High Temperature Heating
13 Jun 2013 - 12:00

The elements of an interrelated system provide an overview of key points to consider when specifying or building heating equipment for process instrumentation. For instrumentation in chemical and petrochemical plants, and especially in sample conditioning systems for analysers, the maintenance of an elevated temperature is often essential in order to prevent the condensation and/or crystallisation of media. Complete insulation of the measurement and analysis station is rarely possible due to the requirement for maintenance and calibration. Some users create ad hoc solutions in the form of a ‘hot air shower’ where a fan (or compressed air) warms the local environment. These can be very energyintensive and can be difficult to build for hazardous areas (and are not usually suitable for applications demanding closely regulated temperatures). The optimal solution is a so-called ‘hot box’ consisting of an enclosure for the equipment in question, fitted with a heating element and controller. For best results when building a hot box, care needs to be taken with the design: choosing and considering the elements as an inter-related system, rather than simply assembling the box from

Configuring Protective Enclosures for Offshore Applications
13 Jun 2013 - 11:57

Engineers tasked with choosing and confi guring enclosures, cabinets and shelters for offshore applications face a multitude of conflicting demands. Not only must the unit provide protection against extreme cold or extreme heat – depending on platform location – but it must also be resistant to a host of environmental and other factors, such as salt spray, sour gas, high wind velocities, UV exposure and possibly high pressure blasts. Topping out this wish list, the enclosure needs to have a robust structural integrity, a very long service life and yet weigh as little as possible – as all topside weight on off shore platforms is an expensive commodity. Many of these demands are common to all types of protective enclosure, regardless of whether they are small instrumentation housings or relatively large shelters. This article looks at some of the issues behind each category.

Avoiding corrosion: a big instrumentation challenge
13 Jun 2013 - 11:54

Most designers protect field process instrumentation and control equipment against the effects of its environment by using some form of enclosure. But if, as is often the case, the environment contains corrosive chemicals, the long term integrity of the enclosure can be threatened. Corrosion is a gradual, diffusioncontrolled process, causing progressive destruction of metal through electrochemical reaction. For any application with a long lifecycle, it is therefore essential that the enclosure fabrication material does not contribute to, or suffer from, corrosion.