Certified Pipefitter Blueprint Reading and Symbols 5

Question 1

On an isometric piping drawing, a line that runs diagonally at 30° from horizontal and moves toward the upper-left corner of the drawing represents flow in which direction?

Accepted Answer

Running right-to-left in the real-world horizontal plane

Answer

In standard isometric piping drawings, the three axes are: horizontal (left-right), 30° upper-right (front-to-back going away), and 30° upper-left (front-to-back coming toward). A line running at 30° toward the upper-left represents piping traveling right-to-left in the real-world horizontal plane. Understanding axis orientation is critical for translating isometric drawings into field installations.

Question 2

A piping and instrumentation diagram (P&ID) shows a control valve symbol with a diagonally hatched body and the letter 'FO' next to it. What does this designation mean for system shutdown behavior?

Accepted Answer

The valve fails open on loss of instrument air or power

Answer

'FO' on a P&ID control valve designation stands for 'Fail Open,' meaning that upon loss of the actuating signal (instrument air or electrical power), the valve spring-returns to the fully open position. This is a critical process safety designation — pipefitters must install the correct actuator spring orientation to achieve the intended fail-safe state. 'FC' denotes Fail Closed and 'FL' or 'FI' denotes Fail-in-Last-position.

Question 3

On a plan-view piping drawing, you encounter a break symbol on a pipe run with the notation 'SEE ISO-247' on one side and 'CONT'D' on the other. The break symbol shows a small 'N' written inside it. What does the 'N' signify?

Accepted Answer

The pipe run continues but crosses into a different drawing zone or sheet

Answer

A break symbol on a plan view with a letter (such as 'N') inside indicates a drawing zone or sheet match line — the pipe run continues beyond the current sheet boundary into the referenced drawing (ISO-247 in this case). The letter typically corresponds to the zone grid reference or a match-line identifier. This prevents draftsmen from having to squeeze an entire long pipe run onto one sheet while maintaining drawing continuity. Misreading this as a compass direction or size change is a common and costly field error.

Question 4

A weld symbol on a pipe fabrication drawing shows a circle at the intersection of the reference line and the arrow, combined with a tail containing the notation 'RT 100%'. What is the correct interpretation of this combination?

Accepted Answer

The weld must be a full-penetration groove weld inspected by radiographic testing on the entire weld circumference

Answer

The circle at the junction of the reference line and arrow line is the 'all-around' weld symbol, indicating the weld extends completely around the joint (full circumference for pipe). The tail notation 'RT 100%' specifies Radiographic Testing on 100% of the weld — meaning every inch of the weld must be X-rayed and meet acceptance criteria before the joint is accepted. Together, these symbols define both the weld extent and the non-destructive examination (NDE) requirement.

Question 5

A piping isometric shows a reducer with the callout '6" x 4" ECC RED BOP'. Which of the following installation configurations correctly satisfies this specification?

Accepted Answer

The reducer is installed with the flat side on the bottom, keeping the bottom-of-pipe elevation constant through the transition

Answer

'ECC RED BOP' specifies an Eccentric Reducer installed Bottom-of-Pipe flat. This means the flat side (straight side) of the eccentric reducer faces down, keeping the bottom-of-pipe elevation constant across the size change. This configuration is used in pump suction lines to prevent air pocket formation and to maintain a consistent pipe support elevation. 'BOP' is Bottom-of-Pipe; 'TOP' would be Top-of-Pipe flat, used in gravity-drain or steam condensate applications.

Certified Pipefitter Practice Test

Certified Pipefitter Practice Test

Certified Pipefitter Blueprint Reading and Symbols 5