By Kelly Paffel, Inveno Engineering

Steam safety valves are required by industry standards, as well as insurance and corporate mandates. Therefore, it is important that the safety valve be properly sized and installed to meet all code requirements. The code that establishes the requirements for steam safety valves is written by the American Society of Mechanical Engineers (ASME). ASME, through its committees, has published and continues to update the Boiler and Pressure Vessel Codes (BPVC) for safety valves. It is the responsibility of plant personnel — primarily the plant’s steam team — to know which codes apply to the different parts of the steam system. »

By Guofu Chen, Joule Processing LLC

Two-phase pressure-relief valves (PRVs) have been studied by many researchers. Among the many published works on this subject is the American Petroleum Institute (API) Standard 520 on the Sizing, Selection and Installation of Pressure-Relieving Devices. Part 1 of the API 520 standard (9th edition) describes three methods to size two-phase PRVs, which are described in detail in Annex C. The first method is the HDI (homogeneous direct integration) method (section C.2.1), which has wide applicability. The second method is known as the Omega method for two-phase flashing or non-flashing flow (described in section C.2.2). The third is the Omega method for sub-cooled liquid (described in section C.2.3). This article examines the HDI method and compares it to an easier alternative method, known as HD (homogeneous direct without integration). »