Thursday, June 30, 2016

Corrosion in Geothermal Energy Production

Geothermal Energy Corrosion

Geothermal energy is a sustainable clean energy source, as it draws upon the heat that is naturally being emitted from the Earth’s core into the upper crust. Like other sources of renewable energy, there are many technical challenges posed with the continuous harvesting of the planet’s rising energy. One issue that is unique to the conditions of geothermal power generation is the fast-paced corrosion of materials.

Corrosion occurs when a refined metal begins to return to a more stable form due to the influence of certain chemicals in the environment. For geothermal energy, this can be quite a problem, since the materials are continuously exposed to steam and hot brine in an underground production well, in which the steam spins a turbine that converts heat energy into usable electricity. However, while corrosion in some cases can be surely anticipated, the corrosive potential of geothermal energy is incredibly varied, and is dependent on the materials selected for constructing the well, turbines, and other equipment, in addition to the chemicals present within the geothermal fluid and steam.

Polyethylene and Plastics in Geothermal Energy

Polyethylene is the most commonly used material for geothermal pipe, and it is often found in the strengthened form of high-density crosslinked polyethylene. To create a system out of this material, according to ANSI/CSA C448 SERIES-16 - Design and installation of ground source heat pump systems for commercial and residential buildings, fittings for crosslinked polyethylene piping should “be protected against corrosion by selecting corrosion-proof non-ferrous materials or by applying a liquid-tight polyethylene or crosslinked polyethylene corrosion protection covering.” Using this material guarantees lack of rust on geothermal pipes, but it is not without its drawbacks.

Corrosion in Geothermal Energy

Polyethylene pipe has good physical characteristics, as high-density crosslinked polyethylene pipe is given a 50-, 75-, or even 100-year warranty by manufacturers, but it cannot be connected or glued like other types of pipe materials, instead needing to be heat fused. However, the process of heat-fusion isn’t too complicated, and leaves secure seals. Different guidelines that oversee the installation of polyethylene and other plastic pipe systems in geothermal energy plants are covered in the following documents:

Geothermal Fluid

Some of these standards, while intended to prepare the synthetic piping material for installation, address testing procedures for exposing the materials to the aqueous solution of geothermal fluid. Geothermal fluid is a naturally occurring mineralized mixture of pressurized water and steam heated underground to 200–325 °C, and these materials are drawn up from a production well.

As stated in IEC/TS 61370 ED. 1.0 B:2002 - Steam turbines - Steam purity, “high purity steam is required to ensure steam turbine operation with a high degree of efficiency, output, and availability. Impurities can form deposits, which can lead to loss of efficiency or output or to corrosion.” The chemical composition of the steam used to spin the turbine in a geothermal plant can lead to corrosion that impacts the rotation of the turbine blading or the structure of the production well. Excessive concentrations of sodium, silica, or chlorate can assist the corrosion process.

Geothermal Energy Corrosion

The corrosion rates of most materials increases as the pH of the fluid decrease. Geothermal fluids that are generally cooler are of high pH (8-10), while warmer waters are more neutral. However, this trend greatly varies among geothermal fluids of extreme temperatures, which exist with pH as low as 2 and as high as 12. When considering the corrosivity of fluids, it is important to look at the temperature and not just the composition of the fluid itself.

Metal Materials in Geothermal Energy

While the corrosivity of the geothermal fluid solvents isn’t too great of an issue with synthetic piping, it does pose serious dangers for metal-based materials. ANSI/CSA C448 SERIES-16 states that “it is imperative that pH, corrosion inhibitors and other essential water chemistries be maintained throughout the life” for steel and copper piping systems. It is incredibly important that these metals, when used in production wells with corrosive geothermal fluids, are part of a well maintained system.

The choice of steel as piping material was a major problem with earlier geothermal plants, since iron corrodes quite easily from oxidation. However, many of these have been offset with nickel alloys, which are far less reactive with the geothermal brine solution.

All geothermal piping systems, regardless of their material composition, should be in compliance with ASME B31.1-2016 - Power Piping.

Growth of Geothermal Energy

Overcoming the challenge of managing corrosion is essential for a more widespread usage of geothermal energy. Unfortunately, the source of power, despite having a very high capacity factor, does not get as much attention as other renewable energy sources, such as wind or solar. Despite this, the International Energy Agency (IEA) predicts that geothermal energy has the potential to increase tenfold by 2050.

Corrosion in Geothermal Energy

It’s true that geothermal energy is more reliable and useful in certain areas, such as Iceland, which actually derives 25 percent of its electricity from the source of power due to its placement on a fault line, but that doesn’t meant that one cannot harvest geothermal energy in areas of the globe that don’t have those advantages. Take, for example, the energy load in the United States, for which geothermal only accounts for 0.4 percent. Shallow ground temperatures are relatively constant throughout the nation, so geothermal heat pumps, which easily heat and cool homes by capturing the underground heat, can be used almost anywhere. In addition, there are immense opportunities for the areas near fault lines.   

Expansion of geothermal power not only requires perfection of its technology, but also knowledge and acceptance of the benefits it can bring.

Further Reading

Wednesday, June 29, 2016

ANSI/ISEA Z89.1 - Industrial Head Protection

ANSI/ISEA Z89.1-2014 Industrial Head Protection

The human brain is an incredibly complex organ, bearing a mass amount of folds and wrinkles just so its large surface area can be packed into the head. A system that is so essential to a person’s basic functions needs appropriate protection, something that is accomplished by the cranium and meninges, a system of three membranes beneath the skull. However, the natural protection given to our brain is only suitable for minor hazards, and is insufficient for scenarios in which an individual is exposed to greater dangers. In industry, workers wear hardhats to protect their heads.

According to the OSHA standard 29 CFR 1910.135, “employees working in areas where there is a possible danger of head injury from impact, or from falling or flying objects, or from electrical shock and burns, shall be protected by protective helmets.” However, the standard does not specifically cover any criteria for the protective helmets, instead requiring that they comply with ANSI/ISEA Z89.1-2014 - American National Standard for Industrial Head Protection.

As a general rule of thumb, industrial hardhats should not only absorb the impact of blows to the head, but should also serve as insulators against electric shocks, be water resistant and slow burning, and shield the scalp, face, neck, and shoulders. ANSI/ISEA Z89.1-2014 prepares hardhats for any of these anticipated forces through rigorous testing of the helmets.

In addition to testing procedures for flammability, force transmission, apex penetration, wetness, and temperature, among others, ANSI/ISEA Z89.1-2014 classifies the different kinds of protective helmets according to their uses. Manufacturers should mark compliant helmets with the ANSI/ISEA Z89.1-2014 designation, along with the applicable class and head size range, a value that is also listed in the standard.

ANSI/ISEA Z89.1-2014 Industrial Head Protection

Despite the security given to workers from the standard, there are still incidents of traumatic brain injury, especially in construction, in which it caused 2,200 fatalities between 2003 and 2010. However, according to a survey about worksite accidents and injuries conducted by the Bureau of Labor Statistics (BLS), 84 percent of all workers who suffered head injuries were not wearing head protection.

Because of this irresponsibility in preparing for unanticipated head injuries, ANSI/ISEA Z89.1-2014 makes user recommendations to ensure the added safety that comes from wearing a hardhat. Some of these allow the wearer to make use of the helmet’s protection under unique conditions. For example, the standard addresses reverse wearing of the helmets, for which the applicable helmets must be properly tested and marked.

As we discussed in our past post, Preparing Outside Workers for the Summer Heat, workers should not alter their safety garments and equipment to enhance their own comfort, as it can compromise the integrity of the precautionary wearables. The standard advises along these lines, stating that the users should never alter or modify the helmet for any purpose, as it will limit its reliability. Related to the heat, it is also important for users to remember that long-term exposure of heat can degrade a helmet.

Tuesday, June 28, 2016

Speech Intelligibility Index

Speech Intelligibility Index

Intelligibility of speech is important for comprehending the amount of speech information that is both available and audible to a receiver during disruptive conditions that could prevent comprehension of a spoken message.

Speech intelligibility index (SII) is a measure, between 0 and 1, that represents the intelligibility of speech under a variety of adverse listening conditions, such as noise masking, filtering, and reverberation. Speech cues interrupted by fewer of these conditions will be more available to the listener, and will thus have a higher SII value.

First established by ANSI/ASA S3.5-1997 (R2012) - American National Standard Methods for Calculation of the Speech Intelligibility Index, SII is defined as the “product of band importance function and band audibility function, summed over the total number of frequency bands”. In symbols, this can be understood as:

Speech Intelligibility Index Formula

Where n is the number of SII computational bands, while Ii and Ai are the values of the band importance function and the band audibility function associated with the frequency band designated by the summation index i. The band referred to is a frequency band, which designates the high and low frequencies in which a sound is emitted. This concept is essential for establishing the basis of speech in its regular conditions.

Workers at Bell Telephone Laboratories in the 1960s conducted the earliest examination of the interaction of different noises influencing speech-recognition performance. Their extensive work led to the definition of the acoustical index, known as the articulation index (AI). The calculation for the AI was first presented in the original version of the S3.5 standard, ANSI/ASA S3.5-1969.

However, the 1997 revision of the document replaced articulation index with speech intelligibility index. While these two terms are very similar, actually deriving from the same philosophy of understanding disruptions and their influence on the delivery of speech, they contain some differences that made SII more suitable for the newer version of the document. Specifically, the standard now allows for the input of various variables, due to the support of its wider framework. This makes SII more applicable because AI is incapable of handling the necessary variety of inputs.

Speech Intelligibility Index

ANSI/ASA S3.5-1997 (R2012) - American National Standard Methods for Calculation of the Speech Intelligibility Index addresses the method for calculating the physical measure of speech intelligibility index. The document provides the means by which a user can estimate all of the input values, such as equivalent speech spectrum level, equivalent noise spectrum level, and equivalent hearing threshold level, that become part of the final calculation.

Through the guidance of ANSI/ASA S3.5-1997 (R2012), SII may be computed through four different methods: critical frequency band, one-third octave frequency band, equally contributing critical band, and octave frequency band. The requirements and formulas needed for carrying out these calculations are addressed in the standard.

The applications of this standard are plentiful, as it is stated in the document that it extends to all listening conditions where the specified input variables exist. This has many different uses, such as in research, e.g. for determining the impact that hearing loss has on the audibility of speech, or for testing PA systems, which can be present in a variety of venues, public or private.

Due to the complexity of the topic, there are three different programs available for calculating speech intelligibility index that make use of the guidelines covered in this standard, However, before using the software, the Acoustical Society of America (ASA) recommends that users familiarize themselves with the standard. The programs can be downloaded from here: Programs for SII

Monday, June 27, 2016

Achieving Quality Through Six Sigma

Six Sigma ISO 13053

Six Sigma is a disciplined quality management process that brings about improved business practices and quality performance within an organization through the elimination of defects. Specifically, Six Sigma strives for no more than 3.4 defects per million opportunities. While it is a younger method for assessing the quality performance of organizations, Six Sigma derives from some of the best business practices of the past that have consistently stood superior to others.

The concept of quality has been a necessity since the early days of industrial mass production, but it wasn’t heavily managed until the 1920s, when Walter Stewhart sparked the age of statistical quality control. In the United States, statistically based levels of quality control became a requirement, but most companies still focused on volume and output instead of quality improvement and cost reduction.

After World War II, experts on this method of quality control attempted to introduce their ideology to war-torn Japan in an effort to rebuild the nation’s infrastructure. Interestingly, Japanese professionals chose to follow a different path in terms of quality. As the Americans focused on increased volume and maintenance of a lucrative market share, the Japanese centered their quality management operations on defect elimination and time cycle reduction. This made the Japanese products cheaper and, ultimately, more successful in the global market.

In response to being outperformed by Japan, the U.S. industry began making efforts to improve upon the nation’s quality management processes. The U.S. government introduced the Malcolm Baldrige National Quality Award, which was meant to reward innovations in quality. In its introductory year, it was granted to Motorola for the invention of Six Sigma.

Six Sigma was established in the 1980s by Motorola engineers who wanted to improve the traditional quality levels of the time that measured defects only within thousands of productsMeasuring defects was a new concept for the American markets, as the practice was responsible for the Japanese competitive advantage. Over the next decade, it was popularized by industry leaders, such as former GE chair and CEO Jack Welch, and was soon adopted by tens of thousands of companies to enhance their businesses’ performance.

Since this time, there has been a need to provide a standard practice by which Six Sigma can be attained. A strong methodology for completing objectives through Six Sigma is the key factor that allows an organization to reap the system’s benefits.

Six Sigma ISO 13053

According to ISO 13053-1:2011 - Quantitative methods in process improvement - Six Sigma - Part 1: DMAIC methodology, “Six Sigma projects should be undertaken only when the solution to a problem is not known.” The methodology for Six Sigma includes five phases: define, measure, analyze, improve, and control (DMAIC). The ISO 13053-1:2011 standard provides the criteria by which an organization can use the DMAIC methodology to achieve a beneficial goal through the identification of a problem and the execution of its solution.

This standard, in addition to providing a thorough background on the different concepts related to the Six Sigma process, including the formula needed to determine defects, details each of the steps of the DMAIC methodology, demonstrating how they help to achieve the overall goal for the project. Each of these phases is relatively broad, but the standard addresses every aspect within them that can prove beneficial to an organizations efficiency and product. The Six Sigma project specified in the document can be used for any organization in any industry.

ISO 13053-2:2011 - Quantitative methods in process improvement - Six Sigma - Part 2: Tools and techniques adds to the guidelines addressed in the first part of the standard by describing the tools and techniques used at each phase of the DMAIC approach. This provides the user with a stronger understanding on the steps needed to achieve goals with Six Sigma.

Also essential to the Six Sigma methodology, in the “define” stage, is the process of benchmarking to establish a reference point by which the compliant organization can seek self-improvement. This is addressed by ISO 17258:2015 - Statistical methods - Six Sigma - Basic criteria underlying benchmarking for Six Sigma in organisations, which we discussed in length in this previous post: Six Sigma Benchmarking Criteria for Organizations.

It is also important to remember that Six Sigma can be used in complement to another quality management system, such as that specified by ISO 9001:2015. In fact, Six Sigma can be the means by which an organization meets the guidelines specified in ISO 9001. Since much of Six Sigma involves handling uncertainty, it is recommended that compliant organizations make use of a risk management system as well.

Friday, June 24, 2016

ASTM D4169 - Testing Shipping Containers

ASTM D4169-16 Performance Testing of Shipping Containers

ASTM D4169-16 - Standard Practice for Performance Testing of Shipping Containers and Systems provides a uniform basis of evaluating the ability of shipping units to withstand their distribution environment.

Shipping and transport were long used throughout human history as part of distant exchanges, and some type of shipping container has been in use since the utilization of rail- and horse-drawn transport in late Eighteenth Century England. However, modern shipping was conceived in 1955 when Malcom P. McLean, a trucking entrepreneur from North Carolina, bought a steamship company with the idea of transporting entire truck trailers with their cargo still inside. His later realized it would be simpler to have a container that could be lifted directly from a vehicle and into a ship, establishing the system of “intermodalism”.

Intermodalism means that the same cargo, within the same container, could be transported with minimum interruption using a variety of transport modes. These containers were to be moved seamlessly between ships, trucks, and trains. Since this immensely simplified the logistics of the shipping process, this type of container was soon standardized so that it would fit well with other containers on these different modes of transportation. It has been actively used now for 60 years.

The enhanced shipping capabilities that were brought forth from the establishment of this industry standard are one of the primary causes of society’s current state of mass globalization. Prior to the birth of the Internet and other contributing factors of globalization, the standard shipping container made it possible for products and materials to easily spread throughout the planet in ways that were far too difficult before. By assuring their performance, ASTM D4169-16 helps to support the globalized web of individuals, companies, and nations that comprise our society.

ASTM D4169-16 Performance Testing of Shipping Containers

ASTM D4169-16 covers a laboratory testing method that exposes the shipping containers to a sequence of anticipated hazards for their journey. The test specimen to be used should consist of complete shipping containers that are representative of the container system as a whole. This includes the actual cargo contents, but dummy test loads are acceptable under certain conditions.

The standard addresses a wide range of concerns through its different testing procedures. Some of these are applicable to almost any shipping container being used, while others are more specific to a particular usage. For example, the hazard of rail switching, which is tested through longitudinal shock, would not apply to shipping containers that are not transported using railways.

Other hazards that ASTM D4169-16 prepares for include handling, warehouse stacking, vehicle stacking, stacked vibration, vehicle vibration, loose load vibration, environmental hazard, low-pressure hazard, and concentrated impact. The appropriate procedures for these are detailed in the standard.

Thursday, June 23, 2016

Powered Exoskeletons

Powered Exoskeleton for Workers

Tools exist to meet the needs that humans cannot physically accomplish. Industrial practices have always combined the efficiency of tools and the ingenuity of human interactions for any kind of production. However, the creation of the seemingly improbable powered exoskeletons is making it possible to enhance directly a human worker’s strength and efficiency.

A powered exoskeleton is a kind of external attachment that, when worn, enhances the power output of the user without having to increase the amount of energy that they consume. One of the more practical purposes of this power armor is for the military, since it can help to lighten the load that a soldier has to carry. Another use of this bionic assistance is for the disabled and individuals undergoing rehabilitation in hospitals.

However, one major problem that makes it nearly impossible to make a full-blown Iron Man suit is the difficulty with concentrating enough power into the exoskeleton to let it function for a meaningful period of time. According to Esko Bionics, an exoskeleton company, the human body can use up to just 10 watts standing around. Thus, it is very impractical with current technology to design a system that attempts to store a day’s worth of energy. This is troublesome for its usage in the military, which would require continuous reliability from the exoskeleton’s power.

Industry, on the other hand, generally only requires short bursts of power to lift and move objects. The newest developmental product of Esko completely avoids the issue of battery energy storage by designing their exoskeleton to rely completely on counterweights and a sprung arm used on image-stabilizing steadicams. This system makes use of a carbon fiber harness and metal-tube frame running down a user’s legs to translate the weight at the end of the arm through the suit and directly into the ground. However, this system does not work if the user moves a heavy object away from his or her body.

While Esko does not use battery power for its exoskeleton to function, other companies are embracing the challenge. Cyberdyne, a Japanese company with locations throughout Asia and Europe, has created the world’s first cyborg-type robot, called the HAL. HAL (Hybrid Assistive Limb) uses its advanced technology to improve, support, and enhance the wearer’s bodily functions.

With detectors in the exoskeleton that can sense “bio-electric signals”, or the faint signals that leak to the skin after being sent to the muscles from the brain, HAL can recognize the sort of motions that the user intends and enhances them ten-fold. Interestingly, the continuous repetition of the cyberkinetic motions is stored in the brain from feedback signals in the body, which can be the first step in allowing a disabled person to walk again. Additional applications for the HAL include factory work and rescue activities in disaster sites.

Similarly, the robot development branch of Panasonic, Activelink, is working on several robotic powered exoskeletons. The first, called the Power Loader, works by strapping around the user’s shoulder, waist, and one thigh, with four embedded sensors sending signals to the 20 engines in the suit that let a human lift heavy objects while decreasing the stress placed on that user’s back.

Activelink is also developing a much smaller exoskeleton, called the Power Assist Suit AWN-03, which is meant for lifting heavy objects in a factory. While also limiting stress placed on the wearer’s lower back, the Power Assist Suit can reduce weight by up to 15 kg. It features an automatic assist system and has a battery life of up to eight hours.

With a similar purpose, Activelink is also working on an upper body exoskeleton that can help people lift weights of at least 24 kg. Beyond these few examples, Activelink is developing many other robotic exoskeletons, such as the PLN-01 "Ninja" exoskeleton suit, which is designed for steep and rough terrain.

Activelink’s Power Loader gets its name from the similar Power Loader that Sigourney Weaver uses to fight the Xenomorph Queen at the end of Aliens, but Cyberdyne’s HAL is unintentionally linked to the ominous sophisticated computer HAL 9000 from 2001: A Space Odyssey. Interestingly, Cyberdyne is actually the name of the fictional robots company in The Terminator series that led to the singularity Skynet, another coincidence that came from the combination of “cybernics” and “dyne”, a unit of force.

Whether they are aware of it or not, these companies are drawing upon popular culture to bring new ideas to the real world that can lead to innumerable benefits in the near future, as they not only help the disabled but increase efficiency and worker safety.

Wednesday, June 22, 2016

Basic Safety and Essential Performance of Electrocardiographs

IEC 60601-2-25 ED 2 Electrocardiograph

IEC 60601-2-25 ED. 2.0 B:2011 - Medical electrical equipment - Part 2-25: Particular requirements for the basic safety and essential performance of electrocardiographs addresses a standard method for assuring the strong performance of an electrocardiogram (ECG or EKG) used in assessing the muscular and electrical functions of the heart, along with concerns of safety directly related to its use.

The human heart is the core of our bodies, something that humanity has long known, even if the citizens of the past often had a relatively tenuous grasp on the topic. For example, Aristotle identified the heart as a three-chambered organ in the center of the body that served as the seat of intelligence, with the surrounding organs existing to cool the one vital organ.

Today, we know much more about the complexities of the heart, and, due to Willem Einthoven's invention of the first practical electrocardiogram in the early 1900s (for which he received the Nobel Prize in Physiology or Medicine in 1924), medical professionals are able to accurately measure the activity in the four-chambered heart through the non-invasive method of placing electrodes on the patient’s skin. Because of this ability to analyze the organ that grants us life, ECGs must follow a standard practice to prevent any threats to the patient and accurately collect data.

IEC 60601-2-25 ED. 2.0 B:2011 calls for preparation of the ECG machine through appropriate testing of it and its accessories in service activities. These tests should be conducted under appropriate humidity, as specified in the standard, and are intended to calibrate the ECG for accuracy. Tests used to check the voltage of the ECG with the use of a circuit board are thoroughly detailed in the standard.

IEC 60601-2-25 ED 2 Electrocardiogram

The standard also addresses guidelines that help to assure the reliable performance of the ECG, such as the recommended position of the electrodes as they are in use. In addition to covering the general performance of the ECG, IEC 60601-2-25 ED. 2.0 B:2011 also helps to prevent electrostatic discharge and electric transients and bursts that could damage the ECG or compromise its results.
IEC 60601-2-25 ED. 2.0 B:2011 also provides the means to protect against electric shock that could hurt the patient or the professional administering the ECG. In addition, it addresses the mechanical hazards that can come from its use.

ECG equipment that is intended for use under uncontrolled environmental conditions away from a hospital environment, such as in ambulances or air transport, should comply with the content of this standard.

It is also worth noting that this document is intended mainly to address the performance of an electrocardiogram that will ultimately help to provide a diagnosis, and not for the analysis and interpretation of the electrocardiograph results for the determination of that diagnosis. While IEC 60601-2-25 ED. 2.0 B:2011 does include information on the definitions and rules for the measurement of electrocardiograms, further information and knowledge is likely needed.

IEC 60601-2-25 ED. 2.0 B:2011 amends and supplements IEC 60601-1 ED. 3.1 EN:2012 - Medical electrical equipment - Part 1: General requirements for basic safety and essential performance, a general document that covers broader guidelines for the safety and performance of medical equipment.