Azbil Corporation No. SS2-BSL100-0100 - 7 - Note: . Bellows seals have a limited service life. Replace them at the appropriate time. . The estimated lifespans of bellows seals are not guaranteed. . The lifespan of bellows seals is affected by the following factors in addition to the number of cycles. . Repetitive application of pressure due to pump pulsations, etc. . Temperature cycles . Vibration transmitted through pipes . Corrosion due to fluids . Shock due to water hammer . Excessive hunting because of improper adjustment of the positioner or controller, etc. Therefore, the estimated lifespan calculations shown in this document should be used as reference data. Handling Precautions When using control valves with a bellows seal, there are some points regarding which caution needs to be taken that are different from those for general control valves. Correct handling keeping the following points in mind is essential. . NEVER turn the valve stem Never rotate the valve stem with the bellows seal assembly. The bellows may become twisted resulting in damage. . Pressure-resistant airtight test pressure For the pressure-resistant airtight pressure test for control valves with a bellows seal, use the LOWEST pressure from out of the following conditions. . Highest usable pressure for the selected bellows seal . Test pressure determined by the pressure rating of the valve itself . Test pressure stipulated by the High Pressure Gas Safety Law (in Japan) If the test pressure based on the pressure rating of the valve or the test pressure stipulated by the High Pressure Gas Safety Law is higher than the highest usable pressure for the bellows seal, applying the test pressure to the bellows seal may damage the bellows. Preventive maintenance for bellows seals Bellows seals have a limited lifespan, and to use them properly the following measures are recommended. . Leak and damage detection using the leak detection hole By connecting a pressure sensor or a gas detector to the leak detection hole (Rc1/4), damage to the bellows and the resulting fluid leakage can be detected. . Cycle number management using the control valve maintenance support system The Valstaff control valve maintenance support system allows on-line tracking of the actual number of operation cycles of the control valve, for purposes of preventive maintenance. For details about Valstaff, refer to the following product specifications. . SS2-VMS100-0100 (HART. protocol support system) . SS2-VMS103-0100 (FOUNDATION. fieldbus support system) Figure 9. management of number of cycles using Valstaff Every time the control valve operates, Valstaff tracks the distance the valve stem has moved and totalize this data. This figure is called “Total Stroke” diagnostics parameter of Valstaff. The number of cycles, an index of the bellows seal lifespan, is calculated by the following equation using the Total Stroke parameter. Number of cycles (times) = Total Stroke (%) / 200 (%) HART. is a trademark of Hart Communication Foundation. FOUNDATION. is a trademark of Fieldbus Foundation. 8 4