The allowed range for tolerance is ±8° C for stress-relieving, tempering and ageing process and ±14° C in general. In my use case we need to meet both due to our planned applications.
The equipment used to calibrate the furnace shall have accuracy of 1% from its full working range and the equipment used to calibrate that equipment shall have 0.25% accuracy from its full range.
For smaller furnace size than 10 cubic feet, three thermocouples minimum for the heat survey, for larger a minimum nine is required with orientation similar like the atom lattice.
Recording to be taken every 3 minutes from furnace start heating, ramp up to the range we want to calibrate, then recording should be every 2 minutes for at least 10 minutes then record every 5 minutes for at least 30 minutes or until it reaches the set point temperature, then no recordings required during cooling down.
Calibration interval needs to be minimum 3 months if there’s no prior record and up to 1 year once records are established. The 1 year interval may start from calibration date or the date first use after calibration but this start date shall not be more than 3 months from date of calibration.
I’m summarizing is because I need to remember the most important parts of it but I never go without a copy of the actual API specification for reference.
Hope it didn’t bore you, back to our favorite Tuesdays.
Cheers 🥂 MFR