Nace - Sp0170 Pdf

If the equipment does not require internal inspection or mechanical work, the simplest and most effective defense is to keep oxygen out.

Equipment is isolated, sealed, and continuously blanketed with high-purity dry nitrogen gas ( N2cap N sub 2

By eliminating liquid water, sulfide scales cannot hydrolyze into polythionic acid. Material Selection Considerations Under SP0170

Understanding NACE SP0170: Protection Against Polythionic Acid SCC nace sp0170 pdf

NACE SP0170 serves as the definitive global engineering standard for preventing this specific failure mechanism during non-operational periods. It provides operating companies, inspection personnel, and maintenance contractors with clear, actionable procedures to safeguard equipment from the moment a unit begins cooling down until it is safely brought back online. The standard applies to:

The standard details several methods to protect equipment, which can be used individually or in combination based on risk assessment. 1. Nitrogen Purging

Refinery heaters, heat exchangers, piping, and pressure vessels. Standard austenitic stainless steels (300 series). If the equipment does not require internal inspection

NACE SP0170 is a standards-guidance document focused on welding practices for nickel-chromium-molybdenum and nickel-chromium alloys commonly used in corrosive-service equipment (e.g., sour service, hydrogen sulfide exposure). It provides recommendations to ensure weld quality, corrosion resistance, and mechanical integrity for these alloy systems when used in oil, gas, chemical, and related industries.

Outlines specific steps to take immediately upon cooling down.

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AMPP - The Association for Materials Protection and Performance NACE SP0170-2018

If the equipment does not need to be opened for internal inspection or maintenance, the simplest and most effective strategy is to exclude oxygen completely.