Articles

Intrinsic Safety Made Easy

Ts. Dr. Teik Hua Kuan

• Intrinsic Safety
• Hazardous Area (Ex)

This paper aims to provide a quick understanding on the concept of Intrinsically Safe, various available intrinsically safe products and their technologies used including HART and Foundation Fieldbus (FISCO solution and Fieldbus Barrier). The paper begins by introducing the origin and how the concept of Intrinsically Safe (I.S.) is started then it move on to explain how the zener and galvanical/isolation designed and its working principles with the famous ignition curves. barriers are It then attempt to provide a brief comparison on conventional point to point DIN rail mounting barrier solution to a system approach solution. The paper also provides some background on HART and points to take note when using HART and HART Mutiplexer as HART protocol has been available for quite some time. Foundation Fieldbus is a hot topic as a number of recent projects in Malaysia applied foundation Fieldbus technology. This paper outline the concept of Foundation Fieldbus and explain the different between FISCO and Fieldbus Barrier and also point to take note when selecting them.

Verification of Intrinsic Safety on Instrumentation Loop

Ts. Dr. Teik Hua Kuan

• Intrinsic Safety
• Hazardous Area (Ex)
• Instrumentation

Intrinsic safety is one of the explosion protection techniques implemented in an industry where a flammable substance is present. It is a technique that reduces the electrical energy level at the hazardous area below the ignition curve so that it is not sufficient to initiate an explosion. In addition to limiting the energy to the field, the energy stored in the circuit and thermal ignition due to hot surfaces in hazardous areas must also be considered. Intrinsically safe is the preferred explosion protection method for instrumentation and control signals as it allows live maintenance, the use of an uncertified simple apparatus, and is applicable to all Zones. All intrinsically safe circuits must carry out a safety assessment and verify their compliance with intrinsic safety before implementation to avoid explosion. The verification process could be complex for mixed circuits and non-simple intrinsically safe systems; moreover, there has been much confusion for many years until the 4th Edition of the installation stan dard, IEC 60079-14, provided a clearer picture. This paper carries out an intrinsic safety verification assessment on a mixed circuit involving surge protection devices according to EC and NEC standards. It also highlights the common mistake made by system designers when verifying the safety parameters.