Engineers and machinists often opt for the conventional solution when it comes to valves for demanding tasks that need to be solved quickly and ideally in the best possible way. A good example of this is processes requiring the transport of abrasive and corrosive media in pipes. Such processes need to work optimally with as little maintenance as possible. And conventional valves are often chosen because they make the design phase easier. However, every now and then these choices prove not to be the best ones. 
According to Scanrox A/S, that imports Larox pinch valves to Denmark, the Danish production companies and industries handling solids and slurries typify this situation. The heart of the matter is that Larox Valve's installation dimensions are different to those of conventional ball, slide and butterfly valves and these have to be replace. As a rule the cheapest and simplest functional alternative is installed, which can lead to expensive rebuild at a later date. In general one could say that conventional valves are designed for clean media and the Larox Valves for everything else. 
Modern pinch valves like Larox Valves enable major resource savings as a result of superior functionality and longer service life. The company only sells directly to the end user so it is vital to know every aspect of the process concerned. And only the company knows what these valve can or can't do.
Today there are more than 50,000 Larox valves in existence around the world. These are all installed in applications for which the service life of traditional valves is simply not long enough.

For Difficult Conditions
Larox pinch valves are manufactured by Finnish Larox Flowsys Oy, an associated company of Larox Oyj which is widely known as a filtration solution provider in solid and liquid separation. Pekka Suokas, Vice President, responsible for valve business at Larox Flowsys, sees the experience received from solid liquid separation applications extremely valuable as the media is often the same. One of the most common applications where pinch valves are used in various industries are in lime slurry or milk of lime, says Pekka Suokas.
Lime slurry is very difficult for many valves because lime does not dissolve in solution but rather it is a suspended solid. So any pockets, cavities or voids are often filled with settling out particles of lime. These particles then solidify in the void area and then turn solid as a rock making the valve immovable if this solid mass is touching any of the moving parts in the valve. Again the valve has no problem with this scaling slurry and is very trouble free and effective at self cleaning itself. Lime slurry is used in a wide array of industries such as pulp & paper, chemical for ph neutralization, mining, iron & steel, coal power, food and beverage and various others.
Pinch valves are also ideal for demanding applications in mines such as flotation level control valves. This is typically 20 - 40 wt percent slurry and the valve is controlling a set level in a column. They need a reliable and precise control valve to handle this demanding control service. Other valves typically will not survive in this type of service.
Earlier this year Larox Flowsys also launched a new series of valves to supplement the pinch valve family. Larox Heavy Duty Knife Gate Valves are engineered to be used in tough environments with demanding media in the same industrial applications as company's pinch valves. 

Main Components
Pinch valves are often used by companies due to their simplicity. The Larox valve has three main components. The most important of these is the sleeve, which is the only part that comes into direct contact with the medium. The sleeve is chosen according to pressure, temperature and medium. The sleeve material is durable and wear resistant. When opened the valve sleeve is at full bore and when closed the valve is 100 percent tight. The valve sleeves are available in eight different standards and in different pressure classes; from 25 mm up to 1,000 mm and even more. The temperature limit for standard SBRT sleeve material is 110°C and the maximum temperature achieved with HNBR is 160°C. Standard sleeve pressure classes are 1 bar, 6 bar, 10 bar and right up to 100 bar. The valve sleeves are all hand-made at Teknikum Oy in Finland. The pinch valve sleeve is easily removed and replaced quickly without any special tools or any detailed training. There is only one spare part to be put into inventory and that is the appropriate rubber sleeve.
The valve housing comes in several different designs and materials including cast iron, aluminium, stainless steel and polyamide plastic. With regards to regulation, the customers have very different preferences and they must be able to choose anything from a simple hand wheel to the most complex regulation package.
The valve closes on the centreline and is not affected by crystallising or sediment-forming media. The valve is self-cleaning under normal operating conditions.

Customers Participation
Larox Flowsys Oy is ISO 9001 certified and the entire production is based on this standard Research and tests on new materials are constantly carried out at Larox Flowsys and the development goes very well in every aspect. Larox Flowsys representatives such as Scanrox A/S play an active role in this development, often together with the customers when special products are developed in partnership with them. Samples of different media are also regularly sent to Larox Flowsys for testing. The testing facility at the factory allows the process to be simulated as if at the customer's premises and ensures that their choice of valve is the right one.

Tommy Moller, Scanrox A/S
India Contact: Pramod Vaidya Email- pv@mcanallyblr.com