Checks (3) Flashcards
Ammeter Accuracy / Current Output Checks
Equipment ammeter readings are compared to a control test ammeter.
- a shunt (current transformer) monitors the amount of current output provided by the unit when affixed between the units contact plates through the entire “tap” switch or amperage range.
- 6 month intervals
- accurate within +/- 10% (+/- 5% on multidirectional) true value
- plotted on graph (tap setting vs amp values. lines for both test and unit ammeter)
Timer Control Checks
Done with a suitable electronic timer
- 6 month intervals
- current flow / magnetizing shots should be in 1-2 second bursts
- accurate within +/- 0.1 seconds
Quick Break Checks
“quick break” refers to the sudden stopping or ending of magnetizing current, in longitudinal magnetization a quick break can induce eddy currents, causing strong bar end polarity making inspection difficult.
- quantified by how quickly the magnetic field collapses
- oscilloscope
- 6 month intervals
Internal Short Circuit Checks
Setting amperage to maximum setting and activating current with nothing clamped (no conductor).
- any measured amperage on ammeter indicates an internal short circuit - discontinue equipment use
- check periodically or by manufacturer recommendation
Black Light Intensity Check
Verify performance using a calibrated UV intensity meter.
- recommended to check before each use
- ASTM E709 check at intervals not exceeding 1 week and/or every time the bulb is changed
- battery powered lamps must be checked before each use
- 300 to 390nm
- minimum 1000μW/cm²
- ASTM E709 distance during intensity check should be 38cm (15in)
Other Black Light Check Information
- filters checked weekly (max filtering of visible light and harmful UV rays)
- Mercury Vapour Arc Lamps warm up times: some are 2-3min, most 5-15min
- some LED UV-A need warm up minimum of 5min
- intensity checks in darkened area
- adaption time 3 minutes
- maximum visible light should be = or <21.5 lux (2ft candles)
Visible (White) Light Intensity Checks
Visible light intensity should be:
- > 1076lux (100ft candles) at exam surface
- > 538lux for field inspections with non-fluorescent particles
- fluorescent inspections in darkened areas no >21.5lux (2ft candles)
- performed on weekly
(ASTM E709)
Stationary Unit Particle Concentration Check
- Visible bath: 1.2 - 2.4ml/100ml vehicle (optimum: 1.5 - 2.0ml/100ml)
- Fluorescent bath: 0.1 - 0.4ml/100ml vehicle (optimum: 0.15 - 0.20ml/100ml)
Particle additive methods:
- Dry powder (measured)
- Paste (weighed)
both are poured into bath with agitation system running, drawn into pump and dispersed, settling test performed after 10 minutes.
Suspension bath changes from use:
- drag out of particles
- drag out of liquid
- evaporation
- accumulation of contaminants
- objects dropped in tank
- dilution from wet test pieces
Agitation time required when system has been off
- off for >4 hours, 30min agitation time
- off for 30-60min = 10min agitation time
- off for >1 week, 60min agitation + stirring
When the contamination exceeds ___% of the volume of the particle layer, formation of proper indications will be _impeded, and the bath must be discarded.
30%
- as often as 1 week when unit is in constant use
Water Break Check
Ensure suspension provides necessary wetting characteristics, particle dispersion and corrosion protection.
- Conditioned Water vehicles: wet a specimen and observe suspensions appearance on part surface, if it breaks exposing the parts surface or forms droplets, more wetting agent is necessary.
- pH Test of conditioned water vehicles: verified using a pH meter or pH paper
Types of System Performance Checks
- production verification on parts with discontinuities
- fabricated test parts with discontinuities
- test plates
- test ring specimens (ketos ring)
Performance Check - production verification on parts with discontinuities
particle and equipment performance
- discontinuities of known shape, size and placement
