A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A R C H 2 0 2 3 3 5 9 FEATURE It was observed to be capable of reaching target positions within 0.1%, or 19 µm, of the commanded positions and with a dead band smaller than 0.25%. PERFORMANCE TESTING Experiments were conducted to evaluate the performance of an SMA-based industrial valve actuator (Fig. 2). The test program was carried out at the ETC and involved the actuator as the equipment under test (EUT). Experiments were designed to evaluate the EUT’s positioning performance at various environmental temperature conditions and the ability to develop the necessary force to maintain a pressure differential across a control valve. Inputs to the EUT were restricted to electrical power from a 24 VDC power supply and Modbus serial communication through an RS-485 interface for position command signals. The EUT was mounted to a Fisher D-Body NPS 2 control valve featuring a 32-mm port diameter and 19-mm travel, which is commonly used at natural gas production sites. The upstream side of the valvewas attached to a source of regulated high-pressure CO2 gas and the downstream side was exposed to atmospheric pressure. All tests were conducted inside a controlled environment test chamber specially constructed for the program. The test chamber was instrumented to monitor and control environmental temperature, pressure differential across the valve, position commands and feedback, and measured valve position. Position measurements were acquired from a high-resolution LVIT linear position sensor. SMA VALVE ACTUATOR CLOSING FORCE A pressure differential test was conducted to validate the EUT’s ability to remain in a fully closed position when the connected valve was subjected to pressure differentials. The maximum inlet test pressure was set at 4000 kPa, which corresponded to the maximum pressure that could be supplied by the test equipment. With the valve’s internal port size diameter of 32 mm, the minimum force required to maintain the valve in the closed position at the maximumpressure differential is 3170 N. The EUT was placed inside the environment chamber at the specified test temperature long enough to reach equilibrium. The EUT was commanded to remain closed throughout the test while the pressure differential ramped up to 4000 kPa for approximately 60 seconds for the first run, and approximately 25 seconds for the second run. Valve position and gas flow across the valve was monitored throughout the test. No measurable changes of valve position were found in any of the test iterations. These results indicate that the EUT was able to provide sufficient closing force to maintain a pressure differential of 4000 kPa across the control valve. POSITIONAL ACCURACY Experiments were conducted to evaluate the positional accuracy of the EUT under various temperature environments. Testing was performed in a cold environment (-43°C), a room temperature environment (+23°C), and a hot Fig. 3 — Valve actuator positional accuracy test results. TABLE 1 − VALVE ACTUATOR POSITIONAL ACCURACY TEST RESULTS Conditions -43°C environment +23°C environment +46°C environment Heat Run 1 Run 2 Run 1 Run 2 Run 1 Run 2 Dead time <0.8 s <0.8 s <0.8 s <0.8 s <0.8 s <0.8 s Dead band <0.25% <0.25% <0.25% <0.25% <0.25% <0.25% Positional accuracy 0.1% 0.1% 0% 0.1% 0.1% 0%
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