Some Basics To Know When Specifying and Using On … SPE 2011 Presentation - Leak... · Some Basics...

© 2011 Air Logic Power Systems, LLC

Leak Testing Equipment

“Leak Testing 101”

Some Basics To Know When Specifying and Using

On-Line Leak Testing Equipment

Scott Heins ALPS Sales Manager

SPE Blow Molding Conference Oct 13, 2011



MACHINE TYPES

PLANT CONDITIONS

TEST METHOD

WHY LEAK TEST?



Back to Outline

• Functional Test - Verifies each container will seal and hold

pressure

• Detects most critical defects

• Prevent moisture, oxygen or foreign material ingress

• Process monitoring

• Protection for random quality issues

• Protection of inventory

• Industry best practice in manufacture of blow molded containers

Supports Market Trends

• Light-weighting

• Recycled material content

• New container types and processes

Benefits of On-Line Leak Testing



Pressure Decay Theory of Operation

How It Works:

• “Pressure Decay” test method is dominant for blow molded containers

• A test probe is extended to form a leak tight seal on each container

• The container is pressurized

• Detect leaks as a larger pressure drop compared to good containers

Back to Outline Back to Test Method



Typically 3-Step Test

• Fill: Container filled to target pressure

• T1: Measure an initial pressure change

„Stabilization‟ time (adiabatic cooling)

• T2: Measure a final pressure change

Pressure Decay Test Method


Detection Result:

• ‘Gross’ reject

• ‘Medium’ leak

• ‘Small’ leak




Realities of Blow Molded Container Leak Testing:

• Larger Volume Parts will require more time to detect the same hole size

• Takes longer to detect change in pressure

• Detecting loss of a drop of water in a thimble vs. bathtub analogy

• Longer Test Times are required to detect smaller leaks in a given container

• Pressure will tend to level out in good containers

• Pressure will continue to drop in leaking containers

Pressure Decay Test Method



• P = Pressure (atm)

• V = Volume (liters)

• n = number of moles (mass/molecular mass)

• n stays constant for non leaking parts

• n decreases for leaking parts

• R = Universal gas constant (0.0821 L-atm/mol-K)

• T = Temperature (Kelvin)


Ideal Gas Law: PV = nRT or P = nRT/V

Some Effects of the Laws of Physics:

• Pressure Loss will typically occur in Good parts due to adiabatic cooling and

(Temperature drop) and container stretch (Volume increase)

• Temperature variations in the product will cause Pressure variations. The

main effect of hot plastic is creation of a pressure rise inside the container

when it is closed for the leak test.

• Bottle Compression (Volume drop) during the test will cause a pressure rise



Test Verification Methods

Self Test Pushbutton


• Metal Orifices with a known diameter are used to simulate leaks

• This is more precise and repeatable than poking a hole in a bottle

• These can be installed directly into Test Bottles (image at left) and run through the

leak tester to verify performance

• The Metal Orifice can be installed onto a Test Leak Valve on the machine

• A Self Test function can be performed by pressing a button that activates the Test

Leak Valve prior to the next leak test of a bottle

Test Leak Valve



Typical Parameters for Blow Molded Containers


Bottle Sizes

• From 3cc vials/droppers up to 300 oz Detergent / 5 Gallon Edible Oil for

common automated machines

Metal Paper Clip

0.030”

(0.75mm)

Avg. human hair

0.003”

(0.075mm )

Hole Sizes

• From 0.004” to 0.020” / 0.030”

Speeds

• Up to 1000 BPM applications in the market today

Test Times

• From tens of milliseconds on very small parts to several seconds

http://www.usplastic.com/catalog/ImageViewer.aspx?description=Cylinder+and+Boston+Round+Bottles+with+Dropper+Caps&curimage=Bottles%2fsku%2f66437psku.jpg&image=Bottles%2fsku%2f66437psku.jpg&catid=750&itemid=43968



Lab vs. Production Line Results

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A leak test will be more accurate, consistent and repeatable

under lab conditions vs. on the production line

Reasons for Test Variations on Production Lines

• Greater population of containers

• Container dimensional variations (volume, stretch behavior)

e.g. motor oil container „paneling‟

• Changes in elasticity or stretch

e.g. wall thickness variations

• Container temperature variations

e.g. mixture of hot and cured bottles

• Handling and presentation to the leak tester



Recommendations on the Production Line

Back to Outline Back to Plant Conditions

• Do not position the leak tester next to a heat source (e.g. flamer or blow

molder) if possible

• Present the containers to the tester in as close to „cured‟ state as practical

• Set up the leak tester to maximize test time

• Do not expect the same hole size for every container if the bottle volumes

and test times vary

• Pay attention to container handling through the leak tester

• Minimize sealing force as much as possible

• Considering the range of container variability when choosing reject limits

i.e. don‟t set too tight based on feedback from a few bottles

• Have a plan in place to „challenge‟ the leak tester – Determine method

(e.g. Self Test) and how often

• Watch your seals carefully



Importance of Seals

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The seal is the conduit for the leak test – it must be

reliable and leak tight for good results

• The leak test provides a functional test of the Seal Surface integrity, which

can be tuned to the desired sensitivity

• Select an appropriate seal durometer (hardness) for the application

• Select an appropriate sealing force to reduce false rejects and detect the

desired level of seal defects

• Probes and seals can be customized to focus on a specific area of the

seal surface if desired

• If you are focusing on a specific Seal Surface test for a particular

container, create „challenge samples‟ for the leak tester



Machine Type #1: Bottle Stop, Conveyor Method

Back to Outline Back to Machine Factors

• Separate, dedicated leak tester conveyor

• Stops bottles for the leak test by stopping the conveyor

• Vacuum conveyor assists bottle stability and handling speed

• Requires transfer of bottles to/from the leak tester conveyor

Requires Conveyor Transfers



Application Examples #1 – Bottle Stop, Conveyor


General Purpose

• Bottles that transfer effectively between conveyors

• Line layouts that can accept separate leak tester conveyor

• Generally faster than a “Bottle Stop, Cylinder” machine



Machine Type #2: Bottle Stop, Cylinder Method


• Stops bottles for the leak test, using a cylinder

• Requires Gate cylinder to regulate containers; and downstream Reject

• Conveyor is typically running continuously underneath

• Bottles must be stable enough to be stopped on-the-fly



Application Examples #2 – Bottle Stop, Cylinder


Angle neck bottles

• Bottles are stopped/captured

• Requires test probe mount with adjustable angle

General purpose

• Cases in which a conveyor transfer of bottles is not desired

• Bottles must be stable enough to be stopped „on the fly‟



Machine Type #3: Linear Continuous Motion


Timing Screw Handling

• Mounts over existing conveyor

• Uses timing screw to separate bottles for the

leak test

• Test head(s) follow the bottle during travel in

the timing screw

Timing Screw

Slide & Test Probe Assembly Encoder Wheel

Conveyor Following

• Mounts over existing conveyor

• Follows and tests bottles „on the fly‟

• Probe carriage driven by linear slide

• Slide speed is matched by monitoring

conveyor with encoder wheel



Application Examples #3 – Linear Continuous Motion


Very small pharma bottles • Tiny footprints

• Avoid conveyor transfers

• Avoid touching of bottles (Conveyor Following version)

Teardrop shapes • Small, non-straight sides; often „sticky‟ polypropylene

• Avoid conveyor transfers


‘Tri’ shaped drug bottles • Avoid conveyor transfers, bottles „wedging‟


Personal care bottles • Reverse tapers and sharp corners


http://www.usplastic.com/catalog/ImageViewer.aspx?description=Cylinder+and+Boston+Round+Bottles+with+Dropper+Caps&curimage=Bottles%2fsku%2f66437psku.jpg&image=Bottles%2fsku%2f66437psku.jpg&catid=750&itemid=43968



Machine Type #4: Rotary Continuous Motion


• Timing screw separates bottles to the machine „pitch‟

• Bottles travel through the machine in a continuous motion

• Dedicated change parts for each container

• Longest test time approach by creating bottle path on turntable

• Most sensitive leak test for a given speed



Application Examples #4 – Rotary Continuous Motion


Hot Fill & Custom PET

Long Stroke Shuttle Blow Molded Containers

Wheel Blow Molded Containers



Comparison of Machine Types


#1 Bottle Stop, Conveyor Method good for general purpose

• Conveyor type and speed is optimized for the leak test

• Setup is simplified = one photoeye and simple conveyor stop handling

#2 Bottle Stop, Cylinder Method is lowest cost for conveyor mount

• Bottles must be stable enough to be stopped on the fly

• Speeds are not as high as other unit styles

• More setup items = Gate, Stop and Reject eyes and cylinders

#3 Linear Continuous Motion for harder-to-handle containers

• Severe ovals (shinglers), reverse tapers, high height-to-base ratios (3:1

to 4:1+), very small bottles

• Setup is simplified = one photoeye

• Mounts and tests over existing conveyor, to avoid bottle transfers

#4 Rotary Continuous Motion for high speeds and/or micro leak testing



1745 S. 38th Street, Suite 100 Milwaukee, WI 53215-2017

Phone: 414-671-3332 ; Fax: 414-671-6645 24-Hour Service Hotline: 800-325-8717

Email: [email protected] Web: www.alpsleak.com

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Thank You

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http://www.alpsleak.com/

Some Basics To Know When Specifying and Using On … SPE 2011 Presentation - Leak... · Some Basics...

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