Metering valves are designed to provide accurate and stable flow rates in analytical and research applications. As metering valves are similar in construction to needle valves, a common question from customers is: can metering valves be used as shutoff valves? The answer is simple: not all metering valves can be used as shutoff valves.
Recently there is a typical case: a customer bought FITOK MS series metering valves and the site operator mistakenly thought that these metering valves provide shutoff service. When he rotated the handle to the end but found that the flow rate was still not zero, he further rotated the handle until breaking the stem. See the figure.
When choosing metering valves, it is important to consider parameters such as flow rate, orifice size, working temperature and pressure, but the shutoff service cannot be ignored. For example, FITOK ML and MH series metering valves provide shutoff service because they have a tapered surface at the stem to form a seal with the valve body, and the stem materials are hardened 316 stainless steel and 440C stainless steel, which have higher strength than general 316 stainless steel. However, for FITOK MS and MV series metering valves, the shutoff service is not available.