Tunnelling into true efficiency16 May 2023
Milnor explains the benefits of tunnel washers in terms of the environment, efficiencies and truly topping utilities conservation
Since the 1960s, laundry managers have been making the switch from washer-extractors to tunnel washers to accommodate their growing businesses. If your laundry has recently increased or expects to increase the amount of goods it processes yearly, you may be looking to purchase new equipment to handle the extra poundage. Many laundry managers choose to switch from washer-extractors to a tunnel, add a second tunnel to their existing line of equipment, or build a new laundry with a tunnel washer.
There are several factors to consider when selecting one of the aforementioned options. Most laundry managers seek out the least expensive combination of equipment and operating costs (water, sewer fuel, chemicals, and labour) over the life of the equipment. The initial solution for small quantities of linen is a washer-extractor and manual dryer. However, if your threshold grows to 450- 900 kg of goods processed per hour, the amount of goods may justify investing in a tunnel washer.
At higher production volumes, such as 1100-1360 kg per hour, tunnel washers become the least expensive washing equipment to purchase. However, lower production volume tunnels are still extremely frugal with consumables and offer lower labour requirement due to their automation.
When contemplating the addition of a tunnel, consider these factors to help determine if this purchase is the solution for your laundry.
1. Tunnels should typically wash about 90% of the required production volume. The remainder should consist of small quantities of various items that are best handled in a small washer-extractor or two.
2. While possible, it is not necessary to purchase an entire system that includes a shuttle and dryer. Many small tunnel systems consist of a loading device and an extractor. The extracted goods are moved via cart or sling to conventional dryers.
3. If a tunnel is planned for a new building, many additional costs can be saved due to reduced water and fuel consumption attributable to the tunnel. This would include smaller boilers, water softeners, and heat reclaimers, which in turn results in smaller internal piping for water, steam, condensate and natural gas. Utility connections to the building, such as water, sewer and natural gas can also be downsized.
4. Tunnel installation costs are often less than the costs for installing several large washer-extractors, because a tunnel has the same number of water, power, steam and compressed air connections as one washer-extractor.
5. Redundant equipment is not necessary for backup – tunnels have developed a reliability reputation like air compressors and boilers.
6. Compact tunnel designs, offered by Milnor’s PBW (PulseFlow Batch Washer), paired with extraction devices with a wide variety of discharge options, helps reduce footprint restrictions when converting from washer-extractors to a tunnel.
Additionally, Milnor’s continuous batch washers (CBW tunnels) are engineered with advanced technologies that makes the total cost of ownership worth the investment.
In 1979, Milnor tunnels introduced the True Top Transfer feature, which leaves the excess dirty water behind in each module. To qualify as a ‘top transfer’ machine, the batch washer must lift the linen load completely out of the wash bath via a perforated scoop and transfer it over the top of a fixed, welded-in-place bulkhead into the next module. The baths in each module must be completely separated, with no wearable seals nor perforated bulkheads in between. The wash water and rinse water must be allowed to counterflow through all such modules against the flow of linen to properly carry all the dirty and unused chemicals back towards the soil (loading) end of the machine. The required water flow between modules must be entirely external to the washer shell. Furthermore, all batch washers must have internal cylinder volumes with volumetric loading more than 41.6 litres per kilogram (based on rated batch size), sufficient to prevent the linen from packing too tightly and thus allowing good mechanical action and proper dispersion of wash fluids.
Milnor’s True Top Transfer design allows for faster washing (approximately 30-40% faster than bottom transfer designs), better rinsing and superior wash quality, as chemicals are better targeted to proper baths.
In 2009, Milnor enhanced the True Top Transfer tunnel concept with PulseFlow technology, which incorporates standing bath washing with controlled intermittent high velocity counterflow in every process module. The inverter-controlled pumps, electronic flow meter and external weirs offer more effective washing and rinsing.
PulseFlow technology begins with the patented RecircONE pump arrangement feature, producing high-speed water recirculation within the first module at a rate of almost 400 litre s per minute. This process allows for fast and nearly instant wet-down, causing the water and wash chemistry to instantly penetrate the soiled linen. This saves time and the need for dedicated wet down modules that are utilized in bottom transfer tunnels.
The PulseFlow wash process then continues with a three-step wash/ dilution process in each module. The first step is the wash process that employs standing bath washing similar to a washer- extractor’s wash step. This allows the chemical energy to release and suspend the soil from the linens. The next step begins dilution – high velocity counterflow rinsing takes place, which dilutes the loosened suspended soil, similarly to a washer-extractor’s drain/ fill step. The last step is the True Top Transfer feature, submerging the goods in progressively cleaner water in just a few seconds. Changing baths upon each transfer helps achieve the equivalent of a second dump and fill and nearly twice the dilution of bottom transfer tunnels.
This three-step wash process produces clean linen that exceeds industry cleanliness standards while utilizsng very low fresh water consumption. Milnor’s PulseFlow technology was even awarded a Hohenstein Hygienically Clean ‘Certificate of Innovation,’ for achieving as low as 2.5 L/kg fresh water consumption for light to medium soil linen, and as low as 5.4 L/kg for heavy soil, such as food and beverage. This low water consumption is achieved without compromising wash or rinse quality and without the use of ancillary water reuse or reclamation systems. PulseFlow tunnels are not only proven to save an unprecedented amount of fresh water but have also been successfully implemented in every type of commercial laundry (including healthcare, hospitality, and linen supply applications) around the world. Hundreds of PulseFlow technology tunnels are installed in the healthcare, hospitality, food and beverage, and many other applications, helping laundry managers wash better and save more.
Tunnel washers, combined with Milnor’s state-of-the-art technology, helps make the transition from either washer-extractors to a tunnel, adding a second tunnel to your line, or building a new laundry with systems equipment, into an investment that pays off over the life of the machine. If you process goods in excess of 450 kg per hour and are in areas where high water, sewer, fuel or labor costs exist, you may just fin d that the best washer-extractor solution is not a washer- extractor.