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Subchapter 15. Petroleum Safety Orders--Refining, Transportation and Handling
Article 2. Definitions

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§6755. Definitions.

(a) The following definitions shall apply in the application of these orders.

Alteration (Pressure Vessels). An alteration is any change in the item described on the original Manufacturer's Data Report which affects the pressure containing capability of the pressure vessel. Nonphysical changes (re-rating) such as an increase in the maximum allowable working pressure (internal or external) or design temperature, or the addition of loadings not considered in the original design, shall be considered an alteration. A reduction in the (minimum) design metal temperature such that additional mechanical tests are required shall also be considered an alteration.

Approved. See Section 6751.

A.N.S.I. American National Standards Institute.

A.P.I. American Petroleum Institute.

A. S. M. E. American Society of Mechanical Engineers.

A. S. T. M. American Society for Testing and Materials.

Atmospheric Tank. A storage tank which has been designed to operate at pressures from atmospheric through 0.5 psig (3.5 KPa).

Authorized Employee. (in reference to an employee's assignment). Selected by the employer for that purpose.

Auto Ignition Temperature. See Ignition Temperature.

Barrel. A liquid measure of 42 U.S. gallons (158.9 liters).

Blind. A device, other than a valve, used to isolate equipment for the purpose of preventing the passage of liquid, gas or vapor.

Boiling Point. The temperature at which a liquid boils at a pressure of 14.7 psia (760 mm Hg).

Chain or wire rope access equipment (Jacob's ladder). Specialized equipment approved for use to access constricted locations and having rigid rungs suspended between two vertical chain or wire rope stringers instead of the rigid rails used on fixed or portable ladders.

Code. Consensus Standards as referenced in the Petroleum Safety Orders.

Combustible Liquid. See Liquid.

Competent Person. One who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.

Confined Space. See Article 108, General Industry Safety Orders.

Consumer. One who uses up or consumes petroleum, natural gas or their products either in serving his own wants or in the production of another article of value when such use or consumption does not involve processing as defined in these orders.

Corrosive. A substance that causes visible destruction of, or irreversible alterations in living tissue by chemical action at the site of contact. For example, a substance is considered to be corrosive if, when tested on the intact skin of albino rabbits by the method described by the U.S. Department of Transportation in Appendix A to 49 CFR Part 173, it destroys or changes irreversibly the structure of the tissue. This term shall not refer to action on inanimate surfaces.

Crude Oil. Hydrocarbon mixtures that have a flash point below 150o F and which have not been refined.

Division. Division of Occupational Safety and Health.

Existing Installations. All equipment installed in California prior to the adoption of these orders and in compliance with applicable safety orders of the Division in effect at the time of installation and that have not changed ownership and location since the adoption of these orders.

Fire Watch. A qualified person designated by the employer to perform the duties as required by General Industry Safety Orders, Section 4848.

Fired Equipment. Equipment heated by an externally applied flame.

Flammable Gas. A gas that will burn in air.

Flammable Liquid. See Liquid.

Flare. A device in which excess gases and vapors are burned in the atmosphere.

Flash Point (of a liquid). The minimum temperature at which it gives off vapor in sufficient concentration to form an ignitible mixture with air near the surface of the liquid within the vessel as specified by appropriate test procedure and apparatus as follows:

(1) The flash point of a liquid having a viscosity less than 45 SUS at 100o F (37.8o C) and a flash point below 200o F. 93.4o C), (refer to General Industry Safety Orders, Section 5194.)

(2) The flash point of a liquid having a viscosity of 45 SUS or more at 100o F. (37.8o C) or a flash point of 200o F. (93.4o C) or higher, (refer to General Industry Safety Orders, Section 5194.)

(3) For a liquid that is a mixture of compounds that have different volatilities and flash points, its flash point shall be determined by using the procedure specified above on the liquid in the form it is shipped. If the flash point, as determined by this test, is 100o F. (37.8o C) or higher, an additional flash point determination shall be run on a sample of the liquid evaporated to 90 percent of its original volume, and the lower value of the two tests shall be considered the flash point of the material.

(4) Organic peroxides, which undergo auto accelerating thermal decomposition, are excluded from any of the flash point determination methods above.

Fumes. Solid particles generated by condensation from the gaseous state, generally after volatilization from molten metals, etc., and often accompanied by a chemical reaction such as oxidation.

Gas. A fluid, such as air, that has neither independent shape nor volume, but tends to expand indefinitely.

Gas Free or Free of Gas. Free from harmful or hazardous concentrations of vapors, fumes and gases.

Hazardous Substance. One which by reason of being explosive, flammable, toxic, poisonous, corrosive, oxidizing, irritant, or otherwise harmful is likely to cause injury.

High Vapor Pressure Hydrocarbon. Any liquid hydrocarbon component of petroleum or natural gas, or a mixture of two or more liquid petroleum or natural gas components, having a vapor pressure greater than 23 P.S.I.A. at 100o F., as determined by means of recognized test methods.

Hot Work. Electric or gas welding, cutting or brazing or any extreme heat, flame or spark producing procedures or operations.

Ignition Temperature. The minimum temperature to which a flammable vapor or gas mixture in air must be heated in order to initiate or cause self-sustained combustion.

Isolation. A procedure whereby equipment is removed from service and completely protected against the inadvertent release or introduction of material or energy.

Laboratory. A plant or a generally recognized department or subdivision of a plant where the primary purpose is testing, analysis, inspection, research, experimentation or process development in connection with petroleum, natural gas or their products, derivatives or related commodities. This shall not include places where simple routine tests, not requiring the use of a source of ignition, are done incidental to the processing or handling of petroleum, natural gas, or their products as, for example, by gaugers, process equipment operators, and others not generally considered to be laboratory personnel.

Liquid. See General Industry Safety Orders, Section 5415.

(A) Combustible liquids shall be subdivided as follows:

Class II liquids shall include those having flash points at or above 100o F (37.8o C) and below 140o F (60o C).

Class IIIA liquids shall include those having flash points at or above 140o F (60o C) and below 200o F (93.4o C).

Class IIIB liquids shall include those having flash points at or above 200o F (93.4o C.)

(B) Flammable Liquid. A liquid having a flash point below 100o F (37.8o C) and having a vapor pressure not exceeding 40 lb. per sq. in. (absolute) (176 kPa) at 100o F (37.8o C) and shall be known as Class I liquid.

Class I liquids shall be subdivided as follows:

Class IA shall include those having flash points below 73o F (22.8o C) and having a boiling point below 100o F (37.8o C).

Class IB shall include those having flash points below 73o F (22.8o C) and having a boiling point at or above 100o F (37.8o C).

Class IC shall include those having flash points at or above 73o F (22.8 o C) and below 100o F (37.8o C).

Natural Gas. Mixture of hydrocarbon gases and vapors consisting principally of methane.

Opening of Pipelines or Equipment. Exposing the contents of pipelines or equipment to the atmosphere, through means other than valves.

Owner-User. (Pressure Vessel) An owner or user of pressure vessels who maintains a regularly established inspection department whose organization and inspection procedures have been accepted by the Division.

Pilot Plant. See Laboratory.

Plant. See Refinery.

Portable Tank. A tank not intended for a fixed installation.

Pressure Relief Device. A device such as a spring-loaded safety valve or rupture disk for relieving excess pressure.

Pressure Vessel. A container, including cylinders, used for the storage or accumulation of any gas or liquid under pressure. This definition is not intended to include boilers as defined in the Boiler and Fired Pressure Vessel Safety Orders, or pressure chambers that are integral parts of such devices as pumps, motors, engines, clothes presses, flatwork ironers, tire molds, etc., where the pressure-containing part is subjected to severe mechanical stresses.

Qualified Inspector. An inspector as defined in Title 8, Unfired Pressure Vessel Safety Orders, and who holds a valid certificate of competency issued by the Division.

Refinery. A plant for the separation, refining, or processing of petroleum, natural gas, and products thereof. The entire operating facilities within clearly defined boundaries used for the operations to which these orders apply. A refinery may include numerous processing units or groups of activities.

Repair (Pressure Vessels). A repair is any work necessary to restore a pressure vessel to a safe and satisfactory operating condition, provided there is no deviation from the original design. Examples of repair include:

(1) Weld repair or replacement of pressure retaining parts or attachments that have failed in a weld or in the base material;

(2) Addition of welded attachments to pressure parts;

(3) Replacement of pressure retaining parts identical or equivalent to those existing on the pressure vessel and described on the original ASME Manufacturer's Data Report;

(4) Replacement or addition of a nozzle where reinforcement is not required to be considered by the code under which the vessel was constructed;

(5) The addition of a nozzle where reinforcement is a consideration provided the nozzle is identical or equivalent to the one in the original design and located in a similar part of the vessel;

(6) Repairs of base material by weld overlay;

(7) Repair or replacement of a pressure part with an ASME code accepted material that has a nominal chemical composition and strength equivalent to the original material, and is suitable for the intended service.

Reservoir. A roofed excavation for the storage of petroleum liquids.

Respiratory Protective Equipment. A breathing device designed to protect the wearer from oxygen-deficient or hazardous atmospheres (General Industry Safety Orders, Section 5144).

Source of Ignition. Any flame, arc, spark, or heat which is capable of igniting flammable liquids, gases or vapors.

Static Electricity. The type of electrical charge resulting from the separation of materials, friction, or similar causes.

Sump. An unroofed, lined or unlined, pit or excavation for holding liquids.

Tank. A fixed receptacle (covered or uncovered) of greater than 60 gallons capacity other than a pressure vessel or reservoir used for holding or storage of liquids.

Toxic Material. A material listed in Sections 5155, 5208, and 5209 of the General Industry Safety Orders which has the capacity to produce personal injury or illness to persons through ingestion, inhalation, or absorption through any body surface.

Tubular Gage Glass. An unsupported level indicator comprised of a glass tube or cylinder.

Vapor. The gaseous form of a substance normally liquid or solid.

Valve. A device for regulating or controlling the flow of material by a movable part or parts which open or close a passage.

Wall-Diversion. A wall made of concrete, earthwork, or other noncombustible material, built for the purpose of protecting employees, by diverting the flow of hazardous substances that may be released by tank failure, tank overflow, or other causes.

Wall-Retaining (Dike). A wall made of concrete, earthwork, or other noncombustible material, built for the purpose of protecting equipment and employees by confining hazardous substances that may be released by tank failure, tank overflow, or other causes.

Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Amendment of subsection (22) filed 12-11-68; effective thirtieth day thereafter. Approved by State Building Standards Commission. (Register 68, No. 47.)

2. Amendment of section and Note filed 9-6-94; operative 10-6-94 (Register 94, No. 36).

3. Amendment of definition of “Owner-User. (Pressure Vessel)” filed 6-26-2006; operative 7-26-2006 (Register 2006, No. 26).

4. New definitions of “Chain or wire rope access equipment (Jacob's ladder)” and “Competent Person” filed 7-28-2011; operative 8-27-2011 (Register 2011, No. 30).

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