Why isn’t my vacuum system reaching its target pressure?

If a vacuum system stops reaching its usual pressure, the pump is one possible cause. Leaks, contamination, restricted pipework and misleading gauge readings can produce similar symptoms.

First establish whether the system has lost performance or has never achieved the required pressure. A previously reliable installation calls for a different investigation from a new system being commissioned.

Start with what changed

Think back to the last satisfactory run. Has the chamber been opened, a seal replaced or a different material introduced? Has anyone changed the oil, moved a valve or fitted a new hose?

A disturbed seal may admit air. A wet sample may release more vapour than the previous batch. A smaller-bore replacement hose may slow evacuation. Record the starting pressure, evacuation time and where the pressure settles. Note whether the behaviour occurs with an empty chamber, during the process, or both.

Check what the gauge is telling you

Is the gauge suitable for the pressure range? Are its units and settings correct? Has it been exposed to contamination? Some gauges respond differently to different gases, so a change of process gas can affect the indicated pressure.

While gas is flowing, a gauge near the pump may read lower than one on the chamber, particularly if the line is restrictive. If the reading seems implausible, have the gauge checked or compared with a suitable reference instrument. See vacuum gauges explained for the main measurement considerations.

Separate slow evacuation from a pressure limit

These are starting points, not diagnoses. More than one problem may be present.

Look at the gas load and connection

Air can enter through a leaking connection. Moisture and other substances can leave internal surfaces through outgassing. The product being processed may release vapour too. A chamber recently exposed to humid air may take longer to evacuate even when the pump is working normally.

A pressure-rise test can help assess the combined gas load where the system is suitable for that test. It does not, on its own, prove a leak. The guide to leaks and outgassing explains what the result can establish.

Check accessible valve positions and look for damaged or collapsed flexible connections. Consider whether a filter or trap has become restricted. Any inspection or isolation should follow the equipment’s operating procedure.

Then assess the pump

For an oil-sealed pump, check the specified oil, level and condition using the manufacturer’s instructions. Process contamination can affect lubrication and vacuum performance.

Check the gas-ballast setting alongside the process conditions. On many pumps, an open gas ballast raises the attainable ultimate pressure; it may be necessary while handling vapour.

Where the manufacturer provides a blank-off test, a competent technician can use it to assess the pump separately from the chamber. The correct arrangement, gauge and operating conditions are essential. Failure to meet the specified result warrants further investigation rather than an immediate assumption about a particular worn part.

What to send with a service enquiry

Include the pump model, gauge type, pressure reached and time taken. Explain whether the fault appeared suddenly or gradually, and list recent changes. Photographs and a pressure record help, along with the gases or vapours being pumped.

Contact Girovac about diagnosis and servicing with those details.