Effect of Hydrogen Sulfide on Equipment

Wet hydrogen sulfide service damage is frequently seen in carbon and low alloy steel equipment contained within facilities that produce hydrocarbons, such as the oil and gas, chemical, and petrochemical industries. Assets that are in an aqueous sour environment that combines H2S content greater than 50 ppm and temperatures below 82° C (180° F) are particularly susceptible to wet H2S damage. Older or “dirty” steels are more prone to wet H2S damage because they generally have more volumetric inclusions, laminations, and original fabrication imperfections in both base metal and weld deposit regions. Wet H2S damage is observed more in pressure vessel shells, tanks, or sections of larger diameter longitudinal seam-welded piping components than conventional seamless piping, tubing, or forgings

In the presence of moisture, H2S interacts with the iron of the steel wall releasing hydrogen into the oil stream. The hydrogen diffuses into the steel, coalescing to form molecular hydrogen at discontinuities. Over time, more and more hydrogen becomes trapped building up pressure thus stress in the steel leading to local failure. Here are some of the various defects that can be observed:

• Stress causes cracks that are generally laminar and oriented parallel to the inside and outside surfaces of the component. Over time, these cracks tend to join due to internal pressure build-up and possibly local stress fields in damaged regions propagating through the thickness of the component. This is known as Hydrogen Induced Cracking (HIC) or stepwise cracking.
• If the lamination occurs near the surface, we can end up with a blister rising from the inside surface, outside surface, or within the wall thickness of pressure equipment. Additionally, cracks can extend from the perimeter of a blister, potentially propagating in the through-wall direction, especially near welds.
• Stress Oriented Hydrogen Induced Cracking (SOHIC) appears as arrays of cracks stacked on top of each other potentially resulting in a through-thickness crack around the base metal directly adjacent to the Heat Affected Zone (HAZ).

When it comes to Non-Destructive Testing (NDT) methods, conventional Ultrasonic Testing (UT) has been used extensively using normal incident and shear wave probes. It has, however, difficulty differentiating between lamination/inclusions from in-service damage. It is also a laborious and slow process that is highly operator dependent.

The new hydrogen sulfide resistant composite (fiberglass) bridge plug designed and developed by Vigor's R&D department has achieved satisfactory results in the laboratory and at the customer's site, and Vigor's technical team can now design and produce it according to the customer's needs to meet the customer's on-site needs. If you are interested in Vigor's bridge plug products, please do not hesitate to get in touch with the Vigor team for customized products and exclusive quality services.

For more information, you can write to our mailbox info@vigorpetroleum.com & marketing@vigordrilling.com