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100+ Free MS Welding Practice Questions

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2026 Statistics

Key Facts: MS Welding Exam

70%

Passing Score

PSI MS Contractor Bulletin 4/23/2026

60 Q

Official Exam Questions

PSI MS Contractor Bulletin 4/23/2026

2 hours

Time Allowed

PSI MS Contractor Bulletin 4/23/2026

$120

PSI Exam Fee

PSI MS Contractor Bulletin 4/23/2026

Open book

Exam Format

PSI MS Contractor Bulletin 4/23/2026

MS Welding PSI trade exam: 60 questions, 70% pass, 2 hours, fee $120. Open-book MSBOC classification (bulletin 4/23/2026).

Sample MS Welding Practice Questions

Try these sample questions to test your MS Welding exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.

1On oxyacetylene equipment, fuel-gas (acetylene) hose and torch fittings are made with which thread to keep them from being connected to the oxygen side?
A.Left-hand (reverse) threads, often with a notched nut
B.Right-hand threads identical to oxygen fittings
C.Metric fine threads with no handedness convention
D.Pipe threads that seal only with Teflon tape
Explanation: US oxyfuel practice uses left-hand (reverse) threads on acetylene and other fuel-gas connections so they cannot be screwed onto oxygen fittings. The fuel nut is often notched so a welder can identify it by feel. Oxygen uses right-hand threads. Never force a mismatched fitting or install a right-to-left adapter.
2Under OSHA 29 CFR 1910.253, acetylene shall not be generated, piped (except in approved cylinder manifolds), or utilized at a pressure in excess of:
A.15 psig (103 kPa gauge)
B.50 psig
C.200 psig cylinder pressure
D.5 psig
Explanation: OSHA 1910.253(a)(2) states that under no condition shall acetylene be generated, piped (except approved cylinder manifolds), or utilized at a pressure in excess of 15 psig (103 kPa gauge) or 30 psia. Free acetylene becomes unstable above that pressure. Shop working pressures at the torch are kept well below this legal ceiling.
3When oxygen cylinders are in storage, OSHA 1910.253 requires them to be separated from fuel-gas cylinders by:
A.A minimum of 20 feet, or a noncombustible barrier at least 5 feet high with at least a one-half-hour fire-resistance rating
B.A cardboard partition if both cylinder valves are closed
C.Three feet of open space and a painted stripe on the floor
D.Any convenient aisle, regardless of distance
Explanation: OSHA 1910.253(b)(4)(iii) requires stored oxygen cylinders to be kept at least 20 feet (6.1 m) from fuel-gas cylinders or combustible materials, or separated by a noncombustible barrier at least 5 feet (1.5 m) high with a fire-resistance rating of at least one-half hour. The rule exists because oxygen intensifies any fuel-gas fire.
4A correctly adjusted neutral oxyacetylene flame is recognized by:
A.A long white acetylene feather extending well beyond the inner cone
B.A short, pointed inner cone and a loud hissing sound from excess oxygen
C.A well-defined bluish-white inner cone and a light-blue outer envelope, with the acetylene feather just gone
D.A yellow sooty flame produced with the oxygen valve closed
Explanation: A neutral flame uses essentially equal volumes of oxygen and acetylene. It has two zones: a sharp bluish-white inner cone and a larger light-blue outer envelope. The acetylene feather of a carburizing flame has just disappeared. Neutral is the usual flame for fusion welding carbon steel because it neither carburizes nor oxidizes the puddle.
5In standard US oxyfuel color coding, the acetylene hose is typically which color?
A.Red
B.Black only, with no fuel identification
C.Yellow with an oxygen stripe
D.Green
Explanation: US practice colors the acetylene (fuel) hose red and the oxygen hose green. Combined with left-hand fuel threads and right-hand oxygen threads, the color code is a first-line defense against cross-connection. Confirm the gas by the cylinder and regulator labels, not by hose color alone if the hoses have been replaced incorrectly.
6A carburizing (reducing) oxyacetylene flame is produced by excess acetylene. Its distinctive appearance is:
A.Three zones, including a white acetylene feather between the inner cone and the outer envelope
B.A short purple inner cone and a sharp hiss
C.No inner cone at all
D.Two zones only, with no acetylene feather
Explanation: Excess acetylene produces three visible zones: the inner cone, a whitish acetylene feather, and the outer envelope. The length of the feather shows how carburizing the flame is. That extra carbon can harden or embrittle steel, so a carburizing flame is not the usual choice for fusion welding mild steel, though it is used for some hardfacing and nonferrous work.
7Compressed-gas welding cylinders in the shop should be stored and used:
A.Upright and secured (for example, chained) so they cannot tip over
B.Loose on a hand truck with the caps off at all times
C.Inside an unventilated locker to hide them from traffic
D.On their sides so the valve is easier to reach
Explanation: Cylinders are stored and used valve-end up and secured so they cannot be knocked over and shear a valve. Acetylene cylinders especially must remain upright because the gas is dissolved in a solvent. OSHA also requires assigned, well-ventilated storage away from stairs and combustibles, and valve-protection caps hand-tight when cylinders are not in use.
8What is the primary difference between a check valve and a flashback arrestor on an oxyacetylene outfit?
A.Check valves are used only on oxygen; flashback arrestors are used only on acetylene
B.They are identical devices with two trade names
C.A check valve only stops reverse gas flow; a flashback arrestor is built to stop or quench a flame front traveling back toward the hose or regulator
D.A flashback arrestor only measures pressure; a check valve extinguishes flame
Explanation: A check valve (non-return valve) lets gas flow one way and blocks reverse mixing of oxygen and fuel. It will not stop a flame. A flashback arrestor contains a flame-quenching element and often a check valve and thermal or pressure shutoff. Cornell EHS and equipment makers emphasize arrestors on regulator outlets and/or torch inlets because check valves alone do not prevent flashback.
9In oxyacetylene cutting of mild steel, the cutting oxygen jet removes metal primarily by:
A.Electric arc erosion from the torch tip
B.Melting the steel and blowing liquid metal out of the kerf with no chemical reaction
C.Rapid oxidation (burning) of iron that has been preheated to kindling temperature, with the molten oxides blown from the kerf
D.Dissolving the steel in acetylene
Explanation: Oxyfuel cutting is a chemical process. Preheat flames bring the steel to kindling temperature, then a high-velocity jet of pure oxygen oxidizes the iron. The molten oxides are blown out of the kerf. That is why the process works on carbon steel and other metals that oxidize readily, and why stainless and nonferrous metals generally do not cut the same way.
10Why must oil, grease, and oily gloves be kept off oxygen cylinders, regulators, and fittings?
A.Grease is required to seal CGA 540 oxygen connections
B.Oil only stains the brass and has no safety effect
C.Oxygen can cause hydrocarbons to ignite violently, even without an open flame
D.Oil improves regulator diaphragm life and should be applied lightly
Explanation: High-pressure oxygen supports rapid combustion. Oil or grease on a regulator, hose, or fitting can ignite or explode when oxygen is introduced. Keep oxygen equipment clean and use only oxygen-compatible lubricants specified by the manufacturer. Never use ordinary oil to free a stuck regulator or to 'help' a thread seal.

About the MS Welding Exam

Mississippi Welding is an MSBOC specialty classification trade examination administered by PSI. Official scope is unlimited welding work, including oxyacetylene welding and cutting, brazing, and pipe welding. The official open-book exam has 60 questions, a 70% passing standard, and 2 hours allowed. PSI fee is $120 per portion (Candidate Information Bulletin updated 4/23/2026). This English-language MCQ bank is a study aid for the official content outline; it is not an official PSI form, does not replace the required Law and Business Management exam, and is not a substitute for MSBOC application review, welder performance qualification, or the official open-book examination.

Questions

60 scored questions

Time Limit

2 hours

Passing Score

70%

Exam Fee

$120 (PSI Services LLC (for Mississippi State Board of Contractors))

MS Welding Exam Content Outline

18%

Oxyacetylene Welding and Cutting

Oxyfuel setup, cutting, and fusion welding

10%

Blueprint and Plan Reading

Welding symbols, views, and shop drawings

8%

Brazing

Brazing filler metals, flux, and joint design

10%

Pipe Welding

Pipe joint preparation, positions, and procedures

17%

Materials

Base metals, filler metals, and material identification

15%

SMAW

Shielded metal arc welding electrodes and technique

15%

GTAW

Gas tungsten arc welding setup and technique

7%

Testing and Inspection

Visual inspection and common NDT methods

How to Pass the MS Welding Exam

What You Need to Know

  • Passing score: 70%
  • Exam length: 60 questions
  • Time limit: 2 hours
  • Exam fee: $120

Keys to Passing

  • Work through all 100 available questions
  • Review every answer and explanation
  • Track weak areas and revisit them
  • Use our AI tutor for tough concepts

MS Welding Study Tips from Top Performers

1Study only the approved references listed for Welding in the current PSI Mississippi Contractor bulletin (updated 4/23/2026): Modern Welding, 11th Edition (2013) and Pipe Welding Procedures (Rampaul, 2003)
2Practice open-book navigation of process chapters (oxyfuel, SMAW, GTAW, brazing) and inspection chapters
3Work pipe-position and electrode-classification questions with real calculations where the handbook supports them
4Confirm MSBOC classification scope and eligibility at msboc.us before scheduling with PSI
5All applicants must also pass Law and Business Management unless it is waived

Frequently Asked Questions

How many questions are on the MS Welding exam?

The official PSI examination has 60 scored questions (plus possible unscored experimental items). Passing is 70% within 2 hours.

How much does the MS Welding exam cost?

PSI lists $120 per examination portion (Candidate Information Bulletin updated 4/23/2026). MSBOC application fees are separate: $400 commercial or $50 residential. Additional classifications are $100 each.

Is the Mississippi contractor exam open book?

Yes. PSI administers MSBOC classification exams as open book. Only bulletin-listed approved references are allowed; temporary tabs such as Post-it notes are prohibited.

Do I still need the Law and Business Management exam?

Yes. MSBOC requires the Mississippi Law and Business Management exam (50 questions, 70%, 2 hours) of all applicants. Reciprocity may waive a trade exam in some cases but does not waive Law and Business.