Failure Modes

The failure mode is the way in which a failure is observed on the failed item. The failure mode describes how the failure occurs and what the malfunction is. For example, an electrical motor is not turning.

ISO 14224 prescribes the following best practice failure modes:

Failure mode type	Failure mode	Suggested failure mode code	Description of the failure mode
Desired function not obtained	External leakage	01-ELU	For example oil leakage
	Failure to connect	01-FCO	Failure to connect
	Failure to rotate	01-FRO	Failure to rotate
	Failure to close on demand	01-FTC	Doesn't close on demand
	Failure to function on demand	01-FTF	Failure to respond on signal or activation
	Failure to function as intended	01-FTI	General operation failure
	Failure to open on demand	01-FTO	Doesn't open on demand
	Failure to start on demand	01-FTS	Doesn't start on demand
	No output	01-NOO	No output
	Plugged or choked	01-PLU	Partial or full flow restriction
	Structural deficiency	01-STD	For example burst, rupture
	Failure to stop on demand	01-STP	Doesn't stop on demand
Specified function lost or outside of acceptable limits	Abnormal instrument reading	02-AIR	False alarm, faulty instrument indication
	Delayed operation	02-DOP	Opening or closing time below specification
	Erratic output	02-ERO	Oscillating, hunting, instability
	Failure to disconnect	02-FDC	Doesn't disconnect on demand
	Faulty output frequency	02-FOF	Wrong or oscillating frequency
	Faulty output voltage	02-FOV	Wrong or unstable output voltage
	High output	02-HIO	Overspeed or output above acceptance
	Insufficient heat transfer	02-IHT	Cooling or heating below acceptance
	Internal leakage	02-INL	Oil leakage
	Low oil supply pressure	02-LBP	Low oil supply pressure
	Load drop	02-LOA	Load drop
	Loss of buoyancy	02-LOB	Loss of buoyancy in idle position
	Low output	02-LOO	Delivery or output below acceptance
	Loss of redundancy	02-LOR	One or more redundant units not functioning
	Parameter deviation	02-PDE	Monitored parameter exceeding limits, for example high or low alarm
	Plugged or choked	02-PLU	Obstructed piping
	Power or signal transmission failure	02-PTF	Power or signal transmission failure
	Spurious high alarm level	02-SHH	For example 60% of the lower explosion limit (LEL)
	Spurious low alarm level	02-SLL	For example 20% of the lower explosion limit (LEL)
	Slippage	02-SLP	Wire slippage
	Spurious operation	02-SPO	Unexpected operation
	Structural deficiency	02-STD	Material damages including cracks, wear, fracture, corrosion
	Unexpected shutdown	02-UST	Spurious stop
	Very low output	02-VLO	Delivery or output far below specifications
Failure indication is observed, but there is no immediate and critical impact on asset function	Abnormal instrument reading	03-AIR	For example wrong oil level indication
	Breakdown	03-BRD	Serious damage for example seizure or breakage
	External leakage - fuel	03-ELF	External leakage of supplied fuel
	External leakage - process medium	03-ELP	External leakage of oil, gas, condensate, water
	External leakage - utility medium	03-ELU	External leakage of water, lubricant, barrier oil
	Internal leakage	03-INL	Internal leakage of process or utility fluids
	Noise	03-NOI	Abnormal or excessive noise
	Overheating	03-OHE	Overheating of machine parts, exhaust or cooling water
	Plugged or choked	03-PLU	Flow restriction due to contamination, objects, wax
	Minor in-service problems	03-SER	Loose or missing items, discolouration, dirt
	Structural deficiency	03-STD	Material damages including cracks, wear, fracture, corrosion
	Vibration	03-VIB	Abnormal or excessive vibration

Also refer to Failure Mode Types.