Considerations When Leak Checking Your Vacuum System

A leak is a small opening in a system’s many or single components that permits gas to leave or enter uncontrollably. The pressure differential between the interior and outside of the system, as well as the gas type and hole size, determine the leak rate. Some of the factors that can cause system failure include contamination and outgassing.

Leaks can affect the vacuum levels. Leaks in the pipes can stop vacuum systems from attaining the required vacuum level for the process to properly function.

Some of the common areas where you can find leaks include couplings, tubes, threaded pipe joints, FRLs (Filter, Regulator, Lubricator combinations), valves, packings, hoses, fittings, quick disconnects, condensate pipes, flanges, and pneumatic holding tanks.

Eliminating and rescuing leaks is important for several reasons that include:

• Safety of the products.
• Ensuring the long user-life of the products.
• The efficiency of the process.
• Safety of the operation.
• Maintaining and ensuring the vacuum pressure.
• Quality and environmental standards.

Vacuum leaks can cause several negative results that include:

• Toxic leaks into the environment
• Explosions
• Contaminant entry
• Systems damage

It is important to note that the system of vacuums doesn’t always have to vacuum-tight to run efficiently and safely. All they need to do is maintain gas balance, reach and maintain ultimate pressure, and maintain proper operating pressure.

Leak Detection Methods

The methods employed for leak checking are highlighted below:

Bubble Test

Placing a punctured bicycle tube underwater and recording the location of the bubbles is how the bubble test is demonstrated. You can also see whether washing-up liquid develops a froth around the junction of an operating gas/water pipe by placing it around the joint. Both of these methods are effective at detecting low-pressure leaks.

Pump-Down Test

During the pump-down test, a closed vacuum vessel is removed until the desired pressure is reached, then the pump’s inlet valve is closed. Once the predetermined period has passed, the inlet valve is opened, and the time is recorded to the pump to return the vacuum to the initial evacuated level.

This procedure is repeated multiple times. If the time remains constant, it indicates that there is a leak. If the time decreases, it indicates that there is less gas liberation on the interior of the system, yet this does not rule out the possibility of a leak.

Pressure Rise Test

If there is a leak, the pressure rise test is carried out by charting the vacuum level against time after the system has been isolated and a vacuum level has been established. If a leak is present, the curve will be a straight line. If the rise in pressure is caused by gas escaping from the system walls, it will gradually subside until it reaches a final stable value.

Helium Sniffer/Vacuum Mode Test

When this method is employed, the object to be examined for leaks is internally evacuated after which the exterior is sprayed with tracer gas. Helium is usually the test gas for this process. Helium enters through any defects that are present in the object and is detected using a leak detector.

Physical Verification

This method requires a person to gently wander around the vacuum system, listening for any whistling or hissing sounds. The sound could reveal where the leak is coming from. This method, despite its simplicity, can only be used to detect major leaks.

How To Fix a Vacuum Leak

When a vacuum leak is discovered, and the leakage rate is determined, it is time to repair it. Repairs restore the vacuum performance to the levels required to achieve the system’s purpose. The repairs to fix vacuum leaks include:

View Glass and Feedthrough Vacuum Leak Repair

Feedthroughs and view glasses are welded or glued. As time goes by, temperature cycling or mechanical force can crack at the junction between these materials, thus creating a crack. Repairing feedthrough and view glass vacuum leaks is impossible. The components have to be replaced, though they can sometimes be patched with Vacseal or low-degassing resins.

Seal Failure Vacuum Leak Repair

The majority of the system leaks occur at component’s joints(system’s leaks). The leaks are common around chamber doors, electrical feedthrough areas, and pump lines. These can easily be repaired by replacing leaky seals.

Prevention of Vacuum Leakages

Some of the ways you can prevent leakages are featured below.

Proper Maintenance of Gauges

Faulty gauges can result in leakages. Maintaining gauges is very important as they are highly sensitive equipment. Maintaining them will prevent time wasted looking for leaks.

Silicone Grease with a High Vacuum

When applied to the O-rings, good quality vacuum grease goes a long way toward avoiding leaks. This is because it adds to the vacuum seal and prevents the O-rings from hardening and damage. The grease should be sticky and have a low vapor pressure.

Virtual Leak

A virtual leak is a trapped volume of gas connected to the chamber’s vacuum side that can’t be easily pushed out due to a constraint in the channel linking the chamber volume to the trapped gas volume. The systems of vacuums are designed in such a way that air cannot escape easily. Proper design is essential for preventing leaks.

Proper Maintenance of O-Rings

The problem of leaks can be solved by using good quality O-rings with good compressibility. If the O-rings soften, inflate, or stiffen too much, discard them.

Baking

From time to time, under vacuum, systems should be kept at 250°C for a minimum of 12 hours. This aids in the removal of volatile vapors clinging to the vacuum’s walls.

High Vac Depot is Your One-Stop Shop

The most efficient, fast, and cost-effective way of leak checking in vacuums is through using a helium leak detector. A good leak test requires the right use of helium tracer gas, the proper selection of the leak-detector, and the proper connection of the detector to the vacuum system. High Vac Depot is the number one provider of practical vacuum solutions. High Vac Depot strives to provide you with the best gauges, fittings, leak detectors, pumps, valves, and hardware.