a warm (120°F/49°C) 4.0 molar KCl (potassium chloride) solution or warm 4.01 pH buffer solution for about 1 hour.

Organics: Immerse the electrode in 0.4M HCl (hydrochloric acid) for about 10 minutes.

Fats, Oils and Greases: First, carefully rinse the electrode in a 1% (0.5N) HCl solution. If the buildup is very heavy, soak the electrode overnight in a warm detergent and water solution—standard dish soap or laundry detergent works well for this. Follow the overnight soak with a deionized or distilled water rinse and a further soak for 10 minutes in 1% HCl. As an alternative, methanol or ethanol can also be effective.

Proteins: These can get into and block the reference porous junction. Soak the pH electrode in a 1% pepsin and 0.1M HCl solution for 1 hour to dissolve the blockage and open the junction again. Alternatively, use an enzymatic cleaning solution (such as contact lens cleaner) overnight.

Sulfides: These can react with the silver ions in your pH electrode’s electrolytes, creating a precipitate and blocking the reference junction. In all-glass electrodes, this is easy to diagnose, because the electrode will become discolored. Immerse the electrode in 0.1M thiourea/HCl solution for 1 hour or until the discoloration disappears.

Alkaline Deposits: Immerse in a weak acid or vinegar solution until the deposits are dissolved from the glass bulb.

Acidic Deposits: Immerse in 0.1M NaOH until the deposits are dissolved from the glass bulb.

Heavy Metals: If your pH electrode is being used in a solution with heavy metals, the glass bulb of the electrode may become scratched and the hydrated gel layer essential to electrode operation worn away.

You can try regenerating your probe using a solution of hydrofluoric acid to fix the issue. This wears away one the outermost layer of glass, exposing a new one underneath. Hydrofluoric acid is extremely dangerous, so it’s important to follow all safety precautions (goggles, gloves, and long sleeves or lab coat) while using it, and only use the minimum amount needed. Ensure that the container you’re using is resistant to hydrofluoric acid—glass and many other materials are not. When cleaning the electrode, only allow the glass bulb of the sensor, not the main shaft, to touch the liquid, because it will corrode whatever it touches. Only submerge the sensor bulb into the acid solution for about a minute. Any more than that could destroy the electrode entirely. Rinse the electrode thoroughly with deionized or distilled water immediately afterward and leave it to soak in a pH 7 buffer for about an hour.

After cleaning with any solution, rinse thoroughly with deionized/distilled water and soak the electrode in storage solution overnight. If the electrode is a refillable electrolyte type, you should drain and refill with fresh reference solution. After an overnight soak, test and recalibrate the pH electrode. If the electrode response is slow or the electrode does not calibrate correctly, you may need to replace it.

What are the general guidelines for cleaning pH and ORP electrodes? Expand
  1. Do not wipe or rub the electrode. The glass used in electrodes is very soft and can easily be scratched by your fingers or a piece of cloth. Rubbing an electrode can also create an electrostatic charge which may make the signal unstable and pH readings inaccurate.
  2. Swirl the electrode gently in the cleaning solution. Because of the electrode’s fragility, it’s important not to knock it into the sides of your cleaning solution container while cleaning it, as this can break or damage it. The electrode does not need the cleaning solution to be pressure-washed against it to be effective. Gentle agitation is enough to soak the electrode and chemically remove contaminants.
  3. Gently rinse with deionized or distilled water. After you’ve finished cleaning, lightly rinse the electrode with deionized water. It’s important not to leave any cleaning solution on the electrode, as this could erode the surface of the pH sensor and destroy it. Always use deionized or distilled water. Using tap water can create an electrostatic charge that will make your readings inaccurate.
  4. Store in a storage solution. A pH glass electrode has a hydrated layer that affects the voltage level reading. Calibrating a dry electrode will cause your readings to be inaccurate until the hydrated layer is formed. Between measurements or after cleanings, store your electrodes in a storage solution (3 molar KCI) to maintain the hydrated layer. DO NOT store your pH electrode in distilled or deionized water, as this will cause ions to leach out of the glass membrane and reference electrolyte, causing slow and sluggish pH response when the electrode is used.
  5. When possible, use a specialized electrode. No matter how much cleaning and maintenance you do, traditional glass pH electrodes will wear down over time. If your process contains proteins, heavy metals, or sulfites, you should really consider using a specialized electrode to ensure that your readings remain accurate and damage to the electrode is prevented. Electrodes with non-porous reference junctions are most suited to these hard-on-the-electrode applications.
Is it possible to automate electrode cleaning? Expand

Cleaning electrodes is a labor-intensive process, particularly with pH electrodes in process applications that are used continuously, where access to them for service becomes a challenge.

For process installations, devices are available to allow probes to be withdrawn from the process while the process line is live. Safety interlocks in these retractable housings ensure that the process is properly contained while the probe is removed for cleaning and servicing. These devices are fitted with cleaning ports to allow process fluids to be rinsed from electrodes before they are removed and handled.

A further step is to use an automated retraction system with a cleaning controller, such as the Exner EXtract and EXmatic products. These systems will retract a pH (or other parameter) probe from a process and execute a pre-programmed cleaning cycle on the electrode without the need for anyone to be present. Maintenance on such a system is just to ensure a local supply of the required cleaning solution(s) remains stocked. Automated systems allow pH probes to be cleaned far more frequently than manual cleaning alone and this translates into much longer electrode life.

Have more questions? Take a quick moment to get in touch with our expert sales engineers and technologists and we'll guide you to a solution.

Refex Combination Probes

Refex combination probes are available in industry standard sizes and designed to fit in any existing or new ‘socket’ where pH or ORP measurements are made. These sensors can be used in all applications, particularly those where fouling and drift are common, and have a usable lifetime five times longer than conventional sensors.

The Refex reference utilizes a patented, highly stable, non-porous polymeric interface instead of the traditional porous liquid junction as used by conventional reference electrodes. The active reference area comprises the entirety of the outside surface of the electrode. This extremely large contact area means that electrode performance is supremely resistant to coating. Poisoning effects such as drift and slow response are eliminated because the polymeric reference material is conductive to ions but not porous. The reference operates electrically, but electrolyte and process fluids are not exchanged.

Products in this product line currently include:

  • 2001 Series 12mm pH Combination Probes
  • 2001 Series NPT pH Combination Probes
  • 2002 Series NPT Redox/ORP Combination Probes
  • 2002 Series 12 mm Redox/ORP Combination Probes

What distinguishes Refex electrodes from competitors?

Refex electrodes represent a revolutionary technology advance in pH and ORP measurement. Refex reference junctions are manufactured from an electrochemically conductive, salt-loaded, polymeric matrix. When installed inline, there is no porous junction to allow liquid contact between process fluids and the internal (sealed for life) Ag/AgCl reference half-cell. Refex provides a stable mV output for measurement and ensures that process fluids do not poison or deplete reference cell electrodes or electrolyte.

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Refex electrodes continue to perform even when completely coated, as long as the coating remains wet and is conductive. Even when severe coating of the sensor inevitably slows electrode response, pH and ORP measurement remains accurate. Proven applications range from clean, cold river water to crude oil, sewage sludge and nasty chemical streams—all can be measured with a Refex reference interface.

Refex electrodes have a range of benefits, including:

  • Ultra-low maintenance
  • Lifespan five times longer than standard sensors
  • Work in vacuum and high pressure (300 psi) conditions
  • Never clog
  • Never leak
  • Provide faster response than traditional pH/ORP sensors.
How do Refex electrodes work? Expand

At the heart of every Refex electrode is non-porous reference junction technology.

Basically, most pH/ORP sensors have a porous junction—ceramic or Teflon frit/diaphragm, wood stack, ‘solid’/immobilized gel, even paper—that creates an intimate connection between process fluid and the actual reference electrode. This porous junction is the Achille’s heel of traditional electrodes.

Refex pH/ORP combination sensors have an impermeable barrier between the process liquid that you’re measuring and the electrode’s reference half-cell and electrolyte—essentially, no liquid-liquid contact. The barrier surrounding the Ag/AgCl reference half-cell is a solid polymeric casing that has a large immobilized KCl loading, making it electrically conductive.

So, why is this important? Because porous junctions in pH/ORP probes cause all sorts of problems and inaccuracies.

What are the shortcomings of traditional electrodes? Expand

Traditional technology pH/ORP sensors generally work by having a porous ceramic frit or micro-capillary sleeve acting as a semi-permeable membrane between an internal salt bridge and ions in the process stream/sample.

While this works relatively well, it can be prone to a number of problems, especially over time and in harsh conditions. First, it often has a very small surface area, which means that there can be issues from sensor fouling. With something so small (and it has to be small or the salt bridge will be too exposed to the sample and be washed away, leading to inaccurate and drifting readings), it’s prone to being covered with something akin to an oil slick. The process sticks to the sensor, preventing proper measurement and causing an incorrect pH measurement value.

Second, it’s essentially a semi-permeable membrane, so anything that affects the speed at which the salt bridge ions diffuse through it will affect the measurement. Slow diffusion rates create sluggish readings while rapid diffusion depletes the cell prematurely. Thirdly, porous membranes allow the process to get inside the reference half-cell, diluting or reacting with the reference electrolyte to create drift and destruction of the electrode. For example, under high pressure, electrolyte will simply be diluted or replaced by process fluid being pushed through the junction.

So, there are many circumstances where traditional sensors either don’t work for long (or at all) or don’t work as accurately as needed.

What are the practical and financial benefits of using Refex electrodes? Expand

One of the most significant benefits is probe lifetime. Refex electrodes last much longer in areas where traditional pH/ORP sensors are commonly used, and can be used in applications where traditional electrodes are quickly destroyed.

For example, in the oil and gas industry, the fluids that you’re measuring the pH or ORP of are often reactive, volatile, and corrosive (and definitely not something you want to get on yourself). Refex electrodes have been reported to last five times as long (or longer) in these extreme applications, compared to typical electrodes. In some cases where traditional porous junction reference electrodes last only days—such as chemical production or bioreactors where it’s necessary to measure pH under pressure—Refex electrodes deliver excellent performance.

In the long term, you'll spend much less money on replacement probes and spend much less time maintaining them. Plus, with more accurate readings over a longer period of time, you can count on faster corrections to chemical imbalances, helping improve process efficiency by preventing correction chemical overdosing (reducing costs further).

Refex sensors can also dramatically reduce plant downtime, and for any company focused on manufacturing, reducing downtime is absolutely essential to running an economically efficient operation.

To summarize, the benefits of using Refex sensors include:

  • Measurement is accurate, repeatable and above all, reliable
  • Confidence in meeting statutory and regulatory measurement requirements
  • Low maintenance saves manpower—no need to calibrate every week!
  • Maximize plant throughput by dramatically reducing downtime
  • Long life—fewer sensor changes means real cost savings
  • Reduced cost of ownership from greater reliability & reduced maintenance
  • Improve process quality control through reliable measurement
  • Fast response provides real savings by preventing chemical over-dosing
  • Are virtually maintenance free
  • Have exceptionally long lifespans (>5 times longer than traditional probes)
  • Have large surface contact area
  • Work in vacuum without electrolyte reservoirs and at pressures up to 300 PSI
  • Do not leak electrolyte into the process (critical in low-ionic and UPW applications)
  • Do not become clogged (important where precipitates are present)
  • Do not become poisoned (perfect for H2S and chemical process applications)
  • Much faster response times prevent control overshoot
  • Greater accuracy and repeatability
What makes Refex electrodes resistant to fouling and coating? Expand

Electrode fouling is one of the major problems requiring frequent maintenance and recalibration. The problem in conventional electrodes is the porous liquid junction for the reference electrode. This porous junction, whether ceramic, Teflon, paper, or even wood, can over time become clogged by process medium, increasing impedance and affecting performance.

Clogging can become so significant that the electrode stops responding at all. Lime scale, manganese, precipitation between hydrogen sulfides and AgCl, and protein/fat build up in sewage and industrial effluents are all examples of material that can affect electrode performance in this way. Fine particle clogging—pigments and dye stuffs, etc.—are particularly bad and have been known to shorten conventional electrode life considerably.

To review, reference electrodes are low impedance sensors (typically 10 kΩ), while the pH glass element is a high impedance sensor (typically 100 MΩ). Coating and deposits on sensors can increase impedance by 1 MΩ, but this is not a major problem for the pH glass electrode. The impedance changes to 101 MΩ, an increase of only 1%. However, this same effect on the reference side (across the porous junction) changes the impedance from 10 kΩ to 1010 kΩ, orders of magnitude of change. This is where the problem lies.

One solution to this problem has been to use a flowing junction electrode where liquid electrolyte is pressurized to create a positive KCl outflow through the junction, keeping it clear of contaminants. While this helps, it is maintenance and consumable intensive, and still allows poisoning of the reference element with resultant precipitation within the sensor body. The pressurization and flow of the electrolyte then seals the electrode’s fate by blocking the junction from the inside.

Refex electrodes are far more resistant to fouling and buildup. Being non-porous, there is nothing to block, and provided any coating on the electrode is conductive, it will continue to operate as if clean. Note that eventually, it will be necessary to clean off heavy buildup from the electrode. It is difficult to accurately measure the process with the electrode buried in its own ‘micro-environment’ of buildup.

How do Refex electrodes eliminate diffusion potential errors? Expand

As an example, raw water (such as water sourced from reservoirs, lakes, and rivers) can be bitterly cold with low ionic strength and trace quantities of magnesium and iron. Conventional pH sensors with porous reference junctions can quickly foul because of the trace metals, requiring frequent cleaning and recalibration. Because of the difference in salt concentration between the reference electrolyte (typically KCl 3 mol/l) and the water being measured, diffusion occurs through the porous junction and the reference cell electrolyte becomes depleted. This causes a diffusion potential error—which is significant when a tight pH value must be maintained. When conventional electrodes with porous junctions are installed in low ionic strength water applications, they often exhibit instability in the form of continuous drift.

The opposite is true when working with process solutions with high ionic strength. Here, diffusion occurs in the opposite direction with a consequent change to the electrolyte properties.

Refex probes, being non-porous, eliminate measurement error caused by diffusion potential. There is no electrolyte loss or dilution while the electrode is in service, producing an extremely stable reference output, with drift of less than 1mV/month. Ingress of poisoning material is eliminated, greatly extending electrode life.

How is it possible for Refex probes to instantaneously respond to pH change? Expand

The Refex solid state polymeric reference system allows sensors to respond instantaneously to pH change. This is a very important quality when titration and chemical dosing is required. The entire outside wetted surface of the Refex reference electrode is electrochemically active without diffusion potential or flow errors, ensuring rapid response to pH changes and preventing dosing over-shoot and the unnecessary use of expensive dosing chemicals. This response characteristic can result in significant cost reduction through chemical savings.

Conventional electrodes respond far more slowly due to ion diffusion time through the porous junction. The use of tortuous paths and double junction techniques to extend electrode life only adds to the slowing of response, and as the porous junctions become obstructed, response time slows further. Slow response inevitably results in set point overshoot.

Refex electrode responsiveness to pH changes

What challenging applications can Refex electrodes be used for? Expand

There are dozens of practical applications for Refex electrodes in heavy industry and oil and gas production. However, you might be surprised where else you would find Refex electrodes.

For example, in the food and beverage industry, Refex electrodes are used to test pH during production. Refex probes are favored in this application because they have protein-resisting properties, leading to better accuracy and enhanced longevity.

They’re also used where sulfides are present (e.g. flue gas desulphurization). Sulfides will destroy a porous pH sensor by causing silver precipitation, thus rendering the measurement useless.

Refex sensors are also used to measure pH in oil and gas boilers. These systems generally use ultrapure water (UPW) mixed with anti-corrosion agents. Maintaining the right pH is essential to keeping the ratio of water to anti-corrosion agent stable. However, when you submerge a porous pH sensor into the UPW, it bleeds KCl, creating drift and eventual failure of the sensor. With a Refex non-porous pH sensor, this issue is avoided.

What third-party measurement systems are Refex electrodes compatible with? Expand

Refex also offers direct replacement electrodes to upgrade and improve installations where other brands are already in use. Replacements are available for:

  • ABB/TBI
  • BAT (Barben Analytical Technologies)
  • E+H
  • Ingold/Mettler Toledo
  • Yokogawa
  • Sensorex
  • Rosemount Analytical
  • Foxboro
  • Van London/Phoenix

If you have specific compatibility requirements, contact South Fork Instruments for assistance.

Have more questions? Take a quick moment to get in touch with our expert sales engineers and technologists and we'll guide you to a solution.

Refex 12mm Separates pH, ORP and Reference Probes

Refex 12mm separates are available in all industry standard lengths and a variety of connector/integral cable styles to ensure they will fit in any 12mm ‘socket’ where pH or ORP measurement is made. Refex sensors work will all popular pH/ORP transmitters with high impedance inputs.

Refex reference sensors are a tremendous upgrade to traditional porous/flowing junction reference probes and can be used in all applications, especially those where fouling or poisoning conditions exist. With lifetimes expected to be at least 5 times longer than traditional designs, Refex reference electrodes represent significant savings in maintenance and replacement costs.

Refex 12mm sensors are available in a variety of packages to suit all pH and ORP applications, including pH glass sensors, platinum ORP sensors, and reference sensors. Currently, models in the product line include:

  • 5610 Series 12mm pH Glass Electrodes
  • 5710 Series 12mm Reference Probes
  • 7610 Series 12mm Platinum Redox/ORP Electrodes

What applications are Refex pH and ORP electrodes typically used for?

Refex electrodes are exceptionally resistant to applications containing poisons such as cyanide, ammonia and sulfides. This is because the polymeric reference junction is non-porous and prevents process material from invading and contaminating the electrode internals, causing drift and inevitable failure.

Here are a few applications where Refex sensors make a real difference.

Petroleum Refining—Sour Water Stripper Expand

Used to remove gases such as ammonia and dissolved hydrogen sulfide from sour water, sour water strippers present an extremely challenging pH measurement environment. Strippers are operated at about 176°F/80°C to facilitate removal of these gases. Hydrogen sulfide can block a porous pH reference with precipitated silver from the reference electrolyte while ammonia and cyanide poison the reference electrode and prevent it working by forming a complex with silver ions. These applications can be so aggressive that traditional porous reference electrodes may last only a few days before being rendered useless. Refex sensors do not suffer these effects because the unique polymeric reference is non-porous, presenting an impermeable barrier to poisoning from the process stream. Consequently, the typical lifetime of a Refex sensor in this application exceeds 12 months and represents a significant savings in operating costs.

Municipal Wastewater Treatment Expand

Sulfides build up in wastewater systems due to the anaerobic (unoxygenated) conditions that such plants are operated under. As with sour water applications in the petroleum industry, the non-porous polymeric Refex reference is a barrier to these dissolved sulfides in the process stream, preventing their ingress to the reference cell and subsequent precipitation of silver from the reference electrolyte. pH measurement loops using Refex reference electrodes do not exhibit the pronounced measurement drift and rapid failure rates common with traditional porous reference electrodes. Measurement remains stable and long-term performance provides significant savings in both replacement probes and labor costs.

Refex water treatment pH/ORP measurement systems are designed to give reliable, continuous real time measurement of water quality in both water purification and wastewater applications. Designed to be operated as a side steam, the system is supplied complete with a purpose built flowcell assembly that houses the measurement electrodes.

Refex reference and glass pH/ORP separates are provided with the system. The robust reference sensor uses a highly stable non-porous polymeric interface instead of a traditional porous liquid junction as used by all conventional reference electrodes. The active reference area is the whole of the outside surface of the electrode. This extra-large contact area means that the electrode is supremely resistant to coatings, even in the harshest of applications. Poisoning effects are eliminated because the polymeric reference material is conductive to ions but not porous. The reference can operate electrically but electrolyte and process fluids are not exchanged.

Systems are available with combination probes and electrode/reference separates. All are configured from the Refex standard electrode range depending upon application requirements.

Many users have their own preferred brand or type of pH analyzer. Refex sensors will interface with any of the high dual-impedance instruments available in today’s market. However, where no preference is given, we will be happy to source and supply a suitable multi-parameter analyzer unit that will interface with local SCADA and control systems. Talk to us about your requirements.

Ultrapure Water Expand

The Refex Ultra-Pure Water pH System is designed to give reliable, continuous real time measurement of water quality in water purification and distribution systems. Designed to be operated as a side steam, the system is supplied complete with a purpose built flowcell assembly that houses the measurement electrodes.

Refex reference and glass pH separates are provided. The robust reference sensor uses a highly stable non-porous polymeric interface instead of a traditional porous liquid junction as used by all conventional reference electrodes. The non-porous nature of the electrode interface prevents the loss of electrolyte into the flow stream, a serious problem in all conventional probes. The maintenance of the reference cell in this way prevents the rapid degradation of the measurement, greatly reduces the maintenance overhead and no longer requires the frequent replacement of consumable probes.

Where needed, an optional conductivity sensor with low cell constant can be fitted into the measurement loop as an additional parameter.

To complete the package, a multi-parameter analyzer unit is used to transmit real-time pH, conductivity and temperature information to local SCADA and control systems.

Oil Refinery Desalter Wash and Brine Water Expand

Crude oil contains many contaminants that must be removed before refining processes can be carried out. Typical contaminants are salts such as KCl, NaCl, MgCl and CaCl, and solids such as sand.

The salts are removed by mixing wash water to the crude feed to a desalter vessel, assisted by electrolysis within the vessel itself. The wash water should be as clean as possible, but is often condensate from other parts of the refinery, so pH should be monitored in real time, and wash water diverted to a sour water stripper or otherwise treated should pH be out of spec.

From the desalter, the cleaned oil is directed into the refinery process. The underflow is brine that is directed to wastewater treatment and from there either recycled or discharged.

Both the wash water feed and brine discharge are challenging measurements. Wash water can have a pH of 5.5 to 7.0, and may be contaminated with ammonia and phenols. Temperatures can be higher than 212°F/100°C. The brine effluent can contain sulfides, heavy metals, and oil plus sediment and sand—this cocktail is often very abrasive, and electrode erosion, fouling and poisoning is an ever-present risk.

Refex pH combination and separate reference electrodes have a patented non-porous, ionically conductive interface that separates wash water and brine effluent from the electrode’s Ag/AgCl reference half-cell and KCl electrolyte. This is 100% resistant to H2S and ammonia poisoning and prevents electrode fouling.

Refex sensors combine ultra-fast response to pH changes (preventing over- and under-shooting of pH setpoints) and an extremely long operating life to provide real, measurable savings in terms of chemical costs, manpower, and replacement parts.

Have more questions? Take a quick moment to get in touch with our expert sales engineers and technologists and we'll guide you to a solution.

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