September 2008

Documenting skills is value-add

ISA certification provides an objective, third-party assessment, and confirmation of a person's skills. It gives manufacturing and factory staff the opportunity to differentiate themselves from their peers and gain recognition. InTech covers two certification areas in this monthly Certification department.

ISA Certified Automation Professional (CAP) program

Certified Automation Professionals (CAPs) are responsible for the direction, design, and deployment of systems and equipment for manufacturing and control systems.

The following question comes from the CAP study guide, Performance Domain III, System Design, Design, specify, and procure the hardware/software used in the system

CAP question

Which of the following protection techniques is acceptable for equipment located in a Class I, Division 1 area?

A. Explosion-proof apparatus and nonincendive equipment

B. Explosion-proof apparatus and intrinsic safety

C. Dust ignition-proof and nonincendive equipment

D. Hermetically sealed and intrinsic safety

CAP answer

The correct answer is B, explosion-proof apparatus and intrinsic safety. 

Hazardous location protection techniques are defined by NEC 500.7 (NEC 2002 Code). The protection techniques are permitted as follows:

  • Explosion proof apparatus: Class I, Div1 or 2
  • Intrinsic safety: Class I, Div 1 or2; Class II Div 1 or 2; or Class III, Div 1 or 2
  • Non-incendive equipment: Class I, Div 2; Class II, Div 2; or Class III, Div 1 or 2 (Does NOT Include Class 1, Div 1)
    Dust ignition proof: Class II, Div 1 or 2 (Does NOT include Class I, Div 1)
  • Hermetically sealed: Class I, Div 2; Class II, Div 2; or Class III, Div 1 or 2 (Does NOT include Class I, Div 1)

Reference: Earley, NEC 2002 Handbook, NFPA, 2002

The operational definitions of explosion proof and intrinsically safe are useful in this context. An explosion proof apparatus is one enclosed in a case that is capable of withstanding an explosion of a specified gas or vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby.

An intrinsically safe apparatus is one in which all the electrical circuits are intrinsically safe, which is to say the power that courses through the circuit is incapable of causing ignition of a mixture of flammable or combustible material in which the circuit is operating.

ISA Certified Control Systems Technician (CCST) program

Certified Control System Technicians (CCSTs) calibrate, document, troubleshoot, and repair/replace instrumentation for systems that measure and control level, temperature, pressure, flow, and other process variables.

This question comes from the Level I study guide, Domain 3, Troubleshooting. Level I represents a professional who has a five-year total of education, training, and/or experience.

CCST question

Which of the following is not necessary when zeroing or calibrating a magnetic flowmeter?

A. Calibration factor for the flow tube assembly

B. Flow tube full of process material

C. Proper grounding

D. Warm-up period for the fluid in the system

CCST answer

Magnetic flowmeters use Faraday's law of magnetic induction as the basis of their operation.

Magnets apply a magnetic field to a tube through which the fluid is flowing and an electric potential generates across the tube that is proportional to the velocity of the fluid flowing through the pipe.

Then, knowing the density of the fluid, the velocity of the fluid, and the cross sectional area of the pipe, the meter has enough information to calculate the mass flow rate of the fluid.

To work, this flowmeter must be on a pipe that is insulating type, so the potential that generates does not short circuit. Another requirement is the fluid that is flowing needs to be able to conduct electricity, at least to some degree so Faraday's laws of induction can apply.

Water, for example, works as it has a sufficiently high level of conduction for the flow meter to operate.

The magnetic flowmeter is the third most common flowmeter behind differential pressure and positive displacement flowmeters.

The correct answer is D, a warm-up period for the fluid in the system is not necessary.

Nicholas Sheble (nsheble@isa.org) writes and edits Certification Review.