his 2-part series of articles will focus on hardware compliance aspects of specific information technology electronics equipment which includes mainframes, server computers, and subcomponents. In Part 1 of this series, we will provide a technical overview of server components and subcomponents and discuss specifics regarding product safety regulations and testing.
Part 2 of this series will address additional areas of regulatory compliance, including electromagnetic compatibility and environmental concerns. We’ll also discuss how IT equipment is tested and certified to compliance standards for worldwide shipments.
The goal of this 2-part series is to provide our readers with a better understanding of the requirements for executing hardware compliance testing and certification, as well as the technical details of every compliance discipline.
Before diving into the details of each discipline of hardware compliance, it is important to understand the product being tested. This article focuses on the application of hardware compliance to information technology (IT) server computers and their subcomponents, such as processor drawers, input/output (I/O) drawers, cooling subsystems, cryptographic security cards, etc.
A maximally configured server computer with the front doors removed is shown in Figure 1. The mainframe is made up of many subcomponents that fall into one of the following three categories: 1) subcomponents that are designed and manufactured by the information technology (IT) company that will own the end‑product; 2) subcomponents designed in partnership with another company who owns the sub-component and that sells it to IT company that will own the end-product; or 3) completely off-the-shelf original equipment manufacturer (OEM) parts.
Figure 2 shows a breakdown of the subcomponents within a single rack air-cooled server.
The system in Figure 2 contains two processor drawers, three (IO) drawers, two one-rack unit (1U) servers that manage the built-in service network, and two Ethernet switches that support communications between subcomponents for the built-in service network. Each of these subcomponents contains anywhere from one to four power supply units (PSUs), which take single-phase input within a rated range of 200Vac to 240Vac RMS. In addition to the processors themselves, the processor drawers contain memory and I/O cards to communicate with either other processor drawers or I/O drawers.
Each of these mini graphic symbols (marks) indicates that the product has been tested and certified that it meets/complies with specific country requirements in the areas of product safety (e.g., doesn’t exceed the current rating of a power cord), electromagnetic compatibility (e.g., doesn’t interfere with nearby devices), and environmental compliance (reduction of hazardous materials). The scope of certifications around the world is partially determined by voltage rating or power consumption, and the agency marks that appear on a compliance label are not going to be universal for all the products. In addition, marks on the label often need to be changed as regulators in various countries and jurisdictions change laws.
Marks can also be displayed differently for each product. Some products list agency marks either on the packaging, supplied documents (manuals), or via the product software/firmware (i.e., smartphones, smaller electronic devices).
To legally display the marks shown on the compliance label, a product needs to successfully comply with specific regulations and standards. Most countries around the world regulate products for adherence to industry standards for product safety, electromagnetic compatibility (EMC), and environmental characteristics. Compliance testing laboratories perform tests required by regulatory agencies or industry standards as shown in Figure 4 on page 24. Regulatory product certification for ship support requires that internal company testing and reports be submitted to external product safety and EMC agencies for full worldwide country certification. Some companies have the ability to self-certify while others use third-party companies for certification. For instance, for some companies the U.S. and the European Union (EU) allow parties to self-certify EMC compliance, which can help to significantly shorten the certification process.
Even with pre-evaluations, products still need to go through the final compliance stage prior to the release. This final stage is where the approvals and the certifications are obtained for the product so it can ship globally. The final stages of testing include minimum ship-level hardware testing (hardware being used by a potential client). Material declarations are obtained in this stage to ensure they need environmental compliance. Component vendor safety certifications are also obtained during this stage to figure out if there will be any issues prior to shipping. Once all the final stage compliance requirements are met, the product is allowed to go to market.
Another defining cost for compliance work is finding a balance between obtaining the minimum ship‑level hardware for testing while still securing the certifications and testing approvals needed to ship the hardware globally. Each compliance test has different requirements that drive the hardware needed for testing and its associated cost. Each of these aspects will be further defined in the rest of this article. Ultimately, EMC requires all configurations to be tested, while Product Safety testing and volatile organic compounds (VOC) emissions testing require worst-case maximum configuration. However, VOC emissions testing needs brand-new hardware, while Product Safety testing can use hardware that has run-time hours on it. There is always a balance in the corporate world between the cost of the hardware and scheduling all the hardware compliance testing required to meet ship support dates.
Other costs include costs associated with test equipment calibration, especially when the compliance testing laboratories are ISO/IEC 17025:2017 accredited. This also includes the cost of the accreditation and all the activities associated with it. Some companies’ expenses can also be attributed to external compliance testing. Each company must determine what schedule and cost work best for their product release cycle.
For these reasons, compliance engineers need to be familiar with the regulatory activity by geography and know what tests are required for those geographies. Effective scheduling also requires internal coordination of the compliance testing sequence. For example, certain tests, such as VOC testing, must be conducted with brand-new hardware, so they must be scheduled before any other testing that uses the same equipment.
The specific tests required by each standard are similar, but testing limits can vary from standard to standard. To ensure compliance with all the standards, a superset of worst-case test limits is typically utilized for each test case; a server or subcomponent that meets the worst-case limits of all of the applicable standards is best positioned to meet the requirements in any regulatory jurisdiction.
Product safety compliance efforts begin during the earliest development stages of the server. Because of the potential costs and scheduling changes that can result from non-compliant hardware, it is incumbent on the product safety engineer to attend design meetings and to review both electrical and mechanical designs as early in the development process as possible, and provide feedback for design improvements that will ensure the final design passes all the requirements of the standards.
Some of the early work includes: 1) reviewing prints; 2) reviewing electrical schematics to ensure any power outputs are current-limited; 3) reviewing printed circuit board (PCB) layouts to ensure proper spacing of components (e.g., creepage and clearance distances); 4) reviewing 3D mechanical CAD models and/or early mechanically-good hardware for access to energized parts, hazardous moving parts, and sharp edges; 5) reviewing thermal simulation data to identify locations that may exceed touch temperature limits (potential burn hazards) or critical components that may exceed their operating limits and could result in smoke or fire, and 6) reviewing the overall grounding scheme of the server or subcomponent.
For server subcomponents, the safety engineer must consider the worst-case configuration for that subcomponent, which may not match the configuration for that same subcomponent when implemented within a fully configured server. The subcomponent may be over-tested (e.g., tested in a higher room ambient temperature, utilizing fan speeds that are suboptimal for each test, etc.) which provides some buffer against failure when that same subcomponent is installed in a server during system-level product safety testing. For server-level product safety testing, the maximum system configuration is selected for testing which includes the highest number of processor drawers, I/O drawers, PDUs, and server racks.
To assess accessibility to electrical energy sources and safeguards, the test engineer uses a test finger instrument and applies that to all user-accessible areas to determine if a part of a specific current, voltage, or power level can be touched. During this test, the engineer can remove any door, cover, or component that does not require a specialized tool to gain access. The same test finger instrument is used to evaluate accessibility to moving parts. Here, the test engineer determines if the instrument can access components such as a moving fan blade or pump motor.
Capacitor discharge after disconnecting a connector requires the test engineer to measure the capacitance present at the input pins to the PDU (at the system level) or power supply unit (PSU) (at the component level) to ensure that the voltage reduces to a safe level within a given amount of time (e.g., 2 seconds).
Figure 5 shows an image of a safety engineer performing a touch current measurement.
The system can also operate in a condition known as N-mode. The power subsystem is designed for full redundancy, meaning that there are twice as many PDUs and PSUs as required such that if a failure happens in the field, the system will continue to run. N-mode is the minimum number of PDUs or PSUs required before functionality is lost and the system or subcomponent goes down.
Input measurements are made under normal and N-mode conditions at the ends of the rated voltage ranges, common voltages used in specific countries around the world, and tolerance voltages 10% above and 10% below the rated voltage ranges. Worst-case measurements are obtained during N-mode testing because the total power required to run the server or subcomponent is divided between a smaller number of PDUs or PSUs. The testing ensures that the measured current at all these voltage and configuration permutations does not exceed the input rating of the server or subcomponent.
To perform this testing, thermocouples are attached to safety-critical components and common touch locations. The maximum configuration is then tested with the highest power I/O cards and memory DIMMs installed, the system or subcomponent is tested in the highest supported ambient temperature (e.g., 40°C), the cooling fans and pumps are set to perform as they normally would in the current ambient condition and may be set to an even lower speed for subcomponents to provide buffer when that subcomponent is tested at the system level, and an exerciser is executed on the system that simulates the high end of a customer workload. Tests are executed at multiple voltage setpoints, including at the ends of the rated voltage ranges, common voltages used in specific countries around the world, and at tolerance voltages 10% above and 10% below the rated voltage ranges. Each test lasts a minimum of 1 hour or until temperatures on all thermocouples reach equilibrium.
An example of a blocked ventilation test is shown in Figure 6.
In conclusion, product safety testing is a critical aspect of hardware compliance that evaluates a product’s electrical components to ensure they meet safety standards and regulations. By conducting product safety testing, manufacturers can ensure that their products are safe for use and that they meet the applicable safety standards. It also protects against foreseeable misuse, helping to ensure the safety of clients, support engineers, and anyone exposed to a product.
John Werner is a Senior Electromagnetic Compatibility/Product Safety Design Engineer with IBM in Poughkeepsie, NY, and can be reached at wernerj@us.ibm.com.