safety bulletin #022

SAFETY BULLETIN # 022

CONFINED SPACE ENTRY (PART I)

One of the most frequently performed and potentially dangerous tasks is the entry into a confined space. There are many conditions that can turn a safe confined space into a dangerous place. A mishap in a confined space has a high probability of being fatal or resulting in serious injury.

Emphasis on safety should be the first priority in a confined space entry.

DEFINITIONSConfined space refers to a space which by design, has limited openings for entry and exit, and/or poor natural ventilation which could contain or produce dangerous air contaminates and which is not intended for continuous employee occupancy.

Confined spaces includes, but are not limited to, tanks, towers, columns, vessels, sump pits, sewers, boilers, exhaust ducts, tunnels, pipelines, compartments of ships, underground utility vaults, and duct bank system manholes.

A.Isolation of a confined space is a process whereby the confined space is removed from service and completely protected against the inadvertent entry of material. The isolation process includes building off or removing a section of pipe and installing blinds on each end of the remaining pipes, vents, drains, relief valves and instrument lines. Isolation also includes the electrical lockout of all power sources and blocking or disconnecting all mechanical linkages.

B.Flammable limits are the extreme concentration limits of a combustible gas or vapor in an oxidant (air, oxygen, etc.) through which a flame, once initiated, will continue to spread at the specified temperature and pressure. These extreme limits of combustion are referred to as Lower Explosive Limit (LEL) and the Upper Explosive Limit (UEL).

(i)Lower Explosive Limit (LEL) is the minimum concentration of a combustible gas or vapor in air, which will ignite if an ignition source is present.

(ii)Upper Explosive Limit (UEL) is the maximum concentration of a combustible gas or vapor in air, which will ignite if an ignition source is present.

C.Lockout both mechanical and electrical of all sources of power by electrical isolation of electrically-driven equipment or disconnecting all mechanical linkages that service the confined space. This includes the physical disconnection of electric power circuits and just locking out the electrical controller or drive mechanisms. "HOLD" tags shall be used at all locations where devices or equipment have been locked out.

D.Oxygen Deficient Atmosphere is any atmosphere with an oxygen concentration of 20 percent or less at normal atmospheric pressure.

E.Oxygen Enriched Atmosphere is any atmosphere with an oxygen concentration greater than 21 percent at normal atmospheric pressure.

F.Purging is the method by which gases, vapors or other air-borne impurities are displaced from a continued space. Purging a confined space is accomplished by the displacement of the confined space atmosphere with a non-reactive gas or vapor (such as nitrogen or steam) to such an extent that the resulting atmosphere will not support combustion.

G.Pyrophoric refers to a substance that will burn upon contact with air with no external ignition source.

Pyrophoric Iron (Iron Sulfide), is a common pyrophoric substance encountered in hydrocarbon process.

H.Respirator Protection refers to a device designed to protect the wearer from breathing harmful materials that may be present in the atmosphere where the wearer is working.

All respirators must be approved by SAUDI ARAMCO. The Scott Air Pack breathing systems are self-contained breathing apparatus and not considered as respirators.

I.Sludge refers to the solids that can accumulate in the bottom of a tank or vessel. Sludge can be a very serious hazard. Volatile and/or toxic hydrocarbon compounds can be present in tank bottom sludge and the inhalation of the vapors from this tank sludge can cause serious illness or death. Before initial tank entry, any tank sludge must be tested for potentially hazardous materials and the results reported prior to authorization for tank entry.

Tank bottom sludge can also be pyrophoric (see item G) and will smolder and ignite with no external ignition when the sludge is exposed to dry air.

To avoid this hazard, any tank bottom sludge to be removed from a tank must be kept wet during removal and transportation, until it is safely disposed of.

J.Stand-By Man is a person involved in the confined space entry procedure who is designated, by the person responsible for the workers involved in the confined space entry, to remain on the outside of the confined space.

The stand-by man must be qualified to take appropriate action to protect those personnel inside the confined space if any conditions should arise inside or outside the space which may endanger the personnel inside the confined space.

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