All PosiTector 6000 models comply with the IMO MSC.215(82) performance standard for protective coatings in ballast tanks. Contained in this standard is a PSPC 90/10 rule.
The PosiTector 6000 PSPC 90/10 mode simplifies the process of determining pass/fail criteria under the IMO directive. Although developed for maritime applications, this mode can be used by other industries looking for a statistical method of ensuring correct dry film thickness over a surface area.
Begin taking measurements. With each measurement the following occurs...
There are 4 methods for examining the 90/10 batch results:
The PosiTector 6000 90/10 feature is intended to support the PSPC Application Standard, not replace it. It is the responsibility of the user to read and understand the document, and to verify the accuracy of the gage's conclusions.
In this example, 10 measurements have been taken. The last measurement was 340 microns. Both the 90% and 10% rules have failed resulting in a B1 FAIL result. Why?
To find out why the batch PASSED or FAILED, select the Memory-View menu option.
In this example, the user entered a NDFT value of 320 microns.
Use (-) or (+) to review all measurements in the 90/10 batch.
NOTE: In this example, measurements 9 and 10 were both below 288 microns, causing the 10% rule to fail.
The International Maritime Organization (IMO) is a specialist United Nations agency tasked with improving maritime safety and preventing pollution from ships.
Premature failure of protective coating systems is often found in ballast tanks of ships in service and as a consequence will lead to rapid corrosion of unprotected steel. Following coating breakdown it is extremely difficult, if not impossible, to repair or reinstate the coating to new building standard. It is therefore of the utmost importance that coatings be correctly applied at the new building stage. The Committee felt that the best way to achieve this would be the development of mandatory performance standards, including a minimum target life, for ballast tank coatings.
On 8 December 2006, the IMO adopted the new Performance Standard for Protective Coatings (PSPC), as resolution MSC.215(82). This important new standard will also be included in the International Convention on Safety of Life at Sea (the SOLAS Convention).
The PSPC is intended to improve safety at sea by reducing corrosion encountered in steel ships. It applies specifically to the protective coatings used for dedicated seawater ballast tanks in all types of ships, and also in the double-side skin spaces of bulk carriers. The PSPC enters into force for all shipbuilding contracts placed on or after 1 July 2008.
The PSPC sets out requirements for improved procedures and better quality control via increased inspection requirements at all stages within a number of areas including dry film thickness (DFT). It introduces a new performance standard for dry film thickness – the PSPC 90/10 rule.
"90% of all thickness measurements should be greater than or equal to NDFT (nominal dry film thickness) and none of the remaining 10% measurements should be below 0.9xNDFT".
Application practice of recent years appears to have approached the common standard of a 2-coat epoxy system. While different thicknesses are allowed, each coat is usually 160 microns for a total thickness of 320 microns.
"Dry film thickness shall be measured after each coat for quality control purpose and the total dry film thickness shall be confirmed after completion of final coat using appropriate thickness gauges."
The common understanding is that there is no guarantee that the 90/10 rule is perfectly achieved for the entire surface, but that such a sampling method is enough for making a practical judgment. If the sample measurements do not satisfy the criteria, additional spot checks should be taken for any area considered necessary by the coating inspector.
There are several ways to evaluate film thickness with the PosiTector 6000 ...
A large surface usually cannot be characterized accurately by a single measurement. Variations in substrate preparation, painting technique, measuring technique, etc. require an analysis of several measurements taken over a large portion of the surface.
The PosiTector 6000's statistics mode displays individual measurements AND maintains a running average value. It also displays minimum and maximum values.
Advanced (3) versions of the PosiTector 6000 have a 90/10 mode that helps the user collect measurements in conformance with the PSPC standard. Then, based on user-set target thickness, the gage indicates a pass or fail condition.
The PosiTector 6000 has on-board memory into which all measurements are stored. Individual measurements are grouped into a "batch". The gage continually monitors thickness results and reports a pass/fail condition on the current batch as a whole.
Stored results can be viewed on the display, modified or deleted. A formatted printout can be sent to the optional Bluetooth printer. Or all results can be downloaded to a PC using the included PosiSoft software and USB cable.
ASTM D7091 “Standard Practice for Nondestructive Measurement of Dry Film Thickness of Nonmagnetic Coatings Applied to a Ferrous Base and Nonmagnetic, Nonconductive Coatings Applied to Non-Ferrous Metals”
ISO 19840 “Paints and varnishes -- Corrosion protection of steel structures by protective paint systems -- Measurement of, and acceptance criteria for, the thickness of dry films on rough surfaces”
PosiTector 6000 Standard (1) and Advanced (3) gages have a statistics mode. When selected, the gage continuously updates running average and standard deviation calculations. Maximum and minimum values are also tracked while measurements are being taken.
The last measurement can be deleted with the (-) button, while the (+) button clears all statistics.