Scotch whisky: Blending technology with tradition

The production of single malt Scotch whisky is a venerable ritual that is steeped in as much mythology as tradition. Although the recipe that William Grant & Sons follows to make the scotch is the same now as it was 150 years ago, the process itself is open to improvement, which is why the distiller turned to Siemens. 

Age-old recipe 

•  Malted barley and water are mixed in a round metal vessel with mechanical stirrers called a mash-tun, to produce a sugar solution known as wort. 

•  The wort is then cooled and pumped into pear-shaped fermenting vessels called wash stills, where operators add yeast to create a weak spirit mixture called a wash. 

•  The wash is distilled in order to strengthen and purify the spirit. 

•  This spirit is then matured in oak casks for a minimum of eight years (often longer) to become Scotch.

The challenge

Prior to vaporisation in the wash stills, foam is produced. If the level of that foam gets too high, it results in an unwanted situation where boiling high levels of froth mix with the 'low wines' from the first stages of distillation. 

The foam can be controlled simply by turning off the burners until it dissipates, but the problem is knowing when to turn those burners off, and when it’s appropriate to turn them back on. Because foam is neither liquid nor air, it has traditionally been impossible to detect with older level measurement equipment such as floats or vibrating forks.

The Dufftown plant wanted to automate the wash still operation, but it couldn’t do this unless it could reliably detect the level of the foam within those stills.

The solution 

A solution to this long-standing problem lay with modern technology, in the form of the Siemens Pointek CLS200.

Pointek capacitance instruments are suitable for situations such as this, where the material being measured has a low dielectric value. Although traditional capacitance devices measure voltage drop or current flow, and are affected by changes in material properties, Pointek sensors monitor the effect of capacitance based on frequency change. Because even small level changes create large changes in frequency, the result, says Siemens, is better resolution and accuracy.

The Pointek CLS200 has a high frequency oscillator with the sensor encapsulated in the probe tip. The sensitive tip is a very accurate and repeatable switchpoint, and the probe is unaffected by material build-up, humidity or moisture. In addition, the device is easy to install and calibrate.

To solve its foam detection problem, the Dufftown technicians installed a Siemens Pointek CLS200 on the neck of each wash still. Now, when foam reaches the tip of the instrument probe, the Pointek CLS200 detects it, and automatically turns off the burners. The device will then restart the burners when the froth level diminishes enough to clear the sensor.

Benefits

Reliable level detection allows the distillery to deal effectively with the foam produced in the wash stills, effectively preventing spills as well as protecting the process. 

What’s more, because the burners only operate when they are needed, the distillate is much more consistent. In addition, the new method also reduces both staff and maintenance requirements, freeing the operators for other duties, and allowing production to continue at weekends. 

Willie Thomson from the Dufftown Distillery, says: “This technology helps us ensure quality product and enhance efficiency. It’s an ideal meeting of our time-honored traditions with modern technology.”

Sounds like a perfect excuse to enjoy a 'wee dram'.