Wet hydrogen sulphide service is where ordinary heat exchangers fail fastest. Yuhong Group has completed qualification of its shell and tube line for NACE MR0175 / ISO 15156 environments and NACE TM0284 hydrogen induced cracking resistance, opening the sour gas, hydrocracker and amine regeneration segments to customers who previously sourced these units from Europe.
The qualification is not a paperwork exercise. Sour service failures are almost always hydrogen related: atomic hydrogen diffuses into the steel at the wet H2S surface and recombines at inclusions, blistering plate or cracking welds and heat affected zones. Preventing it requires control of chemistry, hardness, inclusion shape and welding procedure simultaneously.
| Service | Typical Equipment | Key Requirement |
|---|---|---|
| Wet H2S crude preheat | shell and tube, floating head | TM0284 plate, hardness control |
| Hydrocracker effluent | AES type with C70600 tubes | MR0175, high pressure |
| Amine regeneration | kettle reboiler, lean/rich exchanger | SS cladding, stress relief |
| Sour water stripper | fixed tubesheet, TP316L tubes | chloride and H2S resistance |
For sour service, the documentation package is part of the product. Yuhong Group supplies HIC test reports on the actual heat of plate used, hardness survey records, PWHT charts, NDT reports, hydrotest certificates and full EN 10204 3.1 certificates traceable to heat numbers stamped on the unit. Where the client nominates third party inspection, BV, TUV, SGS or Intertek witness points can be arranged for fit up, welding, testing and final painting.
One process detail worth noting: a sour service exchanger is not simply a standard exchanger in better material. Nozzle reinforcement, baffle clearance and welding sequence all affect residual stress, and residual stress is where cracking starts. Our design team reviews each sour service enquiry against the specific partial pressure of H2S and the pH of the aqueous phase before selecting material, rather than applying a single default specification.
Sour service shell and tube heat exchangers are quoted from 30 to 60 working days depending on cladding scope, with expedited handling for turnaround projects. Buyers are invited to send process conditions, H2S partial pressure, chloride level and design pressure and temperature for a material recommendation and preliminary thermal design.
NACE MR0175 / ISO 15156-2, Table 1 limits carbon and low alloy steels to 22 HRC, equivalent to 248 HV10 (approximately 250 HV), for sour service. The same ceiling applies to welds and heat affected zones, and hardness records are issued with the material certificates. Hardness is verified on production welds and heat affected zones, not only on the base metal test coupon.
Solution A conditions: pH 2.7 to 3.3; H2S partial pressure at or above 2,300 ppm; exposure time 96 hours, per NACE TM0284. Acceptance is based on crack length and thickness ratios, not on the absence of visible blistering, and plate is released only where both ratios stay inside the agreed criteria.
Any exchanger in wet H2S service should be reviewed against MR0175 using H2S partial pressure and aqueous pH. Crude preheat, hydrocracker effluent, amine regeneration and sour water stripper duty are the most common sour service applications, and each is reviewed against the design basis before material selection is fixed.
