Subject:           General Description of Our Range of Vacuum Chambers & Pumps

Our range of vacuum equipment has evolved during 20 years of manufacturing vacuum outfits to customer requirements. Special attention has been given to:

Low Capital Outlay

Ease of Use

Adaptability

Easy Maintenance

Low running costs.

By standardising methods and materials of manufacture and having a range of vacuum pumps and accessories available off the shelf, we can offer excellent price, quality and delivery for a vacuum outfit to meet your needs.

Our speciality is ex-stock, reconditioned vacuum pumps. Our standard vacuum outfits comprise two basic units linked together by a flexible hose.

1)         A Vacuum Chamber with controls, removable lid and 'L' Section Gasket and,

2)         A motorised vacuum pump.

The Vacuum Chambers

Are cylindrical mild steel vessels, strengthened where needed and enamelled. The diameters used are nominally 175mm, 225mm, 305mm, 460mm and 610mm to take standard vacuum gaskets. Stock sizes range from 3 to 150 litres. Others constructed according to your needs.

Standard Controls

Vacuum dial gauge, vacuum valve, vacuum release valve.

The Vacuum Lid

Clear polished acrylic or metal with glass viewing port to give full view of the vessel contents under vacuum. Easily removable for access to the interior.

The Vacuum Gasket

Fits between the tank and lid. A nitrile 'L' section ring gasket specially made in 4 standard sizes. It has a long life but is easily obtained and replaced when needed.

The Vacuum Pump

Two classes of vacuum pump are used in our equipment.

a)         New Edwards High Vacuum Single or Two Stage Rotary Pumps. (See data sheet for full details)

b)         A wide selection of reconditioned vacuum pumps in good order. All vacuum pumps covered by 6 months warranty. Motors are normally 3 phase 415V or single phase 240V.

Typical Applications of our Vacuum Equipment

A selection from the uses to which our vacuum equipment has been put: (Further details available on request).

Lost Wax Casting

The investment for the mould is mixed, then exposed to a vacuum to remove the air bubbles, especially from the surface of the wax model where blemishes would otherwise occur in the finished casting. Used in dentistry, jewellery making and sculpture.

Impregnation of Castings

Some industrial castings are porous when made. By vacuum impregnation the pores can be filled, i.e., remove the air from the casting and replace with epoxy resin or similar, e.g., aluminium alloy vacuum valves.

Degassing

Liquids for use in vacuum impregnation, casting etc., should have the trapped air removed before being used. Liquid SILICONE RUBBER can be degassed when making moulds for alloy casting, resin casting etc.

Transformer Impregnation

High quality coils and transformers are dried by heating and evacuation followed by impregnation of the whole assembly with varnish to permanently keep out moisture, dirt and air.

Resin 'Marble and Resin Bronzes' etc.

Vacuum degassing is used on mixes of polyester resin and marble dust or resin and metal powder to produce even, dense mixtures, bubble free for casting statuettes, chess pieces, models etc.

Printing

A paper or negative can be held flat without clamps or jigs on a vacuum backed porous plate by removing the air behind the paper so that atmospheric pressure pushes the paper on to the plate.

Encapsulation

Many electronic circuits, biological specimens, teaching specimens, etc., can be usefully embedded in a clear liquid which subsequently sets to a transparent solid. This is best done in vacuum so that the specimen is dry and free from air bubbles. The finished article will then stand fairly rough treatment without affecting the specimen inside.

Secrecy

By encapsulating electronic circuits using epoxy resin materials which are practically impossible to remove from the specimen without damaging it beyond recognition, your circuits cannot be easily copied.

Vacuum Chuck

Awkward shaped components e.g., TV tube faces, metal discs can be securely held on a vacuum chuck. By removing the air from the chuck, atmospheric pressure pushes the work against it. Vacuum can be obtained from a pipeline pumping outfit i.e., an automatic outfit.

Vacuum Drying

Chemicals, powders and various materials can be dried under vacuum with little or no heating. Accelerated drying occurs when the material is heated in a vacuum oven. A gas ballasted pump together with cooled pipeline trap is recommended, or possibly a water ring pump, depending upon the amount being removed.

Plastic Dipping

PVC for dipping and other mixtures can be degassed before dipping articles to be coated. A clearer better quality finish is obtained.

Plastic forming

By removing the air from a plastic forming mould, the plastic sheet warmed to softening point, will be pushed by atmospheric pressure in to the mould. The vacuum should be created quickly so that the plastic sheet assumes its required shape before being cooled by contact with the mould. This necessitates the use of a vacuum pump and reservoir as large as practical.

Vacuum Storage

Many specimens and components deteriorate whilst exposed to the atmosphere. This deterioration can be reduced by storage under vacuum e.g., metallurgical specimens, chemicals, electron microscope slides, components for vacuum systems.

Vacuum Filling

Bottles, ampoules and containers can be filled removal of the air from the container, immersing the neck below the surface of the liquid and then releasing the vacuum. Atmospheric pressure pushes the liquid into the container.

Vacuum Packing

By evacuating the air from a plastic pack or bag containing the article to be preserved, the shelf life is increased. The package reaches its smallest possible size.

Vacuum Mixing

By mixing powders into liquid under vacuum, the formation of a foam or sponge mixture is avoided. This saves degassing afterwards but vacuum mixers are expensive. Mixing in the open air followed by vacuum degassing can be carried out at much lower capital cost.

Vacuum Distillation

A gas ballasted vacuum pump plus a vacuum reservoir is generally needed. The reservoir evens out the vacuum in the system to aid regular boiling and can also be used as a desiccant or vapour trap.

Cathode Ray Tube Recovery

Recovery by fitting a new electron gun and processing.

WARNING: HEALTH & SAFETY

Vessels under vacuum are potentially dangerous because of risk on implosion. Material used should always be strong enough to stand the external atmospheric pressure of up to 15 psi plus any mechanical knocks or handling under vacuum condition. Glass vessels and jars are especially at risk. Implosion guards should always be used over glass vacuum chambers.

The capabilities of all equipment featured in our literature are described as accurately as we feel necessary. However, because of the individual characteristics of each material being processed, it is the responsibility of the buyer to ensure that the equipment will suit his particular requirements. Our technical sales engineers will be pleased to provide advice and guidance.

Notes about Vacuum Measurement

Vacuum is the term used to describe pressures below our atmospheric pressure. The air about us is under pressure due to the amount of air above. This pressure is lower at the top of the a mountain, lower still outside an aeroplane and very low out in space. We can show the atmospheric pressure by using a simple barometer consisting of a column of mercury in an evacuated tube.

Our atmospheric pressure supports the column of mercury. If it is measured in terms of the height of this column of mercury then normal atmosphere is 30" (Hg). (1013 Millibar). This figure varies from day to day especially with the weather. A 0-30" Hg simple dial gauge will read the atmospheric pressure when fully evacuated. Thus a full vacuum can read 29" Hg on a wet day and 30" Hg on a fine day. The vacuum could be exactly the same on each day.

Vacuum Conversions (General Guide Approximate Figures)

NB:     The information in this pamphlet is offered in good faith and is based on our general experience. The method of use of Island Scientific Ltd equipment and materials are outside our control, the responsibility to ensure that the equipment is properly used and suitable for intended application rests with the user. No responsibility will be accepted by this company nor any person or other company associated with this leaflet for loss or consequential losses as a result of them using this information.

For advice, information, general literature, prices or a discussion of your needs, telephone 01983 855822, fax 01983 852146 or E-Mail: sales@island-scientific.co.uk.

A full list of Technical Notes is available free on request.