1915 diaphragm relief valves are used to protect liquid- or inert gas-filled pressure systems against exceeding the required pressure. The choice of valve size, depending on the heat output, is shown in the table in the manufacturer’s data sheet. Valves can be selected using a software, available to download as a compressed file. Relief valves can be used in pressurized water systems and with other perfect fluids or inert gases, with a maximum temperature not exceeding 140°C. SYR relief valves can be used in systems filled with a mixture of water and glycol. The maximum glycol content must not exceed 50%.