Electrical and Instrumentation Enclosures

Jump to Subject:- Electrical and Instrumentation Enclosure Design and Specification | Electrical and Instrumentation Cabinet and Enclosure Construction | Fieldbus Enclosures | Electrical and Instrumentation Enclosure Standards | Electrical and Instrumentation Enclosure Cooling | Enclosure Fire Protection | Enclosures for Arctic Conditions | Instrument Enclosures, Sunshades and Supports | Electrical and Instrumentation Enclosure Maintenance


Electrical and Instrumentation Enclosure Design and Specification

Know your Instrument and Electrical Enclosure - This document details some pertinent design requirements for Instrument and Electrical Enclosures.

Typical Instrument and Electrical Enclosure Specification Index - Although you will need to "fill in" all the technical details, this typical index does make sure that most requirements are covered.

Electrical Enclosures - This Typical Standard from CSBP covers the design, manufacture, works testing, supply and on site delivery for the following:

  1. 415V motor control centre
  2. 415V switchboards
  3. 415V lighting and small power distribution boards
  4. Control panels
  5. PLC cabinets

Designing for EMC - The main EMC problems for electronic products are the emissions of internally-generated high frequencies which may interfere with on-board or nearby radio reception, and susceptibility to transient or radio frequency interference from the external environment which may degrade the quality of analogue signals, or corrupt digital processes. EMC standards specify levels and test methods for both of these groups of phenomena. A further requirement which comes under the umbrella of the EMC Directive is that the mains supply input current should be limited in its harmonic content. If they are dealt with as an integral part of the product design, these requirements are not hard to meet. Too often, because they do not affect the visible performance of the product, they are not considered until the design is substantially complete and production is about to start. Incorporating EMC principles as an afterthought is expensive and time-consuming. Only 15% of products which have not been designed for EMC are likely to pass EMC testing first time; on average between one and two re-designs (and re-tests) are necessary before such products are certifiable - from (www.elmac.co.uk).

Typical Instrument Enclosure Specification - This document highlights the typical items that need to be considered when specifying an enclosure. From INTERTEC Instrumentation.

Avoid Thermal 'short cuts' to Improve Protection Efficiency - Specifying an enclosure for field-based instrumentation is not a trivial task. If the enclosure is destined for an extreme environment - such as desert or Arctic regions - starting such a configuration process with one of the commonplace styles of metal enclosures used for electrical panel gear is usually not such a good solution, and can pose problems for the inexperienced - from Intertec.

GRP Composites are the Material Of Choice for Tomorrow's Offshore Enclosure Applications - Enclosure designs for protecting offshore equipment are evolving rapidly to combat the widespread problem of corrosion, and to meet industry demands for higher levels of safety and reliability, and new functionality. Among the demands satisfied by enclosures made from GRP (glass reinforced polyester) based composite materials are superb resistance to the corrosive forces of the offshore environment, an ability to make pressurised explosion proof (Ex p) enclosures in any size - not just the small types that are commonly available - as well as the ability to withstand blast forces and jet-fires - from Intertec.

The following links are compliments of Weidmüller:

Hazardous Areas Technical Guide - This excellent 70 page technical guide. This is a large pdf download at 5 Megs, however it is worth the wait!

Enclosures and Cable Glands - This useful technical catalogue from Weidmüller covers the specification and requirements of enclosures which are often used in harsh environments. They remain reliable for many years thanks to the high quality levels, even when exposed to external influences like water, dust, hard impacts, shock, vibration, corrosion, and extreme temperature fluctuations. All components used in potentially explosive atmospheres are subject to strict safety regulations and are checked to the finest detail in terms of their functionality as well as their resistance and resilience against the prevailing environmental conditions. As each enclosure is only as strong as its weakest point, it is ensured that each individual component is of the highest quality and that it will not therefore cause a weak point in the enclosure. This is a large download but jut about provides all the information required for Enclosures and other Accessories.

ATEX Information - ATEX 95, formerly known as ATEX 100a, is aimed at manufacturers. It applies to equipment and protective devices intended for use in potentially explosive atmospheres. Safety and controlling devices for use outside the hazardous area, but essential for the safe operating of equipment inside it are also covered.

Hazardous Areas Poster - A useful poster which details ATEX and Hazardous Area technical information.

Technical Dictionary - This excellent 44 page document includes Certificates, Electrical data including clearance and creepage distances, and Current load curve. It also covers;


Electrical and Instrumentation Cabinet and Enclosure Construction

Electrical Cabinet Construction - Lots of examples and technical information along with some innovative solutions are detailed - from Weidmüller.

Safe Enclosures for Rough Seas - Sturdy Distribution Enclosures Defy the Harsh Environmental Conditions - Details on marine applications enclosures which have a corrosion resistant surface, absolute seal and Ex approval - from Weidmüller.


Fieldbus Enclosures

Fieldbus Enclosures - Enclosures fully assembled and certified for use with Fieldbus Foundation or Profibus PA application requirements.


Electrical and Instrumentation Enclosure Standards

Global Enclosure Standards within the Electrical Industry - Industry standards for electrical enclosures exist to promote safety, encourage design efficiency and define minimum levels of product performance. In the European and North American electrical industries, several standards are enforced for these reasons. Across the global marketplace, these or other standards may be followed or there may be no standards at all, which can lead to wide variations in product performance and price. In many cases, the end customer is not aware of the standards or does not clearly understand them and, therefore, does not insist that suppliers provide products that meet the standards. Focusing solely on low price without fully understanding or requiring industry standards can yield a low initial product cost, but could ultimately lead to high maintenance expenses, component failure and in the worst case, worker safety issues. The purpose of this paper is to: (a) Clearly define the industry standards that exist for electrical enclosures (b) Compare the most commonly used standards so enclosure users can understand the key differences (c) Equip decision makers with the knowledge needed to select an electrical enclosure that has the appropriate rating and price to value relationship for its intended application - from Hoffman.

Standards for Enclosures - A useful technical note from Omega.com.

New Standard 61439 for Switch and Control Gear - Compliant Switchgear and Controlgear will supersede the previous standard IEC 60439 from November 2014 - from Rittal.


Electrical and Instrumentation Enclosure Cooling

Cooling System Options for Electronic Enclosure Cooling: Do Thermoelectric Air Conditioners Have the Advantage? - This white paper discusses four popular options for cooling electronic/electrical equipment housed in enclosures and cabinets. These options include thermoelectric air conditioners, compressor-based air conditioners, vortex coolers and air-to-air heat exchangers (heat pipes). Each cooling method is explained and the advantages of thermoelectric air conditioners are examined as compared to the other cooling methods - from EIC Solutions Inc.

Cooling Oil Drilling Electronics in Class 1, Division 2 Environments - Details on a cost-effective air conditioning solution for enclosures to be used to protect electronics in drilling rig equipment - from EIC Solutions Inc.

Instrument Protection Shelter Employs Passive Cooling to Meet Challenges of Middle East Gas Project - One of the largest passively-cooled instrumentation shelters ever constructed is being supplied by Intertec to house remote control and instrumentation equipment required for a new natural gas collection project in the Middle East. Without any electricity, the cooling system reduces interior shelter temperatures by some 20 degrees Celsius - to enable the instrumentation to operate at its desert location - from Intertec.

Passively-Cooled Cabinets Protect Sample Conditioning and Process Analyzer Instrumentation on World’s Largest Vessel - Much of the on-line process analysis instrumentation on the Prelude FLNG vessel will be housed in purpose-built environmental protection cabinets. The cabinets are required to be capable of withstanding severe Category 5 tropical cyclones with wind speeds in excess of 252 km/h (157 mph) and to have a minimum service life of 25 years - with 50 years as a design aim. Additional requirements include a high degree of resistance to corrosion being caused by the saline environment and the presence of sour or acid gas, and the ability to cool electronics equipment without using explosion-proof air conditioning systems, which incur high capital and operating costs - from Intertec.


Enclosure Fire Protection

Enclosure Passive Fire Protection

Innovative Passive Fire Protection Cabinets Extend Margin of Safety for Critical Plant Shutdown Equipment - The cabinets ensure that equipment such as emergency shutdown valves remain operational by keeping them below 60 degrees Centigrade for periods of up to 64 minutes in the event of a hydrocarbon-based fire, to allow time for controlled shutdown - from Intertek.

Novel Passive Fire Shelters Enhance Safety Management for Offshore Gas Project - Fabricated using lightweight composite GRP (glass reinforced polyester) materials, these shelters employ patented techniques to resist fire for two hours - allowing critical electronic safety equipment to remain operational. Although there are currently no standards for this application area that cover containment temperatures, Intertec designs, manufactures and tests its fire shelters to a rigorous proprietary specification which demands that their internal temperature must remain below 60 degrees C throughout the rated protection time. The novel shelters are also capable of withstanding both conventional and more severe hydrocarbon fires - from Intertek.

Unique Passive Fire Shelter Technology Provides New Protection Choice for Process Plant Designers - Includes shelters for hydrocarbon fires with 90-minute protection which are light, corrosion proof, maintenance-free construction and ideal for offshore applications. They are designed to protect critical safety equipment from exposure to high temperature fires in hazardous areas. The shelters are entirely passive, maintenance-free and impervious to a wide range of corrosive chemicals - including salt, sulphur dioxide and sour or acid gas - from Intertek.

Enclosures Protected by Gaseous Fire Fighting Systems

Guidance on the Pressure Relief and Post Discharge Venting of Enclosures Protected by Gaseous Fire Fighting Systems - This document provides guidance on fulfilling the requirements contained in BS EN15004-1 and BS 5306-4, in respect to over and under pressurisation venting - clauses 7.4.1 and 10.3.3. respectively and post discharge extract - clauses 5.3 h) and 15.9 respectively. It considers the design, selection and installation of vents to safeguard the structural integrity of enclosures protected by fixed gaseous fire fighting systems and the post discharge venting provisions where used - from the FIA.

Clean Agent Enclosure Design for ISO 14520 & AS4212 - Clean agent fire suppression systems are required in enclosures where a sprinkler system would cause damage to sensitive contents such as computer servers or historical artefacts. Upon fire detection the compressed agent, which can be a halocarbon or an inert gas, is released into the enclosure causing a peak pressure of around 250 to 1250 Pascals to occur for a fraction of a second, the magnitude of which is dependent upon total enclosure leakage area. Once the enclosure is completely flooded, the agent will begin to leak out at a rate that primarily dependent upon lower enclosure leakage area. The distribution of the remaining agent will either be constant throughout the enclosure due to continual mixing or will establish an interface with air above and agent below an interface that descends in time. Up until 1988, enclosures protected by Clean Agents used full discharge tests to determine the Hold Time but since 1988, Door Fans have been used for measuring the leakage area which is entered into formulae in Annex E of ISO 14520 to predict how long the agent will stay in the enclosure (Hold Time) - from Fire Protection Technologies.


Enclosures for Arctic Conditions

Outdoor Equipment Enclosures Simplify Instrumentation Installations in Ultra-Cold Environments - These enclosures provide a versatile alternative to free-standing cabinets for the environmental protection of field-based process instrumentation. Developed at the request of a Russian oil refinery, the enclosures are made from tough glass reinforced polyester (GRP) and include highly insulated options for use in extremely cold climates. They also offer more space than typical instrument enclosures, to allow plant personnel to use gloved hands when accessing the equipment. Typical applications include housing differential pressure flowmeters and process transmitters in refineries, petrochemical and chemical processing plants - from Intertek.


Instrument Enclosures, Sunshades and Supports

It is essential that Instrument Enclosures and Sunshades are considered where Instruments are subjected to a wide range of environmental factors which might impair the efficiency and operation of process instrumentation, such as extremes of temperature, the ingress of dirt, dust and moisture, corrosion, accidental damage and tampering. Options can include electrical or steam heating, ventilation or integral insulation for protection from the world’s climactic extremes, such as Siberia, where the temperature can fall as low as -76°F (-60°C), or Australia / Middle East, where it can reach in excess of 104°F (+40°C).

Enclosure systems are typically used to protect process instrument manifolds and transmitters, solenoid valves, general field instrumentation and remote chemical sealed instruments.

These types of enclosures can be used with a specific range of enclosure manifold systems which enable ease of instrument installation and provides external process and vent connections.

Instrument Enclosures, Sunshades and Supports - Maintaining the integrity of process measurement instrumentation, protection from the effects of the industrial and the natural environment, both on and offshore, is vital, this technical bulletin from Anderson and Greenwood and Prochem Pipeline Products gives a good technical overview of what is required. The bulletin covers Purpose and Applications, Features and Benefits, Technical Specifications Enclosures, EM Manifold Needle Valve, EM Manifolds, Electrical Heating, Electrical Heating, Enclosure Mounting and Instrument Shades.


Electrical and Instrumentation Enclosure Maintenance

Enclosure Maintenance - David Crooks - Installed enclosures require periodic maintenance. The more hostile the environment, the greater the frequency of maintenance needed, and if done with vigilance, the greater the reward. Vibration, shock, or thermal expansion/contraction may loosen enclosure parts and fasteners. Constant flexing of conduit connections and stresses on liquid tight hubs may erode rubber fittings and seals. Routine inspections and periodic tightening of fasteners can prevent minor annoyances growing into major problems - from Fibox Enclosures.

Standard for an Electrical Preventive Maintenance (EPM) Program - The purpose of this standard is to provide recommended practices and frequencies that would form the core of a regularly scheduled electrical preventive maintenance program. There is a useful section on maintenance of enclosures - from Hartford Steam Boiler. 

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