Maryland Stationary Engineer Grade 3 License Exam Prep 2026: Complete Study Guide with 300+ Practice Questions, Detailed Explanations, 100–299 HP Operation Limits, Boiler Safety, Water Treatment, and PSI Testing Strategies – Pass with Confidence

Maryland Stationary Engineer Grade 3 License Exam Prep
2026: Complete Study Guide with 300+ Practice Questions,
Detailed Explanations, 100–299 HP Operation Limits, Boiler
Safety, Water Treatment, and PSI Testing Strategies – Pass
with Confidence

The Grade 3 license authorizes operation of boilers and equipment rated between 100 and 299 horsepower in any

building. Qualification requires 2 years as a Grade 4 or Grade 5 engineer, or 1 year of experience combined with

6 credit hours/CEUs in boiler operations. A valid Navy certificate with steam boiler training is also accepted. Grade

3 engineers operate and maintain boiler systems in commercial buildings, schools, and light industrial facilities.



SECTION 1: BOILER OPERATION & COMBUSTION
1. What is the maximum horsepower (HP) a Grade 3 stationary engineer is authorized to
operate in Maryland?

 A) 30 – 99 HP
 B) 100 – 299 HP
 C) 300 – 499 HP
 D) 500 HP or more

Explanation: A Grade 3 license authorizes operation of boilers and equipment in the
range of 100 to 299 horsepower. Grade 2 is required for 300–499 HP, and Grade 1 for 500
HP and above.




2. What is the minimum experience required to qualify for the Grade 3 examination via the
progressive pathway?

 A) 6 months as Grade 4
 B) 1 year as Grade 4 or 5
 C) 2 years as Grade 4 or 5

, D) 3 years as Grade 5

Explanation: The standard progressive pathway requires 2 years of documented
experience as a Grade 4 or Grade 5 stationary engineer.




3. What alternative qualification can reduce the Grade 3 experience requirement?

 A) High school diploma
 B) 1 year as Grade 4/5 plus 6 credit hours or CEUs in boiler operations
 C) Valid driver's license
 D) First aid certification

Explanation: A combination of 1 year of experience plus 6 credit hours or CEUs in boiler
safety or operations qualifies for the Grade 3 examination.




4. What is the first step before lighting off a boiler burner?

 A) Open the fuel valve
 B) Verify water level in the gauge glass
 C) Close the steam outlet valve
 D) Increase combustion air

Explanation: Before any startup, the operator must confirm that the boiler has a safe
water level to prevent overheating and tube damage.




5. What is the purpose of a low-water fuel cutoff?

 A) Reduce fuel pressure
 B) Shut off fuel supply when water level drops below safe limits
 C) Increase feedwater flow
 D) Control steam pressure

, Explanation: A low-water fuel cutoff is a critical safety device that interrupts the fuel
supply if water level falls to a dangerous point, preventing boiler failure.




6. What is the function of a safety valve on a boiler?

 A) Control steam temperature
 B) Relieve pressure if maximum allowable working pressure is exceeded
 C) Regulate fuel flow
 D) Monitor water chemistry

Explanation: The safety valve automatically opens at the set pressure to prevent
overpressure and potential explosion.




7. What is the purpose of a gauge glass on a boiler?

 A) Measure steam pressure
 B) Visually indicate water level in the boiler
 C) Control feedwater flow
 D) Monitor flue gas temperature

Explanation: The gauge glass provides a direct visual indication of the water level, which
is essential for safe boiler operation.




8. How often should gauge glasses be blown down?

 A) Weekly
 B) At least once per shift or daily
 C) Monthly
 D) Annually

, Explanation: Blowing down gauge glasses daily confirms that water passages are clear
and the water level indication is accurate.




9. What is the purpose of a try lever on a safety valve?

 A) Adjust pressure setting
 B) Manually test the valve operation
 C) Lock the valve closed
 D) Increase valve capacity

Explanation: The try lever allows manual testing of the safety valve to ensure it is not
stuck and will open freely when required.




10. What is the function of a burner management system (BMS)?

 A) Adjust fuel viscosity
 B) Control safe startup, operation, and shutdown of burners
 C) Monitor stack emissions
 D) Regulate feedwater temperature

Explanation: The BMS ensures proper purging, ignition sequencing, flame monitoring,
and safety interlocks to prevent unsafe conditions.




11. What is the minimum required purging time for a boiler before ignition?

 A) No purge required
 B) 30 seconds
 C) 5 to 10 air changes or as specified by manufacturer
 D) 1 minute