Sensors: Make Sure They Suit Your Application

Posted by Ray Sullivan on Tue, May 14, 2013 @ 11:14 AM

At times we see sensor specifications in plant upgrade or new treatment plant projects that don't appear to suit the particular application in the most cost effective manner.

Usually we see a pH sensor specified for potable water treatment with characteristics that far exceed the requirements of the process fluid. The sensor will work satisfactorily, but it costs much more than it should.

For one project a non-contacting torroidal conductivity sensor was specified for a non-corrosive surface water application with low conductivity, about 500uS.

There were several problems with this:

  1. As conductivity goes down, the uncertainty of the measurement for inductive type torroidal conductivity sensors goes up significantly.

  2. Inductive sensors are primarily a good choice for cases where there are very corrosive acids, bases or electrolytes that would otherwise quickly degrade the metal electrodes on a contacting conductivity sensor.

  3. Inductive sensors are an excellent choice to measure VERY high conductivity samples.

  4. Inductive sensors are a good choice to avoid fouling, bubble formation in the measuring cell, or the accumulation of debris.

None of these conditions applied to the application.

Providing more than is expected or paid for is a good thing for customers. Paying more for something that's not needed is not so good. Paying double for decreased accuracy and unneeded features, as in this case, just can't happen for municipalities with tight or shrinking budgets and for all of us who live in those municipalities.

For this project we proposed a contacting conductivity sensor with a cell constant and range appropriate for the application. The sensor design we offered, shown below, features a CPVC insulator for typical water treatment plant chemical resistance, 316 SS electrodes, double O-rings,and provides little if any potential for debris build up.

Foxcroft conductivity sensor resists fouling

 

Reducing sensor cost isn't achieved by reducing price or quality, it's achieved by selecting a sensor with appropriate characteristics. The benefit my be seen through better process control, less frequent cleaning, less frequent calibration, longer sensor life, or a lower purchase price.

For some applications, like fluoride resistant pH measurement, you may initially pay more than you would for a "competitive" sensor. But, you can actually lower your cost with our HF and acid resistant pH sensor by obtaining accurate measurements, replacing the sensor less frequently, and by surviving infrequent process upsets that wipe out most sensors when the pH drops dramatically.

Our sensor mentioned above does not contain antimony, extra thick or coated standard pH glass. Rather, it features a specially engineered pH glass, actually a glass like material, for fluoride resistance and a reference junction engineered to function in acid. It not only resists deposits on the glass surface, it can survive acid service and cleaning. Since this is now a "standard" sensor, you get a high performance sensor without a "custom engineered" price.

In many applications you may lower operating cost by simply matching sensor components to suit your process instead of using a "one size fits all" approach that may actually be over or under engineered for your particular type of water.

A customer monitoring wastewater for low pH influent with a lowest cost general purpose probe can dramatically increase sensor life with a sulfide resistant submersible pH sensor.

It's important to note that not all sensors are designed, or, "created" equal. Many of the sensors used in our instruments were designed specifically, and rigorously field tested, to overcome longstanding difficulties in process measurement while providing accuracy and repeatability. Some of these sensors have no design or functional equivalent anywhere in the market.

The take away from this is to check that the sensor being offered to you is actually suitable and optimal for your process. Among many questions you should consider:

  • Is it accurate in the range required?

  • Does the sensor body material's chemical compatibility, pressure and thermal resistance match the process fluid?

  • Can the sensor withstand the process fluid, and perhaps more importantly, the chemicals and physical force needed to clean it? Even though your wastewater may have a mid-range pH, your pH sensor may need to withstand acid cleaning of scale buildup. In some cases we recommend using a 15% HCL solution because 5% dilute HCL solution is insufficient.

  • Does the reference junction and or ion selective membrane have the design and chemistry suitable for the application?

  • Can a sensor with an external preamplifer provide equal performance than a more costly sensor with an integral preamplifier? With this approach you buy the preamplifier one time instead of with every replacement sensor.

Before making your next sensor purchase, don't automatically settle for what is offered, you may be able to get better process performance while helping your staff's workload and budget.

Request a Quote

 

 

 

 

 

Tags: sensor, pH sensor, conductivity sensor, ISE electrode

Service: From Instrumentation Upgrades to Automatic Gate Openers

Posted by Ray Sullivan on Fri, May 03, 2013 @ 10:08 AM

While we're primarily known for the chlorine residual analyzers and chlorine control systems we manufacture, our service department is perhaps better known for building custom equipment to optimize operations and solve problems in regional water and wastewater treatment plants.

Although we provide advanced control systems and upgrades for entire water systems or treatment plants, some jobs are rather small scale, but still result in cost savings and improved efficiency for utilities that need to carefully allocate their resources.

In addition to flow meter installations, calibrations, long distance SCADA system programming, comunication system troubleshooting and repairs, our service department has made a variety of items not found in our standard parts and equipment list:

turbidity blow off valve controller   describe the image

  • A wireless gate opener for a treatment plant to avoid work interuptions  caused by walking a distance to open the gate for delivery trucks.

  • Wired & wireless telemetry and telemetry hardware conversion.

  • A turbidity blowoff valve control system, which uses the signal from an installed turbidimeter to automatically control motorized valves to divert flow when the well pumps first come on, and to redirect flow when the desired set point is reached.

  • Level sensors and tank level displays.

  • Filter controls

  • Medical facility temperature controls

Whether you're in our region and need someone to perform the work for you, need technical assistance on a range of issues, or are simply in need of custom instrumentation, our SERVICE department has over 20 years of experience to serve you.

Tags: instrumentation service, water plant service, wastewater plant service, control upgrade, telemetry

What's New? Electronics Upgrade For Foxcroft Analyzers and Detectors

Posted by Ray Sullivan on Thu, Mar 28, 2013 @ 08:00 PM

As part of our continuous development to provide better products and services to our customers, we are pleased to give you a preview of our latest project - the electronics upgrade to our FX-1000P amperometric chlorine residual analyzer, our FX-1500 series toxic gas detectors, and FX-8D gas flow control valve.

The goal was to maintain the high standards of rugged design and performance set back in 1984 by the FX-1000 series while providing enhanced usability and versatility. The first phase of the upgrade focuses on our chlorine analyzer, followed by the gas detectors and pacing valves.

The final review of the circuit board components and layout was completed this week. During the design process we made many requests to our embedded systems engineer for more features and capabilities that we considered to be "must haves" in a field instrument. This week we were happy, and he was justifiably proud, to say that he was able to provide everything we wanted in the package size required.

The newest versions will be easier to setup, calibrate and use with a high resolution full color touchscreen interface that our engineer has used on other projects. A preliminary "Run" screen layout is shown below. On-board memory in the display provides smooth page navigation clearly and instantly.

Foxcroft touch screen

There are too many new features to mention here, but in brief, the system includes a powerful microprocessor and will operate anywhere in the world on 24 VDC with a universal international power suppy.

For application versatility the upgraded electronics will include a variety of inputs and outputs:

  • Digital RS485 Modbus communications
  • (4) Channels of 4-20mA output
  • (4) General purpose digital open drain on/off outputs
  • (8) 1-amp single pole form C relay outputs.
  • (4) 4-20mA or 0-5 volt inputs with fused 24V power
  • (8) General purpose external switch inputs.

The new electronics and interface can be supplied with our time tested FX-1000P bare electrode self cleaning gravity flow cell systems, which will include new cooler running brushless geared 24VDC motors.

For clean water applications that require or can tolerate membrane covered amperometric probes, an analyzer model without any moving parts will be available with several ranges of amperometric free chlorine sensors. Eventually it will be available with total chlorine and chlorine dioxide sensors as well.

Integral pH measurement and output will be available optionally for either model.

The main circuit board is just one of several phases of the design and testing process. As such we're not ready to project a release date yet. Check back for updates on our progress.

 

 

Tags: new technology, FX-1000P, amperometric chlorine analyzer, FX-1000P calibration

FX-8D Gas Flow Control Valve Is In Production

Posted by Ray Sullivan on Thu, Mar 28, 2013 @ 01:05 PM

In June 2012 we noted that our updated model FX-8D auto gas flow control valve was going into field trials after months of extensive testing here in our manufacturing facility.

We are pleased to announce that the FX-8D has been fully cleared for production and has started shipping recently. The units shipped are controlling chlorine gas feed, but the FX-8D can also automatically control the feed rate of ammonia, sulfur dioxide and carbon dioxide gases.

Click on this link to open the FX-8D web page for more information and to request a quote.

As with our chlorine residual analyzers and chlorine gas detectors, we keep units in stock in case of emergencies and for prompt delivery.

FX-8D gas flow control valve

Tags: chlorine gas flow control, ammonia gas flow control

Brain Eating Amoeba & DPB's: Pass Me The Chlorine Please

Posted by Ray Sullivan on Fri, Oct 19, 2012 @ 11:21 AM

What's in your waterA recently published article reported the Center for Disease Control found that two adults from different households in Louisiana died from primary amebic meningoencephalitis (PAM) after using their household tap water in neti pots to irrigate and clean their sinuses.

PAM is an infection with a fatality rate of over 99% caused by the amoeba Naegleria fowleri (N. fowleri), often referred to as brain eating amoeba. The median time from the onset of symptoms to death is 5 days.

According to the CDC report the organism has been found in freshwater lakes, ponds, rivers, hot springs, thermally polluted water, warm groundwater, inadequately treated swimming pools, sewage and soil. Although extremely rare, PAM is typically contracted when water containing N. fowleri enters the nose while swimming in warm freshwater lakes and rivers.

Although most cases have occurred in the south, the range of cases has expanded northward with cases reported in Minnesota, Kansas, and Virginia.

The CDC report on the Louisiana cases stated that the municipal water was treated with monochloramine, and that cultures developed from samples from the distribution system and point of entry of municipal water into the two residences returned negative results for N. fowleri.  The organism was found in tap water and neti pot samples in both homes.

While reading this I thought of all the outcry to eliminate the use of chlorine in drinking water; and the communities that are fighting proposals to safeguard public health by chlorinating their water.

Waterborne diseases such as cholera, typhoid, and dysentery have been virtually eliminated where water is treated with chlorine. The World Health Organization estimated in 2008 that over 4,000 people die each day from diarrhoeal diseases caused by contaminated water and lack of sanitation. Most of them are children under the age of 5 in developing countries.

The proven benefits of chlorination far outweigh any perceived benefits that can possibly be gained by avoiding, reducing or eliminating the use of free chlorine to disinfect drinking water. It's mind boggling that anyone would prefer to expose their families to the possibility of contracting a waterborne disease common in some developing countries or a rare infection such as PAM that can kill within 5 days.

Chlorine also provides residual protection from microorganisms beyond the point of treatment, in your home plumbing for example, something that ultraviolet and ozone treatment cannot. 

The samples taken from the kitchen and bathroom faucets of one of the Louisiana cases, (the other wasn't tested), were found to contain a total chlorine residual that ranged from 0.0 to 0.02 mg/l . The expected residual in the distribution system is 0.2 to 4 mg/l.

These cases highlight the importance of the annual temporary switchover to free chlorine disinfection employed by many water systems.

Although free chlorine is a more effective disinfectant against more pathogens than monochloramine, concern over possible long term health effects from disinfection byproducts (DPB's) that form in the reaction of chlorine with organic materials is beginning to limit its use.

I still haven't seen a report that definitively proves that DPB's cause cancer or reproductive problems in humans. If somone has, please forward me a copy. As a country we've been chlorinating drinking water for over 100 years. During that time mortality rates have fallen, the population has boomed, even after factoring out immigration. If properly chlorinated drinking water was that dangerous wouldn't we have known that by now?

When it comes to public safety it's good to be cautious. But wholesale changes in drinking water disinfection shouldn't be made until we know the changes will be more effective than our current proven course of action.

On balance, suspected possible long term health problems don't outweigh the known harm of immediately life threatening pathogens that can occur in untreated or ineffecively treated water. I couldn't live with myself if my 4 and 6 year old grandsons died from PAM because they were just goofing around while taking a bath in "pure and natural" water, or water that potentially, might possibly, be found to cause problems in the future.

Would I like pure and natural water in my house? No thanks, pass me the chlorine, and make it free please.


Tags: drinking water, potable water disinfection

How Often Should I Calibrate The FX-1000P Chlorine Analyzer?

Posted by Ray Sullivan on Thu, Aug 09, 2012 @ 11:04 AM

This is a commonly asked question, as is “when do I need to recalibrate my analyzer?”

 The FX-1000P Amperometric Chlorine Analyzer is designed to operate continuously, 24 hours a day, 365 days a year. The system requires little routine maintenance other than changing the vinegar buffering agent bottle as it becomes depleted and occasional calibration checks.  

 When to calibrate FX-1000P chlorine analyzerAs part of a standard quality control procedure, we recommend the analyzer readings be verified using an accurate chlorine residual test instrument once every 7 days. In many applications, using a portable DPD colorimetric residual analyzer for routine calibration checks is sufficient to meet reporting requirements. For the utmost precision or in critical applications we recommend comparison with an amperometric titrator.

Calibration is typically done on an as needed basis, or at the minimum frequency specified by regulatory requirements. Barring any changes to the process or analyzer, the analyzer should be calibrated at least once per year.

You Need to Calibrate When:

If any of the following situations occur you should first verify residual measurements, make any required corrective measures, and recalibrate the analyzer.

  • If readings are not within ± 0.1 mg/L or ± 15% of a routine grab sample measurement.

  • If there is a change in sample flow rate to the analyzer.

  • If readings gradually drift up or down and there have been no apparent changes to the process.

  • If readings suddenly or unexpectedly change by a large amount. (NOTE: if the residual drops dramatically or to zero, first make sure you have sample flowing into the measuring cell, as evidenced by a discharge from the left drain under the measuring cell).

  • If the analyzer has been off line long enough to discolor or oxidize the copper negative cell.

  • If there is a change in the sample or if the analyzer is sampling a different source.

  • If the measuring range is changed or the decimal point is shifted.

  • If the 4-20mA output is adjusted.

  • After performing maintenance.

Calibration Guidelines:

Calibration is always performed using water from your process.

When calibrating the zero point use dechlorinated process water, not distilled or deionized water. An accurate zero point is critical to accurate measurement.

Allow the measuring cell to stabilize to the process for 2-24 hours upon initial startup, after returning an offline analyzer to service, or after replacing the negative cell.

The Zero and STD potentiometer settings do interact with each other; so adjusting one may affect the other. You may need to alternately adjust Zero and STD several times to get an accurate calibration.

Don't Forget - if you change the operating range of the analyzer, remember to reset the alarm range, relays, as well as the scaling of your SCADA, controller, or chart recorder!

Tags: amperometric chlorine analyzer, FX-1000P calibration, tech tip, calibrate FX1000, chlorine analyzer maintenance

It's Coming .......The Foxcroft Gas Flow Control Valve Makeover

Posted by Ray Sullivan on Tue, Jun 26, 2012 @ 10:36 AM

The upgrade to our FX-8 and FX-8E automatic gas flow control valve is going into field testing this week after running for months in the Foxcroft manufacturing plant.

Foxcroft updated digital gas flow control valve
 

"Upgrade" may be a bit of a misnomer, because although we've kept the valve body, we've completely replaced the drive and electronics. Perhaps "makeover", "remake" or "transformation" would be more accurate.

The result is the FX-8D automatic gas flow control valve, a digital version of our previous series of valves. The basic function remains the same, to automatically control chlorine, ammonia, sulfur dioxide, or carbon dioxide gas feed, but the way it's done is totally different.

We've added a more user friendly design, more features, and have built-in as standard what were once options available at additional cost. While adding extra features is nice, one of the best parts is what we left out: MANDATORY FACTORY SERVICE. Returning the unit to the factory for service is no longer necessary since the FX-8D is FIELD SERVICEABLE.

Some of the changes we've made include:

  • Cooler running modular digital electronics and drive

  • Increased accuracy and repeatability

  • User adjustable input signal dampening

  • Built-in diagnostics

  • Signal loss protection-the valve will hold its position if input signals are out of range or disconnected.

  • User calibration of all input signals

  • Built-in manual & test modes

  • Remote dosage control from SCADA or PLC

  • Graphical display

Although the original FX-8 valve worked extremely well back in the day, it certainly needed a transformation to meet today's expectations. Please click here if you would like more information or progress updates.

 

Tags: chlorine gas flow control, ammonia gas flow control

Foxcroft Back to Ecuador: Step 1 Toward Reducing Water Losses

Posted by Ray Sullivan on Mon, Feb 06, 2012 @ 08:56 AM

As mentioned in a previous post, Foxcroft assisted in providing a water meter test bench to the City of Ambato, Ecuador last September.

In January of 2012 we and representatives of the MARS Company, the test bench manufacturer, were pleased to visit and provide start up assistance for the system delivered just after Christmas.

The process started when officials with EP-EMAPA, the Municipal Drinking Water and Wastewater Company of Ambato, estimated the city was losing about $1 million dollars per year in drinking water revenue between meter tampering and inaccurate water meters.

Management decided the first step was to address the most widespread issue, questionable meter accuracy. Rather than continue past practices, he believed the city would be best served by conducting its own meter testing and upgrading to the latest technology built to meet AWWA recommendations and NIST Handbook 44 specifications.

Electro-Mechanical Systems Engineer Max Pico chose the MARS Model 5-1000, an automatic double row bench that can test up to (10) meters 5/8" through 1" in one row, and up to (5) 1-1/2" through 2" meters in the second row with 1/10 of 1% repeatable accuracy using the gravimetric method. The system included a 500 gallon stainless steel tank and a 10 gal / 100 gallon duplex stainless steel tank. The system was provided and installed by our partner Amimechanical S.A of Quito, Ecuador.Mars test bench coontrol panel

Engineer Max Pico, left, at the MARS Co. computer control panel with a plant operator.

The test bench, which is compliant with ISO 4064 specifications, will help the city recover revenue lost to inaccurate water meters. In addition to testing the performance of their existing and newly purchased water meters, the bench will also provide valuable data to help evaluate future meter purchases.

Mars model 5-1000

Mars Co. president Floyd Salser with the MARS Model 5-1000 test bench in Ambato Ecuador

Since these test systems often pay for themselves in less than one year, we're looking forward to updates on how the test bench is contributing to their meter management program.

Tags: drinking water, water loss, Mars test bench

How to Save Chlorine Gas Money and Protect Your Operators

Posted by Ray Sullivan on Mon, Jan 30, 2012 @ 11:38 AM

I wanted to share a good idea that can help save money on chlorine gas while protecting your personnel.

Brian Gunn, of Coastal Chlorinators in Savannah, GA has a customer who prefers dual channel chlorine gas detectors in his remote well sites instead of the typical one sensor gas detector.

The customer places one sensor inside the well house to protect personnel, and the other sensor outside at the vent, so it will alarm if the chlorinator malfunctions. With the detector's alarm relay connected to a phone dialer, officials can be notified immediately instead of being surprised during an onsite visit after a month of wasting gas.

 

Dual channel gas detector for well sites

Of course, the environment is also protected from a prolonged chlorine gas leak.

If you have any other "cool tricks" please feel free to share them. When it comes to water and the environment, a good idea can benefit everyone.

Tags: gas detectors, chlorine gas detector, chlorine safety, safety

Foxcroft Participates in Technical Conference in Ambato, Ecuador

Posted by Ray Sullivan on Tue, Oct 04, 2011 @ 02:56 PM

Foxcroft Equipment & Service was honored to participate September 29, 2011 in an international conference "Technologies for Efficient Potable Water Service"  hosted by EP-EMAPA, The Municipal Company of Potable Water and Sewage Systems of Ambato, Ecuador.

Held in the Hotel Miraflores in Ambato, the conference was attended by EMAPA of Ambato officials, water system officials, technicians, and companies from other cities, as well as Foxcroft sales manager Ray Sullivan.

Foxcroft with EMAPA officials at potable water conference

Pictured L to R: Leonardo Herrera, Amimechanical, SA; Engineer Max Pico, EMAPA Chief of Electromechanical Systems; Ray Sullivan, Sales Manager Foxcroft Equipment; Engineer Rafael Maldonado, General Manager EMAPA; Galo Hinostroza, General Manager ASUBSA Aguas Subterraneas.

 

 

One objective of EMAPA for the conference was to share with other municipalities the method to improve the quantity and quality of drinking water while reducing operating costs through automated control systems. Savings allow the possibility of reinvestment in other projects to serve their customers.

Engineer Rafael Maldonado, General Manager of EMAPA, believes investment in high quality, current technology is essential to provide his customers with a reliable supply of safe drinking water in a  cost effective manner.

Foxcroft offered two presentations: the disinfection of potable water, and the Mars Company automatic water meter test bench being supplied to EMAPA of Amabato.

Engineer Max Pico, Chief of Electromechanical Systems for EMAPA presented the SCADA system recently installed by Leonardo Herrera of Amimechanical, SA; Foxcroft's representative in Ecuador. The SCADA system included equipment and instrumentation supplied by Foxcroft.

Technical Director Victor Mendez EMAPAR Riobamba

Pictured L to R: Leonardo Herrera, Amimechanical, SA; Ray Sullivan, Sales Manager Foxcroft Equipment; Victor Mendez, Technical Director, EMAPAR, City of Riobamaba; Engineer Rafael Maldonado, General Manager EMAPA.

 

Tags: drinking water, potable water disinfection