Arc welding is a common unit operation in the construction industry, where frequent changes in location and welding position make it more difficult to control fume exposures than in industries where fixed locations are the norm. Welders may be exposed to a variety of toxic airborne contaminants including manganese (Mn) and hexavalent chromium (CrVI). Local exhaust ventilation (LEV) is a well-known engineering control for welding fumes but has not been adopted widely in the construction industry. This literature review presents data on the performance of a variety of LEV systems for welding fume control from the construction (five references), shipyard (five references), and other industries. The studies indicate that LEV can reduce fume exposures to total particulate, Mn, and CrVI to levels below currently relevant standards. Field studies suggest that 40-50% or more reduction in exposure is possible with portable or fixed LEV systems relative to natural ventilation but that correct positioning of the hood and adequate exhaust flow rates are essential. Successful implementation of extraction guns for gas metal arc welding (GMAW) and flux core arc welding has been demonstrated, indicating that a successful balance between extraction airflow and shielding gas requirements is possible. Work practices are an important part of achieving successful control of fume exposures; in particular, positioning the hood close to the arc, checking exhaust flow rates, and avoiding the plume. Further research is needed on hood size effects for controlling welding fume with portable LEV systems and identifying and overcoming barriers to LEV use in construction.

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Local Exhaust Ventilation for the Control of Welding Fumes in the Construction Industry—A Literature Review

A survey of separated airflow patterns at inlet of circular exhaust hoods

A wind turbine for wind power generation accommodated a heat-generating device therein is always properly cooled by accurately detecting clogging of a filter. A wind turbine accommodates a heat-generating device and includes a column disposed in an upright position on a foundation, a nacelle disposed on a top end of the column, and a rotor head supported by the nacelle so as to be rotatable about a substantially horizontal axis, and the wind turbine includes an intake which is provided in an outer surface of the wind turbine and through which outside air is taken into the wind turbine to cool the heat-generating device; an exhaust which is provided in the outer surface of the wind turbine and through which air inside the wind turbine is discharged outside the wind turbine; an impurity-removing mechanism disposed in a flow path of air from the intake to the exhaust to remove impurities contained in the outside air; and a control unit for determining the condition of the impurity-removing mechanism by comparing, as a parameter serving as a criterion for determining the condition of the impurity-removing mechanism, latest data obtained while a wind speed outside the wind turbine is substantially stable with reference value data input in advance and serving as a reference.

Wind turbine for wind power generation

Effect of velocity non-uniformity of supply air on the mixing characteristics of push-pull ventilation systems

Disclosed is an air blowing device that, when using the air blowing device arrayed horizontally and/or vertically, can obtain a uniform flow of air in the downstream direction from device to device. An air-permeable front surface (11f) is formed to the blowing device (1) at the downstream side of a rectifier mechanism, and side surface sections (11a) that extend in the upstream direction of the device (1) are formed at both edges of the air-permeable front surface (11f). First ventilation holes (70a) are distributed at the air-permeable front surface (11f), and second ventilation holes (70b) are distributed at the side surface sections (11a).

Air blowing device

Recently, open-type push-pull ventilation systems have been widely employed as effective substitutes for the conventional local exhaust ventilation system, and have prevailed at many welding workshops in Japan. In this study, the effect of the uniform velocity on carbon dioxide (CO2) shielding arc welding was examined by laboratory experiments. The ventilation system examined in the experiments successfully fulfilled the requirement for open-type push-pull ventilators prescribed in Japanese regulations (ordinances). It was proved that the velocity at any points in the capture zone fell in the range of 50 to 150% of the average capture zone velocity. Welding defects could be avoided by controlling the flow rate of shielding gas. Unless the capture velocity exceeded a 0.8 m/s, the formation of blow-holes in the welded metal could be prevented at the shielding gas flow rate of 20 L/min. If the flow rate was provided at 30 L/min and 40 L/min, blow-holes didn't form at the capture velocity of 1.2 m/s and 1.6 m/s, respectively. At a capture velocity of faster than 0.3 m/s, the fume concentration at welder's breathing zone was reduced to a level below the limit values: ACGIH (TLV) and Japan Welding Engineering Society (CLV#). These data are important for designing open-type push-pull ventilation in the welding workshop. The other engineering countermeasures currently employed in the welding work in Japan, such as fume collecting torch and general ventilation, are also concerned in this report. #: Control Limit Value

Some engineering countermeasures to reduce exposure to welding fumes and gases avoiding occurrence of blow holes in welded material.

Provided is a local clean zone forming apparatus which has an excellent operability and can provide an excellent clean air space without restricting the installation location or the purpose of an operation. In the local clean zone forming apparatus, a pair of push hoods having air blowing surfaces between which an airflow alignment mechanism is formed to form uniform airflows, are disposed so that the uniform airflows discharged from the push hoods are opposite to and collide with each other in a positional relationship wherein the air blowing surfaces are parallel to each other, and the centers of the air blowing surfaces are not directly opposite to each other; and the uniform airflows are obliquely discharged at an angle with respect to the air blowing surfaces.

Local clean zone forming apparatus

PROBLEM TO BE SOLVED: To provide a local air cleaning device that can reduce electric power consumption, while maintaining a clean air space to a high cleanliness.SOLUTION: A local air cleaning device 1 is configured such that a cleaned uniform air flow blown out from an air flow opening surface 23 collides with an air collision surface W and flows outside the area opened, and thereby the cleanliness in the inside of a guide 3 and the inside of the opened area is made higher than that of other areas. Also, the local air cleaning device 1 includes at least one of a device for measuring a pressure in the inside of the guide 3 and in the inside of a push hood 2, a device for measuring the cleanliness of the inside of the guide 3 or the opened area, and a device for measuring a gap area between the guide 3 and an air collision surface W. The local air cleaning device controls a flow rate of the cleaned uniform air flow blown out from the air flow opening surface 23 in such a manner as to be decelerated or accelerated from measured results for securing the cleanliness.

Local air cleaning device

A local air purification device (1) is provided with: push hoods (2, 3) having air flow opening faces (23) for discharging purified uniform air flows; and a pair of guides (4, 5) forming opening faces (41, 51) at downstream end sections of the pair of guides (4, 5), the pair of guides (4, 5) being provided on the sides of the push hoods (2, 3) which face the air flow opening faces (23) and extending from the air flow opening face (23) sides toward the downstream sides of the uniform air flows. The push hoods (2, 3) are disposed in such a manner that the respective air flow opening faces (23) face each other. The opening faces (41, 51) of the guides (4, 5) are made to face each other at an interval to form an open region between the opening faces (41, 51) of the guides (4, 5). Purified uniform air flows which are discharged from the air flow opening faces (23) hit each other within the open region and flow to the outside of the open region, and this causes the inside of the guides (4, 5) and the inside of the open region to have a higher level of cleanliness than other regions.

Local air cleaning apparatus

The purified air discharge device comprises a push hood (2) comprising an air flow discharge surface (23) discharging a uniform purified air flow. The push hood (2) is provided with a lateral air discharger (28) for creating a purified air flow that collides against a surrounding wall that is formed as the push hood (2) is installed and that is situated close along the circumferential direction of the air flow discharge surface (23) of the push hood (2).

Yuki Fujishiro

Papers

Some engineering countermeasures to reduce exposure to welding fumes and gases avoiding occurrence of blow holes in welded material.

Local clean zone forming apparatus

Local air cleaning device

Local air cleaning apparatus

Purified air discharge device