Holiday Detectors - Albuquerque Industrial
Holiday Detectors - Albuquerque Industrial


 
Frequently Asked Questions

FUNCTION All Holiday (Porosity) Detectors
OPERATING PRINCIPLES - High Voltage Units
-PRINCIPLES
-USAGE
-COMPLIANCE
-MAINTENANCE AND SAFETY
OPERATING PRINCIPLES - Low Voltage Units
USAGE - Low Voltage Units
PCWI Compact High Voltage Crest Meters


FUNCTION All Holiday (Porosity) Detectors

Q1. What is the function of PCWI Holiday Detectors?
A1. They are test instruments that detect and indicate the location of pinholes and bare spots (Holidays) on non-conductive coatings, linings or films that have been applied for corrosion protection on metal and concrete surfaces.

Q2. What types of non-conductive coatings are applied in corrosion prevention?
A2. Thin epoxies, vinyl, paints, polyethylene, rubber, porcelain, enamels, etc., hot applied coal tar, asphalt and heavy mastic materials. Most anti-corrosive coatings are of a dielectric material and in order to detect defects through these surfaces a suitable test voltage is applied.

Q3. What is corrosion and how is it caused?
A3. Corrosion is the gradual wearing away to destruction of material. It can be caused by atmospheric exposure or by chemical reaction with corrosive agents - hence the necessity to apply complete sealing coatings to eliminate moisture permeable defects.

Q4. When would a PCWI Porosity Detector be used?
A4. They would be used in both pre and post installation by the contractor (manufacturer), to confirm the efficiency of his original sealing coat, and by the maintenance engineers in periodic examinations.

Q5. In what industries is corrosion of major concern?
A5. Because corrosion is of serious concern over almost all aspects of industry, both operationally and cost-wise, a short list of major industries would include: Mining; Fabrication; Engineering and Construction; Paint Companies; Oils and Petrochemicals; Municipal and Government Authorities such as City Councils, Electricity, Water and Sewage, Defense; and others.

Q6. How is the testing of coatings by PCWI Holiday Detectors cost effective?
A6. For newly constructed tanks, pipelines and other installations where corrosion prevention coatings have had to be applied, specifications will normally call for a specific coating to a specific thickness. With the use of a PCWI Detector in verification of the competency of the sealing coating, the contractor can be assured that his coatings responsibility has been met: In terms of cost effectiveness, with the low capital and operating costs of PCWI Detectors, the contractor will have an element of freedom from claims at a very low price.

OPERATING PRINCIPLES - High Voltage Units

PRINCIPLES

Q1. On what principle do PCWI Porosity Detectors operate?
A1. The unit is a low frequency high voltage detector that delivers a stabilized pre-set pure DC output via a probe to an inspection electrode. As the electrode moves over the coating surface, if it encounters a pin hole or bare spot, a small current flows actuating a visible (non-hazardous) spark at the point of contact and a visible and audible alarm in the unit. A neon alarm in the probe handle provides 360 visibility to the user.

Q2. How is the applied voltage pre-set?
A2. The voltage required is pre-set manually on the unit to a minimum level determined by the thickness of film of the coating product and its generic type i.e.: Rubber, Vinyl, Epoxy etc. Detailed instructions are set out in the unit Operator Handbook. It is important to follow these instructions in setting voltages as some surfaces have a much higher dielectric strength than others - consequently offering a high resistance to the conduction of electricity. Applied test voltages should only be sufficient to detect faults, otherwise overstressing of the dielectric strength may occur with possible surface rupturing.

Q3. What are the minimum and maximum film thicknesses that can be tested with PCWI Detectors?
A3. This depends on the type of coating applied. Australian Standard AS3894.1-1991 states a minimum of 150m - see Operator Handbook for coatings/voltages relationship. Refer to Operating Instructions.

Q4. It has been said that AC Porosity Detectors offering output ranges from 5 to 30kV at 1.5mA are preferable to direct DC units at high voltages, because direct DC Detectors may experience excessive voltage drop due to special conditions of testing, location, weather, testing object, or coating thickness etc. It is further stated that unlike high voltage direct DC types, with AC there is no danger of residual voltage discharges. How does this relate to PCWI Detectors?
A4. They have a voltage sensor that holds the voltage to the desired level.

Q5. Do the PCWI Detectors provide the same voltage automatically on various pipe diameters without resetting and what is the tolerance?
A5. Yes - the feedback circuit automatically adjusts for this.

Q6. Can a PCWI Detector be supplied with a mains power pack suitable for varying AC Voltages e.g.: 100, 110, 200/240v etc.?
A6. Yes - although any 1 amp 12 volt lead-acid battery charger will be adequate.

Q7. Do damp coatings or moist and humid conditions affect the operation of the PCWI Detector?
A7. As wet surfaces are generally conductive, this could affect the unit operationally. Atmospheric moisture is unlikely to do so. Some user preference exists for DC pulse units over direct DC units under wet operating conditions. This choice could be misleading, however, because the loss depends on the size of the electrode and the possible conductivity of the moisture. These circumstances could cause the test voltage to drop to such an extent that there is insufficient test voltage to locate faults.

Q8. In relation to the PCWI DC Detector, what is the function and limitations of an AC Detector?
A8. These are generally used for the testing of rubber coatings in excess of 1.5 mm thickness. Because they have a high dielectric constant, they tend to overheat with prolonged use and should only be considered, useful for intermittent use. They are considered a crude method with erratic output voltage.

Q9. What checks are available on the functioning of the PCWI Detectors?
A9. A range of tests can be undertaken by employing the appropriate PCWI Detector Crest Meter. Details are available in Crest Meter brochure and Crest Meter Operator handbook. (i.e.: Voltage output and visual display; Continuity of leads etc.)

Q10. Is the PCWI Detector wired for earphones?
A10. Yes.

Q11. Can the PCWI Detector be operator belt mounted?
A11. No - the unit is supplied with an adjustable harness for waist, chest or shoulder mounting. The waist mounting is equivalent to a normal belt position.

USAGE

Q1. Can the PCWI Detector be kept in continuous service?
A1. Yes! The PCWI Detector has a slip out battery pack that is interchangeable. The battery pack can be fully recharged in 10 hours via the charger and the unit can also operate off mains power via the Charger.

Q2. Is the high voltage application destructive to any of the generally used sealing coatings?
A2. No! The applied voltage to the coating is non-destructive, provided the voltage applied is within the parameters set down in the Operator Handbook for the type and thickness of coating.

Q3. It is noted that the PCWI Detector employs wire brush inspection electrodes and not wet sponges. What are the advantages of the wire brush electrodes and the limitations of the wet sponge electrodes?
A3. Wire brush electrodes are faster to use, larger areas can be covered and there is no contamination from the water. Wet Sponge (cellulose) electrodes are used in low-voltage detectors, having an output of less than 100 VDC. The wet sponge method is not satisfactory for the detection of other than gross faults in thin film coatings, and is unsuitable for use where thicker coatings in excess of 150m have been applied.

Q4. PCWI offers a maximum internal and external pipe-brushes at 20" (500 mm). Can brushes of greater diameter be provided to complement the Detector?
A4. Brushes larger than 20" (500 mm) are too large to handle; hence we do not offer brush sizes in excess of 20". Coils are substituted when larger pipes are tested. Note: All coil sizes can be used in place of brushes.

Q5. Under what conditions are Carbon filled silicone-rubber brush electrodes of advantage?
A5. These can provide longer life but require the application of higher voltages.

Q6. Are PCWI wire brushes interchangeable or compatible with competitive detectors and vice-versa?
A6. Yes, with suitable adapters, which PCWI can manufacture to suit.

Q7. Will wire brush electrodes insure good inspection even in corners and around irregular shapes where pinholes or bare spots (holidays) are likely to occur?
A7. Yes! PCWI Detectors can accommodate a complete range of brushes (see Brochure for illustrations).

Q8. It is stated that under practical conditions, it is impossible to obtain an absolutely uniform thickness of an applied coating to a metallic surface, due to unevenness, mill scale or other surface blemishes. Using a "dry testing technique" by applying a high test-voltage to locate faults over the thickest section of the film, the thin areas of film could be ruptured due to excessive test voltage, even though these thinner film areas are perfectly homogeneous. Under these circumstances wet sponge testing utilizing a low voltage can be effective - True or false?
A8. This is False! Rupturing will only occur if far too high a voltage is applied when testing. Passing the electrode over a test panel with similar (thinner) coating thickness will quickly determine whether the voltage is set to a level that will cause rupturing in the thinner areas.

Q9. Can cable makers use the PCWI Detector for testing? Does this require a cable tester electrode box?
A9. Yes - this box can be made on special order.

Q10. Can the PCWI Detector be used in the testing of flaws in Heavy-Duty glass?
A10. This depends on the thickness of the glass and the voltage required.

Q11. Can the PCWI Detector be used in the testing of asbestos cement substrates?
A11. No - most of the cementious products are conductive.

COMPLIANCE

Q1. What certifications of compliance do PCWI Detectors carry?
A1. Conforms to Australian Standard AS3894.1-2002, ASTM G62-87 (1998), NACE RP0274-98, NACE RP0490-2001, NACE RP0188-99, ASTM D4787-93 (1999), JIS G-3491, JIS G-3492, ANSI/AWWA C214-89, ANSI/AWWA C213-94, ISO 2746:1998 & AS3894.1-2002

MAINTENANCE AND SAFETY
Note: It is critical that the Operators Handbook is read and fully understood before the unit is turned on.

Q1. What operator safety precautions are required?
A1. Safety precautions are shown in the Operator Handbook in detail and should be followed. As with all high voltage test equipment it should be operated by responsible, trained and authorized Personnel.

Q2. The Operator Handbook recommends the wearing of rubber gloves!
A2. These are recommended as a safety precaution.

Q3. Does the PCWI Detector carry a safety switch incorporated in the test probe handle? This is not shown in the probe handle diagram in the operator handbook.
A3. No - the momentary switch on the front panel serves the same purpose.

Q4. Is the PCWI Detector completely sealed against dirt, water and corrosion to ensure a high degree of reliability?
A4. The unit is completely sealed against dirt and dust but it is not possible to make it completely waterproof.

Q5. What is the battery life expectancy?
A5. Dependent upon usage: The manufacturer rating is four (4) years.

Q6. What warranty is provided with the unit?
A6. All equipment sold by PCWI is guaranteed for one (1) year from date of purchase provided the instrument has not been modified, misused or abused, excluding batteries, probes, brushes and leads - which are subject to wear. Procedures for any guarantee claim are set out in the Operators Handbook.

Q7. What information is given about "Troubleshooting" maintenance on site?
A7. The Operator's handbook sets out Symptoms - Causes - Solutions - for on-site maintenance.

Q8. If on-site maintenance is inadequate and repair becomes necessary what prompt service is available for repair and recalibration?
A8. A full range of replacements is always available and quick return to service is assured.

OPERATING PRINCIPLES - Low Voltage Units (Wet Sponge Method)

Q1. On what principle does the low voltage wet sponge unit operate?
A1. The low voltage instrument employs a cellulose sponge as an inspection electrode. When moistened with water, the electrode is moved over the coated surface under inspection; when the electrode passes a void or bare spot, moisture from the wet sponge (electrode) penetrates the coating making contact with the conductive substrate, resulting in a drop in electrical resistance. As a result, a small current flow activates an audible alarm enabling identification of the defect location.

Q2. Is the applied voltage user selectable?
A2. Yes, each unit has three settings: 9; 67.5; and 90 volts.

USAGE - Low Voltage Units

Q1. What is the most general usage for Wet Sponge Detectors?
A1. Wet Sponge Detectors are generally used extensively to check the surface continuity of very thin applied coatings - less than 150m (i.e.: whitegoods) where potential for rupturing of the coating could occur with high voltage units.

Q2. Can Wet Sponge units be used on thicker coatings?
A2. Yes! But the test process will be slower because of the greater penetration time. Prewashing the coating surface may speed this up.

Q3. Will Wet Sponge electrodes ensure good inspection in corners and around irregular shapes?
A3. Yes. The flexibility of the sponge ensures good inspection.

PCWI Compact High Voltage Crest Meters

Q1. What is the function of the PCWI Compact Crest Meter?
A1. The Crest Meter has the following functions:
1. To test the output of the PCWI Compact Porosity (Holiday) Detector and to verify the voltage on the visual display.
2. To test the continuity of the leads and to verify the voltage on the visual display.
3. To test the PCWI Compact Detector under load with an applied voltage - this test verifies all earth leads and connections, and partially loads the system.
4. To test the PCWI Compact Detector under full load.
This test verifies all earth leads and connections, fully loads the system, indicates pull down voltage and displays actual test voltage. This test is as per Australian Standard 3894.1-1991 for setting test voltages.

Q2. What certification does the PCWI Compact Crest Meter carry?
A2. Certification is an option, however both the Crest Meter and the DC Probe can be supplied as checked against a NATA certified Crest Meter.
 

 
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ABQ Industrial L.P. • 21 Waterway Ave. Suite 300 • The Woodlands, TX 77380 - USA • Tel: 888-275-5772 / 281-516-9292