CPM - Certified Plant Mechanic Blueprint Reading and Schematics Questions and Answers — Questions and Answers
Question 1: On an engineering drawing, what type of line is used to represent an edge or feature of an object that is not visible in the current view?
- A series of short, evenly spaced dashes (Correct answer)
- A thin, solid line with freehand breaks
- A long dash followed by a short dash, repeated
- A thick, solid, continuous line
Correct answer: A series of short, evenly spaced dashes
Hidden lines, represented by a series of short dashes, are used to show surfaces, edges, or corners of an object that are hidden from sight in a particular orthographic projection. They are crucial for understanding the internal or rear features of a part without needing a separate view.
Question 2: A mechanic is looking at a blueprint that uses the standard third-angle orthographic projection system common in the United States. If the mechanic is viewing the front view, where would the top view of the object be located on the drawing?
- To the right of the front view
- Below the front view
- Directly above the front view (Correct answer)
- On a separate sheet designated as "Top"
Correct answer: Directly above the front view
In third-angle projection, the standard in the United States, the views are arranged as if the object is being unfolded. The top view is placed directly above the front view, and the right-side view is placed directly to the right of the front view.
Question 3: While reviewing a Piping and Instrumentation Diagram (P&ID), a technician sees a symbol that looks like a bow-tie (two triangles with their points touching) inserted in a process line. What does this symbol represent?
- A check valve
- A gate valve (Correct answer)
- A centrifugal pump
- An orifice plate
Correct answer: A gate valve
The standard ISA (International Society of Automation) symbol for a generic or gate valve is two triangles with their points touching, resembling a bow-tie, inserted into the process line. Other valves, like globe valves (a filled-in circle) or check valves (a triangle with a line through it), have distinct symbols.
Question 4: A plant mechanic is troubleshooting a hydraulic system using its schematic. The mechanic finds a symbol consisting of a single square (or envelope), a zig-zag line inside representing a spring, and an arrow that is offset from the flow path, indicating it is normally closed. A dashed pilot line connects the inlet to the spring chamber. What is the function of this component?
- It filters the hydraulic fluid before use.
- It cools the hydraulic fluid before it returns to the reservoir.
- It allows fluid to flow in only one direction.
- It protects the system from over-pressurization by diverting flow to the tank. (Correct answer)
Correct answer: It protects the system from over-pressurization by diverting flow to the tank.
This collection of symbols describes a direct-acting pressure relief valve. The normally closed symbol, opposed by an adjustable spring and actuated by a pilot line sensing upstream pressure, indicates its function is to open and relieve excess pressure to the tank, thus protecting the system.
Question 5: When examining a standard electrical ladder diagram, which of the following best describes the typical placement of components?
- Output devices are on the left rail, and input devices are on the right rail.
- Both input and output devices are located on the left side of a rung.
- Output devices are on the top rungs, and input devices are on the bottom rungs.
- Input devices are on the left side of a rung, and output devices are on the right. (Correct answer)
Correct answer: Input devices are on the left side of a rung, and output devices are on the right.
In a standard ladder diagram, the vertical lines (rails) are the power source. The horizontal lines (rungs) represent individual circuits. By convention, input or control devices (switches, sensors) are placed on the left side of the rung, and output or load devices (coils, lights, solenoids) are placed on the right side, just before the neutral rail.
Question 6: A blueprint calls for joining two steel plates at a T-joint. The welding symbol on the drawing shows a triangle placed below the solid horizontal reference line. What does this indicate?
- A fillet weld is required on the "other side" of the joint.
- A groove weld is required on the "arrow side" of the joint.
- A fillet weld is required on the "arrow side" of the joint. (Correct answer)
- The weld must be ground flush after completion.
Correct answer: A fillet weld is required on the "arrow side" of the joint.
According to American Welding Society (AWS) standards, the triangle is the symbol for a fillet weld. Any symbol placed *below* the reference line applies to the "arrow side" — the side of the joint that the arrow is pointing to. Therefore, a triangle below the reference line specifies a fillet weld on the arrow side.
CPM - Certified Plant Mechanic Blueprint Reading and Schematics Questions and Answers
On an engineering drawing, what type of line is used to represent an edge or feature of an object that is not visible in the current view?