OIL RESIDUES ON HVAC COMPONENTS

Transcription

1 OIL RESIDUES ON HVAC COMPONENTS V Asikainen 1*, M Björkroth 2, R Holopainen 2 and P Pasanen 1 1 Department of Environmental Sciences, University of Kuopio, Finland 2 HVAC Laboratory, Helsinki University of Technology, Finland ABSTRACT This paper is the review article of earlier published studies. A sampling and analysis method has been developed for oil residues on HVAC-components. Sampling was made by filter contact method and analysis was carried out by infrared spectroscopy. Amount of oil residues varied considerably both on used sheet metal and manufactured HVAC-components. The mean amounts of oil residues on surfaces of components varied between <10 mg/m² to 700 mg/m². A significant (P<0.0005) linear correlation was found between odour intensity and cumulative amount of oil residues. Cleaning of oil residues from the duct surfaces with typical cleaning methods is also very difficult. Because of that HVAC-components should be manufactured so that the inner surfaces of components are free of oil residues. In Finland, the cleanliness classification of HVAC-components is partly based on the oil residues. For example, for spiral seamed HVAC-ducts the recommended limit value is set to be 50 mg/m². INDEX TERMS HVAC, Oil residues, Measurement methods, Perceived air quality, Effectiveness of cleaning INTRODUCTION Many studies have shown that ventilation systems may be significant sources of sensory pollution (Fanger et al., 1988; Pejtersen et al., 1989; Björkroth et al., 1997b; Morrison et al., 1998.) In some of the studies, the amount of volatile organic compounds (VOC) has been found even to increase when air is passed through a ventilation system (Mølhave and Thorsen, 1991; Sundell et al., 1993.) The components of ventilation systems are usually made of galvanised sheet metal, which needs corrosion protection to avoid oxidation of the zinc surfaces during storage. Thus chromic acid treatment or oils are used to protect the surfaces against corrosion. Manufacturing of components with sharp bends or turns also necessitates lubrication in order to decrease friction between machine tools and sheet metal. If the components are manufactured with insufficient lubrication, the quality of the product may decrease and the components will not fulfil the technical requirements e.g. air tightness. In recent years the demand for clean and high quality HVAC-components by builder contractors and customers has forced the industry to seek solutions to manufacture of oil free components. Most Finnish manufacturers use sheet metal, which is corrosion protected with chromic acid treatment. However, it is essential to use lubrication in the manufacturing of some HVAC-components and that is why there could be oil residues even thought the sheet metal is oil free. Thus, the quality control of the surfaces requires some kind of oil analysis. Information about the amount of oil on the HVAC-components and it is effect on hygiene of the HVAC-components and supply air are required by the Finnish Classification of HVAC- * Contact author Vesa.Asikainen@uku.fi 356

2 components, where the amount of oil residue is one of the criteria for the cleanliness classification. This paper is the review of the studies, which results were published earlier on conference and scientific papers. All studies were carried out in the Finish Clean Ventilation Systems project. MEASURING METHOD FOR THE OIL RESIDUES A sampling method for the oil residues was developed (Pasanen, et al., 1998.) The filter contact method is based on the pressing of a moistened glass fibre filter (Munktell filter MG 160) on the surface with a constant pressure. The filter was first moistened with tetrachloroethylene (0.036 ml TCE/cm 2 ), after which it was placed and pressed on the surface to be sampled. Two different pressurising methods were used: In the first method, the immersed filter was pressed with a constant pressure device. In the second one, the immersed filter was covered with a cleaned polytetrafluoroethene (PTFE) film and pressed down with the fweezers (Figure 1). After the sampling, the filter was sealed in a test tube. Analysis of the oil samples was carried out by infrared spectroscopy. In order to evaporate the solvent the sample was kept in a drying bath for 15 minutes at 36 o C. The oily contaminants were extracted by adding five millilitre of TCE, extracted in an ultrasonic bath (30 min), centrifuged (3000 rpm, 23 C, 10 min) and analysed with a infrared spectrophotometer. Quantification was carried out against a dilution series of the same processing oil or corrosion protection oil, which was used on the surfaces studied. The recoveries and reproducibilities of the sampling were measured with both pressing method for different kind of oils. For example, for the mineral oil Solvac 1535 GD and constant pressure device the recoveries and reproducibilities of sampling shown to be 96±1% and the recovery and reproducibility of the extraction were shown to be 97±2%. The detection limit for Solvac was measured to be 12 mg/m² (Holopainen, et al. 2001b). Figure 1. Sampling filter was pressed with a constant pressure device (left) or with a tweezers (right). AMOUNTS OF THE OIL RESIDUES ON THE SHEET METAL AND HVAC- COMPONENTS The amount of oil residues on the surface of the sheet metal was measured (Pasanen, et al., 1998.) The sheet metal treated with chromic acid had very low amounts of oils (<2-29 mg/m 2 ). On the other hand, sheet metal that has been covered with corrosion protection oil has 357

3 contained mg/m 2 of the oil. Nowadays most of the HVAC-components are made of sheet metal treated with chromic acid, therefore, the oil residues originate mainly from manufacturing processes of the components. The mean amounts of the oil residues of the studied HVAC components are presented in Table 1. Table 1. Oil residues on different kinds of HVAC-components (Asikainen, et al., 2000). HVAC component and number of the samples Oil amount (mg/m 2 ) Mean Range Spiral seam duct manufactured by water draught (6 ducts: 4 samples/duct) 12 <6-38 Spiral seam duct manufactured by oil draught where oil was added outside of the duct (12 duct: 1 sample/duct). 73 <5-270 Spiral seam duct manufactured by oil draught where vegetable oil was added outside of the duct (10 ducts: 4 samples/duct). 7 <3-27 Spiral seam duct manufactured by oil draught where mineral oil was added inside of the duct (6 ducts: 4 samples/duct) Rectangular duct (3 ducts: 2 samples/duct) 6 <10-10 Duct components manufactured with out lubrication (9 components: one sample/component) 13 <5-53 Duct component manufactured by mineral oil lubrication (3 components: 2 samples/component) Lamina of heat exchanger (2 laminas: 4 samples/lamina) Perforated sheet metal of the sound attenuator (1 component: 7 samples) OIL RESIDUES AND THE QUALITY OF THE SUPPLY AIR The effects of oil residues and dust in ventilation ducts on the quality of supply air were studied by a trained sensory panel (Björkroth and Asikainen, 1999). A significant (P<0.0005) linear correlation was found between odour intensity and cumulative amount of oil residues on the dust-free and dusty ducts (Figure 1). Cleaning of the ducts removed dust efficiently, and the amount of oil also was reduced considerably. One week after the cleaning, the odour from the ducts remained still about at same level as before the cleaning, and the correlation between odour and oil residues was still slightly significant (P=0.056). Four weeks after the cleaning, odour had decreased and was no more correlated with oil residues. Factors other than oil residues, such as air velocity in the test system or the dust level on the inner surface of the ducts, did not significantly influence on the odour. 358

4 y = 2.42x R 2 = Odour (PAP) y = 1.95x R 2 = y = -0.84x R 2 = Cumulative amount of oil residues (g) Figure 2. The correlation between the perceived air quality (PAP) and the cumulative mass of oil residues in the test ducts made of sheet metal (Björkroth and Asikainen, 1999.) Ducts manufactured with oil lubricants and stored at building site one are marked with filled circles and the dotted trendline. Ducts with oil residues stored at building site two are marked with plus sign and the dashed trendline. Ducts without oil residues stored at building site two are marked with white circles and the unbroken trendline. OIL RESIDUES AND THE EFFECTIVENESS OF THE DUCT CLEANING In the laboratory was measured the effect of oil residues to the effectiveness of the duct cleaning (Holopainen et al., 2001b.) Two kinds of ducts were studied: Mean amounts of oil residues on the ducts manufactured without oil lubrication (cleanliness category P1) was below the detection limit 12 mg/m 2. On the other ducts, which were pre-treated by spreading oil on the inner surface of the duct, amount of oil residues varied between mg/m 2. This represent high level of oiliness in air duct cleanliness category P2 (FISIAQ, 2001). The ducts were contaminated with standard test dust (ASHRAE, 1992) and after that the ducts were cleaned by mechanical brushing or compressed air cleaning. The amounts of dust were measured before and after the cleaning of the ducts using the vacuum test method (Holopainen et al., 2001a). The lowest mean amount of residual dust was in the category P1-duct (0.2 g/m 2 ) and the highest in the category P2-duct (0.6 g/m 2 ). The category P1 ducts looked visually clean after brushing. The category P2-ducts had residual of the test dust, which had adhered on the surface of the residual oil. The brush was not effective enough to remove the dust from the oily duct surface (Figure 3). 359

5 Figure 3. Oil residues complicated the cleaning of HVAC-ducts. Inner surface of oil free category P1-duct (left) and oily category P2-duct (right) after brushing (Holopainen et al., 2001b). THE FINISH RECOMMENDED VALUES FOR OIL RESIDUES IN THE HVAC- COMPONENTS AND CLASSIFICATION OF HVAC-COMPONENTS In Finland, the cleanliness classification of HVAC-components is partly based on the oil residues. For spiral seamed HVAC-ducts and components, which manufacture does not need oil lubrication, the recommended limit value is set to be 50 mg/m². For duct components, which need oil lubrication the recommended limit value is set to be 300 mg/m² (FISIAQ, 2001.) Classification of HVAC-components, which oil residues could not be measured, for example heat exchanger and plastic air ducts, is based on odour emission tests of HVACcomponents by a sensory panel. Before the oil residue tests the recoveries and reproducibilities of the sampling and extraction, and the detection limit for the tested oil is determined. Also the 50% and 70% odour thresholds of the studied lubricants are determined (Asikainen et al., 2002) and thresholds were compared with odour thresholds of Solvac mineral oil. The odour threshold of the used oil should be higher than Solvac. PRACTICAL IMPLICATIONS Oil residues decrease the hygiene of the HVAC-components because odour emissions of residues and they make cleaning of HVAC-ducts more difficult. Therefore new installations should consist components, in which amount of oil residues should be as low as possible. Finnish Classification of HVAC-components gives recommended values for oil residues. The amounts of oil residues are generally quite simple to measure by the filter contact method and the cleanliness of components could be verified with these measurements. However, there are some HVAC-components like heat exchangers, which surfaces of lamina are difficult to sample for oil residue analysis. That is why the odour emission tests by a sensory panel have also to use for a particular components. ACKNOWLEDGEMENTS This study was carried out as a part of the Clean Ventilation Systems project funded by the National Technology Agency, Finnish industry and participating research organisations. The 360

6 Clean Ventilation Systems project is a part of the Finnish Healthy Building Technology Program. REFERENCES ASHRAE Gravimetric and dust-spot procedures for testing air-cleaning devices used in general ventilation for removing particulate matter. Inc. ANSI/ASHRAE Standard American Society of Heating, Refrigerating, and Air-conditioning Engineers. Asikainen, V., Hyttinen, M., Lappalainen, R. and Pasanen, P Selection of lubricant for manufacture of HVAC-components. Proceedings of Indoor air Asikainen, V., Pasanen, P Processing oil residues on new HVAC-components: the addiction of manufacturing technique to the amount of components oil residue. In: Seppänen O, Säteri J, eds. Healthy Builldings Design and Operation of HVAC Systems, Espoo, Finland, August 6-10, 2000, p Helsinki: SIY Indoor Air Information, Vol. 2. Björkroth, M. and Asikainen, V The Effect of Ventilation Duct Material and Dust Accumulation on Perceived Supply Air Quality. In: Seppänen, O., Säteri, J. (eds.) Proceedings of Healthy Buildings 2000 Conference, Espoo, The 6th Healthy Buildings Conference, Vol. 2, pp Björkroth, M., Asikainen, V., Seppänen, O. and Säteri, J Cleanliness criteria and test procedures for clean ventilation products. Proceedings of Indoor air Björkroth, M., Torkki, A. and Seppänen O Effect of pollution from ducts on supply air quality. Proceedings of Healthy Buildings 97. Healthy Buildings /IAQ 97, Washington DC 1997, pp Fanger, O., Lauridsen, J., Bluyssen, P. and Clausen, G Air pollution sources in office and assembly halls, quantified by the olf unit. Energy and Buildings, 12, pp FiSIAQ Classification of Indoor Climate, Construction, and Building Materials Finnish Society of Indoor Air Quality and Climate, Espoo, Finland. Holopainen, R., Asikainen, A., Pasanen, P. and Seppänen, O. 2001a. The Field Comparison of Three Measuring Techniques for Evaluation of the Surface Dust Level in Ventilation Ducts. Accepted to publish Indoor Air, 12, pp Holopainen, R., Tuomainen, M., Asikainen, V., Björkroth, M., Pasanen, P. and Seppänen, O. 2001b. Effectiveness of Duct Cleaning Methods on Newly Installed Duct Surfaces. Accepted to publish Indoor Air paper on 15 th November, Morrison, G.C., Nazaroff, W.W., Cano-Ruiz, J.A., Hodgson, A.T. and Modera, M.P Indoor air quality impacts of ventilation ducts: Ozone removal and emissions of volatile organic compounds. Journal of Air and Waste Management Association, 48, pp Mølhave, L. and Thorsen, M A model for investigations of ventilation systems as sources for volatile organic compounds in indoor climate. Atmospheric Environment, 25A, pp Pasanen, P., Asikainen, V. and Liesivuori, J Storage and Processing Oil Contamination on New HVAC-Components: Development of Measuring Methods. In: Raw, G., Aizlewood, C., Warren, P. (eds.) Proceedings of Indoor Air 99, Edinburgh, The 8th International Conference on Indoor Air Quality and Climate, Vol. 5, pp Pejtersen, J., Bluyssen, P.M., Kondo, H., Clausen, G. and Fanger., P.O Air pollution sources in ventilation systems. In: Proceedings of CLIMA 2000, Air Conditioning. Sundell, J., Andersson, B., Andersson, K. and Lindvall, T Volatile organic compounds in ventilating air in buildings at different sampling points in the buildings and their relationship with the prevalence of occupant symptoms. Indoor Air, 3, pp