Automating Your Water Treatment Program Presented by

Automating Your Water Treatment Program Presented by:

Cooling Tower Controllers 5 Major Control Functions: • Dissolved Solids Control • Scale & Corrosion Inhibitor Feed • Biocide Feed • p. H Control • ORP Control

Dissolved Solids (TDS) Control Key Facts: • Only pure water evaporates • Dissolved solids (TDS) are left behind in recirculating water • TDS accumulate and fall out of solution in the form of scale

Scale Buildup vs. Energy Loss • 1/1000” of scale can reduce heat transfer efficiency by up to 10% • This translates into a proportionate increase in energy costs

Bleed-Off = Scale Prevention • “Bleed-off” refers to removing water with high TDS and replacing it with fresh makeup water • This process lowers the overall TDS to a safe, nonscale forming level. • Manual bleed-off can result in high and low TDS spikes (forms scale or wastes water)

Results of Manual TDS Control Tendency to Form Scale Deposits TARGET MAXIMUM Excess Water Usage

The Solution: Automated Bleed-Off • Two common forms of automated bleed-off are “conductivity control” and “proportional bleed” • Bleed-off valves should be installed downstream of the heat exchanger for optimum energy efficiency

Conductivity Control Systems • TDS in the water conduct electricity • Conductivity controllers measure the ability of the water to conduct electricity • Conductivity controllers automatically open a bleedoff valve when TDS levels approach scale forming levels

Conductivity Control Systems • Conductivity controllers keep TDS levels near the target maximum at all times • Automated controllers account for changes in load demands and atmospheric conditions -manual bleed does not Target Maximum

Conductivity Control Systems Installation Guidelines: • • Bypass assembly with 3 -10 gpm flow rate No air pockets Upstream of chemical injection points Probe should be mounted near controller for ease of cleaning/calibration, but wire extensions in excess of 300’ are permissible • Conductivity probe wire must be separated from high voltage lines

Conductivity Control Systems Pros: • Extremely accurate • Easy to use Cons: • Maintenance required (periodic probe cleaning and calibration) • Installation requirements (piping/wiring)

Proportional Bleed Systems • Also called “water meter timer” systems • Bleeds-off proportionally to the volume of incoming makeup water • Contacting head water meter initiates timed bleed-off cycle

Proportional Bleed Systems Pros: • Very little maintenance • Ease of installation Cons: • Doesn’t account for changes in makeup water quality • Leakage or “windage” can lead to excess bleed-off

Proportional Bleed Systems Installation Guidelines: • Water meter wire can be extended up to 1000’ • Low voltage water meter wire must be separated from other high voltage lines

Automated Inhibitor Feed “Feed With Bleed” “Feed After Bleed” • Chemical is injected as bleed valve opens • Potentially wastes chemical • Chemical is injected after bleed valve closes • Feed is proportional to bleed-off

Automated Inhibitor Feed “Percentage Timer” “Pulse Timer” • Chemical is fed on a repeating time cycle • Doesn’t correspond to water usage • Signal from makeup water meter initiates feed cycle • Chemical is fed proportioanlly to makup water • Most accurate way to dose inhibitors

Automated Biocide Addition • Biocides should not be handled or added manually (health and safety hazard) • Biocides are typically “slug fed” using a chemical pump (or brominator) and timer • A 28 -day timer initiates the biocide feed cycle • Bleed-off is typically “locked out” during biocide feed cycles

p. H Control • Hard water can be “softened” using controlled acid feed • p. H controllers allow acid to be fed at safe and consistent levels

ORP Control • ORP = oxidation-reduction potential • ORP is a relative measurement of the amount of free chlorine or bromine in a system using a measurement similar to p. H • ORP control is not used widely compared to “slug-feeding” biocides as it is relatively costly and more maintenance intensive

p. H/ORP Guidelines • Routine cleaning of probes is essential • Probe wire shouldn’t exceed 15’ in length without a signal amplifier • Probe wires should never be spliced • All chemicals should be inject downstream of p. H or ORP sensors • p. H/ORP probes have a serviceable lift of approximately 12 months

Analog Controllers • Feature analog meter readout of conductivity • Limited functionality (1 or 2 control functions) • Easy to operate • Economical choice • No modem or Internet communication

Microprocessor Controllers • Keypad programmable • Digital display • Combines many functions • Slight operational learning curve • Initially more expensive • Capable of all forms of remote communication

Chemical Metering Pumps • Most water treatment applications use solenoiddriven diaphragm pumps • Metering pumps are specified by: – Type of chemical being pumps – Desired output – Required injection pressure

Chemical Metering Pumps • Most common pumps have a suction lift of five feet • Injection valves should be installed vertically into the bottom side of a pipe • A foot valve is placed in the chemical drum to help a pump keep its prime

Degassing Considerations • Some “off-gassing” chemicals (bromine, chlorine, etc. ) produce gases that can vaporlock the pump • When vapor-locked, a pump loses its prime and will not pass chemical through the head • Utilize a “degassing valve” to allow gas to escape the pump head and prevent priming problems

Typical System Installation

Equipment Trends • • • Side Stream Filtration “Smart” Pumps Multi-System Controllers Remote Monitoring Online Service Reporting Chemical Volume Measurement • Direct Chemical Measurement ? ? ?

Side Stream Filtration • Reduces energy costs by making heat exchangers more efficient • Reduces fouling and improves water clarity • Typically installed in bypass line sized to 10% of system volume

“Smart” Metering Pumps • Combine pump and controller features into a single pump housing • Inexpensive control option for simple applications • Limited to 2 control features

Multi-System Controllers • Early controllers featured only one or two relay outputs • Modern controllers feature up to 20 control relays • Sophisticated units can control up to four independent water treatment systems

Remote Monitoring • 4 -20 m. A signals and dry contact switch closures can be sent to building management systems • Modem-to-modem communication allows off-site monitoring and control with custom software • Cutting-edge controllers are using the Internet to transmit data and alarm conditions

Web Based Remote Monitoring Snapshot of Web. Advantage Controller Status

Web Based Remote Monitoring • Uses facility’s existing Ethernet for remote access • Eliminates need for phone lines and proprietary software • “Always on” connection detects power interruptions • Allows simultaneous multiple user access • No need to download data

Online Service Reporting • Combine water treatment test results with controller operating data • Receive automated services reports at user-defined intervals • Receive e-mail alarms when operating parameters are out of spec

Chemical Volume Measurement • Volume-activated pulse output device is installed on discharge side of chemical pump • Chemical volume is combined with water meter volume to calculate PPM concentration of chemical

Direct Chemical Measurement • Using specialized probes, direct measurement of phosphonates and other chemicals will be possible • Using proportional control technology, precise chemical levels will be maintained in a system • Precise dosing will maximize water treatment program efficiency

Any Questions?