Kako koristiti termoparove za otkrivanje kvarova kontrole grijača u sustavima s vrućim pogonom?

Heater control failures-such as a shorted solid-state relay (SSR) or a stuck contactor-can cause the heater to remain on continuously, leading to a thermal runaway and serious damage. Thermocouples are the primary sensors for detecting these failures. The first sign of a heater control failure is a rapid, uncontrolled temperature rise. The thermocouple reading will increase significantly above the setpoint (e.g., by 10°C or more) and will not stop. The second sign is a heater power percentage that is at its maximum (100%) even though the setpoint has been reached. This indicates that the controller is trying to turn the heater off, but the switching device (SSR or contactor) is stuck in the "on" position. The third sign is a high temperature alarm. Most controllers have a high-temperature alarm that is triggered when the temperature exceeds the setpoint by a certain margin. The thermocouple triggers this alarm. The fourth step is to implement a redundant safety system. Use a second thermocouple (or a separate high-limit thermocouple) that is independent of the controller. If the temperature exceeds a safe limit, this thermocouple triggers a separate alarm or a hard-wired safety circuit that cuts the power to the heater. The fifth step is to use a rate-of-change alarm. If the temperature rises too fast (e.g., >5 stupnjeva u sekundi), to je znak kvara kontrole grijača. Podaci termopara mogu se koristiti za aktiviranje ovog alarma. Šesti korak je izvođenje testa "isključivanja". Isključite grijač s regulatora. Ako očitanje termoelementa nastavi rasti, sklopni uređaj je zaglavljen. Sedmi korak je korištenje polu{7}}state releja s "dijagnostičkim" izlazom. Neki SSR-i daju dijagnostički signal koji pokazuje njihovo stanje. Upravljač može nadzirati ovaj signal kako bi otkrio zaglavljivanje-na SSR-u. Osmi korak je poduzimanje trenutnih korektivnih radnji. Ako se otkrije greška u upravljanju grijačem, potrebno je odmah prekinuti napajanje toplovoda. Neispravni sklopni uređaj mora se zamijeniti. Korištenjem podataka o termoelementima za otkrivanje kvarova kontrole grijača, kalupari mogu spriječiti toplinski bijeg, što može uzrokovati požar, oštetiti kalup i stvoriti ozbiljne sigurnosne opasnosti.