Process safety management in the oil and gas industry
Health and safety concerns in oil and gas
OSHA’s Process Safety Management standard emphasizes the management of hazards associated with highly hazardous chemicals and establishes a comprehensive program integrating technologies, procedures, and management practices.
Several types of processes in the oil and gas industry have the potential for chemical releases and associated fire, safety, and health hazards due to the nature of these releases.
Petroleum refining begins with the distillation, or fractionation, of crude oils into separate hydrocarbon groups, which are further converted into more usable products through cracking, reforming, and other conversion processes to remove undesirable constituents and improve product quality.
These are some potential process safety management issues to be aware of in oil and gas production.
Crude oil pretreatment (desalting)
As a first step in the refining process, contaminants such as water, inorganic salts, suspended solids, and water-soluble trace metals must be removed from crude oil to reduce corrosion, plugging, and fouling of equipment and to prevent poisoning the catalysts in processing units.
Both chemical and electrostatic separation desalting use hot water with additional chemicals (surfactants, ammonia, caustic, or acid) added to the heated oil so that salts and other impurities will transfer to the water. Desalting can cause potential safety issues.
Inadequate desalting can cause fouling of heater tubes and heat exchangers throughout the refinery, leading to failures due to increased pressures and temperatures.
A fire’s potential is due to a leak or release of crude oil from heaters in the crude heating unit. Low boiling point components of crude oil may also be released if a leak occurs.
When elevated operating temperatures are used when desalting sour (sulfuric) crudes, hydrogen sulfide will be present. There is the possibility of exposure to ammonia, dry chemical demulsifiers, caustics, and acids during this operation.
Safe work practices and the use of appropriate personal protective equipment may be needed for exposures to chemicals and other hazards such as heat and during process sampling, inspection, maintenance, and turnaround activities. Industrial hygiene sampling may be necessary to evaluate potential chemical exposure.
Crude oil distillation (fractionation)
The cleaned crude oil is then separated into various fractions by distillation in atmospheric and vacuum towers. These fractions have specific boiling-point ranges and volatilities.
The crude oil is fed into a heater and distillation column from temperatures of 650°F to 700°F. The crude oil separates into vapor and rises up the tower, where products of various densities are drawn off. Steam is often used in towers to lower the vapor pressure and create a partial vacuum.
Fractionation can cause the following safety concerns
Even though these are closed processes, heaters and exchangers in the units could provide a source of ignition, and the potential for a fire exists should a leak or release occur.
There are multiple areas of the process that can be susceptible to corrosion from HCl, H2S, sulfur compounds, and organic acids. Ammonia and alkaline solution may be injected into steam or hot crude oil feed, which can then be present at high wastewater concentrations.
An excursion in pressure, temperature, or liquid levels may occur if automatic control devices fail. Control of temperature, pressure, and reflux is needed to prevent thermal cracking within distillation towers. Relief systems should be provided for overpressure and operations monitored to prevent crude from entering the reformer charge.
Solvent Extraction and Dewaxing
Since distillation (fractionation) separates petroleum products into groups only by their boiling-point ranges, impurities may remain. Solvent refining processes usually remove these undesirables at intermediate refining stages or before sending the product to storage.
The solvent extraction process separates impurities from the product stream by dissolving or precipitation. Dewaxing involves mixing feedstock with a solvent and cooling to dissolve and precipitate out wax and separate dewaxed oil; usually, two solvents are used, toluene and methyl ethyl ketone. Solvent Extraction and Dewaxing have the potential for the following safety issues.
Because solvent extraction is a closed process, exposures are expected to be minimal under normal operating conditions. However, there is a potential for exposure to extraction solvents and other process chemicals.
Although operating pressures are relatively low, the potential exists for fire from a leak or spill contacting a source of ignition such as the drier or extraction heater. Insolvent dewaxing, the vacuum disruption will create a potential fire hazard by allowing air to enter the unit.
Simple distillation of crude oil produces various amounts and types of products that are not consistent with those required by the marketplace. The product mix must be changed by altering the molecular structure of the hydrocarbons.
The thermal cracking or catalytic cracking processes break heavier, higher boiling-point petroleum fractions into more valuable products such as gasoline, fuel oil, and gas oils. High heat and pressure are used in thermal cracking.
In catalytic cracking, catalysts are added to the cracking reaction increasing the yield of products under less severe operating conditions.
Thermal cracking also has potential safety issues.
Regular testing of the feedstock, product, and recycling streams should be performed to ensure that the cracking process is working as intended and that no contaminants have entered the process stream. Inspections of critical equipment should be conducted as needed.
The possibility exists of exposure to scalding (700 °F) hydrocarbon liquids or vapors during process sampling or if a leak or release occurs.
Process Safety Management Systems
All process safety management systems should include process safety information, process hazards analysis, operating procedures, mechanical integrity, and management of change information. These written plans should be up-to-date, complete, and accurate.
They should provide clear instructions of specific steps for normal operations, non-routine or upset conditions, temporary operations, safe work practices, and emergency shutdown.
Procedures should be performed as written. If operators deviate from procedures, management, and technical staff should meet with operators to review the effectiveness of procedures and revise if necessary.
All physical (e.g., fire, explosion) and chemical hazards and their effective controls to prevent incidents should be documented and made available to all employees. If a hazard is found that has not been adequately addressed, the employer shall establish a system to mitigate the findings promptly.
Equipment deficiencies such as lack of proper maintenance or repair, inappropriate installation, missing protective system (e.g., not including relief devices), and insufficient structural support should be corrected immediately.
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