Friday, March 1, 2013

Safety: PROPANE

PROPANE

INTRODUCTION

Packaged under pressure, propane gas presents three hazards if misused:

1. high flammability and explosive potential
2. displacement of breathable air in confined spaces (also, being heavier than air, propane will collect in low areas)
3. contact injury from accidental exposure to a substance under high pressure.

Physical Characteristics

Propane or liquefied petroleum gas (LPG) is a by-product of petroleum or natural gas refining
which is packaged under pressure in cylinders. In its stored state it is a liquid but is released from the cylinder or tank in a gaseous form. The boiling point of propane, the point at which the liquid converts to a gas, is -42.2°C (-44°F). If the surrounding air temperature is above this, gas will form in the upper part of the cylinder.

The pressure within the container is variable depending on the temperature to which the container is exposed. The pressure increases as the temperature rises, causing expansion of the liquid. For this reason containers are never fully charged with liquid, but have a vapour space at the top of the tank to allow for normal expansion.

Should the temperature rise above safe limits, a relief valve will open to allow release of the gas in a measured amount. This release is generally over in seconds. The valve reseals and remains closed until the pressure builds up again. Cylinder relief valves are set at 2585.5 kPa (375 lb per square inch)......

Safe Handling of Cylinders

In construction, most propane applications dispense the fuel in a vapour form. For this reason, it is essential that portable cylinders be transported, stored, and used in an upright position. Propane liquid must never come in contact with the cylinder relief valve. If liquid escapes through the valve, large volumes of gas will be released.

The simplest way to avoid the problem is to fasten cylinders in an  upright position with rope, wire, or other means. When transporting by truck, take extra care to
keep cylinders upright and stationary.

Cylinders should not be transported in an automobile trunk or in a closed van. Escaping gas can collect in a confined space and create an explosive atmosphere, as well as threaten life by displacing breathable air.

Store cylinders safely on the jobsite. They should be stored in a separate compound out of traffic areas and where they are in no danger of being struck by falling materials or moving equipment. A simple compound can be constructed using a length of snow fence and a few Tbars. When properly constructed, this barrier provides a means of tying up the cylinders as well as controlling stock. Empty cylinders should be stored on one side, full on the other. Don't mix the cylinders.

The compound should not be close to an area where flammable liquids such as gasoline and diesel fuel are stored. Only cylinders that are in use should be inside a building. (“In use” means hooked up to a construction heater or other appliance.)..........

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