Electronics Protection - September/October 2012 - (Page 10)

Feature Emerging Trends in Field Equipment Enclosures Phil Luppke, Intertec Instrumentation Walk around a refinery and the field enclosures and cabinets look much as they did 20 years ago. It’s easy to think that it’s well understood technology with little change, but this is far from the case. For instance, the key applications that drive a lot of this environmental protection business, particularly oil and gas, are demanding new features, such as higher energy efficiency and wireless-friendly features. The structural material of field equipment enclosures is critical. While some trends can be satisfied with any of the usual materials (metal or GRP/glass fiber reinforced polyester are used commonly, or thermoplastics for some applications), meeting the new challenges with bent-metal enclosures is becoming increasingly difficult. This article considers some trends, and the generic values of using GRP for future high-performance outdoor protection. Most common safety needs are typically covered by standards, with explosion proof regulations being key. These standards are continually evolving. One interesting recent example is a minor change to IEC 60079-0, the base standard for electrical installations in hazardous areas, that specified that climate testing now has to be done before other testing (IP rating, impact, etc). This turns out to be a real challenge because of the general trend towards operations in harsher climates. If, for example, an enclosure is destined for Siberia then it might be tested to -65°C and 85°C. These temperatures are so extreme that they can change the properties of the material (e.g. a thermoplastic-based enclosure would become very brittle). GRP remains stable even down to -100°C. It retains good properties in high temperatures too, so much so that GRP is highly suited for creating fireproof cabinets for protecting critical valve actuators. Another example is IEC 60079-10, which now defines ventilation requirements more clearly. Ventilation is essential in order to avoid condensation and guard against any build up of explosive atmosphere. Of course, ventilation is at odds with the general need for field enclosures to have the appropriate IP rating to protect against the ingress of dust and liquids. Careful use of breathable membranes has provided the means to provide ventilation and drain points to meet the new definitions. Applications Get Tougher By and large, the ‘easy’ oil and gas fields have all been found. The search for resources now takes places in much harsher environments: deep water, remote deserts and at hostile latitudes. Along with that trend, more Harsher environments are leading to more processing facilities are being built where resourc- challenges for instrument enclosures. es are located. Instrumentation will often be exposed to corrosive chemicals such as sulfur, chlorine or salt. It’s a tough challenge as even 316 stainless steel can corrode in such environments (the influential NORSOK standard recognises this for example). For manufacturers of sheet metal-based enclosures, it’s led to specifications such as acrylic painting with minimum coating thickness. In contrast, GRP is almost immune to the corrosive effects of salt and aggressive chemicals. Reduction in GRP thickness is almost negligible when exposed to most petrochemicals, even when measured over very long periods (decades and more). Only a very few specialized chemicals pose problems for GRP, and in general the material is suited to long lifecycle field protection applications. Insulation Matters Safety and Standards A key focus for instrumentation engineers is human and environmental safety, which has become a huge issue following recent hydrocarbon leakage and fire/explosion incidents. A common new demand is for enclosures to be blast-proof. High pressure waves can easily damage and break bent-metal or thermoplastic. One interesting attribute of GRP in this application is its intrinsic flexibility. This allows the enclosure, cabinet or shelter to flex and absorb blast-wave forces. Such GRP enclosures are typically fabricated using sandwich panels with GRP sheets enclosing an inner core providing insulation and further strength. The manufacturing process does not rely on molds, so the thickness of the inner layer can easily be varied to provide the strength required for particular applications. This is not possible with solid plastic enclosures fabricated using injection molding as they would require new molds in order to vary the properties. Similarly, applications that must withstand seismic events can also be made using custom sandwich style GRP construction. 10 The general need to avoid condensation touches on another challenge, thigher energy efficiency. When positioning the contents of the enclosure and any heating system to keep the interior above the dew point, or protect against freezing, it’s important to avoid creating cold spots, as this is where the condensation will appear. Careful layout is one aspect of minimizing energy usage, for example by positioning internal components close together and maximizing the insulation benefit of the surrounding air. Another trend is better enclosure insulation. Few off-the-shelf metal enclosures are available with the appropriate insulation to minimize the temperature regulation problem. In any event, just adding insulation is rarely adequate, because of fundamental limitations posed by the metal construction. Heat losses are exacerbated by the conducting properties of metal, and often by the typical sorts of metal bulkhead fittings used to mount such enclosures, which can act as rudimentary fins. Moreover, designers almost invariably need to cut access holes, worsening heat loss and creating cold spots. If insulation is used, it’s often rudimentary, such as wrapping mineral wool around the tube or cable. Ideally, purpose-made insulation components need to be used and these tend to be specialist items that are not readily available. Starting a field protection application with the right enclosure material makes a big difference to the efficiency of protection. Polyurethane foam (thermal conductivity: l = 0.02 W/m K) is typically used for insulation in sandwich GRP paneling, in thicknesses from 20 mm to 100 mm, providing a thermal transmittance or ‘k’ factor of around 1.2 to 0.2 W/m²K. (Galvanized or stainless steel enclosures are made of materials with high thermal conductivity: l = 15 to 50 W/m K.) Insulation makes a big difference. To maintain the same internal temperature, insulated enclosures typically require just a sixth of the heating power of uninsulated enclosures. Well considered insulation practice will also save additional energy by providing a stable temperature profile, with no swings between ‘heater off’ and ‘on’ situations. September/October 2012 www.ElectronicsProtectionMagazine.com http://www.ElectronicsProtectionMagazine.com

Table of Contents for the Digital Edition of Electronics Protection - September/October 2012

Electronics Protection - September/October 2012
Table of Contents
HP Intelligent Series Racks Offer Monitoring Capabilities for Data Centers
The Unknown Problem with Airtight Enclosures
Key Drivers When Turning to Captive Panel Screws
Emerging Trends in Field Equipment Enclosures
JV Industrial Solves Power Outage Issues with Battery-Free Flywheel
The Green Data Center Opportunity
The Power-Grid and Protecting Electronic Devices
Maximizing Availability, Capacity and Efficiency with Rising Data Center Temperatures
Canyonwest Cases Releases new Enclosures for Flat-Screen TV Transportation
Ohmite Manufacturing Releases Radial-Fin Heat Sink Extrusions
Rogers Introduces Condux Plus Conductive Foams
FIP Gasketing Resin Offers Advantages over Gasketing Materials
Minmax Power Releases MSGWI06 Series of DC/DC Power Modules
New E-Line Locking Systems Reduce Security Costs and Enhance Locking Solutions
Industry News
Calendar of Events

Electronics Protection - September/October 2012