PROCESS EQUIPMENT UPDATE
Excessive fouling reduces heat exchanger efficiency
Cleaning schedules should be adhered to Example of wrong material choice
correct temperature range will also help to reduce the problem, and where particular problems are anticipated, additional chemical treatment, such as acid dosing, may be required.
Inappropriate handling affects products
certain starches or enzymes. In waste management situations, fouling from limescale, struvite and vivanite can be especially problematic. Te best solution is to avoid excessive fouling in the first place by choosing the right type of heat exchanger for your application. Scraped surface or corrugated tube designs reduce fouling by increasing turbulence in the tube. Maintaining the
WRONG MATERIAL CHOICE Bear in mind that cheaper isn’t necessarily best. Te problems caused by specifying the wrong type of material for your heat exchanger range from the need for additional cleaning, through to catastrophic failure of the unit. For example, although carbon steel is cheaper than stainless steel and easier to work with – making it a popular choice for those on a budget – it is also more vulnerable to corrosion and chemical reaction. Ticker tube walls are required compared to stainless steel, which increases the weight of comparable heat exchanger units and may add to associated costs, such as concrete bases and mounting brackets. Furthermore, carbon steel is brittle and while it may have a higher thermal conductivity than other materials, this can rapidly be degraded by the build- up of corrosion or fouling layers, reducing its service life. If possible, opt for a material that is both hygienic and hard-wearing, but that also provides good thermal characteristics in the design of heat exchanger that you are considering, such as stainless steel.
INCORRECT PRESSURE DROP Pressure problems usually occur when the pressure drop in the heat exchanger is higher than the design parameters. In the worst-case scenario this can lead to leaks, contamination or heat exchanger failure. One reason for an increase in the
pressure drop might be a change in raw material specification (for example,
switching ingredient suppliers). To counteract this, you should always request full details about any new products from your suppliers and, if necessary, ask your heat exchanger supplier to test them before use. Tis will ensure that any new heat exchangers are correctly specified and will also help to prevent problems when switching products or ingredients.
POOR LOCATION We have encountered heat exchangers crammed into corners, obstructed by pipework or other equipment, or fed by excessively long or complex pipework. Although none of these issues will necessarily affect the performance or working life of the heat exchanger itself, if it is inconvenient to clean and service, then such routine tasks may get overlooked or extended beyond the recommended intervals, which can in turn lead to problems. If you are tight on space, then ensure
you specify a heat exchanger suitable for a small footprint. For example, corrugated tube designs are more efficient and require less space than a smooth-tube unit with the same capacity. Tis means that they can often be housed in smaller spaces or novel locations, such as a specially constructed mezzanine, while still allowing full access for cleaning and maintenance.
INSUFFICIENT CAPACITY Although it may be tempting to invest in a smaller unit to save money, this can prove to be a false economy. Specifying a heat exchanger that is not large enough to cope with the maximum volume or processing capacity can result in extended running hours or, in a worst-case scenario, having to turn business away. One option may be to choose a modular solution, so that additional units
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