FHS-MAY24-PG20+21_Layout 1 30/04/2024 11:52 Page 21
MATERIALS HANDLING
sensors to verify that loads are properly positioned before allowing the lift to move.
A
HRS Heat Exchangers uses corrugated tubes in its tubular heat exchangers to create smaller, more efficient systems
wall. In a smooth tube, fluids usually follow a smooth path in which the particles which make up the fluid do not interfere with each other – known as laminar flow. However, where the smooth flow is disrupted, for example by disrupting the surface of the tube, tiny whirlpools form in the fluid creating turbulence – unsurprisingly known as turbulent flow. This turbulence makes tubular heat
exchangers more efficient by preventing viscous or suspended materials sticking to the wall of the tube, where they can form a boundary layer, which acts as insulation and prevents efficient heat transfer. The creation of this turbulent flow, and the resulting improvement over efficiency (compared to a smooth tube) is the key benefit of corrugated tube heat exchangers.
SMALLER FOOTPRINT Because a corrugated tube provides greater levels of heat transfer rate compared to a smooth tube of the same length, a heat exchanger with the same thermal performance can be smaller. For example, if corrugations increase the heat transfer by 10 per cent compared to a smooth tube, then the unit can be made 10 per cent shorter than an equivalent smooth-tube while delivering the same performance. This increased thermal efficiency – which can be up to three-times that of a smooth tube heat exchanger – also means that less space is required to achieve the same level of heat transfer. Depending on the final application, a corrugated tube heat
exchanger can therefore be up to half the size of its smooth tube equivalent. This is why HRS heat exchangers are popular for installations where space is restricted.
REDUCED MAINTENANCE AND CLEANING Because a corrugated tube reduces or prevents the formation of a boundary layer, it also greatly reduces the time and effort which is required to remove it. Therefore, operational time between cleaning cycles is much greater for corrugated tubes than smooth ones, further increasing the overall efficiency of the process. In many situations, a corrugated tube
provides sufficient turbulence to prevent the need for mechanical agitation of viscous materials (such as scraped-surface or screw- driven heat exchangers). With no moving parts, in such situations a corrugated tube is easier to clean and maintain and may be more reliable. However, it is important to remember that for many materials or applications, a scraped surface heat exchanger is still the best choice. When taken together, the benefits of
corrugated tubes are so significant that at HRS Heat Exchangers, we don’t use smooth tubes in our non-scraped tubular heat exchangers. The increased heat transfer efficiency, particularly at higher flow rates, means that less heat transfer area is required, so we can produce shorter, more compact designs which are also cheaper to manufacture.
HRS Heat Exchangers
www.hrs-heatexchangers.com
CUSTOMER APPLICATION Cartons or pallets stacked on a lift platform in the down position may become unstable when the lift position changes. Also, if a load has any protruding parts, they may snag the edge of a floor as the lift rises or descends. This causes tipping, which can result in damage to both the load and the installation, with a risk of injury to persons nearby. A metal bar is fitted on the lift to ensure the
correct load position. Unless this bar has been pivoted into its cradle, the lift will not start. Also, any subsequent movement of the safety bar caused by an unstable load will stop the platform. Generally, this is a very simple electrical scheme with only AC power available on site. Mechanical limit switches were proving to be
unreliable because the frequent switching was wearing out the mechanical contacts, whilst dust and moisture also adversely affected reliability. The customer therefore wanted an equally simple, non-contact solution.
IMPROVING LIFT PLATFORM PERFORMANCE
n upgrade project for a platform lift used in a materials handling installation had its old mechanical limit switches swapped-out for 2-wire inductive
SOLUTION A Contrinex inductive sensor from the 600 Series family fulfils the customer’s requirements. To verify that the bar has cleared the load and lodged in the cradle, a 2-wire AC/DC sensor with a 4mm operating distance is embedded in the cradle itself. The sub-flush mounting position protects the sensing face from any mechanical contact. With a wide voltage range and short-circuit
protection, these sensors also meet the customer’s on-site electrical requirements. Since the safety bar can become deformed with prolonged use, a sensor is chosen with an increased operating distance. This allows compensation for gradual target drift by simple range adjustment, rather than by repositioning the sensor itself. The sensor closes an enabling circuit for the
start button, which in turn latches a relay controlling the lift motor. Any movement of the safety bar caused by an unstable load will open the circuit and unlatch the relay, stopping unsafe movement of the platform.
PLUS Automation
plusautomation.co.uk
FACTORY&HANDLINGSOLUTIONS | MAY 2024 21
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