MacDermid Plc Offshore Div. Particle Analysis And Contamination Control Simon McManus

INTRODUCTION WHY PARTICLE COUNTING IS CARRIED OUT WHAT ARE PARTICLES? AUTOMATIC PARTICLE COUNTERS CALIBRATING A MICROSCOPE COUNTING CONCLUSION

WHY PARTICLE COUNT? PREVENTATIVE MAINTENANCE EXAMINATION OF DEBRIS CHANGES IN CONTAMINATION LEVEL PREDICT FILTER BLOCKAGE AND SYSTEM FAILURE (SEALS, PUMPS AND VALVES)

WHAT ARE PARTICLES? AN INDIVIDUAL UNIT OF PARTICULATE MATTER SIZE AND SHAPE VARY GREATLY WHAT THEY ARE MADE FROM HOW THEY HAVE BEEN FORMED INTRAMOLECULAR FORCES PRESENT

DAMAGE EFFECT FROM PARTICLES SOFT PARTICLES (PASTE, FILTER MEDIA, SEALS ETC.) CAN BLOCK FILTERS. HARD PARTICLES CAUSE ABRASION AND WEAR. THESE ALSO BLOCK FILTERS BUT TO A LESSER EXTENT. HARD PARTICLES INCREASE CONTAMINATION LEVELS.

Polymers and Fibres

Black Metal

Bright Metal

Rust

Silica

AUTOMATIC PARTICLE COUNTERS (APC’s) LIGHT SCATTERING OR OBSTRUCTION USE LIGHT REACTIVE ELECTRONICS TO SIZE THE SHADOW OF PARTICLES OTHERS USE PRESSURE DIFFERENTIAL ACROSS MESH FILTERS OF A SET SIZE

PROBLEMS WITH APC’s IRREGULAR PARTICLES ARE ‘ROUNDED’ TO AVERAGE SIZE LONG FIBRES ARE SEEN AS A STRING OF SMALL PARTICLES GAS BUBBLES AND INSOLUBLE LIQUIDS ARE SEEN AS PARTICLES APC’s HAVE PROBLEMS WITH OCEANIC HW 500 FLUIDS

CALIBRATING A MICROSCOPE THE MICROSCOPE SHOULD HAVE A GRATICULE SCALE THE GRATICULE MUST BE CALIBRATED A CALIBRATED STAGE MICROMETER SHOULD BE USED IN REALITY THIS IS NOT ALWAYS POSSIBLE

FIELD CALIBRATION OF GRATICULES TOTAL FILTER MEMBRANE AREA SHOULD BE KNOWN. STANDARD MEMBRANES ARE 960mm squ EACH INTERIOR SIDE OF ONE SQUARE IS 308µm.

PARTICLE ANALYSIS. ARP598B 100 ml OF FLUID IS USED A MICROSCOPE SLIDE IS PREPARED (FILTER MEMBRANE) AREAS OF THE SLIDE ARE EXAMINED AND CONTAMINATION LEVELS ARE MATHEMATICALLY CALCULATED FOR THE WHOLE SAMPLE SIZES OF 5, 15, 25, 50 AND OVER 100 µm ARE EXAMINED

GENERAL RULES DURING COUNTING TRY TO EXAMINE AREAS OVER THE WHOLE MEMBRANE, DO NOT CONCENTRATE ON THE MIDDLE FEW SQUARES USE THE LARGEST DIMENSION OF THE PARTICLE FIBRES ARE SIZED USING THEIR LENGTH. A FIBRE HAS A LENGTH MORE THAN 10 X ITS WIDTH.

TAKING A SAMPLE TURN ON THE SAMPLE VALVE TO OBTAIN A STEADY FLOW LET HALF A LITRE OR SO FLUSH THE VALVE FLUSH THE SAMPLE BOTTLE AND LID AT LEAST TWICE IN THE STREAM OF FLUID DO NOT TOUCH THE VALVE UNTIL THE SAMPLE HAS BEEN TAKEN.

SAMPLE PREPARATION SAMPLE HANDLING WILL ALWAYS INCREASE CONTAMINATION LEVELS SAMPLING WILL ALWAYS INCREASE CONTAMINATION LEVELS THE CONTAMINATION IN THE SYSTEM IS ALWAYS LESS THAN THE COUNT THE ERROR SHOULD BE KEPT TO A MINIMUM

SAMPLE CARE IF SAMPLES ARE TO BE PACKAGED CHOSE THE PACKING MATERIAL CAREFULLY AVOID BOTTLE LIDS WITH PAPER INSERTS CLING FILM OVER THE TOP OF THE BOTTLE CAN PREVENT DIRT INGRESS

CARE DURING PREPARATION SLIDES SHOULD BE PRODUCED IN A CLEAN ROOM DO NOT BREATH ON OR LEAN OVER THE SAMPLES MAKE SURE ALL THE EQUIPMENT THAT THE FLUID MAKES CONTACT WITH HAS BEEN FLUSHED.

BLANK ANALYSIS PREPARE A BLANK SLIDE USING FILTERED WATER, 100ml +or- 5ml THIS COUNT WILL GIVE AN INDICATION OF BACKGROUND CONTAMINATION THE TOTAL COUNT SHOULD NOT EXCEED 10% OF THE LEVELS BEING INVESTIGATED.

COUNTING PROCEDURE IF DEBRIS DISTRIBUTION IS RANDOM, UNEVEN DISTRIBUTION WILL INVALIDATE THE COUNT. COUNTING IS DONE TO ARP 598 TO GIVE A NAS OR AS CLEANLINESS LEVEL. ERROR IN COUNTING SHOULD NOT BE GRATER THAN 10% BETWEEN OPERATORS OR LABORATORIES

NAS 1638

AS4059 Counts are reported as cumulative rather than interval Optional Smaller size code Numeric Cleanliness Class in a specified Letter coded size.

AS4059