Leak & Burst Testers

Standard Models: (select a model to learn more)

AB-LT
Allen Bradley PLC Leak Test System

EH-BT
Electronically Controlled Hydraulic Burst Testing System

For increased quality assurance of welded components, Forward Technology can incorporate leak testing into your assembly cells. Our PLC based leak testing systems employ a non-destructive test to insure the integrity of the part. Air testing detects small leaks, and eliminates the need for part drying. We offer several air testing methods: pressure decay, vacuum decay, chamber decay and occlusion testing. Our engineers will assist in analyzing your particular testing application. We understand how plastic parts react to leak testing applications. Our systems combine user-friendliness with detailed data analysis and collection.

Each leak test system is custom designed around the customers test requirements and often includes functional testing and component inspection while performing the leak test.

Forward has been designing and building both standard and custom leak test systems since 1977. Our experience building leak test systems allow us to design fast, accurate, and readily adaptable systems to many unique applications. Forward Technology leak testers have multi-channel capacity, allowing simultaneous testing multiple parts during each test cycle. Our testers also have built-in capability to operate complex fixturing and perform other value-added testing/inspection during the leak testing operation.

We also offer hydraulic (H²O/Glycol Mix) liquid burst testing machines capable of generating pressures of up to 750psi in a built-in safety enclosure. Our engineers can assist in analyzing your particular leak or burst testing application.

Advantages of Air Decay Leak Testing
Why Leak Testing?
Common Leak Testing Methods
Air/Gas Leak Testing Techniques
Systems Forward Technology Offers
Pressure Decay Testing
Negative Factors that Effect Leak Testing

Advantages of Air Decay Leak Testing

Fastest, most consistent test technique for 90+% of welded plastic components.
Non-Operator Dependant and test data can be collected by printer or computer.
Passed product can be automatically marked (ink, stamping, engraving) to insure parts are tested prior to subsequent processes.
Accurate on leak rates as low as 0.1 sccm.
No cleaning/drying operations required after testing.
System accuracy immune to most environmental conditions.
Can be configured for 100% testing downstream of most bonding operations.

Why Leak Testing?

What is Leak Testing?

Finding holes or voids in parts which allow them to pass air or fluid when they are designed not to leak.

The Goal of Any Leak Test

Differentiating clearly and consistently between good parts and failures in as fast a timeframe as possible

Reasons to Leak Test

Product Safety & Liability
- Medical components may cause injury or death when leaking during or after procedures (heart catheters, IV sets, etc…).
- Automotive components may cause injury or death when leaking in operation (flammables and brake related components).
- Appliances may cause electrocution of the user (irons & steamers).
Quality Control
- Most common method of testing bonded plastic components which require hermetic joints.
- Testing parts following assembly can alert maintenance to setup problems with welding equipment.
- 100% testing virtually eliminates field failures related to the bonding/joining process.

Common Leak Testing Methods

Pressurized Fluid

Leaks are detected visibly or by measured decay by specialized fluid pressure gauges or electronic sensors.

Advantages

Simulates "real-world" conditions for parts designed to contain or pass fluid.
Performs superbly for testing at pressures above 500PSI.
Preferred for destructive testing (pressurize to burst).

Disadvantages

Added Costs: Parts often require cleaning/drying after test.
Time Consuming: The time required for fluid to leak through a small void in the part can be considerable, sometimes hours.
Messy: Fluid gets everywhere when testing using this method.
Costly Equipment: Equipment for fluid testing is often custom made per application and must consider containing fluid.

Pressurized Air/Gas

Leaks are detected visibly when immersed in fluid, or audibly when using sensitive "listening" devices or by electronic sensors when using pressure-decay instruments.

Advantages

Fast: As air molecules are roughly 500X smaller than water molecules. Can detect much smaller voids in parts in considerably less time than fluid testing.
Low Cost: Sensitive equipment is available by many manufacturers at far lower costs than sensitive fluid systems.
Clean: Parts do not have to be cleaned of fluids after test.

Disadvantages

Very costly to achieve pressures above 500PSI.
As air compresses so much more than fluid, can be difficult to use for some destructive tests.
Only represents (does not duplicate) "real-world" testing for parts containing or passing fluid.

Vacuum

Leaks are detected visibly when immersed in fluid (liquid entry into part) or by specialized electronic vacuum sensors or gauges with vacuum-decay instruments.

Advantages

Ideal for parts that will have internal vacuum applied.
Can create leak paths that cannot be replicated by pressure testing such as dynamic seals ("o" rings and rubber diaphragm valves).

Disadvantages

Not good for testing parts that would otherwise have pressure applied internally in actual application as the vacuum may inadvertently seal small voids in flexible parts.
Vacuum is limited to approximately -14.7 PSI (ideal vacuum). With typical vacuum pumps, only -10 PSI or so may be possible.

Air/Gas Leak Testing Techniques

Water Immersion / Soap Solution

Pressurize part under water and look for air bubbles or spray outside of part with soap/water solution and look for bubbles caused by air leakage out of the part.

Advantages

Can be fast for larger leaks on small parts when testing multiple at one time.
Can be fast for testing extremely large parts with larger leaks few areas for possible leak.
Best method for detecting exact leak location detection.
Low equipment cost.

Disadvantages

Risky: An extremely operator dependant technique with a high possibility of passing actual failures.
Slow: Detecting small bubbles on typical parts can take much longer than other methods.
Added cost: Parts must typically be dry and free of fluid before shipping.
Less sensitive than other techniques on most parts.
No leak rate or test result information.

High Frequency Sound

Pressurize part and use hand held "listening" device around potential leak areas and watch for high pitched noise caused by leakage of air out of the part.

Advantages

Good for detecting leak location.
Low Equipment cost.

Disadvantages

Background noise can reduce sensitivity of the device.
Can be very slow for finding small leaks.
No leak rate or test result information.
Cannot test internal cavities.

Trace Gas Detection (Mass Spectrometer)

Pressurize part with Trace Gas such as Helium or Argon inside a high-vacuum chamber and detect the quantity of trace gas caused by leakage out of the part using an electronic Mass Spectrometer sensor. Can be hand held "sniffer" as well.

Advantages

Outstanding sensitivity. Best solution for leak rates below .1 cc/min.

Disadvantages

Very expensive: Equipment investment typically starts at or above $100K. Fixturing usually elaborate.
Expensive to operate: Trace gas consumed is often high.
Slow: Typically, the part is placed into a chamber and closed off. A hard vacuum must be pulled on that volume before the actual test can take place.

Mass Flow

Pressurize part and measure air flow caused by leakage out of the part using electronic mass flow sensors.

Advantages

Very fast for large leak rates (over 100 cc/min).
Works best for checking size of fluid/air path or detecting restrictions in part channels.
Non-Operator dependant and test data can be obtained.

Disadvantages

Sensitivity too low for leak rates below 100 cc/min.
Accuracy of readings very dependant upon air temperature and actual system pressure.
More costly than pressure decay testing as it requires both a mass flow and a typical pressure decay transducer for each test channel.

Pressure/Vacuum Decay

Pressurize or apply Vacuum to the part and measure pressure/vacuum change within the part caused by leakage using electronic pressure-decay sensors.

Advantages

Fastest, most consistent test technique for 90+% of welded plastic components.
Non-Operator Dependant and test data can be obtained.
Accurate on leak rates as low as .1 cc/min.
No cleaning/drying operations required after testing.
System accuracy immune to most environmental conditions
Can be configured for 100% testing downstream of most bonding operations.

Disadvantages

Not usable for leak location.
More costly than immersion testing.
Slow with large part volumes and small leak rates.

Systems Forward Technology Offers

Electronic Pressure/Vacuum Decay Leak Testers

Pressure/Vacuum Decay method is default
Can be equipped for Differential Decay, Occlusion and Chamber decay/increase testing.
Can test up to 8 parts at one time (8 Test Channels).
Can quantify leak rate in straight pressure/vacuum decay or in cc/min.
Complete tooling capability. All tooling fabricated at FTI.
PLC Based system offers almost limitless expansion capabilities

Electronic Fluid (Water) Burst Testers

Ramp to Burst method is default
Can perform user-programmed cyclic tests
Stores digital readout of burst pressure
Housed in Heavy Duty Stainless enclosure
Test pressures up to 750 PSI

Pressure Decay Testing

Elements Involved In Electronic Pressure Decay Leak Testing

FTI leak testing systems use Air Pressure, Electronics and Pneumatic components to perform leak tests.
Air pressure and/or vacuum are the media used to test for leakage on all FTI systems
The electronics control the timing of each step in a leak test and monitor the pressure in the test part.
Pneumatic components control where the pressure goes and convert the pressure in the test part to an electrical signal.

System Components

Precision Regulator: Usually available in a variety of sizes and have precision diaphragms for precise pressure adjustment
Precision Valves: Normally poppet style with small orifices designed for zero leakage. Spool valves are not used as they do not seal adequately enough for precise leak tests.
Electronic Pressure-Decay Transducer: Hyper sensitive device capable of measuring to the nearest .0001PSI or better by converting pressure to an electronic signal. NOTE: Transducers are sensitive to temperature changes

Leak Tester System Resolution

Theoretical Resolution using 16 Bit Processor
Pressure (PSI)	Transducer Range (Volts)	Bits	Pressure Resolution
0-5 psi	± 10vdc	32767 bits	.000076 psi / bit
0-100 psi	± 10vdc	32767 bits	.0015 psi / bit
0-1000 psi	± 10vdc	32767 bits	.015 psi / bit

NOTE:
The minimum pressure drop (decay) of .01 -.02 psi is required to assure a reliable and repeatable test.

Principles of Pressure Decay Leak Testing

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

P = Pressure
V = Volume
n = number of moles (atomic wt of the gas)
R = Universal gas constant
T = Temperature (in Kelvin's)
- T= tc + 273
n stays constant for non leaking parts
n decreases for leaking parts

Negative Factors that Effect Leak Testing

Temperature Changes (aka: Adiabatic Heat)

Heat resulting from molecular movement of air during pressurization of the test part or from parts cooled inadequately from thermal operations prior to testing.
Results from molecular movement during pressurization of the test part
The higher the test pressure = the faster the air molecule velocity = the more adiabatic heat
The higher the part volume = the more air molecules moving = the more adiabatic heat
The Pressure Transducer sees a temperature increase as a pressure increase
Heating stops when part is fully pressurized
The air inside the part cools
The Pressure Transducer sees a temperature drop as a pressure drop

Volume Changes (aka: Elastic Creep)

Expansion of the part during pressurization reults in an increase in the part volume. As volume increases, pressure trapped inside the part drops.
Results from expansion of the part during pressurization increases the part volume, dropping the internal pressure of trapped air
Amount of Creep depends on composition of the part
Soft plastic parts yield more than rigid plastic parts
The thinner the wall sections of the part, the more creep
The higher the pressure, the more potential for creep
The more creep = the more lost volume = the more lost pressure
The Electronic Sensor sees this pressure drop as leakage