Flammable materials liquids

OSHA requires flame retardant clothing (FRC) for workers at sites based on the quantity of flammable materials (liquids, solids, and gasses) and reactive chemicals that are handled and/or processed with activities at a facility. Both OSHA and NFPA 2113 see the need for FRC if 1) flash fire hazards exist on a continuous basis in various site areas and 2) when employees such as operators and maintenance personnel are in the areas where flash fire hazards exist. FRC can significantly reduce a bum injury by giving the wearer precious escape time from an ignition source and can greatly increase the chance for survival if the wearer is caught in a flash fire or electric arc. 

OSHA Requirements Based on the large quantity of flammable materials (liquids, solids, and gasses) and reactive chemicals that are handled/processed with associated on-site movement activities at your facility, we believe any worksite assessment required by OSHA or NFPA 2113 would conclude that ... 

Trace impurities in the feed streams can lead to combination of an oxidant with a flammable material (e.g. acetylene in liquid oxygen, solid oxygen in liquid hydrogen) and precautions must be taken to eliminate them. 

Application of a welding torch or burner to a tank or drum containing flammable material, either as solid, liquid or vapour or their residues, can cause an explosion. Such vessels, although apparently empty , may have residue in the bottom and/or in seams and crevices. 

Flashpoint — the lowest temperature of a liquid at whieh it gives off enough vapor to form an ignitable mixture with air near the surfaee of the liquid within the vessel used. Two tests are used—Open Cup and Closed Cup. Generally, the Open Cup method results in flashpoints 5° to 10° higher than the Closed Cup method. Flashpoint < 140°F (Closed Cup) is the eriterion used by EPA to deeide whether a ehemieal is hazardous by ignitability. DOT defines materials with flashpoints of < 100°F as flammable materials, and between 100° and 200°F as eombustible. 

Unconfined Vapor Cloud Explosion (UCVE) Occurs when a sufficient amount of flammable material (gas or liquid having high vapor... 

Avoid direct sunshine on containment surfaces in hot climates. Direct spills of flammable materials away from pressurized storage vessels to reduce the risk of a boiling liquid expanding vapor explosion (BLEVE). 

The main hazard posed by a BLEVE of a container filled with a flammable liquid, and which fails from engulfment in a fire, is its fireball and resulting radiation. Consequently, Lewis (1985) suggested that a BLEVE be defined as a rapid failure of a container of flammable material under pressure during fire engulfment. Failure is followed by a fireball or major fire which produces a powerful radiant-heat flux. 

Fire is more likely tlian an explosion where tliere is a loss of contaimiient of a flammable material from a railroad car, barge, ship tank, or from a pipeline. However, both unconfmed vapor cloud explosions (UVCES) and boiling liquid-e.xpanding vapor e.xplosions (BEEVES) can occur as a result of transport accidents, (see Section 7.5)... 

Ref. [40] points out that the effects of a Bleve depends on whether the liquid in the vessel is flammable. The initial explosion may generate a blast wave and fragments from the vessel. For a flammable material, the conditions described in Ref. [34] above may result, and even a vapor cloud explosion may result. 

Location and General Requirements. Locations shall be classified depending on the properties of the flammable vapors, liquids or gases or combustible dusts or fibers that may be present and the likelihood that a flammable or combustible concentration or quantity is present. Where pyrophoric materials are the only materials used or handled, these locations shall not be classified. 

Minimum recommended spacing distances Flammable liquids Storage of Flammable Liquids in Tanks (HSE, HSG 176) Storage of Flammable Liquids in Containers (HSE, HSG 51) Storage of Highly Flammable Liquids (HSE, CS2) Highly Flammable Materials on Construction Sites (HSE, HSG 3) Storage of Flammable Liquids in Fixed Tanks, up to 10 000 m Total Capacity (HSE, HSG 50)... 

Failure of a vessel containing a liquid at a temperature above its atmospheric boiling point may produce a BLEVE, with resulting blast and fragment effects. If flammable material is involved, a BLEVE may also produce a fireball. 

Heat transfer operations. Heat transfer fluids other than steam and cooling water utilities are sometimes introduced into the design of the heat exchange system. These heat transfer media are sometimes liquid hydrocarbons used at high pressure. When possible, higher boiling liquids should be used. Better still, the flammable material should be substituted with a nonflammable medium such as water or molten salt. 

A worker walking across a high walkway in a process plant stumbles and falls toward the edge. To prevent the fall, he grabs a nearby valve stem. Unfortunately, the valve stem shears off and flammable liquid begins to spew out. A cloud of flammable vapor rapidly forms and is ignited by a nearby truck. The explosion and fire quickly spread to nearby equipment. The resulting fire lasts for six days until all flammable materials in the plant are consumed, and the plant is completely destroyed. 

VCEs have increased in number because of an increase in inventories of flammable materials in process plants and because of operations at more severe conditions. Any process containing quantities of liquefied gases, volatile superheated liquid, or high-pressure gases is considered a good candidate for a VCE. 

Determine the concentration of toluene over a diked area (100 ft2) that contains toluene as a result of a spill. Assume that the process area (2500 ft2) is designed to handle Class I flammable materials and that the liquid and air temperature is 65°F. The vapor pressure of toluene at 65°F is 20 mm Hg. The LEL is 1.4% by volume. 

These concentrations are considerably below the LFL of 1.4% by volume, which illustrates that the specified ventilation rate for Class I liquids is satisfactory for handling relatively large spills of flammable materials. The concentrations do, however, exceed the TLV for this substance. 

First, there must be a release of a flammable material at suitable conditions of pressure or temperature. These include liquified gases under pressure, ordinary flammable liquids (especially at elevated pressures and/or temperatures), and flammable gasses. When a flammable liquid spills, some or all of it will vaporize and/or form an aerosol. This dispersion is called a vapor cloud. 

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