Page 15 - CCPS Golden Rules - Hydrogen Sulfide

Golden Rules for Hydrogen Sulfide (H2S)
Golden Rule #2: Always know where the H2S hazard exists or can be produced
❖ How – Engineers and Designers:
Attend process hazard analysis (PHA) studies, especially those with knowledge of the process with
respect to H2S. These engineers will understand the normal and abnormal situations that can create H2S.
PHA studies should be archived and communicated in a manner that enhances process safety
knowledge of where the H2S hazard exists or can be produced [11, pp. 169-244].
Asset Integrity Engineers must be aware of where H2S exists and can be produced and assess the
potential impact of H2S on the mechanical integrity of the containment equipment. See Supplemental
Reading “Guidelines for Mechanical Integrity Systems” [34].
For example, the combined effect of H2S and tensile stress can cause sulfide stress cracking corrosion
(SSC) of metallic material. Asset Integrity Engineers can provide forecasting of known SSC hazards. This
is especially true where welding (e.g. fittings) should be done with an approved welding procedure (e.g.
avoid excessive manganese and chrome in the welding material, insufficient weld material deposited, or
inadequate leg size). Adequate preparation is necessary (e.g. bake-out procedure especially on carbon
steel) [35] [36].
Use a risk-based approach when relying on check valve(s) for the prevention of H2S gas or liquid
backflow when there is a possibility of an H2S release to atmosphere. An active (non-passive) positive
isolation should be installed unless it can be justified through the risk-based approach [37].
Avoid open-to-atmosphere designs when the process involves H2S. When H2S exists or can be
produced, engineers should evaluate closed (contained) system designs to avoid activities like opening
equipment to do pH or level measurements [23] [38].
Know the chemistry and the physics of the process (specifically Henry's Law) to determine if and when
H2S may be liberated from a solution. H2S gas may be liberated directly from the original source or
place where it is generated, or in downstream locations due to its solubility in water and hydrocarbons.
See Supplemental Reading, “Hazards of Molten Sulfur Storage & Handling [39]” for further information.

Higher temperatures and lower pH enhance the release quantity. H 2S gas venting locations should be
engineered under all credible operating conditions. For example, a wastewater tank containing
dissolved H2S can liberate H2S gas with increased temperatures. If an engineered solution is not
possible, then use the hierarchical control philosophy (see Figure 5).

Determine the criteria and location for H 2S fixed gas detection and associated alarm systems.
Considerations may include the potential release locations, the characteristics of H 2S (e.g., heavier than
air), and the migration potential of H2S in the event of a release (e.g., the dominant wind speed, wind
direction and distance to downwind sensitive receptors such as people).
❖ How – Emergency Responders:

Consider factors such as the wind direction, building ventilation, and terrain when responding to an H2S
release.
Use monitoring equipment to know where the presence of H2S exists or can be produced during
emergencies. See also Golden Rule #4.

Updated January 2024 Page 12 of 28