Inspection frequencies and OSHA

The most commonly cited equipment for non-compliant inspection frequencies (of any type, not only thickness measurements) have been piping circuits followed by pressure vessels, relief devices, and monitoring alarms. As part of the inspection program, an appropriate inspection frequency must be established for equipment in order to determine whether pipe/vessel thickness is decreasing as expected. API 570 identifies three classes of piping services and recommends a thickness measurement inspection frequency based on the class. For example, Class 1 includes:

• Flammable, 
• Pressurized services that may rapidly vaporize and explode upon release,
• Hydrogen sulfide, 
• Anhydrous hydrogen chloride, 
• Hydrofluoric acid 
• Piping over water of public throughways, and
• Flammable services operating above their auto-ignition temperature.

As discussed in API 570, Class 1 requires a thickness measurement inspection frequency of at least every five years. Classes 2 and 3 require a thickness measurement frequency of at least every 10 years. The inspection interval for specific piping is established by the inspector or piping engineer in accordance with the owner/user’s quality assurance system, but not to exceed the limits set by API 570

Source:Osha.gov