Design Lab Eval 8 ((EXCLUSIVE))
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The EVAL-AD7124-8-PMDZ is a minimalist 8-Channel, Low Noise, Low Power, 24-Bit, Sigma-Delta ADC (Analog to Digital Converter) with PGA and Reference, SPI Pmod board for the AD7124-8. This module is designed as a low-cost alternative to the fully-featured AD7124-8 evaluation board and has no extra signal conditioning for the ADC.
The AD7124-8 also has extensive diagnostic functionality integrated as part of its comprehensive feature set. These diagnostics include a cyclic redundancy check (CRC) on the SPI data, signal chain checks, and serial interface checks, which lead to a more robust solution. These diagnostics reduce the need for external components to implement diagnostics, resulting in reduced board space needs, reduced design cycle times and cost savings. The failure modes effects and diagnostic analysis (FMEDA) of a typical application has shown a safe failure fraction (SFF) greater than 90% according to IEC 61508.
Trained laboratory personnel must understand how chemical laboratory facilities operate. Given the chance, they should provide input to the laboratory designers to ensure that the facilities meet the needs of the functions of the laboratory. Laboratory personnel need to understand the capabilities and limitations of the ventilation systems, environmental controls, laboratory chemical hoods, and other exhaust devices associated with such equipment and how to use them properly. To ensure safety and efficiency, the experimental work should be viewed in the context of the entire laboratory and its facilities.
Some laboratories have office spaces within research areas. In this design, it is best to have an obvious separation between the laboratory area and the office area using partitions or, at a minimum, aisle space, but preferably using a wall and a door that can be closed. Occupants should not have to walk through laboratory areas to exit from their office space. Visitors and students should not have to walk through laboratories to get to researchers' offices, because those persons do not have personal protective equipment (PPE). (See Vignette 9.1.)
Traditionally, laboratories were designed for individual research groups with walls separating the laboratories and support spaces. Group sizes ranged from 2 to 10 people, and most groups were completely self-contained, each with its own equipment and facilities (Figure 9.1).
Since the 1990s, the trend has been for researchers to collaborate in a cross-disciplinary nature; chemists, biologists, physicists, engineers, and computer scientists work together on a common goal. At the same time, laboratory designers have moved to open multiple-module laboratories that allow a wide variety of configurations for casework and equipment setups. These laboratories often support large or multiple teams and are configured with relocatable furnishings.
When designing new laboratory spaces, consider the equivalent linear feet (ELF) of work surface within the laboratory. ELF can be divided into two categories: bench and equipment. Bench ELF is the required length of benchtop on which instruments can be set and where preparatory work takes place, as well as the length of laboratory chemical hoods. Equipment ELF includes the length of floor space for equipment that does not fit on a bench. Typically, every two laboratory personnel whose work mostly involves hazardous chemicals should have at least one chemical hood, and these should be large enough to provide each person with a minimum of 3 linear ft, but it could be 8 ft or more depending on the planned activities and type of chemistry.
Typical chemistry laboratories are designed to provide from 28 to 30 ELF per person. Quality control, biology, and analytical laboratories range from 20 to 28 ELF per person. Quality control and production laboratories tend toward the low end of this range, whereas research laboratories are at or above the high end of the range. This number includes the support space outside the laboratory that is needed. These values can vary widely and must be addressed carefully for each project.
Current design practice is to locate fixed elements such as laboratory chemical hoods and sinks at the perimeter of the laboratory, ensuring maximum mobility of interior equipment and furniture. Although fixed casework is common at the perimeters, moveable pieces are at the center to maximize flexibility. The central parts of the laboratory are configured with sturdy mobile carts, adjustable tables, and equipment racks.
Another trend for new laboratory buildings is to design interstitial spaces between the floors and to have all the utilities above the ceiling. The interstitial spaces are large enough to allow maintenance workers to access these utilities from above the ceiling for both routine servicing and to move plumbing and other utilities as research demands change.
Casework should be durable and designed and constructed in a way that provides for long-term use, reuse, and relocation. Some materials may not hold up well to intensive chemistry or laboratory reconfiguration. Materials should be easy to clean and repair. For clean rooms, polypropylene or stainless steel may be preferable.
Large equipment such as centrifuges, shakers, and water baths often work best in separate equipment rooms. Pumps for older mass spectrometer units are both hot and noisy and are often located in either a small room or a hall. If in a closet, the area must have extra exhaust to remove heat, or else equipment may fail from overheating. With smaller and newer mass spectrometers, the pumps are often small and can fit into cabinets specifically designed for them. These pumps work especially well when water cooling is not required. Very few researchers need to hear their instrumentation running, but many want to see the equipment.
Another consideration crucial to equipment-intensive areas is the allowable vibration tolerance. Most analytical equipment such as NMRs, sensitive microscopes, mass spectrometers, and equipment utilizing light amplification (laser) require either vibration isolation tables or an area that is structurally designed to allow for very little vibration. Clarify the tolerance requirements with the user and equipment manufacturer during the equipment-programming phase, or early design process, so that the appropriate structure can be designed and the construction cost can be estimated more accurately.
Each laboratory should have an adequate number and placement of safety showers, eyewash units, and fire extinguishers for its operations. (See Chapter 6, section 6.C.10, for more information.) The American National Standards Institute (ANSI) Z358.1-2004 standard provides guidance for safety shower and eyewash installation. The 2004 version recommends provision of tepid water, which can be complicated from an engineering standpoint. Although this standard does not address wastewater, most designers agree that emergency eyewash and shower units should be connected to drain piping. It is prudent to have floor drains near the units, preferably sloped to the drain to prevent excessive flooding and potential slip hazards. Consider choosing barrier-free safety showers and eyewash units that can accommodate individuals with disabilities. The maximum reach height for the activation control for safety showers is 48 in.
Title 1 of the Americans with Disabilities Act (ADA) of 1990 requires an employer to provide reasonable accommodation for qualified individuals with disabilities who are employees or applicants for employment, unless doing so would cause undue hardship. The design team and the owner are responsible for identifying what reasonable accommodations should and can be made to meet ADA guidelines or requirements.
NOTE: Clean benches are not designed for use with hazardous materials. These are appropriate for use in work with materials that necessitate clean work conditions and should only be used for materials or chemicals that one could safety use on a benchtop.
A well-designed hood, when properly installed and maintained, offers a substantial degree of protection to the user if it is used appropriately and its limitations are understood. Chemical hoods are the best choice, particularly when mixtures or uncharacterized products are present and any time there is a need to manage chemicals using the ALARA principle.
Face velocity is only one indicator of hood performance and one should not rely on it as a sole basis for determining the containment ability of the chemical hood. There are no regulations that specify acceptable face velocity. Indeed, modern hood designs incorporate interior configurations that affect the airflow patterns and are effective at different ranges of face velocity.
With the desire for more sustainable laboratory ventilation design, manufacturers are producing high-performance hoods, also known as low-flow hoods, that achieve the same level of containment as traditional ones, but at a lower face velocity. These chemical hoods are designed to operate at 60 or 80 fpm and in some cases even lower. (See section 9.C.22.214.171.124.)
When first installed and balanced, a laboratory chemical hood must be subjected to the ASHRAE/ANSI 110 or equivalent test before it is commissioned. When multiple similar chemical hoods are installed at the same time, at least half should be tested, provided the design is standardized relative to location of doors and traffic, and to location and type of air supply diffusers.
Conventional glass or plastic sashes are not designed to provide explosion protection per ANSI/NFPA (ANSI, 2004; NFPA, 2004). Sash panes and viewing panes constructed of composite material (safety glass backed by polycarbonate, with the safety glass toward the explosion hazard) are recommended for chemical hoods used when there is the possibility of explosion or violent overpressurization (e.g., hydrogenation, perchloric acid).
Performance should be evaluated against the design specifications for uniform airflow across the chemical hood face as well as for the total exhaust air volume. Equally important is the evaluation of operator exposure. The first step in the evaluation of hood performance is the use of a smoke tube or similar device to determine that the laboratory chemical hood is on and exhausting air. The second step is to measure the velocity of the airflow at the face of the hood. The third step is to determine the uniformity of air delivery to the hood face by making a series of face velocity measurements taken in a grid pattern. 2b1af7f3a8