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Sash Arrangements

The sash is the front window of a fume cupboard. Fume cupboards typically feature a 6mm toughened glass sash which slides open and closed vertically, allowing access to the internal chamber. However, there are multiple sash arrangements available with both vertical and horizontal operations.

The sash provides containment and protects the fume cupboard operator from any hazardous gases, fumes, aerosols, etc. given off by experiments and chemical reactions within the chamber. The closed sash also protects the experiment from external disturbance from air flows and turbulence. In addition, it allows light into the fume cupboard chamber.

The sash rises and lowers smoothly on a weighted counterbalance system. Generally, spring-loaded adjustment screws in the sash guide track can be turned in or out to vary the tension of the guide on the sash. This allows the sash to travel freely.

The Different Sash Arrangements

The radius profile frontal design of the APEX fume cupboard range provides a smooth curved entrance and the high-level glass panel gives full viewable access to the internal chamber. Both the APEX-2 and APEX-3 operate at low volume flow rates down to 0.3 m/s.

Plain Vertical Sliding Sash

The plain vertical sliding sash is the most common sash arrangement by Clean Air. It slides upwards, allowing access to the fume cupboard chambers.

Plain Horizontal Sash

Horizontal sashes slide sideways on a track. They are commonly used for robotics enclosures and ventilated enclosures, but rarely for fume cupboards.

Combination Sash

Combination sashes feature horizontal sliding panes in a vertical rising frame. This sash system offers simple and safe access to the operator.

Bespoke Sash Arrangements

Double Sash

The experienced Clean Air design team will also design bespoke sash arrangements to suit any application.

For example, these unique double-sash fume cupboards have been designed and built to meet our client’s exact specifications. The double sash arrangement is ideal for this client’s life sciences R&D.

Sashes for Walk-In Fume Cupboards

Walk-in fume cupboards can also have sliding vertical sashes and combination sashes. Because the walk-in units are taller, they will feature at least two sashes. If they have three or more, the Clean Air team will develop a linked pulley system to allow them to rise quickly and smoothly.

For example, with a three sash arrangement the middle sash will be designed to rise twice as fast as the top one, so both arrive at their final position simultaneously. This makes manoeuvring equipment into or out of units simple and safe

Different Sash Materials

Toughened Glass Sash

Sashes are typically constructed from 6mm toughened safety glass. This glass is up to five times stronger than ordinary glass of the same thickness. If it is broken, it shatters into small, blunt chunks, not sharp shards, which are safer to clear up.

Toughened glass is not fire-resistant, but it can withstand temperatures of up to 300 degrees centigrade (570 degrees Fahrenheit). It is always recommended that any ovens or Bunsen burners are situated at least 150mm back from the sash in a fume cupboard.

For added safety anti-shatter film can be provided to hold the glass in place in the event of damage.

Polycarbonate Plastic Sash

Polycarbonate plastic sashes are recommended for fume cupboards which are used for applications using hydrofluoric acid (HF). The hydrofluoric acid fumes can etch glass. Over time this will cause clouding and the need to replace the sash. Polycarbonate is corrosive resistant and will withstand the acid fumes.

Please note: For any application using HF the fume cupboard liner must also be fabricated from a material which is compatible with hydrofluoric acid use.

The Sash Stop

Most fume cupboards feature a sash stop to prevent the sash being raised higher than a defined safe working height when the unit is being used to contain experiments, etc.

The sash stop can generally be overridden to provide extra room for the loading and unloading of equipment and apparatus into and out of the chamber. Fume cupboards should never be operated with the sash in the fully opened position. The sash should always be returned to the safe working level once this operation is completed.

Because fume cupboards dimensions vary, the sash stop will be configured where the face velocity at the working aperture is specified. The clearing rate of the fume cupboard is increased when the sash is lowered.

Most fume cupboards feature a sash stop to prevent the sash from being raised higher than a defined safe working height.

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