Reasons to Leak Test
1. 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).
2. 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.
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.