- Waterless technology for energy-efficient mould area dehumidification in a closed loop
- Condensation-free production conditions at low temperatures of cooling water on the mould
- Potential for saving up to 85 % of energy
Injection moulding, thermo forming and blow moulding without condensation is possible. Blue Air Systems’ basic range of MSP-Dehumidification units (with process air volumes between 1.000 and 10.000 Nm³/h) was complemented with the new DMS series (Dry Mould System), a dehumidifier which works without the need for chilled water. An enclosed production area is supplied with dry air with a dew point of 4°C (39,2°F). The DMS dehumidification units with process air volumes ranging from 500 to 3.500 N³/h are now available.
Year-round, condensation-free production conditions
The mould dehumidification units MSP are used mainly for supplying dry air to a central dehumidification system. The DMS series are specialized to be used for single production machines (up to 3 units). At the K 2016, the DMS system for demanding injection moulding, extrusion blow moulding or thermo forming applications will be demonstrated to the trade visitors. As inventor of this technology, Blue Air Systems has spent three years developing, testing and improving the system. The DMS units provide year-round, condensation-free production conditions, independent of ambient conditions, without the need for chilled water needed for pre-cooling. This energy-efficient technology guarantees the users of injection, blow moulding or thermoforming machines to run the shortest possible cycle times, therefore guaranteeing higher production output. The DMS series has been installed in various climatic areas, proving its performance. A number of references prove their efficiency and effectiveness.
The phenomenon of condensation on tempered moulds
When the surface temperature of an object sinks below the dew point of the ambient air, condensation builds on this object. This problem especially occurs on moulds of plastic processing machines that are cooled by chilled water. The cooling time, usually the longest part of the cycle time and one of the most sensitive steps of the manufacturing process is an important figure that influences the cost factor of the entire production process.
By reducing the cooling water temperature of the mould, a shorter cycle time and subsequently a higher production output can be achieved. If the water temperature sinks below the dew point of the ambient air, the moisture in the air will condensate on the surface of the mould. To avoid this condensation in facilities located in hot and humid climate zones, process engineers of manufacturing plants tend to increase the water temperature above the ambient dew point of the air. This standard procedure has a crucial disadvantage – the efficiency confines the effectiveness: increasing the cooling water temperature extends the cooling time of the item in the mould, thus reducing productivity and profit (rule of thumb: 1°C increase in cooling water temperature = 2% reduction of productivity).
In many cases a longer cooling time increases the crystallization rates in the moulded plastic resulting in inferior product quality. Furthermore, condensation on the mould leads to possible water marks (“orange skin”) on the final product causing rejects or low product quality.
Limitations of conventional technology for mould dehumidification
A popular way of drying air for mould dehumidification is with the adsorption system. This technology, that uses a desiccant wheel for dehumidification, needs a comparatively high amount of energy. The energetic inefficiency occurs due to the use of large regeneration heaters, ventilators, motors and pre and after cooling with the need for chilled water. Mould dehumidification with the condensation technology, using a refrigerant system, is an alternative to the desiccant system. The MSP (Mould Sweat Protection) units based on this technology have been the backbone of Blue Air Systems for many years. Many MSP units have been installed in facilities worldwide. Due to their reliability and stability, these units bring their full performance even after many years and allow a condensation-free production with the optimal cooling temperature in the mould. A disadvantage of all dehumidifiers, whether they operate on the basis of adsorption or condensation drying, is that relatively large cooling loads are needed to pre-cool the ambient air.
In many cases, the chilled water capacity of the facility is not dimensioned sufficiently to supply the necessary cooling load of chilled water. When investing in a new dehumidification system, besides the cost of the dehumidifier, the manufacturer also needs to take the cost of a new chiller, or the extension of the existing chiller system, into his investment calculation.
A look at the new, waterless DMS (Dry Mould System) in a closed loop
The DMS unit dries air on the basis of the condensation principle. The main difference to the standard systems is that the DMS is not constantly dehumidifying hot and humid ambient air. Instead, dry process air is circulated around the mould in a closed loop, bringing the air back to the DMS unit. By doing this, there is no necessity of using high cooling loads to dehumidify air, as the air returning to the DMS unit is partially dried. This procedure allows the DMS to work without a pre-cooler (chiller) and therefore no chilled water is needed for the DMS dehumidification.
A state-of-the-art refrigerant compressor of the newest technology automatically reduces the needed cooling capacity, as soon as reduction of moisture in the air is detected. Therefore, the DMS only uses electricity for the actual cooling need of the refrigerant system.
Model calculation: mould dehumidification with only 85 % lower energy consumption, compared to conventional systems
Standard dehumidification systems on the market are supplied with a water pre-cooler. The DMS units do not need the chilled water for pre-cooling, which automatically reduces overall investment costs for such a system between 15.000 and 20.000 Euros. A pre-cooler in standard systems, requires only 66 % or less of the overall energy normally needed.
By cutting out the pre-cooler, significant cost and energy savings can be achieved. In production, the actual savings can be seen: For example, a dehumidification unit with a desiccant wheel and a process air volume of 1.800 Nm³/h needs a cooling capacity of 38.700 kcal/h (45 kW) (calculated at ambient conditions of 35°C/ 60% rel. hum.), which adds up to 45 / 3 = 15 kW of electrical energy needed to run the chiller. For the regeneration heater, blower and motors, an additional 20 kW of electrical energy is needed for the dehumidifier. The total electrical consumption of the dehumidification and the electricity for the chiller adds up to 15 kW/h + 20 kW/h = 35 kW/h. This is a large amount of energy when compared to the DMS unit, which runs with an average of 5 kW, as only electrical energy is needed for the refrigerant compressor and the ventilators. The difference of 30 kW/h or in other words, 86 % reduction, is extreme.
If calculated, for example, with 0,15 EUR/kW and a 24/7 production with 168 hours production time per week is considered, the savings become clear: 30 kW x 0,15 x 168 h = 756 EUR per week, or 3.024,00 EUR per month (á 4 weeks).
Optimal energetic mould dehumidification
The DMS units allow optimal energetic mould dehumidification. Until now, no comparable systems exist on the market, according to the company. The process air is run in a closed loop, always brought back to the DMS unit for pretreatment and dehumidification of the air down to a 3°C dew point. The process air is dried by simulating a cold object in the DMS unit (similar to the mould) that allows the moisture in the air to condensate in the DMS unit, before it reaches the mould. The DMS unit cools and dehumidifies the air in a 2 step refrigerant unit with the MPCSC technology (Micro Processor Controlled Segment Condensation). For this version, only electrical energy is needed. A DMS 15 supplies a nominal process airflow of 1.500 Nm³/h. The larger DMS 25 dehumidifies 2.500 Nm³/h and the DMS 25+ up to 3.500 Nm³/h.
Areas of application
The DMS units are designed for all applications where high-performance moulds are cooled with chilled water and which are located in areas where moisture in the air can condensate on the mould. So, generally speaking, all injection molding, extrusion blow moulding and thermo forming systems. Main areas in the plastics industry are packaging systems such as caps and PET performs, as short cycle times of the process and high production outputs require chilled water. The company will showcase the Blue Air Systems at the upcoming K 2016 exhibition.