AutoQuiz: What Is the Liquid Flow Condition Where Falling Static Pressure Causes Formation of Vapor Bubbles?

AutoQuiz: What Is the Liquid Flow Condition Where Falling Static Pressure Causes Formation of Vapor Bubbles?

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

 

Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.

What is the term used for phenomenon in liquid flow where falling static pressure causes the formation of vapor bubbles that subsequently collapse back into the all-liquid state as the fluid static pressure is recovered?

a) cavitation
b) pressure piling
c) saturation
d) vortex shedding
e) none of the above

   

Click Here to Reveal the Answer

 

Answer B is not correct. Pressure Piling is a condition that results from the ignition of pre-compressed gases in compartments or subdivisions other than those in which ignition was initiated.

Answer C is not correct. Saturation is a device characteristic exhibited when a further change in an input causes no further change in the output.

Answer D is not correct. Vortex Shedding is the phenomenon that occurs when fluid flows past an obstruction. The shear layer near the obstruction has a high velocity gradient, which makes it inherently unstable. At some point downstream of the immediate vicinity of the obstruction, the shear layer breaks down into well-defined vortices.

The correct answer is A, Cavitation. Cavitation is a two-stage phenomenon of liquid flow. The first stage is the formation of vapor bubbles within the liquid system because of the fluid’s static pressure falling below the fluid vapor pressure  The second stage is the collapse or implosion of these cavities back into an all-liquid state as the fluid decelerates and static pressure is recovered.

Reference: The Automation, Systems, and Instrumentation Dictionary, Fourth Edition, ISA.

AutoQuiz: How to Interpret Relay Logic for a Pump Control Switch

AutoQuiz: How to Interpret Relay Logic for a Pump Control Switch

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

 

Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.

Given the process shown in the post graphic, with the relay logic shown, which of the following statements is true?

a) when the pump control switch is in auto, and the pump is stopped, a low pressure in the pressure tank will start the pump
b) when the pump control switch is in auto, and the pump is running, a low pressure in the pressure tank will stop the pump
c) when the pump control switch is in auto, and the pump is running, a low level in the pressure tank will stop the pump
d) when the pump control switch is in auto, and the pump is running, a low level in the storage tank will stop the pump
e) none of the above

   

Click Here to Reveal the Answer

 

The pressure tank low pressure switch PSL103 is not in the motor control circuit, so a high pressure or low pressure does not have an impact on the pump status. The pressure storage tank low level switch LSL102 is involved in starting the pump, but does not stop the pump since the motor seal-in circuit is in parallel.

The correct answer is D. The storage tank low level switch LSL103 or the pressure tank high level switch LSH101 can stop the pump.

Want to learn more? Check out these ISA reference sources:

Control Systems Engineering Exam Reference Manual: A Practical Study Guide, by Bryon Lewis, CSE, P.E., ISA Press.

Programmable Controllers, 4th Edition, by Thomas A. Hughes, ISA Press.

 

 

 

 

 

 

AutoQuiz: Motor Shaft Speed Relationship to Frequency and Number of Poles

AutoQuiz: Motor Shaft Speed Relationship to Frequency and Number of Poles

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

 

Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program. The following question comes from the CAP study guide, Performance Domain IV, Development, software development and coding.

Which of the following statements correctly defines the relationship between the shaft speed of an AC squirrel cage motor, the frequency of the power input, and the number of poles for which the motor is wound, assuming negligible slip?

a) the shaft speed is directly proportional to the number of poles and does not depend on the motor frequency
b) the shaft speed is directly proportional to the frequency and does not depend on the number of poles
c) the shaft speed is directly proportional to the frequency and is inversely proportional to the number of poles
d) the shaft speed is inversely proportional to the frequency and is directly proportional to the number of poles
e) none of the above

   

Click Here to Reveal the Answer

The correct answer is C, the shaft speed is directly proportional to the frequency and is inversely proportional to the number of poles. The shaft speed is related to frequency and the number of poles by the following equation: N = [(120 x F) / P] – Slip

where,

N = shaft speed (RPM)
F = frequency of the power supply (Hz)
P = number of stator poles (pole pairs)

Assuming no “slip,” if the power supply frequency increases (assuming the number of poles remains the same), the shaft speed will increase (directly proportional).  For the same motor, as the number of stator poles is increased (assuming a constant power supply frequency), the shaft speed will decrease (inversely proportional).

Reference: Dave Polka; Motors and Drives: A Practical Technology Guide, ISA Press.

AutoQuiz: Nonhazardous Pressurization Systems

AutoQuiz: Nonhazardous Pressurization Systems

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

 

Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.

What ISA RP12.4 (NFPA 496) defined type of pressurization system will reduce the classification within an enclosure from Division 1 to nonhazardous?

a) Type W
b) Type X
c) Type Y
d) Type Z
e) none of the above

   

Click Here to Reveal the Answer

 

A Type X pressurization system reduces the classification within the enclosure from Division 1 to nonhazardous and, therefore, permits the use of ignition-capable equipment inside the enclosure. A Type Y pressurization system reduces the classification within an enclosure from Division 1 to Division 2. A Type Z pressurization system reduces the classification within an enclosure from Division 2 to nonhazardous.

The correct answer is B, Type X.

Reference: Ernest Magison; Electrical Instruments in Hazardous Locations, 4th Edition; ISA Press.

AutoQuiz: What Is the Best Location in an HMI for the Graphic Display of a Distillation Column?

AutoQuiz: What Is the Best Location in an HMI for the Graphic Display of a Distillation Column?

AutoQuiz is edited by Joel Don, ISA’s social media community manager.

 

Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program. The following question comes from the CAP study guide, Performance Domain IV, Development, software development and coding.

The graphic display for a distillation column in a refining train would BEST fit in the HMI display hierarchy at which level?

a) plant
b) area
c) group
d) loop
e) none of the above

   

Click Here to Reveal the Answer

 

A typical hierarchy has displays at four levels:

Plant level: Provides information regarding the entire plant

Area level: Provides information on portions of the plant equipment that is related in some way

Group level: Provides information for the control loops and data points relating to a single process unit within a plant area

Loop level: Provides information that deals with individual control loops, sequences, or data points

A distillation column refers to one piece of equipment in the distillation process, which will contain several loops. Therefore, it falls into the group-level category.

The correct answer is C, the group level.

Reference: Lukas, Michael P., Distributed control systems: Their evaluation and design

 

Pin It on Pinterest