Verification and Analysis

Sample of Methods to Satisfy Verification Requirements

So, your parts have gone through the precision cleaning process, but how do you know and how does your customer know they are truly clean? And how does your customer know they are going to stay that way until their intended use? Performed early in the cleaning process, black light inspection indicates whether much of the hydrocarbons have been removed. Black light (ultraviolet light) inspection shows the cleaning process is proceeding according to procedure. Prior to the start and at critical points in the process, NTS technicians perform a series of visual inspections checking for foreign objects, slag, unexpected weld-scale, discoloration, and any other indication to take additional cleaning measures.

A great majority of NTS clients call out for particulate analysis and non-volatile residue readings as the primary verification standards. NTS follows the preferred, manual count sampling method for verifying particulate matter. Technicians collect particulate from strictly regulated amounts of effluent samples taken from the cleaned part. The rules and laws of gathering such samples would form a book in themselves, but suffice it to say, NTS follows every requirement in gathering the samples and filtering out the particulate. Subsequently, NTS performs gridded microscope examination, and physically counts the particulate. Only highly experienced and trained technicians are qualified to perform this analysis. The manual counting method offers several advantages over automatic methods. Among them are the ability to spot any anomalies (foreign matter deserving further investigation), and the ability to quickly distinguish particulate from fiber.

Non-Volatile Residue Analysis (NVR)

NVR is done via the gravimetric method, essential a series distilling steps culminating in the analysis of the weight of material that did not evaporate. NVR analysis, a widely accepted method of determining whether systems and components are safe for oxygen use, counts not only hydrocarbons, but all other substances (other than particulate). This analysis errs on the safe side - the NVR reading is generally higher than reading for hydrocarbons only.

In some instances clients require knowing the exact reading of hydrocarbons left in the system. Running the test before and after a critical cleaning step, hydrocarbon analysis also helps to determine how well a given cleaning process addresses hydrocarbon removal. NTS performs hydrocarbon analysis using either the FTIR (Fourier Transfer Infrared spectroscopy method) or the IR method.

Gas Bomb Sampling

The gas bomb sampling method provides a way of gathering gaseous medium from vessels or enclosed spaces that for one reason or another should not be subjected to effluent, or could not be properly dried wetting. NTS has extensive experience gathering gas bomb samples - we will be happy to perform this analysis per request.

With aqueous cleaning processes taking the lead in precision cleaning, halogen sniff test isn't as common as it was just a few years ago. However, if your cleaning process absolutely demands that a chlorinated solvent such as freon be used, it's good to know NTS not only has a supply of freon but will gladly perform halogen sniff test to verify the complete absence of freon in the cleaned, dried part.

Conversely with water and aqueous based cleaners being widely used as cleaning agents, many specifications require dryness verification by taking a dew point reading. NTS uses clean, dried and heated nitrogen for purging as well as one of our vacuum bake-out ovens to make sure parts are thoroughly dry. Although a dew point reading is occasionally required for smaller, cleaned and dried components in-house, the dryness verification method is almost always employed on large systems in field service applications.

To assure that parts and systems remain clean and dry, NTS follows all precautions spelled out in cleaning specifications and processes. These may include approved packaging materials like polyethylene, nylon, Aklar, flanges, and blankets of inert gas pressure on closed systems. Every potential entry into the component of system receives our seal and a certification tag, and in some instances, desiccants, and moisture indicators are included between protective barriers for an extra measure of protection.

Contact NTS today for more information!

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