California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 18 - Ship Building, Ship Repairing and Ship Breaking Safety Orders › Article 4 - Control of Hazardous Work › Appendix A to Section 8355 - Compliance Assistance Guidelines for Confined and Enclosed Spaces and Other Dangerous Atmospheres

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
This Appendix is a non-mandatory set of guidelines
						provided to assist employers in complying with the requirements of this
						section. This Appendix neither creates additional obligations nor detracts from
						obligations otherwise contained in the standard. It is intended to provide
						explanatory information and educational material to employers and employees to
						foster understanding of, and compliance with, the standard. The requirements of
						this standard are minimum safety standards for entering and working safely in
						vessel tanks and compartments.
Section
						8354 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.
Section
						8354 Definition of "Lower explosive
						limit." The terms lower flammable limit (LFL) and lower explosive limit (LEL)
						are used interchangeably in fire science literature.
Section
						8354 Definition of "Upper explosive
						limit." The terms upper flammable limit (UFL) and upper explosive limit (UEL)
						are used interchangeably in fire science literature.
Section
						8355(e)(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.
Section
						8355(e)(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.
Section
						8355(e)(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 permissible exposure limit for that substance. In that case, refer to
						subsection (e)(3)(B), (C), and (D).
Section
						8355(f)(2)(D), (h)(3) and
						(h)(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 re-entering and resuming work. In an oxygen-enriched
						atmosphere, the flammable range is severely broadened. This means than 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.
Section
						8355(g)(1) and (2)
						Hot work. This is a reminder that other sections of the shipyard safety and
						health standards in subchapter 18 should be reviewed prior to starting any hot
						work. Most notably, Article 7 Welding, Cutting and Heating, places additional
						restrictions on hot work begun on any metal that is toxic, covered by a
						preservative coating or is begun on any structural voids.
Section
						8355(e)(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 percent by volume in order to account for instrument error. However,
						the cause of excess oxygen should be investigated and the source
						removed.
Section
						8355(i)(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 subsection (i)(1) are posted at
						the gangway and at all other means of access to the vessel.