Page: 1 of 16 TABLE OF CONTENTS SECTION PAGE NO. 1.0 Introduction 2 2.0 References 2 3.0 Personnel Qualification and Certification 3 4.0 Forms 3 5.0 General Requirements 3 6.0 Inspection & Examination 6 7.0 Inspection & Acceptance Standards 12 8.0 Discontinuity Marking 12 9.0 Reports and Documentation 13 10.0 Calibration and Material Certification 13
Page: 2 of 16 1.0 INTRODUCTION 1.1 This specification defines the procedures and materials for magnetic particle inspection of ferromagnetic materials used in the detection of surface and/or subsurface discontinuities. The sensitivity of this examination method is greatest for surface discontinuities and becomes less sensitive with increasing depth of subsurface discontinuities. 1.1.1 When required by contract and a copy supplied, customer specifications or procedures may supersede this specification provided the customer specification is more conservative than this document and the codes referenced within. 1.2 This procedure is intended to define the requirements of magnetic particle inspection with the use of portable equipment, using either the continuous or residual method with wet or dry, visible or fluorescent particles. 1.3 Magnetic particle inspection may be applied to raw materials, semi-finished material, finished material, or welds, regardless of heat treatment or lack thereof. 1.4 Areas to be examined shall be specified on the engineering drawings or process specifications. 2.0 REFERENCES Undated references shall be in accordance with the latest accepted code edition and addenda. For dated references, only the edition that is cited applies. 2.1 Easton Engineering & Inspection PLLC EEI-QA-10 EEI-QC-10 Quality Assurance Manual Quality Control Manual 2.2 American Society of Mechanical Engineers ASME B&PV Section V Article 7, Magnetic Particle Examination, 2015 ASME B&PV Section V Article 25, SE-709, Standard Guide for Magnetic Particle Testing, 2015 ASME B&PV Section VIII Div. 1, 2015 2.3 Military Standards MIL-STD-45662A Calibration System Requirements (Replaced by ISO 10012-1) MIL-STD-1949A Magnetic Particle Inspection (Replaced by ASTM E1444-91) 2.4 American Welding Society (AWS) AWS A2.4 Standard Symbols for Welding, Brazing, and Nondestructive Examination 2.5 American Society for Nondestructive Testing (ASNT) SNT-TC-1A 2011 Qualification and Certification of Nondestructive Testing Personnel
Page: 3 of 16 3.0 PERSONNEL QUALIFICATION AND CERTIFICATION 3.1 Personnel performing magnetic particle inspection shall be qualified and certified in accordance with SNT-TC-1A (2011) as specified by EEI-QC-10. 3.2 Records of personnel certifications shall be maintained on file by Easton Engineering & Inspection and are available upon request. 4.0 FORMS EEI-F-MT-10A Magnetic Particle Inspection Report 5.0 GENERAL REQUIREMENTS 5.1 Equipment/Material Conformance 5.1.1 Equipment and materials shall conform to the requirements of ASME Section V, Articles 7 and 25, SE-709 (see Table 1). TABLE 1 MATERIALS MANUFACTURER COLORS MANUFACTURER TEMPERATURE Magnaflux Red #8A Yellow #2 Fluorescent Black 7HF White Contrast Paint WCP-2 5.2 Magnetizing Equipment 600 F 500 F 40 F to 120 F 60 F to 120 F 40 F to 120 F 5.2.1 The magnetizing equipment used to process parts for inspection shall be either portable prod units or portable yoke units. 5.2.2 The magnetizing power of yokes shall be verified prior to use each day the yoke is used. The magnetizing power of yokes shall be verified whenever the yoke has been damaged or repaired. 5.3 Magnetic Particles 5.3.1 Dry Particles 5.3.1.1 If dry particles are used, the color of the particles shall provide adequate contrast with the surface of the part being inspected. 5.3.1.2 Dry particles are to be used as supplied and be applied with a dusting bulb or powder blower directly onto the surface of the part being examined. Particle will not be collected and reused due to contamination.
Page: 4 of 16 5.3.1.3 Dry particles will not be used if the surface temperature of the part exceeds manufacturer s specifications. 5.3.1.4 Examination shall be conducted in a well illuminated area using visible light as described in paragraph 5.5. 5.3.2 Wet Particles 5.4 Black Light 5.3.2.1 If wet particles are used, the color of the particles shall provide adequate contrast with the surface of the part being examined. White contrast paint may be used to enhance visible particle indications. Wet particles will not be used if the surface temperature of the part exceeds manufacturer s specifications. Particles may be either fluorescent or nonfluorescent. Fluorescent particle examination shall be conducted in a darkened area using a black light as described in paragraph 5.4 of this procedure. Nonfluorescent particle examination shall be conducted with visible light as described in paragraph 5.5. 5.3.2.2 Wet particles shall be suspended in a vehicle such as oil or water at an approved concentration for application to the surface of the part by spraying, flowing or pouring. Concentration of bath shall be verified using a settling test (except spray cans) as follows: fluorescent particles 0.1-0.4 ml/100 ml bath; nonfluorescent particles 1.2-2.4 ml/100 ml bath. If the bath concentration is below recommended strength, weak particle indications will be produced, or possibly no indication will appear; therefore, defects will not be detected. If there are too many particles in the bath, indications may be masked by heavy background buildup. To ensure uniform distribution of wet particles it is essential to shake all aerosols and containers thoroughly before use. Aerosol cans are affected by temperature change. Spray can pressure drops at lower temperatures and rises at higher temperatures. Temperatures below 60 o F may result in insufficient pressure for adequate material performance. 5.4.1 Black lights shall be used when conducting examinations using fluorescent particles. Wavelength of the black light shall be in the UV A range with a peak of 365 nm. 5.4.2 The black light intensity at the surface under examination will be measured at least once every 8 hours and whenever work location is changed, using a black light meter. Black lights shall achieve a minimum of 1000 µw/cm 2 on the surface of the part being examined throughout the examination. Visible or white light shall not exceed two foot-candles (20 Lux) so as not to interfere with detection of fluorescent indications. 5.4.3 Mercury-Vapor based black lights shall be turned on and allowed to warm up for at least 5 minutes prior to examination. The minimum of 5 minutes will also be used for adaptation of the eyes in the darkened area prior to examination. LED based black lights do not require a warm up time, however operators should still allow for eye adaptation.
Page: 5 of 16 5.4.4 Glasses - Inspectors performing fluorescent MT inspection shall not wear glasses with permanent tint or photo chromic (light sensitive) lenses which change color in sunlight because these lenses darken in ultraviolet light and inhibit the ability of the inspector to see fluorescent indications. This does not prohibit the use of lenses treated to absorb UV light. 5.5 Visible Light 5.5.1 Visible light shall be used when conducting examinations using nonfluorescent particles. 5.5.2 The visible light intensity shall be measured at least one time prior to examination or whenever visible light conditions change, using a visible light meter. Additionally a previously verified and documented light source may be used. A minimum light intensity of 100 Foot-candles (fc) or 1000 Lux (Lx) is required to ensure adequate sensitivity during the examination and evaluation of indications. 5.5.3 The light source, technique used, and light level verification is required to be demonstrated, documented, and maintained on file. 5.6 Safety 5.6.1 Safety glasses, gloves, respirators, and appropriate protective clothing shall be worn as applicable. Follow the precautions listed below: - Avoid prolonged or repeated contact with skin. - Avoid prolonged or repeated breathing of vapors. - Do not take internally. - Wash thoroughly after handling and before eating or smoking. 5.6.2 Adequate ventilation shall be provided especially when using oil-based carriers and aerosol products. 5.6.3 Never puncture, heat, or burn spray cans; store at less than 130 o F; keep out of direct sunlight. Spray cans are under pressure and an explosion hazard exists. 5.6.4 National Fire Protection Association (NFPA) Rating - MAGNAGLO Prepared Bath 14AM: Health 1, Flammability 1 (Aerosol Flammability 4), Reactivity 0. MAGNAGLO 14A Redi- Bath: Health 2, Flammability 0, Reactivity 1. MAGNAFLUX Dry Method Powder: Health 1, Flammability 0, Reactivity 0. 5.6.5 Ground Fault Circuit Interrupters (GFCI) must be used with yokes supplied with power cords. 5.6.6 Black Light intensity on unprotected skin or eyes should not exceed 1000 W/cm 2. Never look directly into an ultraviolet light source. Inspect filters before each use, cracked or broken filters shall be replaced immediately. Broken bulbs can continue to radiate UV energy and shall be replaced immediately. Bulbs contain trace amounts of mercury and must be disposed of properly. Never touch the area around the bulb, many ultraviolet lamps become very hot and can cause burns.
Page: 6 of 16 5.7 Field indicators shall be used when necessary to verify the adequacy or direction of the magnetizing field. For the dry powder method a Magnetic Particle Pie Field Indicator shall be used. For the wet particle method a Quantitative Quality Indicator (QQI) / Artificial Flaw Shim shall be used. 5.8 Particle Application 5.8.1 Dry magnetic particle applicators shall be a small rubber bulb type or magnetic powder blower. 5.8.2 Wet magnetic particle applicator shall be Magnaglo Hand Sprayer P/N 14769 or similar. 6.0 INSPECTION & EXAMINATION PROCEDURE 6.1 Areas to be inspected shall be specified by the customer drawings or specifications. Drawings specifying magnetic particle inspection shall be in accordance with AWS A2.4 nondestructive test symbols. 6.2 The customer shall provide suitable illumination in the examination areas. Portable drop lights or equivalent shall be provided. A darkened area for the use of fluorescent particle inspection shall be established if and when they are used. 6.3 Surface Preparation 6.3.1 Prior to inspection, surfaces to be examined and 1 inch on both sides of the area shall be free of lint, oil, grease, loose sand or rust, paint, slag or other extraneous matter that could interfere with the formation and interpretation of magnetic particles pattern. 6.3.1.1 Detergents, organic solvents, descaling solutions, paint removers, vapor degreasing, or ultrasonic cleaning methods shall be used to clean the surface. Chlorinated solvents will not be used on parts consisting of tight crevices. 6.3.2 Surface or contour irregularities shall be removed to the extent that they will not interfere with interpretation of the test results. Unusual surface conditions shall be noted on the inspection report. 6.3.3 If required, all openings shall be plugged or masked to prevent accumulation of magnetic particles or other matter where it cannot be completely removed by suitable means. 6.4 Method 6.4.1 Continuous method - The examination shall be performed while the current is on before, during and after the particles are applied. The continuous method shall be used whenever possible. 6.4.2 Residual method - The examination shall be performed after the current has been discontinued.
Page: 7 of 16 6.5 Magnetizing Current 6.5.1 Magnetizing currents shall be used as follows: a) AC - Alternating current (Sine or Modified Sine Wave). b) DC - 3 phase full-wave rectified AC current. c) DC - Straight current. d) HW - Single phase half wave rectified AC current. 1) AC is most effective for surface defects. 2) AC is not effective for subsurface defects. 3) HWDC shall be used for subsurface defects. 4) HWDC gives less penetration than straight DC. 5) HWDC dry method gives greatest sensitivity to subsurface discontinuities. 6.6 Inspection Technique Requirements At least two separate examinations shall be performed on each area. During the second examination, the lines of magnetic flux shall be approximately perpendicular to those used during the first examination. A different technique for magnetization may be used for the second examination. Circular magnetization shall be used before longitudinal if demagnetization is required. One or more of the following magnetization techniques shall be used: Prod method. Yoke method. Longitudinal magnetization method. 6.6.1 Magnetization shall be accomplished by portable prod type electrical contacts pressed against the surface to be examined. See note 1. The sequence shall be as follows: a) If white contrast paint is used apply an even thin film and wait one minute to allow the film to dry before applying magnetic particles to the test surface. b) Position the prods on the surface to be examined 30 to 50 degrees of the center axis of the weld or object. Prod spacing shall not exceed 8 inches and may be reduced to 3 to accommodate geometric limitations. See sketch 1 for prod placement guide. c) Switch on the magnetizing current either to DC or HWDC. The current shall be 100 amps minimum and 125 amps maximum, amp/inch of prod spacing for thickness of sections ¾ or greater. For sections less than ¾ thickness, the current shall be 90 to 110 amp/inch of prod spacing. d) Apply the magnetizing current when both prods are making good contact. e) Apply the dry magnetic particles with an applicator bulb in a manner that a light uniform dust-like coating settles onto the surface with the current on. Wet particles shall be applied from an aerosol can or approved spray container. f) Remove the excess dry particles with an empty applicator bulb or equivalent.
Page: 8 of 16 g) Switch off the magnetizing current and remove prods from the part. h) Evaluate any magnetic particle indications as per paragraph 7.2. i) Relocate prods to adjacent areas of weld and overlap inspection areas by one inch to insure total coverage. Repeat steps A through G until all areas have been examined. j) Repeat steps A through H with the prods positioned approximately 90 from the original position. k) Standards of acceptance shall be specified as per paragraph 7.2. l) Demagnetize part as per paragraph 6.7., if required. m) Post clean all surfaces when required and remove all masking materials from holes as required. n) Arc burns shall be removed by the customer by grinding as required. o) Complete the Inspection Report as per paragraph 9.1. NOTE 1: Magnetizing Field Adequacy When it is specified by the customer, the adequacy or direction of the magnetizing field shall be verified by using a magnetic field indicator as in paragraph 5.7. When using the indicator, an acceptable flux or field strength is indicated when a clearly defined line of magnetic particles forms across the face of the indicator when the indicator is placed on the object to be inspected and the current and particles are applied. When a clearly defined line of particles is not formed, or is not formed in the desired direction, the magnetization technique shall be changed or adjusted. TABLE 2 PROD PLACEMENT GUIDE PROD SPACING (INCHES) APPROXIMATE DISTANCE FROM WELD CENTERLINE (INCHES) 8 2 3/4 7 2 3/8 6 2 5 1 3/4 4 1 3/8 3 1
Page: 9 of 16 6.6.2 Yoke Method - Magnetization shall be accomplished by portable yoke contacts pressed against the surface to be examined. This method shall only be applied to detect discontinuities that are open to the surface. The sequence of inspection shall be as follows: (also see note 1 of paragraph 6.6.1.) a) If white contrast paint is used apply an even thin film and wait one minute to allow the film to dry before applying magnetic particles to the test surface. b) Position the yoke on the surface to be examined 30 to 45 degrees of the center of the axis of the weld or object. Yoke spacing shall not exceed 8 and may be reduced to 3 to accommodate geometric limitations. c) The magnetizing method shall be either alternating or direct current electro-magnetic yokes. AC yokes shall have a lifting power of at least 10 lbs at a maximum pole spacing to be used. DC yokes shall have a lifting power of at least 40 lbs. at the maximum pole spacing to be used. d) Apply the magnetizing current by depressing the on/off switch on the yoke. e) Apply the magnetic particles in a manner that a light dust-like coating settles onto the surface with the current on. Wet or dry particles shall be used as applicable. f) Remove the excess particles indications with an empty applicator bulb. g) Switch off the magnetizing current and remove the yoke from the part. h) Evaluate the magnetic particle indications as per paragraph 7.2. i) Rotate the yoke 90 degrees from the original position and repeat steps C through G. j) Relocate yoke to adjacent areas of weld and overlap inspection areas by one inch to insure total coverage. Repeat steps C through H. k) Post clean all surfaces when required and remove all masking materials. l) Complete the Inspection Report as in paragraph 9.1. 6.6.3 Longitudinal Magnetization Technique - Magnetization shall be accomplished by passing current through a multi-turn fixed coil or cable that is wrapped around the part or section to be examined (see note 1 in paragraph 6.6.1.). a) If white contrast paint is used apply an even thin film and wait one minute to allow the film to dry before applying magnetic particles to the test surface. b) Mount the object on a suitable fixture and wrap the cables around the part with on/off switch in circuit. c) The magnetizing current shall be DC or HWDC. Current shall be determined by using the formulas below where:
Page: 10 of 16 6.7 Demagnetization L = Length of the part in inches D = Diameter of the part in inches I = Coil current in AMPS N = Number of turns of the wrapped coil (3, 4 or 5) K = Constant, either 35,000 or 45,000 Also, D shall be maximum cross-sectional diagonal for noncylindrical parts, and L cannot exceed 18 for calculation purposes. 1. Parts with L/D ratios equal to or greater than 4: N x I = 35,000 (L/D) + 2 2. Parts with L/D ratios less than 4 but not less than 2: N x I = 45,000 L/D 3. If is not practical because of size or shape to use (1) or (2) above, adequate magnetizing amperage shall be determined using the magnetic field indicator. d) Set the current on the machine and apply the magnetizing current by depressing the on/off switch. e) Apply the magnetic particles in such a manner that a light uniform dust-like coating settles onto the surface with the current on. Wet or dry particles shall be used as applicable. f) Remove the excess particles with an empty applicator bulb. g) Switch off the magnetizing current. h) Evaluate any magnetic particle indications as per Paragraph 7.2. i) Relocate cable to adjacent areas of weld and overlap inspection areas by 1 to insure total coverage. Repeat steps C through G until all areas have been inspected. j) Standards of acceptance shall be specified as per paragraph 7.2. k) Demagnetize parts as per paragraph 6.7., if required. l) Post clean all surfaces when required and remove all masking materials from holes as per paragraph 6.8. m) Complete the Inspection Report as per paragraph 9.1. When residual magnetism in the part could interfere with the subsequent processing or usage, the part shall be demagnetized any time after completion of the examination. Demagnetization shall be required only if specified in the drawings, specification or purchase order. When required, an
Page: 11 of 16 acceptable level of residual magnetism and measuring method shall be specified as it is difficult to remove all residual magnetism. 6.7.1 Unrequired Demagnetization - Demagnetization is not usually necessary in the following cases: a) On parts of soft steel where retentivity is low. b) If, after magnetic particle inspection, the part is to be heat treated to approximately 1400 F thus completely demagnetizing the part. c) On large castings, weldments or vessels where residual fields will have no material effect. d) If the part is to be magnetic particle inspected again in another direction at the same or higher amperage. 6.7.2 Required Demagnetization - Demagnetization is necessary in the following cases: a) When strong residual fields will interfere with subsequent operations as welding or machining. b) When the part is a moving member or is exposed to a moving part of an assembly and may deposit or accumulate magnetizing particles and cause excessive wear. c) Where leakage fields may interfere with nearby instruments which work on magnetic principles. d) Where residual fields may interfere with proper cleaning of the part. e) Where the part is to be magnetized for inspection at a lower magnetizing force in a different direction. f) Where specified by the code, drawing, specification, or purchase order. 6.7.3 Method of Demagnetization - Demagnetization shall be accomplished either by diminishing AC current or DC current which is diminished and continuously reversed. Methods of demagnetization shall be as follows: Coil Demagnetization a) Place the part in the field of an AC coil and hold there as the coil is subjected to smaller and smaller amperages to zero current flow. Small parts shall be kept close to the wall of the coil where the strongest field exists. b) Place the object in an AC coil of fixed current and gradually withdraw the part to about 4 foot. c) Large parts shall be wrapped with cables to effectively form a coil which is subjected to AC diminishing current.
Page: 12 of 16 Yoke Demagnetization a) AC yokes shall be used for local demagnetization by placing the legs (poles) on the surface, moving them around the area, and slowly withdrawing the AC yoke while it is still energized. b) DC yokes shall be used for local demagnetization by placing the legs (poles) on the surface, slowly withdrawing and continuously reversing the direction of the legs 180 o while it is still energized. 6.7.4 After demagnetization, parts shall be verified with a magnetic field indicator at several locations. The indicator shall be placed as close to the surface of the part as possible and checked for fields both perpendicular and tangent to the surface. The part shall be demagnetized again if the maximum deflection of the indicator exceeds ±3 gauss. 6.8 Post cleaning shall be performed as specified in drawings, specifications or purchase orders. Post cleaning shall be specified when magnetic particle materials could interfere with subsequent processing or with service requirements. 6.8.1 Parts shall be cleaned by the following methods: a) Compressed air to blow off unwanted dry magnetic particles. b) Drying of wet particles and subsequent removal by brushing or compressed air. c) Removal of wet particles by flushing with solvent. Demagnetization may be required to ensure ease of solvent cleaning. 7.0 INSPECTION & ACCEPTANCE STANDARDS 7.1 Personnel performing and interpreting indications or test results of magnetic particle inspection shall be certified Level II or Level III. 7.2 The standards for acceptance/rejection criteria shall be specified on the engineering/customer drawings, specifications, purchase orders, or construction code. 7.2.1 All discontinuities will be recorded as per paragraph 9.1.2. 8.0 DISCONTINUITY MARKING 8.1 Unless otherwise specified, rejected areas shall be marked with a permanent, contrasting color marker in the defective areas. 8.2 If specified, discontinuities shall be recorded / preserved by utilizing one of the following methods: a) Photograph. b) Sketch. c) Transfer tape method.
Page: 13 of 16 9.0 REPORTS AND DOCUMENTATION 9.1 A Magnetic Particle Inspection Report (EEI-F-MT-10A) shall be completed for each inspection. It shall be signed by a certified Level II or III and a copy of the report forwarded to the client. 9.1.1 The inspection report shall define the inspection technique used. A sketch may be included to clarify the technique or inspection area. 9.1.2 Nonrejectable indications shall be recorded only as specified by the referencing code section, whereas all rejectable indications shall be reported on the inspection report. As a minimum, the type of indications (linear or rounded), location and extent (length or diameter or aligned) shall be recorded. 9.2 Records shall be retained for a minimum of three years. 10.0 CALIBRATION AND MATERIAL CERTIFICATION 10.1 All equipment shall be calibrated in accordance with MIL-C-45662A. 10.2 The frequency of calibration shall be once a year or sooner if necessary. 10.3 All calibrated equipment shall be provided with a calibration certification label. All calibrations are recorded and maintained in the Easton Engineering & Inspection Maintenance and Calibration Database. Easton Engineering & Inspection form EEI-F-QA-10E; Equipment Calibration Log is available upon customer request. 10.4 Magnetic Particle inspection yokes shall be calibrated at least once a year, whenever yokes are damaged or repaired, or when required by customer specifications. 10.5 Lifting Power - Place Yoke legs on the channeled side of the test bar at the recommended spacing. Energize the yoke in either AC or DC mode and lift the test bar. Alternating Current (AC) electromagnetic yoke shall have a lifting power of at least 10 pounds at the maximum pole spacing that will be used. Direct Current (DC) or permanent magnetic yokes shall have a lifting power of at least 40 pounds at the maximum pole spacing that will be used. 10.6 Visible and black light meters shall be calibrated at least once a year or whenever the meter has been repaired. Calibration will be performed using standards that are traceable to the National Institute of Standards and Technology (NIST). 10.7 Each batch of magnetic particle material shall be certified by the manufacturer. The certification shall include the batch number and statement of specification compliance, and will be kept on file by EEI and made available upon request. Note: Where magnetic particle materials are supplied by the client, it is the responsibility of the client to acquire and retain material certifications. 10.8 Water Break Test Evaluates the surface wetting performance of water-based carriers. Flood the clean surface of the part and observe the surface film. If a continuous film forms over the entire surface, sufficient wetting agent is present. If the film of suspension breaks exposing the surface of the component, insufficient wetting agent is present and the bath shall be adjusted or replaced.
Page: 14 of 16 10.9 Wet Particle Concentration, Condition, and Contamination - Gravity Settling Method When a new batch of particle bath is prepared and periodically thereafter the particle concentration shall be measured by the gravity settling method. The gravity settling method applies to either oil or water suspension. 1. Agitate the bath for a minimum of thirty minutes to ensure even particle distribution. 2. Place a 100 ml sample of the agitated bath in the ASTM pear-shaped centrifuge tube. 3. Demagnetize the sample to prevent the particles from clumping together during settling. 4. Place the centrifuge tube in the stand at a location free from vibration and leave undisturbed for 30 minutes for a water bath and 60 minutes for a petroleum-based bath, to allow particles to settle out. 5. Read the volume of settled particles. A black light must be used for fluorescent particles. Do not include dirt particles in the centrifuge readings. 6. Concentration of bath shall be as follows: Fluorescent particles 0.1 0.4 ml/100 ml bath Nonfluorescent particles 1.2 2.4 ml/100 ml bath. 10.10 Particles shall be examined for brightness and agglomeration. Fluorescent particles are evaluated under ultraviolet light and visible particles under white light. The brightness of the test particles shall be compared with an unused reference solution that was saved at the time the bath was first prepared. The brightness of the two solutions should be relatively the same. The particles should appear loose and not lumped together. 10.11 Contamination is checked by noting the amount of foreign material such as dirt, paint chips and other solids that settles out with the particles in the centrifuge tube. Dirt particles usually settle on top of the magnetic particles. Differences in color, layering or banding within the settled particles would indicated contamination. Dirt will not fluoresce under a black light. In non-fluorescent particles, the appearance of dirt is very different than particles. Dirt will be coarser and irregular in shape. If foreign matter exceeds 30 percent of the settled solids the bath shall be replaced. The liquid portion of the bath shall be inspected for oil in a water bath and water in a petroleum-based bath
Page: 15 of 16 Centrifuge Settling Volume Shaded areas shows typical settling range
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