Good engineering practices (API STD 520 and ASME B&PV Code Section VIII) have long specified/required that inlet piping pressure drop from the vessel to the safety relief device should be limited to no greater than 3% of the safety relief valve’s set pressure. Many companies have taken a more lenient approach to the inlet pressure loss limits; consequently, many installations do not meet the 3% design guideline, as the prevailing company logic assumed that existing installations were “safe” as long as the inlet losses were less than the safety relief device’s blowdown with some built-in safety margin. Up until recent fines by OSHA, there have been no hard and clear industry requirements or penalties for companies to adhere to the 3% inlet pressure loss rule. However, OSHA recently rejected this argument and has now begun levying fines against companies violating this 3% rule. In an April 2010 letter to the API STD 520 Committee, OSHA stated that higher inlet losses may be considered acceptable if safety relief valve stability could be assured with an engineering analysis.