API Publ 2026:1998(2006) pdf download
API Publ 2026:1998(2006) pdf download.Safe Access/Egress Involving Floating Roofs of Storage Tanks in Petroleum Service.
5.1.1 The oxygen content of the atmosphere above the floating roof may be above or below the minimum levels for safe entry. hydrocarbon vapors (tin’ example. gasoline) may be present in the flammable range. and the atmosphere may contain toxic vapors (for example. benzene or hydrogen sulfide) that exceed established exposure limits for safe entry without respiratory equipment.
5.1.2 Before initial descent upon a floating roof is authorized, the entry supervisor shall identify the potential atmospheric hazards, determine the permit entry requirements, and evaluate the test results.
5.1.3 A tester (who could also be the entry supervisor and! or an entrant) shall he designated to conduct appropriate testing for atmospheric hazards in the following sequence:
(a) oxygen. (b) flammability (combustible gases or vapors). and (C) toxic air contaminants. Initial testing of the atmosphere above the surface of internal and covered open-top floating roofs shall be conducted through the sampling and gauging hatches or other appropriate place outside the tank.
5.1.4 As a minimum, atmospheric testing shall be conducted prior to descent at the beginning of each shift, prior to reentry after any prolonged periods of inactivity or work interruption, prior to starting hot work, and any time conditions are suspected to have changed. Testing of the atmosphere in ihe work area above the surface of the floating roof shall be either continuous or conducted as necessary to assure the continuation or maintenance of pennitted safe working conditions. The need for continuous or intennittent monitoring and the use of approved respiratory protective equipment shall depend on the results of the testing and the potential for increased atmospheric contamination or oxygen availability during entry and work operations.
5.1.5 Should subsequent testing indicaie that exposure liinits or permit conditions are not being met or are exceeded, the entry supervisor shall determine whether or not work is to be continued and, if so. under what conditions and requirements. Otherwise, continued entry shall be denied, the entry supervisor or attendant shall cancel the permit, and work shall cease until such time as the established entry requirements are met.
5.2 POTENTIAL OXYGEN CONTENT HAZARDS
5.2.1 Atmospheric testing for oxygen levels shall be conducted before entry onto a floating roof in order to detennine (a) whether sufficient oxygen is present in the atmosphere to conduct flammable vapor testing, (b) whether oxygen levels high to either enter the confined space or to determine correct upper flammable limits and lower flammable limits of any flammable vapor which may be present,
5.2.2 The oxygen content of the aunosphere above the floating roof shall be tested todetennine if ii is below 19.5%. the current OSHA-eslablished minimum level for safe entry into a confined space without using air-supplied respiratory protection.
Noc: OSHA does n0 permit cnt.y into confined spes whenever the oxygeii content cxcccds 215%.
5.2.3 The oxygen content of the atmosphere shall be tested to determine if it is below 10%, in which case there is not enough oxygen present to accurately determine flammable vapor levels.
5.3 POTENTIAL FLAMMABLE VAPOR HAZARDS
5.3.1 Atmospheric vapor testing shall be conducted to determine whether or not a flammable apor air mixture is present in the atmosphere above floating roofs prior to entry. flammable or conihustible liquids may be present on the floating root or in the pontoons. floats, or seal areas.
5.3.2 The flammable vapor or gas content of the atmosphere above the floating roof may be above 10% LFL. the current OSI IA-established maximum level for safe entry into a conhned space. In such cases, the space above the floating root’ may need to be ventilated to reduce the concentrat ion of vapor in air or inerted to eliminate oxygen. and the atmosphere retested prior o permitting entry.
