Intrinsic Safety Attitudes: A Mixed Bag

Aug. 22, 2003
Survey reveals differing opinions about cost and personnel training issues

A survey of user/designers and specifiers of hazardous environment protection systems from consulting engineering/construction firms, end users, OEMs, and systems integrators in Europe and North America, indicates users gravitate to the most widely accepted practices of their particular industries.

The report, conducted by Venture Development Corp. (VDC), also finds that, while not in wide adoption in all markets, intrinsic safety solutions are believed to be a less-costly overall safety solution.

Intrinsic safety is a method used to prevent equipment from causing fires and explosions in areas with hazardous atmospheres such as explosive gas-air mixtures. Equipment and wiring is intrinsically safe if it is incapable of releasing sufficient electrical or thermal energy to cause ignition of a hazardous atmosphere in its most ignitable concentration. Equipment going into hazardous areas for intrinsically safe applications is classified as either simple or non-simple devices.

Simple devices have limitations on voltages, currents, and energy. These include products such as switches, thermocouples, RTDs, non-inductive potentiometers, and resistors.

Non-simple devices, which include field transmitters, solenoid valves, and many other types of equipment, can create and store energy levels high enough to create an explosion, if not limited.

For such applications, the devices have safety limits on the amount of inductance, capacitance, and temperature operating levels. Field wiring to these devices is made through intrinsic safety barriers, which are located outside the hazardous region. The barriers limit the voltage and current levels to the devices to values below those that could cause an explosion.

Methods Used in Hazardous Environment Protection

The study found most users are using multiple methods of hazardous environment protection. Users recognize that one method alone may be insufficient or unsuitable for all situations and installations because of specifications and regulatory issues. However, most users do prefer one method to the others.

For European operations, the greatest share of protection is via the use of intrinsic safety. In contrast for North American operations, much greater use is made of explosion-proof methods.

How Users Choose

Users identified the considerations most important to them in choosing the method of hazardous environment protection. By far, the most cited reason was to choose the standard practice solution locally in their industry. Important reasons for this included:

* Ready availability of trained personnel capable of installing and supporting the equipment when it has local standard practice usage.

* The equipment also is likely to be more readily available when it has local standard practice usage.

The study concludes these issues hinder expansion of intrinsic safety applications into regions and industries where use is not well established. VDC found this to be most prevalent for replacement purchases and minor facility modifications, but less so for new facilities and major modifications.

Cost was not identified as a major issue for users in their selection process. However, when asked what could motivate them to switch to intrinsic safety use, 47% identified reduced cost, more so than the 35% that would first require the method become a standard practice in their industry.

Perceived Cost of Intrinsic Safety Solutions

Users were asked to identify their perceptions of intrinsic safety solution costs compared with other methods. Fifty percent of respondents believe intrinsic safety costs less. Of that group, 11% maintain it's cheaper when the cost of maintenance is included. Ten percent of the group believe it to be less expensive when the cost of installation is included.

Seventeen percent of the respondents reckon that intrinsic safety solutions are equal in cost, while the 33% balance of respondents maintain that intrinsic safety is a more expensive solution.

Those 33% who regard intrinsic safety as expensive view intrinsic safety barriers in particular as adding cost to the solution. These also are identified by some as adding complexity to troubleshooting. Also, some cited ever-changing regulations on installation of intrinsic safety solutions as adding significant cost and time in gaining approvals.

Again based on the survey data, it appears much more likely that users will switch to intrinsic safety in the construction of new facilities, and in major updating projects in existing facilities, rather than for replacements and minor projects, where the perceived benefits of switching are less. The study suggests that a more careful analysis of lifecycle costs and state-of-the art industry practices will likely be undertaken for new facilities, and major updating projects.

Hazardous Environment Protection Methods Chosen as Alternatives to Intrinsically Safe Solutions

(Ranked, Based on Users in Survey)

1. Explosion-Proof/Flameproof

2. Pressurization/Purging of Units

3. Encapsulation of Equipment

4. Non-Incendive Equipment1

5. Fiberoptics in Place of Wire

6. Increased Safety Measures2

1.This type equipment is incapable under normal conditions of causing ignition of flammable-gas or vapor-in-air mixtures due to arcing or thermal effects. Use of this type equipment is limited to areas where there is low probability of an explosive-gas mixture occurrence, and if it does occur, will exist for only a short period of time.

2. These are methods used to reduce the probability of excessive heat, arcs, or sparks occurring on the internal or external surface of equipment in normal operation. This includes methods such as de-rating of current through terminals, giving enclosures high ingress protection, enhancing insulation values, and increasing creepage clearance distances.

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