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Yokogawa Corporation of America

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EXAxt PH450 4-Wire Analyzer for pH and ORP

The new EXAxt 450 series builds on the superior functionality of the industry leading Yokogawa EXA series by enhancing the EXA's proven operation and application flexibility. The Model 450 series feature a uniquely simple touch screen menu structure that offers a choice of multiple languages.

The Model PH450 provides the best pH measurement accuracy in the industry resulting from advanced temperature compensation functionality, preloaded calibration standards, stability checks and online sensor and analyzer diagnostics to provide verifiable results.

In addition to dynamic sensor checking, the Model 450 offers a wash cycle function to assure trouble free and accurate analysis with a minimum of maintenance. The EXAxt 450 also offers full application functionality with PID control on either mA output(s) or on contact output(s).

The PH450 combines pH with Temperature and ORP (Redox) measurement that can be utilized though different output functions: two mA outputs, four independent SPDT contact outputs and a digital HART signal is superimposed on mA1. This information can be used to generate additional current and contact outputs in the HIM monitor and in maintenance optimization programs like PRM or AMS.

The EXAxt 450 series provides a truly unique Human Machine Interface. The high resolution graphical display and touch screen operation provides all information clearly visible and easily accessible to the operator. Simply select the language of choice and on screen instructions assure that the best configuration for the application is obtained.

  • Unique touch screen operation with menu structure in 5 languages
  • Enhanced diagnostics, process trending graphics andon-screen logbooks for data storage
  • Two mA-outputs and four SPDT relay contacts with display indicators
  • Hart® Communications
  • FM Class 1, Div.2, Group ABCD, T6 for Ta-20 to 55°C
  • IP66/NEMA4X 1/2 DIN enclosure for Field Mounting and Panel Mounting
  • Three sets of preloaded pH buffer standards (NIST, US and DIN)
Measuring principle Glass electrode method
Input ranges pH: -2 to 16 pH
ORP: -1500 to 1500 mV
rH: 0 to 100 rH
Temperature: -30 to 140 deg C (Pt1000)
Transmission signals General: Two isolated outputs of 4 to 20 mA DC with common negative. Maximum load 600 Ω. Bi-directional HART® digital communication, superimposed on mA1 (4 to 20 mA) signal.
Output function: Linear or Non-linear (21-step table) output for pH, temperature, ORP or rH.
Control function: PID control.
Burn out function: Burn up (21.0 mA) or burn down (3.6 mA) to signal failure accorded with NAMUR NE43.
Hold: The mA-outputs are frozen to the last/fixed value during calibration/commissioning.
Contact outputs General: Four SPDT relay contacts with display indicators.
Switch capacity:
  Maximum values 100 VA, 250 V AC, 5 A
  Maximum values 50 W, 250 V DC, 5 A
Status: High/Low process alarms, selected from pH, ORP, rH and temperature. Configurable delay time and hysteresis. Failure annunciation.
Control function: On/Off, PID duty cycle or pulsed frequency control.
Wash: Contact can be used to start manual- or interval time wash cycles.
Hold: Contact can be used to signal the Hold situation.
Fail: Contact S4 is programmed as fail-safe contact.
Contact input Remote wash cycle start.
Temperature compensation Function Automatic or manual. Compensation to Nernst equation. Process compensation by configurable temperature coefficient, NEN6411 for water or strong acids/bases or programmable matrix.
Calibration Semi-automatic 1 or 2 point calibration using pre-configured NIST, US, DIN buffer tables 4, 7 & 9, or with user defined buffer tables, with automatic stability check. Manual adjustment to grab sample.
Display Graphical Quarter VGA (320 x 240 pixels) LCD with LED backlight and touch screen.
Housing Cast Aluminum housing with chemically resistant coating; Polycarbonate cover with Polycarbonate flexible window, Protection IP66/NEMA 4X/CSA Type 3S
Power supply PH450G-A:
  Ratings; 100 to 240 V AC, Acceptable range; 90 to 264 V AC
  Ratings; 50/60 Hz, Acceptable range; 50 Hz ±5%, 60 Hz ±5 %
  Power Consumption; 15 VA
PH450G-D:
  Ratings; 12 to 24 V DC, Acceptable range; 10.8 to 26.4 V DC
  Power Consumption; 10 W
Environment and operational conditions Ambient temperature: -20 to 55℃ (-5 to 130℉)
Storage temperature: -30 to 70℃ (-20 to 160℉)
Humidity: 10 to 90 % RH at 40℃ (100℉) (non-condensing)
pH input ≤0.01 pH
ORP input ≤1 mV
Temperature ≤0.3℃ (≤0.4℃ for Pt100)
Step response  

Accurate pH Measurement in Limestone Scrubber

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

Batch Neutralization

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.

Brine Solutions

pH measurement in brine solutions (for example NaCl solutions as found in electrolysis processes or cheese manufacturing) are difficult and inaccuracy and short sensor life are the key problems in these applications. 

Cooling Tower

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.

Cooling Tower: ORP Control of Chlorine

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.

Edible Fat and Oil Processing

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. 

Highly Effective & Efficient Sour Water Stripper Process

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.

Liquid Analyzers for Electrolysis Plants

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.

Measurement of pH of Leachate in Zinc Hydrometallurgy and Air Jet Cleaning to Prevent Scaling

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.

Monitoring pH at the Headbox

Problems at the wet end of a paper machine can rarely be corrected down stream. 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. Variations in the pH value at the head box have a negative effect on the quality of the paper produced.

Oxidation Monitoring in the Cyanide Wastewater Treatment Process

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.

pH Measurement of Wastewater Treatment at Pulp and Paper Plants

The treatment of wastewater from pulp and paper plants is a serious environmental concern. Yokogawa's submersion holder with an ultrasonic+air-jet cleaner (customized product) can reduce the manual cleaning frequency to just once every one or two months.

pH Monitoring of Pulp Stock

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.

pH Solutions for Mash Slurry and Liquefaction pH Measurements

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.

pH/ORP Measurement for Reverse Osmosis

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.

Pulp & Paper: Instruments and Solution for Pulp & Paper Industry

Continuous technology improvement is ongoing in the pulp & paper industry to obtain the best possible performance. The improved plant performance translates to the higher quality improvement and lower cost, and simultaneously environmental friendly plant operation.

Pure Water pH

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.

Reduction Monitoring in the Chromium Wastewater Treatment Process

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.

Sulfur Dioxide Scrubber: pH Control

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.