67 Signs and Causes of Equipment Malfunction
Learning Objectives
Identify signs and isolate causes of malfunction and list corrective actions.
A sign AND cause of equipment malfunction is miscalibration.
Calibration
Using measuring equipment to measure something of known value to see if the measuring equipment is accurate.
Calibration Needs in a Food Plant:
- All equipment and instruments used for ensuring safety, quality, sanitation, and regulatory compliance must be calibrated.
- Calibration ensures the equipment readings are accurate and give control of the process.
- Can contract with the external supplier or conduct in-house
- Needs to have in-house support and management even if contracted.
To achieve this:
- Develop effective procedures for calibration
- Document the procedures in SOPs
- Maintain records of calibration activities, including corrective actions
- Verify to ensure that procedures are being followed
- Put someone in charge
The following is an example SOP documenting the procedure of calibrating a scale. This document is accessible at:
PROCEDURE FOR CALIBRATING, STANDARDIZING, OR CHECKING EQUIPMENT
Revised 06/16
PROCEDURE #46
Equipment Checked: Scales (Balances)
Reference Documents: NIST Handbook 44, AASHTO M231, ASTM E617, ASTM C138
Purpose: To provide instructions for checking the accuracy of scales to be used in area and project labs. All scales shall be checked annually.
Inspection Equipment: Suggested standard weights (checked against calibrated scale) 100g, 200g, 5kg, 10kg, 20kg.
Tolerance: The allowable tolerance throughout the range checked shall be equal to or less than 0.1% of the test load. The allowable tolerance for Platform scales used to determine fresh concrete unit weight shall be equal to or less than 0.3% of the test load.
Procedure:
- Set up the scale in a location away from drafts or excessive air movement.
- Level the scale, and if weighing underwater, observe that the apparatus is free of any obstruction that may affect its movement.
- Perform Span Check:
Place the verification weights in the center of the scale. Record the weight to the readability of the scale.
Confirm repeatability by placing one of the weights on the scale a second time to obtain the same weight. Confirm that the reading returns to zero when the weights are removed.
- For weighing devices with a capacity of up to 1,000 grams, the suggested verification weights are 100g and 200g. External scale calibration weight shall be 200g.
- For 12kg weighing devices, suggested verification weights of 5kg and 10kg. External scale calibration weight shall be 10kg.
- For 30kg weighing devices, suggested verification weights of 10kg, and 20kg. External scale calibration weight shall be 20kg.
- For platform weighing devices used for standard density determination, the suggested verification weights are 10kg and 20kg.
Note: It is desirable to perform additional checks on scales for accuracy after they have been installed in the construction field lab. Not all verification weights are required for additional field checks.
- Perform Cornerload Check:
Place the weight in the center of the scale and re-zero the scale.
Place the weight in the four locations (Front/Back, Left/Right) as indicated on the Calibration Sheet. Record the weight of each reading.
- For 12kg and 30kg weighing devices use a verification weight of 5kg.
- If any readings indicate out of tolerance, perform external scale calibration, if applicable, as per the scale instruction Manual and repeat steps 3 and 4, or remove the scale from service until it can be recalibrated.
- Record results on Balance or Scale Calibration Sheet.
The following video demonstrates many different calibration tests that can be done:
Equipment Requiring Calibration
- Any type of equipment that is designed to check or measure something
- Sensors
- pH meters, water activity meters, flow meters, and any other type of meter
- Timing devices
- Pressure gauges
- Scales
- Metal detectors
- Magnets
- Any other specialized control instrument
Some examples include thermometers, thermostats, thermocouples and any other temperature or recording measuring devices.
Calibration Requires:
- A list of all of the measuring and controlling equipment that directly affects the safety of a food product
- The specific frequency of calibration required for each instrument/equipment
- A means to identify the completion of equipment calibration
- Trained persons to conduct calibration or service
- Consistent records
It is crucial that the employees are properly trained when calibrating and managing equipment failures and maintenance. Untrained persons can contaminate food or the environment, use improper materials, damage equipment, and tools, and cause equipment malfunction.
See the following fact sheet for a summary of calibration.
Corrective Action in Case of Contamination
If food has been inadvertently contaminated during maintenance activities:
- Protect other food in the area: remove or cover it, or other appropriate action
- Notify the quality control department and applicable regulatory authorities
- In consultation with QC and the regulatory authority, inspect the contaminated food and decide how to handle it, depending on:
- Extent and kind of contamination
- Type and amount of food
- Find out how the contamination happened by investigating the incident. Questions to keep in mind are “who, what, when, where, how and why”
- Take corrective action(s) to prevent the problem from recurring:
- Retraining
- Modifications to equipment or facility
- Replacement of materials
- Other actions
- Communicate findings and corrective action to everyone concerned
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