Washington Administrative Code › Title 296 - Labor and Industries, Department of › Chapter 296-155 - Safety standards for construction work › Part Q - UNDERGROUND CONSTRUCTION › Section 296-155-725 - Definitions applicable to this part

Current through Register Vol. 24-14, July 15, 2024
Acceptable
. Any device, equipment, or appliance
				  that is either approved by MSHA and maintained in permissible condition, or is
				  listed or labeled for the class and location under Part I of this
				  chapter.
Bulkhead
. An airtight structure separating the
				  working chamber from free air or from another chamber under a lesser pressure
				  than the working pressure.
Caisson
. A wood, steel, concrete or reinforced
				  concrete, air- and water-tight chamber in which it is possible for persons to
				  work under air pressure greater than atmospheric pressure to excavate material
				  below water level.
Cofferdam
. A watertight barricade or enclosure
				  erected, sunk, driven or otherwise fabricated to permit the performance of work
				  where hydrostatic pressure exists.
Decanting
. A method used for decompressing under
				  emergency circumstances. In this procedure, the employees are brought to
				  atmospheric pressure with a very high gas tension in the tissues and then
				  immediately recompressed in a second and separate chamber or lock.
Emergency locks
. A lock designed to hold and
				  permit the quick passage of an entire shift of employees.
High air
. Air pressure used to supply power to
				  pneumatic tools and devices.
Low air
. Air supplied to pressurize working
				  chambers and locks.
Man lock
. A chamber through which persons pass
				  from one air pressure environment into another.
Materials lock
. A chamber through which
				  materials and equipment pass from one air pressure environment into
				  another.
Medical lock
. A special chamber in which
				  employees are treated for decompression illness. It may also be used in
				  preemployment physical examinations to determine the adaptability of the
				  prospective employee to changes in pressure.
Rapid excavation machine
. Tunnel boring
				  machines, shields, roadheaders, or any other similar excavation machine.
Normal condition
. One during which exposure to
				  compressed air is limited to a single continuous working period followed by a
				  single decompression in any given 24-hour period; the total time of exposure to
				  compressed air during the single continuous working period is not interrupted
				  by exposure to normal atmospheric pressure, and a second exposure to compressed
				  air does not occur until at least 12 consecutive hours of exposure to normal
				  atmospheric pressure has elapsed since the employee has been under
				  pressure.
Pressure
. A force acting on a unit area. Usually
				  shown as pounds per square inch. (p.s.i.)
Absolute pressure
(p.s.i.a.). The sum of the
				  atmospheric pressure and gauge pressure. (p.s.i.g.)
Atmospheric pressure
. The pressure of air at sea
				  level, usually 14.7 p.s.i.a. (1 atmosphere), or 0 p.s.i.g.
Gauge pressure
(p.s.i.g.). Pressure measured by
				  a gauge and indicating the pressure exceeding atmospheric.
Safety screen
. An air- and watertight diaphragm
				  placed across the upper part of a compressed air tunnel between the face and
				  bulkhead, in order to prevent flooding the crown of the tunnel between the
				  safety screen and the bulkhead, thus providing a safe means of refuge and exit
				  from a flooding or flooded tunnel.
Special decompression chamber
. A chamber to
				  provide greater comfort for employees when the total decompression time exceeds
				  75 minutes.
Working chamber
. The space or compartment under
				  air pressure in which the work is being done.
C.F.R.
Code of Federal Regulations.
MSHA
.Mine Safety and Health
				  Administration.
NIOSH
. National Institute for Occupational
				  Safety and Health.
Statutory Authority: Chapter 49.17 RCW. 90-03-029 (Order
					 89-20), § 296-155-725, filed 1/11/90, effective 2/26/90. Statutory
					 Authority:
					 RCW
					 49.17.040 and
					 49.17.050. 86-03-074 (Order
					 86-14), § 296-155-725, filed 1/21/86; Order 74-26, § 296-155-725,
					 filed 5/7/74, effective 6/6/74.