Openings, guards

There are certain necessary operations, such as setting and adjusting, that may need to be carried out with the guards open. This is permitted provided the machine can be moved, either ... 

Outside the space, use guardrails or covers to guard openings into the space, and institute measures to control pedestrian vehicle traffic (follow 1926 subparts M and G). 

Machine guard opening/distance-to-point-of-operation measuring tool/stick (these are available from many machine safeguarding suppliers/consultants)... 

At the end of the sweeping out, the tap Ti is first closed, and then the taps T3, T4, Ts and Tj in this order. The tubes R and S are then detached from the beak of the combustion tube, the guard tube V is then detached from them and replaced on the combustion tube beak. The furnace and thermostatic mortar are then switched off and the combustion tube allowed to cool with the tap to the oxygen supply open. The bung J is removed, and the boat withdrawn by means of a piece of rigid copper wire with a small hook in the end that fits into the small hole in the lip at the back of the boat the bung is then replaced and the boat transferred to its block in the desiccator. 

Air pollutants may enter plant systems by either a primary or a secondary pathway. The primary pathway is analogous to human inhalation. Figure 8-2 shows the cross section of a leaf. Both of the outer surfaces are covered by a layer of epidermal cells, which help in moisture retention. Between the epidermal layers are the mesophyll cells—the spongy and palisade parenchyma. The leaf has a vascular bundle which carries water, minerals, and carbohydrates throughout the plant. Two important features shown in Fig. 8-2 are the openings in the epidermal layers called stomates, which are controlled by guard cells which can open and close, and air spaces in the interior of the leaf. 

Maintenance of guards on machinery, open vessels, handrails, screens at sampling/ drumming-up points etc. and on glass equipment Use of sparkproof tools where appropriate Record-keeping... 

The blowdown valves on the boilers were operated by a special key, which had a lug on it so that it could not be removed when the valve was open. It was therefore impossible, in theory, for two blowdown valves to be open at the same time. However, the boiler fitter kept and jealously guarded a private key w ithout a lug and had used this one to open the blowdown valve on the boiler that was under repair. He forgot to tell the process foreman what he had done or to close the valve. The presence of this key would appear to have been of little moment as long as the correct procedure of complete isolation was maintained, but as soon as it was departed from, the additional key became a menace, which eventually enabled the present tragedy to occur, the accident report said. 

Figure 10-182. Fan blade guard mounted directly below blades. Note that drive shaft connects through the opening. (Used by permission Bui. 107. SMITHCO Engineering, Inc.)...

I. Open motors Open drip-proof Open drip-proof guarded... 

A semi-guarded machine is an open machine in which part of the ventilating openings in the machine, usually in the top half, are guarded as in the case of a guarded machine but the others are left open. 

A guarded machine is an open machine in which all openings giving direct access to live metal or rotating parts (except smooth rotating surfaces) are limited in size by the structural parts or by screens, baffles, grilles, expanded metal, or other means to prevent accidental contact with hazardous parts. 

A dripproof guarded machine is a dripproof machine whose ventilating openings are guarded in accordance with 1.25.4a. 

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