MEI-C offers independent engineering construction/fabrication oversight services, often referred to as construction quality assurance (CQA), to owners, contractors, and architects.

CQA is required on some federally mandated projects and makes good sense on many critical cost/time, private or municipal projects.

An MEI-C registered professional engineer leads each field inspection team. He reviews all inspection and testing documents, and with his experienced technicians, observes, verifies, and documents (including photographs) all critical construction steps.

Written reports, signed and stamped by our project engineer, are submitted to the client as each project phase is completed.

Upon project completion to the preset requirements, our engineer certifies that all contract and code requirements have been fulfilled.

Our engineers are experienced with construction and fabrication codes and have a sound, common sense approach to quality assurance. We work with the client and his contractors to satisfy the project quality requirements.

We are known throughout the Northwest for our quality control documentation, metallurgical and corrosion failure evaluations, nondestructive testing, chemical analysis, and welding certification and inspection.

Our engineers are experienced failure investigators. Based on their significant experience, they are able to focus on quality problems which may lead to future failures, and advise on preventative measures. It has been our experience that for a CQA investment, the payback in terms of extended service life, reduced downtime, and operation dependability is several times greater than the initial expense.

HDPE Flexible Membrane Liner

An example of a CQA assignment that MEI-C has done in the past is the installation of a flexible membrane liner (FML) on a set of decommissioned liquid waste ponds. The FML was to be a 40-mil thick high density polyethylene (HDPE) geomembrane seamed together by hot welding. The project was mandated by the EPA and the Resource Conservation and Recovery Act, RCRA; it required an independent engineering firm to be on-site to review installation of the FML and to document the quality check points.

MEI-C provided an engineer as the CQA manager and technicians as inspectors; we also provided, as a separate service, our mobile testing laboratory for the daily testing of the FML weld seams. The assignment consisted of daily inspections of the FML material as it was being rolled out over the sandfilled ponds, mapping the serial numbers of the FML placement on the various ponds, and observing and photographing the welding, vacuum testing and repair of the seams. In the mobile laboratory, the first seams of the day from each welding machine were tested for tensile and seam adhesion (peel).

At the end of this project (eight months later), the client had received ten formal reports in addition to the daily reports and certifications required by the EPA--all done without shutting down the operation of the facility. The stack of photographs, reports, and FML specimens was about 5 feet high!

CQA engineering services assure designed-life performance of projects and equipment. CQA guarantees that specifications are followed and quality control is documented. Our CQA engineering staff provide an objective, independent team to ensure the clients' interests.

ANALYSIS AND TESTING OF RUBBER

Many years ago "rubber"was a very particular, mechanically and chemically distinct material. Now rubber-like materials include a wide range of versatile synthetic polymers.

MEI-C is sometimes asked to identify the type of rubber in commercial products. We are also asked to identify particulate contaminants which often contain bits of rubber. In a recent case, black spots were showing up in paper stock. By analyzing the black spots with scanning electron microscopy-energy dispersive spectroscopy, we were able to show that most of the spots were from pieces of rubber which had come off of rollers or seals in the paper machine. The technique provided individual elemental analyses for each spot, and showed that many different types of rubber were contributing to the spots. We were able to sort the spots according to the filler, base polymer, and additive component types, allowing for easier detection of the offending parts.

Because normal rubber has so many components, a detailed chemical analysis will usually pinpoint the source of suspected problems. For example, a recent case of white powder formation or "chalking" on rubber was traced to one component of a three-part antiozonant additive diffusing out to the surface and forming crystals. In another case, failure of a rubber liner and subsequent corrosion of a steel tank was found to be from inadequate rinsing of the tank, which led to incompatible chemicals (hydrochloric acid and chlorine bleach) mixing within the pores of the rubber. The mixing had produced chlorine gas within the rubber, causing the corrosion. In this case, microchemical tests and microscopic observations at different depths below the surface determined the extent of penetration of the chemicals, and revealed where the mixing had occurred.

ADHESIVES AND SEALANTS

Adhesives and sealants, by their very nature, are oftentimes not apparent in a product, largely because they perform their function without exhibiting form. They are a chameleon of the engineering world.

New adhesives and sealants are being developed and are showing up on shelves in stores, both as single products and as components of other products. Some of the newer adhesives are the UV light cure adhesives now being used extensively in manufacturing products such as Post-it notes and removable magazine labels. They also are found in the new self adhesive US postage stamps, new super glues, a wide range of glue gun (hot melt) adhesives, and sprayon aerosol can adhesives.

In general, adhesives are very adaptable. Problems often can be solved by changing either the adhesive type, the adhesive formula, or the surface preparation or curing conditions. Consultation with the adhesive manufacturer is oftentimes sufficient; we get involved when the problems go to court or when independent testing or additional expertise in materials science is needed.

The most common adhesive problem is poor adhesion, or delamination. This type of problem is most often caused by water in one form or other. Wet, damp, or cool surfaces are notoriously difficult substrates. Water can prevent adhesion by reacting with chemicals in the adhesive to either prevent cure or break down other polymers. Even after complete cure, water can creep or diffuse (in the gaseous state) into joints and soften or otherwise damage the adhesive. Often the only good solution is to reformulate the adhesive to make it and the substrate less sensitive to water.

One water-sensitive component now often added is the adhesion promoter, or coupling agent. It reacts with the substrate surface and primes it in the first few seconds of contact, making the adhesive a one step self-priming system. Many paints and coatings are formulated with coupling agents. Coupling agents, because of their high reactivity tend to have limited shelf lives and poor stability.

One odd material we have had experience with is a pourable sealant used in electronics industry clean rooms. The material is poured into troughs which hold the edges of HEPA filters. After pouring, the sealant solidifies to form a gel, which provides a very good leak-proof seal. When a new filter is needed the old filter and sealant can be easily pulled out. Interestingly, the same basic material is also used in Jell-O-like novelty toys.

POLYMERIC COATINGS

A rich variety of polymeric coatings are available today. With each polymer, an assortment of fillers, dyes, pigments, copolymers, and binders or curing agents can be used. The coatings are formulated to optimize performance, ease of application, and safety, while minimizing cost.

Performance-related failures prompt most of our investigations. The types of performance our clients are concerned about are corrosion protection, barrier properties, esthetics, and wear protection. Our services range from routine tests to scientific investigations and research.

We measure corrosion protection with a salt fog spray apparatus, or by electrochemical methods. Barrier properties can be assessed by measuring permeability to various chemicals (oftentimes, just water vapor). Staining or bleaching problems usually require detailed chemical analyses of the stains to elucidate the chemical interactions taking place. Wear performance is commonly measured with a Taber abraser, which is an accelerated wear tester in which grindstone wheels roll on a surface for thousands of revolutions.

Actual failures often are complex. The photograph above right, for example, shows architectural exterior paint peeling off of wood trim after one year of exposure to the elements. In this case, you can see that the type of wood substrate had an influence, as the piece of wood on the left had peeled less than the piece on the right.

The joint between the two pieces is the vertical line in the center). Coating thicknesses in this case were per specifications. However, microscopic examination showed that the primer coat was unduly porous, and was the primary cause for the failure. The primer had likely been applied incorrectly. (for example, by holding the nozzle too far away from the surface).

The photograph on the left shows cracking of new kitchen cabinets which had been finished with a clear coating of lacquer. In this case a hard, brittle top coat was applied on a softer seal coat. This type of cracking, called cold cracking, is most often seen on lacquer or shellac finishes. This failure was caused by an incompatibility between the seal coat and the top coat. Additionally, the seal coat was not sanded sufficiently prior to application of the top coat to provide "tooth" for the top coat, and the top coat had marginal strength in tension.

The thickness of polymeric coatings varies a great deal, depending on the coating material and the application. In a recent project involving coated metal roofing, we found that one side had approximately 0.02 inch (20 mils) of baked-on fluorocarbon polymer coating, while the other side had 0.0002 inches (0.2 mils) of a clear polymer coating. The thin coating was not visible to the naked eye and was even difficult to see with a microscope. Similarly, the aluminum pop can you may be holding has a thin polymeric coating on both the outside and the inside, probably an epoxy-acrylic hybrid polymer. At the other extreme, metal playground structures will often have 1/4 inch of vinyl coating.

Many polymer coatings are actually polymer sheets laid down with or without an adhesive, in which case they are called laminates or thermoformed coatings. Some examples are identification cards, milk cartons, flexible circuit boards, resilient floor tile, food wrappings, and vinyl coatings on wood. Many food packaging materials arelaminates with three or more layers. Automotive finishes often have as many as five layers. We use micro-FTIR spectroscopy and scanning electron microscopy to identify and analyze the layers.

Mark Habel, MEI-C engineering technician, and Cayleen Criswell, a medical laboratory technician, were married 27 November 1996 in Lincoln, Nebraska at the Church of Jesus Christ of Latter-day Saints. Congratulations, Mark and Cayleen!

On 26 November 1996, Dr. D.G. Chakrapani, president of MEI-C, presented a seminar on "High Temperature Metallurgical and Corrosion Failures" for the American Society for Metals (ASM) course on "Introduction to Failure Analysis." The course was organized by ASM International, Oregon Chapter to familiarize ASM members with the practical applications of failure analysis in metallic materials.