COMPOSITES OR VACUUM BAGGING

Vacuum Bagging

We often get asked if our vacuum pumps are suitable for vacuum bagging, resin infusion, resin transfer moulding, vacuum pressing (sandwich all types of panels), carbon moulding, veneering and/or vacuum degassing resins and silicon’s for example. The answer is yes they are, with some qualifications. The following chamber is typical of a degassing set-up. More information about this type of chamber can be viewed at the following link. The vacuum pump recommended will link back to this site.

https://www.fibreglassshop.co.nz/products/vacuumdegassingchamber



All oil sealed vacuum pumps with two stages (also known as dual stage) and some single stage vacuum pumps, oil sealed or not will handle the task. If a two stage version, the second stage enables the pump to cope better with solvent based or water based product vapours by utilising the gas ballast valve (if fitted). Most brand new two stage vacuum pumps with new oil will achieve the same vacuum pressure or ultimate pressure. There are no hard and fast rules so the question then becomes……………

What capacity (throughput) do I need ? (Note that vacuum pump capacity is usually rated at atmospheric pressure and as the vacuum declines in pressure, so does the capacity. As evaporation or sublimation starts to occur in your product, the vapour generated also has an effect on the pump capacity as vapour volume will be many times the volume of solids)

The answer to this question is to be found in your very own application as each of the following parameters affect pump capacity.

How large is the volume in your container or bag ??

What is the vacuum pressure at which your solvent will change from a solid or liquid to a vapour ??

What percentage of solvent, air, moisture, or other substance likely to evaporate against total weight of your product is being subject to a vacuum in any one application ??

This has a direct effect on the volume of vapour being pumped and may restrict the pump’s ability to achieve a reasonable vacuum. Please note that we cannot answer the above questions but we can give a very broad guide. A vacuum pump with a small capacity, typically around 40 litres per minute (or 1.5 cfm) should only be used for small hobby containers, bags or chambers under a few litres. Mid-sized volumes up to approximately 50  – 200 litres require at least a mid-sized pump around 90 to150 litres per minute. Larger volumes of approximately a cubic metre or more require a larger pump of 300 litres per minute or higher.

All of the above is also affected by the quality and nature of the vacuum pump oil. This type of vacuum pump requires vacuum pump oil to run. As supplied, the vacuum pump is empty of oil (to avoid leaking during transport) but is supplied with a bottle of vacuum pump oil sufficient to fill the pump to the correct level. Vacuum pump oil level should be checked regularly because the pump will use oil during use. Running out of oil will damage the pump and void the warranty so always ensure you have the correct oil level in the pump.

Degassing materials with a high moisture or solvent content will contaminate the oil. If this occurs the oil will look cloudy and must be changed. Always top-up or replace the oil in your pump using a specialist product designed for high vacuum rotary vane vacuum pumps. Use of inappropriate oil will damage the pump and void the warranty.

All of our single phase vacuum pumps are designed for the refrigeration or vacuum industry. However all refrigeration pumps can be used and are used for degassing of all kinds. Therefore the refrigeration suction fittings are industry standard SAE flare fittings ranging from 1/4" at the low end to 3/8" at the larger end. Dedicated vacuum industry pumps come with world wide industry standard NW or KF size vacuum flanges.
 
We do one small pump with a vacuum gauge and isolating solenoid valve attached at $695. Otherwise all others have the suction port above. There are thousands of variations of vacuum bagging so we do not get involved in any other accessories including bags. We can supply adaptors to fit the pumps for regular under 25mm hose sizes. Otherwise engineering shops can supply all other adaptors. Hose can be purchased from the same type of outlet.

We hope this helps