Hydrogen Sulfide Gas MONITORING AND CONTROL IN THE OIL AND GAS INDUSTRY
H2S Special Precautions
Figure 1. Hydrogen
Sulfide warning sign
Hydrogen Sulfide gas is very corrosive and causes metals to
become brittle. Therefore, employers
need to take special precautions when choosing equipment when they may
reasonably expect to encounter H2S. This
may include appropriate H2S trimming of equipment in accordance with National
Association of Corrosion Engineers (NACE) Standards.
All well-drilling sites should be classified according to areas
of potential and/or actual exposure to H2S. The recommendations and employee instruction
will vary depending on the type of area. The four hazard levels are:
Any well that will not penetrate a known Hydrogen Sulfide
formation would be categorized as a No Hazard Area. Special Hydrogen Sulfide
equipment is not required.
Work
locations where atmospheric concentrations of H2S are less than
10ppm.
Recommended for
Area:- Hydrogen Sulfide warning sign with green flag warning device present.
- Keep all safety equipment in adequate working order.
- Store the equipment in accessible locations.
Work
locations where atmospheric concentrations of H2S are greater than
10ppm and less than 30ppm.
Recommended for
Area:- Legible Hydrogen Sulfide warning sign with yellow flag warning device present.
- Keep a safe distance from dangerous locations if not working to decrease danger.
- Pay attention to audible and visual alarm systems.
- Follow the guidance of the operator representative.
- Keep all safety equipment in adequate working order.
- Store the equipment in accessible locations.
- An oxygen resuscitator.
- A properly calibrated, metered hydrogen sulfide detection instrument.
Recommended for Area:
- Post legible Hydrogen Sulfide warning sign with red flag warning device.
- Post signs 500 feet from the location on each road leading to the location, warning of the hydrogen sulfide hazard.
- Check all Hydrogen Sulfide safety equipment to ensure readiness before each tour change.
- Establish a means of communication or instruction for emergency procedures and maintain them on location, along with contact information of persons to be informed in case of emergencies.
- Ensure usability of two exits at each location.
- Do not permit employees on location without hydrogen Sulfide safety training. (Employees may be permitted on location for specific Hydrogen Sulfide training purposes that does not include general rig training.)
- Pay attention to audible and visual alarm systems.
- Store the equipment in accessible locations.
- Two Hydrogen Sulfide detectors should be present (one should be a properly calibrated, metered detection instrument, and the other should be a pump type with detector tubes. The maximum permissible exposure limit (PEL) is 20 ppm. Respiratory protection would be required if periodic testing indicates employee exposures to H2S at concentrations above the PEL. See OSHA Standard Respiratory Protection, [29 CFR 1910.134].
- Oxygen resuscitator.
- Three wind socks and streamers.
- Two NIOSH/MSHA 30-minute, self-contained breathing apparatus for emergency escape from the contaminated area only.
Additional Information
2.
Search for Standards.
American National Standards Institute (ANSI).
3.
Health,
Safety & Environmental (HSE) Reference Guide. International
Association of Drilling Contractors (IADC).
4.
ANSI Z390.1 - 2006,
Accepted Practices for Hydrogen Sulfide Safety Training Programs. American
Society of Safety Engineers (ASSE).
5.
Hydrogen Sulfide. National Institute for Occupational Safety
and Health (NIOSH) Safety and Health Topic.
6.
Safety
Issues. Association of Energy Services Companies (AESC).
·
Use
of Anchors and Guywires
·
Use
of Compressed Gas Cylinders
·
Crane
Operation
·
Proper
Electrical Safety (including hot sticks)
·
Hot
Work
·
Fall
Protection Systems
·
H2S
- Hydrogen Sulfide
·
Respirator
Usage
·
Use
of wooden, metal and plastic (fiberglass) portable ladders
·
Scaffolding
·
Vehicle
Operation
Hydrogen Sulfide Gas
Figure 1. Hydrogen sulfide warning sign: Warning Hazardous Area is in
yellow letters on a black background. In black letters on a yellow background,
the sign says Hydrogen Sulfide, Extreme Health Hazard, Fatal or Harmful if
Inhaled.
Hydrogen Sulfide or sour
gas (H2S) is a flammable, colorless gas that is toxic at
extremely low concentrations. It is
heavier than air, and may accumulate in low-lying areas. It smells like "rotten eggs" at low
concentrations and causes you to quickly lose your sense of smell. Many areas
where the gas is found have been identified, but pockets of the gas can occur
anywhere. Iron sulfide is a byproduct of
many production operations and may spontaneously combust with air.
Flaring operations
associated with H2S production will generate Sulfur Dioxide (SO2),
another toxic gas.
Active monitoring for
hydrogen sulfide gas and good planning and training programs for workers are
the best ways to prevent injury and death.
Also see: NIOSH Classification of H2S
Hazard Areas.
Hazards may include and/or
be related to the following:
Figure. 2. SCBA
Figure. 3. Gas detector
All personnel working in an
area where concentrations of Hydrogen Sulfide may exceed the 10 Parts Per
Million (PPM) should be provided with training before beginning work
assignments.
Potential Hazard:
H2S exposure
greater than the Permissible Exposure Limit (PEL).
Possible Solutions:
Implement an H2S
contingency plan (see API) including, but not limited to:
Appropriate instruction in
the use of hydrogen sulfide safety equipment to all personnel present at all
hydrogen sulfide hazard areas.
Gas detection where
hydrogen sulfide may exist.
Appropriate respiratory
protection for normal and emergency use. [29 CFR 1910.134]
For emergency response
information, see Hazardous Waste and Emergency Response (HAZWOPER) Standard, [29 CFR 1910.120].
Comprehensive training
should be provided for workers in H2S operations. Example topics
include:
·
Identification of the characteristics, sources,
and hazards of Hydrogen Sulfide.
·
Proper use of the Hydrogen Sulfide detection
methods used on the site.
·
Recognition of, and proper response to, Hydrogen
Sulfide warnings at the workplace.
·
Symptoms of Hydrogen Sulfide exposure.
·
Proper rescue techniques and first-aid
procedures to be used in a Hydrogen Sulfide exposure.
·
Proper use and maintenance of personal
protective equipment. Demonstrated proficiency in using PPE should be required.
·
Worker awareness and understanding of workplace
practices and maintenance procedures to protect personnel from exposure to
hydrogen sulfide.
·
Wind direction awareness and routes of egress.
·
Confined space and enclosed facility entry
procedures.
·
Locations and use of safety equipment.
·
Locations of safe briefing areas.
·
Use and operation of all Hydrogen Sulfide monitoring
systems.
·
Emergency response procedures, corrective
action, and shutdown procedures.
·
Effects of Hydrogen Sulfide on the components of
the Hydrogen Sulfide handling system.
·
The importance of drilling fluid treating plans
prior to encountering Hydrogen Sulfide.
Additional Information:
RP 49, Recommended
Practice for Drilling and Well Servicing Operations Involving Hydrogen Sulfide.
American Petroleum Institute (API), (2001, May/Reaffirmed 2007,
March). Includes well drilling, completion, servicing, workover, downhole
maintenance, and plug and abandonment procedures conducted with hydrogen
sulfide present in the fluids being handled.
Safety Issues.
Association of Energy Services Companies (AESC).
·
Use of Anchors and Guywires
·
Use of Compressed Gas Cylinders
·
Crane Operation
·
Proper Electrical Safety (including hot
sticks)
·
Hot Work
·
Fall Protection Systems
·
H2S - Hydrogen Sulfide
·
Respirator Usage
·
Use of wooden, metal and plastic (fiberglass)
portable ladders
·
Scaffolding
·
Vehicle Operation
Metal fatigue, including
hydrogen embrittlement or sulfide stress cracking, can result in a release of
hydrogen sulfide gas.
Potential Hazard:
Being exposed to Hydrogen
Sulfide.
Getting Injured due to
equipment failure.
·
Possible Solutions:
Select materials in
accordance with the MR0175/ISO15156 criteria for H2S
service.
MR 0175C, Metals for
Sulfide Stress Cracking and Stress Corrosion Cracking Resistance in Sour
Oilfield Environments. National Association of Corrosion Engineers (NACE),
(2003, December) [Also ISO 15156, Petroleum and natural gas
industries-Materials for use in H2S containing environments in oil
and gas production, International Standards Organization (ISO)].
Treat drilling fluids to
chemically reduce corrosion failures.
It is possible for hydrogen
sulfide gas to accumulate in any low or enclosed area, such as a gas venting
system, mud system, cellars, pits, and tanks.
Potential Hazard:
Being exposed to Hydrogen
Sulfide.
Possible Solutions:
Provide adequate
ventilation for the removal of any accumulation of H2S.
Implement effective confined space entry program.
Additional guidance
materials are available from:
RP 49, Recommended
Practice for Drilling and Well Servicing Operations Involving Hydrogen Sulfide.
American Petroleum Institute (API), (2007, March). Includes well drilling,
completion, servicing, workover, downhole maintenance, and plug and abandonment
procedures conducted with hydrogen sulfide present in the fluids being handled.
Spec 6A,
Specification for Wellhead and Christmas Tree Equipment (includes Errata 3
dated June 2006). 19th Edition. (2004, July). [Also ISO10423:2003] Specifies
requirements and gives recommendations for the performance, dimensional and
functional interchangeability, design, materials, testing, inspection, welding,
marking, handling, storing, shipment and purchasing, of wellhead and christmas
tree equipment for use in the petroleum and natural gas industries.
Spec 6A 718,
Specification of Nickel Base Alloy 718 (UNS N07718) for Oil and Gas Drilling
and Production Equipment (includes Addendum dated March 2006). 1st Edition.
(2004, March). Provides specification requirements for Nickel Base Alloy 718
(UNS N07718) that are intended to supplement the existing requirements of API
Spec 6A and ISO 10423. These additional specification requirements include
detailed process control requirements and detailed testing requirements.
For additional information,
see the API website.
Safety Issues.
Association of Energy Services Companies (AESC).
Use of Anchors and
Guywires
Use of Compressed Gas
Cylinders
Crane Operation
Proper Electrical Safety
(including hot sticks)
Hot Work
Fall Protection Systems
H2S -
Hydrogen Sulfide
Respirator Usage
Use of wooden, metal and
plastic (fiberglass) portable ladders.
Scaffolding
Vehicle Operation
MR 0175, Metals for
Sulfide Stress Cracking and Stress Corrosion Cracking Resistance in Sour
Oilfield Environments. National Association of Corrosion Engineers (NACE),
(2003, December) [Also ISO 15156, Petroleum and natural gas
industries—Materials for use in H2S containing environments in oil
and gas production, International Standards Organization (ISO)].
Accident Prevention
Guide. International Association of Drilling Contractors (IADC).
Respiratory
protection as it relates to oil fields. OSHA Standard Interpretation,
(1993, April 14).
29 CFR 1910.134, Respiratory protection. OSHA
Standard.
NFPA 70, National
Electrical Code. National Fire Protection Agency (NFPA), (2014).
State Programs
Alaska Administrative
Code: Title 20 - Chapter 25. Alaska Administrative Code, Alaska Oil and Gas
Conservation Commission, Title 20, Chapter 25.
Petroleum Safety
Orders--Drilling and Production. Cal/OSHA Standards: California Code of
Regulations, Title 8; Chapter 4, Division of Industrial Safety; Subchapter 14.
Chapter
3, Oil
and Gas Division. Texas Administrative Code (TAC); Title 16. Economic
Regulation; Part 1. Railroad Commission of Texas; Chapter 3.
R614-2. Drilling Industry. Title 34A,
Chapter 6, Utah Occupational Safety and Health Act of 1973.
Rules and Statutes.
Wyoming Oil and Gas Conservation Commission.
Training Programs
Drilling Technology Series.
Petroleum
Extension Service (PETEX),
University of Texas at Austin.
Unit I: The Rig and Its
Maintenance
Unit II: Normal Drilling
Operations
Unit III: Non-routine
Operations
Unit IV: Man Management and
Rig Management
ASC Z390.1, Accepted
Practices for Hydrogen Sulfide Safety Training Programs. American Society of
Safety Engineers (ASSE), (2006, June).
H2S Training and
Information Links
API-U Training. American Petroleum Institute (API).
A.1 Physical Data
Chemical Name: Hydrogen
Sulfide
CAS Number: 7783-06-4
Synonyms: Sulfureted
hydrogen, hydrosulfuric acid, dihydrogen sulfide
Chemical Family: Inorganic
sulfide
Chemical Formula: H2S
Normal Physical State:
Colorless gas, slightly heavier than air. Vapor density (specific gravity) at
59°F (15°C) and 1 atmosphere = 1.189.
Auto ignition Temperature:
500º F
Boiling Point: -76º F
Melting Point: -117.2º F
Flammable Limits: 4.3-46
percent vapor by volume in air
Solubility: Soluble in
water and oil: solubility decreases as the fluid temperature increases
Combustibility: Burns with
a blue flame to produce sulfur dioxide (SO2). Refer to Appendix B Odor and
Warning Properties: Hydrogen sulfide has an extremely unpleasant odor,
characteristic of rotten eggs, and is easily detected at low concentrations:
however, due to rapid onset of olfactory fatigue and paralysis (inability to
smell) ODOR SHALL NOT BE USED AS A WARNING MEASURE.
A.2 Exposure Limits
The American Conference of
Governmental Industrial Hygienists recommends a Threshold Limit Value of 1 ppm
and a short-term exposure (STEL) limit of 5 ppm averaged over 15 minutes.
Exposure at the STEL should not be repeated more than four times per day with
at least 60 minutes between successive exposures in this range.
A.3 Physiological Effects
Inhalation at certain
concentrations can lead to injury of death. The 300 ppm is considered by the
ACGIH as Immediately Dangerous to Life and Health. Hydrogen sulfide is an
extremely toxic, flammable gas that may be encountered in the production of gas
well gas, high-sulfide, high sulfur content crude oil, crude oil fractions,
associated gas, and waters. Since hydrogen sulfide is heavier than air, it can
collect in low places. It is colorless and has a foul rotten egg odor. In low
concentrations, H2S sometimes can be detectable by its
characteristic odor; however, the smell cannot be relied upon to forewarn of
dangerous concentrations (greater than 100ppm) of the gas because it rapidly
paralyzes the sense of smell due to paralysis of the olfactory nerve. A longer
exposure to the lower concentrations has a similar desensitizing effect on the
sense of smell.
It should be well
understood that the sense of smell will be rendered ineffective by hydrogen
sulfide, which can result in an individual failing to recognize the presence of
dangerously high concentrations. Exposure to hydrogen sulfide causes death by
poisoning the respiratory system at the cellular level. Symptoms from repeated
exposures to low concentrations usually disappear after not being exposed for a
period of time. Repeated exposures to low concentrations that do not produce
effects eventually may lead to irritation if the exposures are frequent.
A.4 Respiratory Protection
Respiratory protection
shall be worn above the action level. Refer to 6.6 for proper breathing
equipment recommendations for oil and gas well drilling and servicing
operations involving hydrogen sulfide.
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