Strategies for Flow Proportional

Sampling

Presented by: Glenn Hummel, PE

Objective / AgendaOBJECTIVE: Introduce background and technical information with respect to building

FLOW PROPORTIONAL Composite Samples with Automatic Sampling Equipment.

AGENDA:• WHAT YOU NEED TO KNOW (learn & understand – to successfully flow pace)

• SAMPLING BACKGROUND– TIME PACED SAMPLING– FLOW PACED SAMPLING (Why? / What is it? / How?)

• FLOW MEASUREMENT (Select the right approach and technology for the application)– FLOW CLASSIFICATIONS– FLOW MEASUREMENT METHODS (COMMON FOR WASTE STREAMS)– FLOW MEASUREMENT TECHNOLIGIES

• INTERFACING SAMPLERS WITH FLOW METERS

• WRAP UP

Before You Sample – Must Know:1. What Are You Sampling For?

• Permit Parameters2. Determine Minimum required Volume

• Lab Requirements3. Sample Containers

• Materials / Size4. Sample Preservation

• Cooling / Chemicals• Maximum Holding Times

5. Flow Pacing Info• Expected Discharge Volume During Sampling Period• Gallons per Pulse• Span of Analog Signal (20 mA = _?_ GPM)

Sampling Background• FIELD OBJECTIVE:

Build a volume of liquid sufficient for analysis, that is representative of its source / stream over a period of interest.

• KEYS:– Representative of Source– Collection Techniques do not introduce Interferences– Sufficient Volume for Laboratory Analysis

Composite Sample• A composite sample is a single sample

volume constructed of multiple individual samples (aliquots) taken over a specific period of time or volume of flow (period of interest).

Time Paced Composite• “Time Paced” Composite samples are

taken at uniform intervals of time over the period of interest.

• Typical: 100 mL every 15 minutes, over a period of 24 hours. This yields 96 samples deposited to a composite bottle = 9,600 mL = 2.5 gallons 2.5 gal.

(9400 mL)

Time Paced CompositeChallenges of Time Proportional Sampling: • Building/Collecting a

Representative Sample– Intermittent Flow: could lead to sampling

stagnant water or sewage1. Overweighting periods of low to no flow2. Underweighting (missing) periods of high flow

Flow Proportional Sampling• The Objective of Flow Proportional

Sampling is to collect a Representative Sample

relative to a Period of Interest

Flow Paced Composite• “Flow Paced Composite Samples” are built from

aliquots taken at fixed / uniform increments of volume

metered past a flow measurement point

• Challenges Flow Proportional Sampling:– Variability in discharge volume over period of

interest leads to varying sample volume collected.

Flow Pacing a Sampler• Samplers count “Pulses” received as an

input signal from a flow meter• “Pulse” signal indicates when a fixed

volume increment of water has passed the meter.

• Therefore sampling uniform aliquots into a bottle every X pulses produces a “flow proportional” composite sample.

Flow Pacing a SamplerExpected Volume of Discharge during Period of

InterestEXAMPLE: 100,000 gallon discharge

• Flow Meter Pulse = 100 gallons• Sample every 20 pulses = 2,000 gallons• Yields 50 samples * 100 mL/sample = 5,000 mL

= 1.3 gallon composite sample

1.3 gal.

Flow Pacing a SamplerMinimum Sample Volume Required for AnalysisEXAMPLE:

Min. Sample Vol. = 3 L (3,000 mL)If Discharge Vol. = 50,000 gal.(50,000 gal.) / (100 gal./pulse) * (100 mL / 20 pulses)Composite Sample Vol. = 2.5 L (2,500 mL)

Corrective Action: • Larger Aliquots• Fewer Pulses per sample (more aliquots)

2.5 L

3.0 L

Flow Pacing a SamplerMaximum Sample Volume (Bottle Size)EXAMPLE: 200,000 gallon discharge

– Flow Meter Pulse = 100 gallons– Sample every 20 pulses = 2,000 gallons– Yields 100 samples * 100 mL/sample = 10L

• Bottle Overfilled (9,400 mL capacity)Corrective Action: • Smaller Aliquots• Larger Sample Interval• Bigger Bottle (2 Samplers)

>2.5 gal.

Flow Pacing a SamplerMinimum Number of Aliquots to Build a Composite• Example: 100,000 gallon discharge

– Flow Meter Pulse = 20,000 gallons– Sample every 1 pulses = 20,000 gallons– Yields 5 samples * 1,000 mL/sample = 5,000

mL = 1.3 gallon composite sample• Problem: Too Few Sample Aliquots• Corrective Action: Finer Flow Meter Output

Flow Pacing a SamplerWHAT YOU NEED TO KNOW

• Average Discharge Volume over Period of Interest

• Max & Min. Discharge Volume (!!Range!!)

• Minimum Sample Volume Required for Analysis

• Minimum Number of Aliquots to Build a Composite

• Minimum Volume per Aliquot

• Flow Meter Output: Volume Per Pulse

EXAMPLE: Lab Requires 1 gal. (3.8 L)

• RATIO: [Max. Vol to Min. Vol] = 2.5 to 1.0

• Sample Volume Ratio (SVR = 2.5)

2.5 gal.

(9.4L)

Bottle Capacity

1.0 gal.

(3.8 L)

Lab Requires: 1.0 gal. (3.8 L)

[MAX. Vol.]

[MIN. Vol.]

Bottle Capacity: 2.5 gal. (9.4L)

EXAMPLE: 100,000 GPD Facility Average Discharge

MAX: 150,000 GPD MIN: 75,000 GPD

• RATIO: [Max. Vol to Min. Vol] = 150/75 = 2.0

• OK: Discharge Vol. Ratio = 2.0 DVR < 2.5 SVR

[MAX. Vol.]

75,000 gal.

150,000 gal.

[MIN. Vol.]

Bottle Capacity: 2.5 gal. (9.4L) Lab Requires: 1.0 gal. (3.8 L)

EXAMPLE: 100,000 GPD Facility Average Discharge

MAX: 200,000 GPD MIN: 50,000 GPD

• RATIO: [Max. Vol to Min. Vol] = 200/50 = 4.0

• PROBLEM: 4.0 DVR > 2.5 SVR

[MAX. Vol.]

50,000 gal.

200,000 gal.

[MIN. Vol.]

Bottle Capacity: 2.5 gal. (9.4L) Lab Requires: 1.0 gal. (3.8 L)

EXAMPLE: 100,000 GPD Facility Average Discharge

MAX: 200,000 GPD MIN: 50,000 GPD• 100 gal./pulse• sample every 20 pulses = 2000 gal./sam• 100 mL/sam

• 200,000 gal discharge 10,000 mL = 2.6 gal. – BOTTLE OVERFILL (Capacity: 2.5 gal., 9,400 mL)

• 50,000 gal. discharge 2,500 mL = 0.7 gal.– INSUFFICIENT VOL. FOR ANALYSIS (Req.: 1.0 gal., 3.7 L)

RESULT• When Discharge Volume Ratio (DVR) is (>) GREATER

than Sample Volume Ratio (SVR), a single flow proportional sampling program cannot cover all possible discharge volumes.ACTION:1. Field Personnel must use best available information.2. Make an assumption of likely range of discharge volumes.3. Program Sampler for discharge volume range with same ratio

as SVR.

• When Discharge Volume Ratio (DVR) is (<) LESS than Sample Volume Ratio (SVR), all discharge scenarios can be programmed into a flow proportional sampling system.

Flow Measurement

Flow Classifications• Open Channel

– Any open channel where liquid flows with a free surface(Non-full pipe. Example: sewer)

• Closed Channel – Completely Filled Pressure Conduits

(Full Pipe)

Types of Flow Measurement Methods

• Timed Gravimetric• Dilution• Slope – Hydraulic Radius (Manning Eq.)• Area*Velocity• Hydraulic Structure (Primary Device)

Types of Flow Measurement Methods

• Area*VelocityQ (cfs) = v (ft/s) * A (ft^2)

Measure velocityMeasure Level to Calculate Area (A) in a known

Channel Cross Section

• Primary Measuring Device– This method uses a hydraulic structure that creates a

known relationship between flow rate, and a secondary measurement (level)

Flow Metering TechnologiesFull Pipe Open Channel

Area Velocity Mag MeterTransit Time

VenturiOrifice plate

Doppler

Primary Device

FlumeWeir

Flow Metering TechnologiesFull Pipe Open Channel

Area Velocity Mag MeterTransit Time

VenturiOrifice plate

Doppler

Primary Device

FlumeWeir

Magnetic Flow Meter• Area is Fixed (Full Pipe)

• Velocity is measured using Faraday’s Law

Magnetic Flow Meter• 1 to 30 ft/s• +/- 0.5% Accuracy• Full Flow Area• Chemical Compatibility• Straight Pipe

– No Elbows, Valves, Pumps

• Pipe must be full

Transit Time

Transit Time

Flow Metering TechnologiesFull Pipe Open Channel

Area Velocity Mag MeterTransit Time

VenturiOrifice plate

Doppler

Primary Device

FlumeWeir

Venturi Flow Meter• Primary Device (Full Pipe)

– creates d/p in relationship to flow rate• Secondary Measurement is Differential Pressure

Flow Metering TechnologiesFull Pipe Open Channel

Area Velocity Mag MeterTransit Time

VenturiOrifice plate

Doppler

Primary Device

FlumeWeir

Flow MeasurementQ = V x A

To measure flow rate (Q), we need...

1. The pipe or channel geometry.

3. The average velocity of the flow.

2. The depth of the flow.

This is the hard part

Area VelocityContinuous Wave Doppler (CWD)

Pulsed Doppler - Velocity Profiling

Area Velocity SensorMounting Hardware

Area Velocity SensorMounting Hardware

The right technology for the application

Flow Metering TechnologiesFull Pipe Open Channel

Area Velocity Mag MeterTransit Time

VenturiOrifice plate

Doppler

Primary Device

FlumeWeir

Parshall Flume

Palmer Bowlus Flume

V-Notch Weir

Flow Metering Insert (Weir)

Level Measurement

(Secondary Devices for Flumes & Weirs)

Level Measurement Technologies

• Bubbler– Strength: Good

Resolution / Accuracy– Weakness: Contacts

flow, compressor hardware

Level Measurement Technologies

• Ultrasonic– Strength: Non-

contacting (low maintenance)

– Weakness: Foam, gas (speed of sound)

Ultrasonic Level Measurement

Level Measurement Technologies• Submerged Probe / Pressure

Transducer– Strength: Good Resolution /

Accuracy– Weakness: Contacts flow– NOTE: Doppler Area Velocity

Probe uses this technology

Flow Metering Technology Selection Considerations

• Hydraulics:– Full (Closed Pipe)– Non-Full (Open Channel)– Pipe Diameter– Pipe Slope

• Flow Metering Objective:– Flow Pace Sampling– Billing– Process Control

• Maintenance• Installation / Facility Configuration / Constraints

Interfacing Flow Meters with Sampling Equipment

Flow Meter to Sampler Interface• Automatic Samplers utilize “pulses” for

Flow Paced Sampling Programs• Pulse is output from Flow Meter every

“unit volume”• a.k.a. Pulse Frequency Output• Sampler counts pulses and collects a fixed

volume aliquot every X pulses.

Non-Isco Flow Meter to Sampler Interface

• A “pulse” must be:Isolated contact closure5-15 VDC>25 millisecond duration

Not all pulse outputs meet this spec.

Simple 2 wire cable with Military Connector

Analog Flow Signal• Analog Output from Flow Meter can be used to

pace sampler• Requires a 4-20mA Sampler Interface Module• Module converts analog signal to pulses.

– Generates pulses at a frequency proportional to the analog signal

– Full Scale: 20mA = 5 pulses / minuteExample: 20mA = 1,000 gpm => 200 gallons / pulse

4-20 mA Sampler Interface

4-20 mA Interface to Sampler

Wrap Up

Application Considerations for Technology Selection

• Full Pipe vs. Open Channel• Submergence of open channels• Straight Pipe / Straight Channel• High TSS vs. Very Clean• Solids, Silt, Fat Oil Grease, Debris• Aggressive Chemicals, Temperature• Steam, gases

Equipment Considerations• Meter Accuracy vs. Metering Objectives• Permanent vs. Temporary• Routing Signal to Sampling Equipment• Chemical Compatibility• Maintenance Frequency & Cost• Calibration / Validation Frequency

“The PLAN”• Facility Assessment

– Review Discharge Characteristics • Flow & Concentration Variability

– Physical Site Characteristics• Sampling Location(s)• Pipe Size / Slope / Material• Access (Safety)

“The PLAN”• Determine whether to

– Implement Flow Proportional Sampling or– Request an Exception

• If TIME PACED is as representative as FLOW PACED

“The PLAN”• In the Case of Flow Proportional• Determine Flow Metering Objective

– Flow Pacing Sampling (ONLY)– Billing – Process Control

• Select Flow Metering Location• Select Method• Select Technology• Document Flow Metering & Sampling Plan• Establish Validation Plan

What do you need to know?When you have implemented flow paced sampling, what info must be passed on to Inspector or Sampling Crew?

• Desired Sample Volume– Minimum Volume Required for Analysis– Maximum Volume (Composite Bottle Size)

• Expected Vol. of Discharge during sampling period– Range of Discharge Volume (min, max)

• Existing Flow Meter Information– Span of Analog Output: 4mA = 0 gpm, 20 mA = XXX gpm– Volume / Pulse

Thank You!For More Information Contact:

(586) 978-7200info@hesco-mi.com

Sampler ProgrammingPROGRAM / VIEW LOG• Selection is Blinking• Arrow Key to toggle

Selection• Enter Key to Accept

Selection

Sampler PreparationsProgramming• Sample Pacing

– Time Paced– Flow Paced

Sampler PreparationsProgramming• Pacing Interval

– ## of Minutes Between Samples

– ## of Pulses (Volume of Flow) Between Samples

Sampler PreparationsProgramming• Bottle Volume

– Best to enter a volume slightly less than bottle capacity to prevent spilling during recovery

– Example: 10L bottle enter 9400 mL

Sampler PreparationsProgramming• Number of Samples

– Enter number of samples to place in bottle. (Typ. 96)

– NOTE: If “0” is entered, the GLS will sample continuously till bottle is full.

Sampler PreparationsProgramming• Sample Volume

– Enter volume in mL to take each aliquot place in bottle. (Typ. 100 mL)

– NOTE: aliquot volume > 50 mL is suggested

Sampler PreparationsProgramming• Start Time

– Enter number of minutes to wait prior to starting program after pressing “GO”

Sampler PreparationsProgramming• MAX Run Time

– “0” is no maximum– Typical: 24 hours– NOTE: Applies to flow

paced sampling.

Sampler PreparationsProgramming• Suction Line

– Enter DIAMETER– Enter LENGTH

– IF changed, press CALIBRATE button to calibrate pump for new tube size

RUN Sampler ProgramProgramming• Press ENTER to go to

Standby Mode

• Press RUN to start program

• Press STOP to temporarily Pause or permanently Halt active program

Other Key Strokes• Press and Hold “1” to run

Pump FORWARD

• Press and Hold “3” to run Pump REVERSE

• Press GRAB button and remove pump tube to take a grab sample

Automatic SamplersController

Bottle

Pump

Power

Sampler Preparations• Sampler Check

– Pump Tube– Cracks– Debris– Proper Position

Sampler Preparations• Sampler Check

– Discharge Tube• In Place• Extend 1.5” past

guide into bottle

Sampler Preparation: Bottle• Sampler Check

– Bottle Material• Glass• Plastic

– Volume2.5 Gallon (10L)1.0 Gallon (3.8L)2 Gal Pro Pak (7.6L)

Sampler Preparations• Sampler Check

– Power• Ni-Cad (4.5 Amp-Hr)• Lead Acid (6.5 Amp-Hr)• 120VAC• Solar• Other

Sampler Preparations• Sampler Check

– Cooling• 10 lbs. Ice• Gel Packs• Fill & Freeze

• For a composite sample collected with an automated sampler (e.g., using a 24-hour composite sampler; see 40 CFR 122.21(g)(7)(i) or 40 CFR Part 403, Appendix E), refrigerate the sample at ≤6 °C during collection unless specified otherwise in this Table II or in the method(s).

Sampler Preparations• Suction Line

3/8” ID Vinyl¼” ID Vinyl3/8” ID Teflon

– Cut to shortest length feasible– Continuous slope down from sampler to strainer so

suction line will drain fully. No LOOPS or coils where water will pool.

– No dips or low spots where sample can collect.

Sampler Preparations• Strainer

– Place in main flow, not in an eddy– Try not to lie flat on bottom of channel where an

excess of heavy solids could be collected– Attempt to install so weighted end sits on channel and

tube end is slightly off the bottom of the channel• Allows debris / rags to self clear

Sampler Preparations• Other Considerations

– SUPPORT: Weight of Sampler full can reach 65 lbs. (battery, full sample bottle, ice)

– ENVIRONMENTAL: Avoid environments with extreme heat / steam, or aggressive chemical attack

– ACCESSIBILITY: Easily removable when full. Safe for personnel.

– SECURITY: Lockable for tamper prevention. Consider potential for vandalism / theft.