Washington Administrative Code › Title 296 - Labor and Industries, Department of › Chapter 296-304 - Safety standards for ship repairing, shipbuilding and shipbreaking › Section 296-304-02013 - Appendix B - Compliance assistance guidelines for confined and enclosed spaces and other dangerous atmospheres

Current through Register Vol. 24-14, July 15, 2024
This appendix is a nonmandatory set of guidelines provided to
				assist employers in complying with the requirements of WAC
				296-304-020 through
				296-304-02011. This appendix
				neither creates additional obligations nor detracts from obligations otherwise
				contained in this chapter. It is intended to provide explanatory information
				and educational material to employers and employees to foster understanding of,
				and compliance with, this chapter.
WAC
				296-304-020 through
				296-304-02011. These standards
				are minimum safety standards for entering and working safely in vessel tanks
				and compartments.
WAC
				296-304-020(2) 
				Definition of "Hot work." There are several instances in which circumstances do
				not necessitate that grinding, drilling, abrasive blasting be regarded as hot
				work. Some examples are:
(1) Abrasive
			 blasting of the external surface of the vessel (the hull) for paint preparation
			 does not necessitate pumping and cleaning the tanks of a vessel.
(2) Prior to hot work on any hollow
			 structure, the void space should be tested and appropriate precautions taken.
WAC
				296-304-020(2) 
				Definition of "Lower explosive limit." The terms lower flammable limit (LFL)
				and lower explosive limit (LEL) are used interchangeably in fire science
				literature.
WAC
				296-304-020(2) 
				Definition of "Upper explosive limit." The terms upper flammable limit (UFL)
				and upper explosive limit (UEL) are used interchangeably in fire science
				literature.
WAC
				296-304-02003(1)
				 After a tank has been properly washed and
				ventilated, the tank should contain 20.8 percent oxygen by volume. This is the
				same amount found in our normal atmosphere at sea level. However, it is
				possible that the oxygen content will be lower. When this is the case, the
				reasons for this deficiency should be determined and corrective action
				taken.
An oxygen content of 19.5 percent can support life and is
				adequate for entry. However, any oxygen level less than 20.8 percent and
				greater than 19.5 percent level should also alert the competent person to look
				for the causes of the oxygen deficiency and to correct them prior to
				entry.
WAC
				296-304-02003(2)
				 Flammable atmospheres. Atmospheres with a
				concentration of flammable vapors at or above 10 percent of the lower explosive
				limit (LEL) are considered hazardous when located in confined spaces. However,
				atmospheres with flammable vapors below 10 percent of the LEL are not
				necessarily safe.
Such atmospheres are too lean to burn. Nevertheless, when a
				space contains or produces measurable flammable vapors below the 10 percent
				LEL, it might indicate that flammable vapors are being released or introduced
				into the space and could present a hazard in time. Therefore, the cause of the
				vapors should be investigated and, if possible, eliminated prior to
				entry.
Some situations that have produced measurable concentrations of
				flammable vapors that could exceed 10 percent of the LEL in time are:
(1) Pipelines that should have been blanked
			 or disconnected have opened, allowing product into the space.
(2) The vessel may have shifted, allowing
			 product not previously cleaned and removed during washing to move into other
			 areas of the vessel.
(3) Residues
			 may be producing the atmosphere by releasing flammable vapor.
WAC
				296-304-02003(2)
				 Flammable atmospheres that are toxic. An
				atmosphere with a measurable concentration of a flammable substance below 10
				percent of the LEL may be above the WISHA permissible exposure limit for that
				substance. In that case, refer to WAC
				296-304-02003(3)(b), (c), and
				(d).
WAC
				296-304-02005(2)(d),
				296-304-02009(3),
				and 296-304-02009(5).
				The frequency with which a tank is monitored to determine if atmospheric
				conditions are being maintained is a function of several factors that are
				discussed below:
(1) Temperature.
			 Higher temperatures will cause a combustible or flammable liquid to vaporize at
			 a faster rate than lower temperatures. This is important since hotter days may
			 cause tank residues to produce more vapors and that may result in the vapors
			 exceeding 10 percent of the LEL or an overexposure to toxic
			 contaminants.
(2) Work in the tank.
			 Any activity in the tank could change the atmospheric conditions in that tank.
			 Oxygen from a leaking oxyfuel hose or torch could result in an oxygen-enriched
			 atmosphere that would more easily propagate a flame. Some welding operations
			 use inert gas, and leaks can result in an oxygen-deficient atmosphere. Manual
			 tank cleaning with high pressure spray devices can stir up residues and result
			 in exposures to toxic contaminants. Simple cleaning or mucking out, where
			 employees walk through and shovel residues and sludge, can create a change in
			 atmospheric conditions.
(3) Period
			 of time elapsed. If a period of time has elapsed since a marine chemist or
			 Coast Guard authorized person has certified a tank as safe, the atmospheric
			 condition should be rechecked by the competent person prior to entry and
			 starting work.
(4) Unattended tanks
			 or spaces. When a tank or space has been tested and declared safe, then
			 subsequently left unattended for a period of time, it should be retested prior
			 to entry and starting work. For example, when barges are left unattended at
			 night, unidentified products from another barge are sometimes dumped into their
			 empty tanks. Since this would result in a changed atmosphere, the tanks should
			 be retested prior to entry and starting work.
(5) Work break. When workers take a break or
			 leave at the end of the shift, equipment sometimes is inadvertently left in the
			 tanks. At lunch or work breaks and at the end of the shift are the times when
			 it is most likely someone will leave a burning or cutting torch in the tank,
			 perhaps turned on and leaking oxygen or an inert gas. Since the former can
			 produce an oxygen-enriched atmosphere, and the latter an oxygen-deficient
			 atmosphere, tanks should be checked for equipment left behind, and atmosphere,
			 monitored if necessary prior to reentering and resuming work. In an
			 oxygen-enriched atmosphere, the flammable range is severely broadened. This
			 means that an oxygen-enriched atmosphere can promote very rapid
			 burning.
(6) Ballasting or
			 trimming. Changing the position of the ballast, or trimming or in any way
			 moving the vessel so as to expose cargo that had been previously trapped, can
			 produce a change in the atmosphere of the tank. The atmosphere should be
			 retested after any such move and prior to entry or work.
WAC
				296-304-02007(1) and
				(2) hot work. This is a reminder that other
				sections of the WISHA shipyard safety and health standards in chapter 296-304
				WAC should be reviewed prior to starting any hot work. Most notably, WAC
				296-304-040 through
				296-304-04013, welding, cutting
				and heating, places additional restrictions on hot work: The requirements of
				WAC 296-304-04001 and
				296-304-04005 must be met before
				hot work is begun on any metal that is toxic or is covered by a preservative
				coating respectively; the requirements of WAC
				296-304-04007 must be met before
				welding, cutting, or heating is begun on any structural voids.
WAC
				296-304-02003(1)(b).
				During hot work, more than 20.8 percent oxygen by volume can be unsafe since it
				extends the normal flammable range. The standard permits the oxygen level to
				reach 22.0 percent by volume in order to account for instrument error. However,
				the cause of excess oxygen should be investigated and the source
				removed.
WAC
				296-304-02011(2).
				If the entire vessel has been found to be in the same condition, then employers
				shall be considered to be in compliance with this requirement when signs using
				appropriate warning language in accordance with WAC
				296-304-02011(1)
				 are posted at the gangway and at all other
				means of access to the vessel.