Instruments: [Weekly Question] Discussion question for Week 12 of 2011: Instrument calibration issues

1. How do experienced professionals solve the calibration issues of various instruments in this factory? The process is notified one month in advance for self-inspection; generally, the process cannot remove the instruments to be inspected for calibration – it’s more of a formality, after which the instrument technicians replace and verify the scales. Of course, during each major plant overhaul, we test the important monitoring points on our instruments to ensure smooth operation after the overhaul. 2. **What are the specified and predetermined calibration cycles, and what are the calibration standards?** We classify them into Category A and B for municipal inspection, Category B for self-inspection (every six months), and Category C for self-inspection (once a year or on a one-time basis)

1. Once a permit for value transfer is obtained, initial inspections upon arrival at the factory can be carried out independently; for subsequent weekly inspections, relevant process personnel should be notified one month in advance. Generally, these process personnel will remove the instruments that have reached their expiration date and send them for inspection, after which the instrument technicians will perform the calibration and replace the scales as necessary. If it cannot be sent for inspection in the current period, a written explanation should be provided, with an alternative date arranged or the inspection postponed until the plant’s major maintenance. 2. The calibration cycles are divided into three categories: A, B, and C. Class A requires mandatory inspection, Class B involves self-inspection (every six months, one year, or two years, etc.), and Class C also involves self-inspection (once a year, every two years, or just once)

Our approach is provided for reference: 1. Classify instruments into three categories based on requirements – those that require mandatory calibration, those that can be self-calibrated, and those that are exempt from calibration. Among them, the items that require mandatory inspection are specified by laws and regulations; the items for self-inspection are determined through process discussions, usually focusing on key factors that affect product quality; while items that do not require inspection are those less important aspects, such as the pressure gauge at the pump outlet. 2. Create an electronic form listing all the instruments that need to be inspected, specifying key parameters such as specifications, brand, range, allowable error, and calibration cycle. The allowable error must be determined jointly through discussion with the process engineer. 3. At the end of each month, the system automatically provides a reminder of the correction plan for the following month, which is sent to the using unit and the measurement management unit via email. 4. In the case of external schools, the measurement management unit shall submit the instruments to the Quality Supervision Bureau; for schools that conduct the calibration themselves, a technician shall be assigned to carry out the calibration. 5. The calibration results are entered into the calibration record form, which is then automatically sent for confirmation by the relevant personnel. Once confirmation is obtained, the case is closed and archived

This post was last edited by denghl on 2012-12-1 at 19:41. Our factory doesn’t have any instrument technicians; I’m only trained in process engineering. Whenever the plant stops operating, all I know how to do is adjust the positions of the control valves. As for the other instruments, we usually deal with them only when they start to malfunction. Please reply and let me know what others do in such situations; I’d like to learn from them

Our company has the capability to calibrate most of our own instruments, but those related to mass flow and electromagnetism still need to be sent out for calibration. Ordinary transmitters generally require calibration every 2 years; parameters such as zero point and linearity are checked, and if they fail the standards, the instruments are sent back to the manufacturer or discarded.

1) Calibration of pressure gauges: For those subject to mandatory inspection (such as safety valves at key process points on pressure vessels, and those related to environmental protection), they must be sent to a metrology testing institute annually, with a certification report issued as a result. This is due to safety, environmental protection, and production requirements – it is traceable! For self-inspection types (all of them): once or twice a year during major overhauls or after obtaining production permits. 2) For transmitter types: once a year; for those involved in trade settlements, every six months (and they are also sent to a metrology testing institute)

1. Once a permit for value transfer is obtained, initial inspections upon arrival at the factory can be carried out independently; for subsequent weekly inspections, relevant process personnel should be notified one month in advance. Generally, these process personnel will remove the instruments that have reached their expiration date and send them for inspection, after which the instrument technicians will perform the calibration and replace the scales as necessary. If it cannot be sent for inspection in the current period, a written explanation should be provided, with an alternative date arranged or the inspection postponed until the plant’s major maintenance. # \: N" t6 }6 2. The calibration cycles are divided into three categories: A, B, and C. Class A requires mandatory inspection, Class B involves self-inspection (every six months, one year, or two years, etc.), and Class C also involves self-inspection (once a year, every two years, or just once)

In our unit, the pressure gauges are calibrated by us own after the unit obtains the certification for value transmission; the calibration standard is JJG52-1999； They are classified into categories A, B, and C based on their importance according to the table. Pressure gauges used for pressure testing of boiler and pressure vessel products belong to category A and must be calibrated every six months. Pressure gauges for oxygen, acetylene, etc. fall under category B and need to be calibrated once a year ； The pressure gauge installed on the equipment is of Class C; it is generally calibrated or repaired when maintenance of the equipment is required, during major overhauls, or when the gauge is damaged ； The standard tables used for verification must be sent to the local metrology department for calibration every year ； The measurement transfer license must be reviewed every three years.

In addition to pressure gauges, we have other instruments in use, such as the temperature control devices on welding material drying ovens and the instruments used in welding equipment; for these, we invite a calibration laboratory to come to the site every year for calibration, and they then issue a calibration report.