Transcript Automating Your Water Treatment Program

Automating Your Water
Treatment Program
Presented by:
Cooling Tower Controllers
5 Major Control Functions:
• Dissolved Solids Control
• Scale & Corrosion
Inhibitor Feed
• Biocide Feed
• pH 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:
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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
pH Control
• Hard water can be
“softened” using
controlled acid feed
• pH 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 pH
• ORP control is not used widely compared to
“slug-feeding” biocides as it is relatively costly
and more maintenance intensive
pH/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 pH
or ORP sensors
• pH/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
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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 mA 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 WebAdvantage 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?