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Blast Cleaning Equipment_2

Tham khảo tài liệu 'blast cleaning equipment_2', kỹ thuật - công nghệ, điện - điện tử phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 118 4 Blast Cleaning Equipment Table 4.4 Quality classes for compressed air ISO 8573-1 Class Solids dust Moisture Pressure dew point in C XW water in g m3 Total oil content in mg m3 Max. number per m3 of particles with given diameter Size in pm Content in mg m3 0.1 0.1 0.5 0.5 1.0 1.0 5.0 0 According to operator 1 - 100 1 0 -70 0.01 2 - 100 000 1 000 10 -40 0.1 3 - - 10 000 500 -20 1.0 4 - - - 1 000 3 5.0 5 -- - 20 000 7 6 5 5 10 7 40 10 Xw 0.5 8 0.5 XW 5.0 9 5.0 Xw 10.0 Table 4.5 Limits for breathing air according to DIN 3188 Medium Limit Carbon dioxide 800 mg m3 air Carbon monoxide 30mg m3 air Dust Max. 0.01 pm Oil vapour 0.3 mg m3 20 C and 0.7 MPa The supply of breathing air is especially important for all blast cleaning operations. Critical substances in breathing air include carbon dioxide carbon monoxide dust and oil vapour. Regulatory limits for breathing air are listed in Table 4.5. Compressed air without special treatment cannot meet these requirements. Therefore compressed air needs to be treated in breathing air treatment devices. These devices usually perform in multiple steps and they include fine filters to intercept water oil and dust activated carbon filters to adsorb oil vapour and catalysts to strip carbon dioxide and carbon monoxide. 4.3 Blast Machine 4.3.1 Basic Parts The blast machine is a key part of any dry blast cleaning configuration. The major task of the blast machine is the delivery and dosing of the abrasive particles into the air stream. The structure of a typical blast machine is shown in Fig. 4.6. It consists basically of an air inlet line a pressure sealing system the actual storage part and an abrasive metering system. Blast machines are available at numerous sizes. 4.3 Blast Machine 119 abrasive metering valve pop-up valve seal pop-up valve pusher-line hose exhaust muffler remote control outlet valve abrasive trap remote control inlet valve Fig. 4.6 Basic design of a blast pot Clemco Inc. Washington 4.3.2 Abrasive Metering 4.3.2.1