An “Emergency Pressure Control System” has been a requirement in the IFC and IMC for several iterations of these codes, and yet it can be a very confusing requirement as they are not found in the vast majority of mechanical refrigeration systems using Anhydrous Ammonia as the refrigerant. Part of the problem may lie in the fact that the IIAR does not recognize this emergency system as an essential need in the design of an Ammonia refrigeration process (See Appendix I of IIAR-2, 2014). But the gest of this emergency system is to aid emergency responders and refrigeration personnel in mitigating an overpressure condition PRIOR to the operation of relief valve(s). This section of the International Mechanical Code (IMC) establishes a requirement for a fully redundant, automatic, safety control system that ensures that lower pressure zones will be capable of handling additional pressure added by a crossover condition WITHOUT over pressurizing or lifting relief valve(s) in the lower zone. Section 606 of the International Fire Code (IFC) establishes provisions for the automatic crossover valves, overpressure limit set point, manual operation, system design pressure, automatic emergency stop, the operation of an automatic crossover valve and overpressure in low-pressure zones. So let’s break this down…