In the previous article we introduced
the type of process
instrumentation required by AMS 2750 revision F depending on the type of the
The 4 new AMS 2750F requirements for process instrumentation
What are the new requirements of the AMS (Aerospace Material Specifications)
2750F for process instrumentation?
- All process instruments (control, recording, over-temperature) must be digital
from June 2022.
- Furthermore, as of June 2022, all recording instruments in addition to being
digital must have a readability of 0.1 °C or 0.1 °F.
- The sensitivity test it is no longer required for digital instruments,
but attention must be paid to additional customer requirements.
- The recording tools used on heat treatment plants should not be
used to record TUS or SAT sensor temperatures unless it can be demonstrated
that the recording channels of the TUS and/or SAT sensors of an integrated system
are separated from the recording system of the heat treatment furnace
and also meet the requirements of the field test instrument.
The last point is an important change.
From this point it follows that in a process recorder set up with separate groups/systems,
they can be associated, individually, for two different purposes:
- process registration and
- field test instrument for SAT and/or TUS tests.
However, it is necessary to establish the hierarchy between the two systems,
defining accuracy and calibration frequencies.
The process instrumentation must allow to detect the temperature values by measuring
the electromotive force (emf).
In the case of multi-channel instruments (e.g. recorders), all used channels
will have to undergo periodic calibrations; those not used must
be suitably identified and inhibited from use.
The calibration of the instruments must be carried out periodically according to
the manufacturer's and internal instructions with reference to the AMS 2750
At least three checkpoints must be carried out choosing the
temperature minimum, average (1/3 average) and maximum in the qualified
operating temperature range, for each type of input.
Let's see an example.
In a vacuum furnace qualified in the operating temperature range
of 600-1200 °C, calibration must be performed at 600-900 and 1200 °C.
The intermediate calibration point can be performed in the range 800-1000 °C (1/3
average), while the minimum and maximum points must correspond exactly to
the minimum and maximum qualified operating temperatures.
The 18 information to always report on the calibration certificate
Which are the the minimum information to be reported on the calibration
- Unique identification of the instrument.
- Make and model of the calibrated instrument.
- Identification of the test tool used during calibration.
- Identification of the type of sensor in use (example, type K, N, etc.) and
shape (example, V, mA, etc.), if the instrument is used for these scales.
- Identification of the position from where the signal was simulated (only
required for the measurement system involving the
- Requested accuracy requirement.
- Data of each calibration point (as found and as left) and data if any adjustments
were made including:
- Nominal test temperature.
- Test tool error (optional or when requested by customer).
- Error of the instrument under test (corrected or incorrect for the error
of the test instrument, when applied).
- Offset correction and modification as found and as left.
- Sensitivity, compliant/non-compliant (applicable to analog instruments only).
- Result of the calibration of the instrument, compliant or non-compliant.
- Any limitations or restrictions of the calibration.
- Date of execution of the calibration.
- Calibration due date.
- A traceability statement to NIST or other internationally recognized standards
- Identification of the technician who performed the calibration.
- Identification of the agency that performed the calibration, if not done
- Approval of the laboratory manager who performed the calibration, if performed
by a third party source.
- User quality organization approval.
In the next article we will deepen the requirements of the AMS 2750 on calibration
instruments, going to illustrate for example the offsets, their classification,
their amount and the necessary training.
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