Awards & Engraving

2018 Laser Engraving Report

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Page 8 of 32

8 n LER 2018 require 1,300 cubic feet per minute (CFM) of exhaust airflow if you are venting to the outdoors as per the manufacturer's recom- mendations. In New York State (based on New York State average monthly tempera- ture and energy prices for 2017 - New York State Energy Research and Development Authority), it would cost you about $2,340 per year to heat and cool the make-up air. Alternately, you can use a professionally manufactured RFE unit to extract and filter the air from the same two 32-by-20-inch laser engravers in the example above. Recir- culating filtered clean air back into the room avoids the extra costs associated with make-up air heating/cooling and HVAC balancing. However, instead of paying for more energy, you have to replace filters. A good RFE system has at least three inde- pendent filters cartridges in it: a pre-filter, a HEPA filter, and a gas filter. The pre-filter and gas filter are the filters that are consumed first. The HEPA filter can last a few years if the pre-filter, which protects the HEPA, is changed as soon as the RFE's filter alarms tell you to do so. The gas filter should be changed a minimum of once a year, as it has reactive ingredients mixed in with activated carbon that are most effective when fresh. Most RFEs include a full set of filters upon purchase so you can use it right away, but you can expect to purchase a 30-meter- squared pre-filter set and an 80-pound carbon filter each year as a typical min- imum for approximately $900. However, the amount of filters you consume is depen- dent on which material and how much of it you engrave. The main advantage of an RFE is that it is a plug-and-play solution. Connect the suction hose to the laser, plug it in, and you can start engraving. You won't have to bore a hole into an exterior wall or the roof, and you won't have to deal with HVAC bal- ancing or make-up air challenges. It's also nice to know that you are not contributing to air pollution in your community. CONSIDER OSHA AND EPA REQUIREMENTS Whether you choose a vent-to-outdoor or RFE system, the Occupational Health and Safety Administration (OSHA) re q u i re s t h a t y o u r facility meet indoor air quality standards. However, when using a v e n t - t o - o u t d o o r system, the Environ- m e n t a l Pr o t e c t i o n Agency (EPA) must also be satisfied that the contaminated air being emitted to the outdoor environment and the equip- ment used is in compliance with current standards. This can be a lengthy process involving permit applications, testing, equipment evaluations, and regulatory paperwork. You can usually avoid the EPA alto- gether and deal exclusively with OSHA by having zero airborne emissions to the envi- ronment using an RFE system. This is often easier because it requires less paperwork. OSHA is simply interested in verifying that you have met indoor air quality standards, regardless of the equipment selected. Some local EPA may still want to permit RFEs. You should check with local agencies to find out their position on RFEs. You will have to consult an Industrial Hygienist to determine and execute the spe- cific OSHA compliance and test require- ments. The requirements are based on the materials you intend to process, your work environment, regional regulations, and established air quality standards, e.g. American Conference of Governmental Industrial Hygienists (ACGIH) threshold limit values (TLVs), or OSHA permissible exposure limits (PELs). For more informa- tion, check out osta/otm/otm_iii/otm_iii_6.html. IS A DO-IT-YOURSELF SOLUTION DOABLE? At first glance, DIY solutions often seem like viable low-cost shortcuts. Most people move forward with DIY fume extraction projects thinking, "It's a fan. How hard can it be?" In reality, it's much more, so don't consider it unless you're willing to do the following. From an engineering perspective, speci- fying the right fan or blower for the job is actually quite involved and requires calcula- tions and research. When attempting a DIY solution, HVAC make-up air and balancing issues must still be considered. Electrical safety, mechanical safety, and whether or not the final execution reliably keeps the work place safe in terms of air quality are critical liabilities that a business must take seriously. Engineered solutions take all of this into account for you and your business. Here are some of the things that are considered when designing an engineered solution: The smaller duct diameters, surface roughness, duct length, and total number of bends along the duct length all con- tribute to greater air resistance for any given flowrate. The laser itself is also a flow resistance element that varies between makes and models. The more resistance you have against the fan, the harder it has to work. In most cases, the sum of all the resistance in the system ends up being rela- tively high. Thus, for starters, one should use a blower and not a fan. Technically, fans are for low-pressure applications, while blowers are designed to move air under higher resistance conditions. To know whether or not a blower can even deliver the airflow you need, it is nec- essary to have the blower's "blower curve," which is the performance of the blower expressed as a plot of the flow, in cubic feet per minute (CFM) that it can deliver at dif- ferent pressures, i.e. inches water gauge. You also need to have the resistance curve of all the restrictions in your system. You now have to overlay the curves on a graph. The inter- section of both curves tells you what CFM to expect with respect to the combination of laser, ducting, and blower selected. A common but unsafe DIY practice is to use a bathroom ventilation fan for a vent-to outdoor solution. See figure three for how it looks on a graph. from page 5 Figure 3: performance of bathroom ventilation fans. See article text for in-depth explanation.

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