As we ring in the new year 2025, a significant change is coming for several heating, ventilation, air conditioning and refrigeration (HVACR) systems that are currently used in both residential and commercial applications. The 2020 American Innovation & Manufacturing (AIM) Act is bipartisan legislation that was signed into law. The AIM legislation empowers the Environmental Protection Agency (EPA) to reduce the production and consumption of hydroflourocarbons HFCs by 85 percent by the year 2035. (more…)
Hazard can be defined as a potential source of harm. Machine safeguarding seeks to protect people from these potential sources of harm. Often distance from a hazard will play a key role in providing a means of protection.
One would often think of distance as it relates to the location of a barrier guard from a hazard. ANSI B11.19, Performance Criteria for Safeguarding, defines safety distance as “the distance a safeguard is installed from a hazard such that individuals are not exposed to a hazard.” An example from ANSI B11.19 of the recommended distance of a slotted opening in a barrier guard from a hazard is shown in the table below:
Table 1: Minimum Slotted Opening vs Distance from Hazard – From ANSI B11.19
This information will help assess if the opening present in a barrier guard will meet the values established in a consensus standard such as ANSI B11.19. These distances and dimensions should be carefully considered when designing fixed barrier guards.
However, when more sophisticated means such as safeguarding devices are used to protect an individual from a hazard, distance takes on a different meaning. ANSI B11.19 defines a safeguarding device as “a device that detects or prevents inadvertent access to a hazard.”
A light curtain is a well-known presence-sensing device. ANSI B11.19 defines a presence sensing device as “a device that creates a sensing field, area or plane to detect the presence of an individual or an object.” An example of a light curtain is shown below.
If the individual utilizing a machine protected by the light curtain breaks the plane created by the sensing device, then the hazard behind must be rendered safe before it can be reached. For example, a hazardous motion must stop to prevent an injury to the individual that breaks the plane. Here the distances noted in Figure 1 above may not be applicable and a different method of determining the safety distance should be considered.
ANSI B11.19 states in section 6 General safeguarding requirements, 6.3 Safety distance:
“When required by this standard, the guard or safeguarding device shall be located a distance from its associated hazard such that individuals cannot reach the hazard before cessation of hazardous motion (or situation).”
Here we see that the hazard must be rendered safe before an individual can reach it through the presence sensing device and be injured.
Furthermore, section 8 Safeguarding devices, 8.3 Electro-optical, RF and area scanning presence-sensing safeguarding devices, 8.3.2.3 states:
“The presence sensing device shall be installed at a location so that the effective sensing field prevents individuals from reaching the hazard(s) during the hazardous portion of the machine cycle.
How do we determine this location or “safety distance”? Explanatory information in ANSI B11.19 notes:
“The safety distance calculation is dependent upon the:
Speed of approach of the individual
Total response time of the safeguarding device as stated by the supplier
Response time of the interface
Response time of the control system
Time it takes the machine to stop hazardous motion; and
Depth penetration factor of the safeguarding device.”
Here we see that with a presence sensing device, the value for a safe distance has many facets that must be considered to provide for safe operation by a user. ANSI B11.19, Annex D provides a method for determining what a safe distance should be based on factors mentioned above.
Safeguarding is often not a one size fits all activity. Careful consideration should be given to the safeguarding method chosen and proper attention paid to the specific design details. Careful selection and proper design details will lead to a safer machine.
Chad Jones, PE, CFEI, CVFI, CMSE has a Bachelor of Science in Mechanical Engineering from Clemson University. Chad has over 25 years of engineering experience including mechanical, process, and manufacturing engineering. This work has included equipment design, machine safeguarding, cost estimating and safety compliance. Chad also has over 10 years of commercial, industrial, and residential HVAC and plumbing design experience. A lifelong auto and motorcycle enthusiast, Chad is accomplished in the maintenance, repair, and modification of vehicles and engines. Chad is a Certified Fire and Explosion Investigator, Certified Vehicle Fire Investigator, and IFSAC certified Firefighter II in Greenwood County, South Carolina.
No kidding, I’m passionate about fire protection! To prove it, I could tell you stories about the damage I have seen from various failures from freezes to fire pump cooling to what happens when a fire hydrant’s weep holes are clogged…. But instead, I will tell you about smoke alarms!
Although it’s still new in my head, my home just turned 10 years old. The decade has seen the replacement of two household appliances and at least one HVAC repair… now what? A paint and décor refresh? Maybe, but that’s not what the fire protection engineer is thinking! It’s time to replace the smoke alarms! (more…)
A proper collision scene documentation, lovingly referred to as a scene doc, will make or break the investigation… guaranteed! While not necessarily all inclusive, here are a few evidence collection / documentation techniques that have served me well over the years.
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As the holiday season nears, thoughts turn to wonderful home-cooked meals with family. Few things in life are more pleasurable than a traditional holiday turkey feast. Yet for an unfortunate few, holiday meal time can turn tragic if a turkey frying accident occurs. While fried turkeys may be tasty, many fire safety experts feel that the reward is not worth the risk. (more…)
“Was a dark stormy night as the train rattled on…” Anybody? 1985? Scarecrow? Come on… this was when Cougar was still a Mellencamp! Ok… it was called Grandma’s Theme… you’ll have to look that one up… but as I sat down to write this blog on the environment, that song kept running though my head. If you look it up, it will have a similar effect… just a little warning.
In our last installment of the 9-Cell Collision Matrix let’s travel down the wet, slippery slope of environmental factors that can contribute to car crashes, and maybe take a closer look at the things around us, at or near our crash scene that may reveal some important clues. (more…)
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Photo by Mark Turner
Let’s begin with the most basic human element at the root cause of car wrecks, our old friend inattention. Inattention… a vast word that encompasses many lackadaisical conditions. The daydreaming 16-year-old in math class, the radio knob turner, the back seat talker, the quarter pounder with cheese eater, and perhaps the most offensive, the cell phone user. All very dangerous behind the wheel, and one very dangerous to your future… as it turns out, you will always need good math skills… ask me how I know? Driving is of course a divided attention endeavor, (more…)
How far away from a hazard should you stay? Your parents or grandparents would probably have told you to stay far away, but what are you to do when a hazard is present, and you must work around or near the hazard? And what exactly is a hazard? ISO 12100 Safety of machinery – General principles for design – Risk assessment and risk reduction defines a hazard as a “potential source of harm.”
Where would a designer of a machine or product start if they wished to protect the user from a known hazard? Consensus standards are a great place to begin the quest for safety. (more…)
In a previous blog post, we began to delve a little deeper into the vehicle aspect of the 9-Cell Collision Matrix by taking a look at tires. Let’s now take a closer look at the very diverse and interesting topic of Event Data Recorder (EDR) data. (more…)
In my two previous blogs, we first discussed wet sprinkler systems (Wet), the most basic and most common fire system type followed by dry sprinkler systems (Dry), which are a bit more complicated. Ratcheting up another level, in this last edition on sprinkler systems, let’s take a look together at preaction and deluge systems. These can be complex and variable, so we’ll operate at the 30,000 ft level. (more…)
