Welcome to Helmco Manufacturing Welcome HMI Products Warranty Helmco Manufacturing, Inc. AN INDEPENDENT DIVISION OF HMS, INC. Est. 1973 Demand the best. Always insist on HMI Quality Excess Flow Check Valves.....the original and still the number one choice. HMI A LEADING MANUFACTURER of Excess Flow Check Valves for liquids, gas, or vapor flow lines in refineries, chemical plants, city water lines, local gas company lines, ships, barges, tankers, tanker trucks; anywhere a break in a flow line poses a hazard or simply to limit the flow to a predetermined amount. We offer many standard flows in a