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NM Boiler Operator practice questions

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Question 1Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Under the ASME Boiler and Pressure Vessel Code, which section contains the construction requirements for power boilers?

  1. Section IV
  2. Section VIII, Division 1
  3. Section I Correct answer.
  4. Section II, Part D

Explanation

Section I applies to power boilers, including electric boilers and high-temperature water boilers, and covers materials, design, fabrication, inspection, and stamping. Section IV is for heating boilers, while Section VIII and Section II address pressure vessels and material properties, respectively.

Question 2Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A newly constructed power boiler that complies with ASME Section I receives which Code symbol stamp on its nameplate?

  1. S Correct answer.
  2. R
  3. U
  4. H

Explanation

The 'S' symbol stamp identifies a power boiler built to Section I. The 'H' stamp is used for heating boilers, 'U' for pressure vessels, and 'R' for repairs.

Question 3Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

For a Section I power boiler, the lowest set pressure of any safety valve must not exceed which pressure?

  1. 110% of the maximum allowable working pressure
  2. The maximum allowable working pressure Correct answer.
  3. 150% of the maximum allowable working pressure
  4. 125% of the maximum allowable working pressure

Explanation

Section I requires at least one safety valve set at or below the maximum allowable working pressure so that the boiler is protected before the MAWP is exceeded. Higher pressures listed are associated with accumulation allowances or hydrostatic testing, not normal safety-valve set pressure.

Question 4Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A new Section I power boiler with a maximum allowable working pressure of 200 psig is to receive the standard hydrostatic test. At what test pressure should it be conducted?

  1. 200 psig
  2. 250 psig
  3. 300 psig Correct answer.
  4. 400 psig

Explanation

The standard hydrostatic test under Section I is conducted at 1.5 times the maximum allowable working pressure, which for 200 psig is 300 psig. The test verifies pressure-tightness and structural integrity before the boiler is placed in service.

Question 5Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What is the intended function of a fusible plug installed in a fire-tube boiler?

  1. To relieve steam pressure before the safety valve lifts
  2. To drain sludge from the lowest point of the boiler
  3. To prevent backflow of feedwater into the boiler
  4. To warn of low water by melting when the plug is uncovered Correct answer.

Explanation

A fusible plug contains a low-melting alloy that melts when the plug is no longer covered by water, releasing steam or water as a warning of low water. It is a warning device and does not replace a low-water fuel cutoff or a safety valve.

Question 6Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which value is required to be marked on the nameplate of a Section I power boiler?

  1. The model of the feedwater pump
  2. The maximum allowable working pressure Correct answer.
  3. The heating value of the fuel
  4. The name of the boiler operator

Explanation

Section I nameplates identify the boiler's design limits, including maximum allowable working pressure, design temperature, and capacity. Operator names, feedwater pump models, and fuel heating values are not Code nameplate markings.

Question 7Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What is the minimum number of safety valves required on a Section I power boiler?

  1. Three, regardless of boiler size
  2. One Correct answer.
  3. None, if a relief valve is installed
  4. Two, regardless of boiler size

Explanation

Section I requires each power boiler to have at least one safety valve, with total relieving capacity sufficient for the maximum steam generation. Additional valves may be required by the design or by the capacity of a single valve, but two or three are not universal minimums.

Question 8Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A Section I power boiler has a maximum allowable working pressure of 200 psig and its safety valve is set at 200 psig. During an accumulation test, what is the maximum pressure permitted?

  1. 220 psig Correct answer.
  2. 200 psig
  3. 230 psig
  4. 210 psig

Explanation

During the accumulation test, Section I limits the pressure to 10% above the maximum allowable working pressure when the boiler is fired at maximum capacity. Ten percent of 200 psig is 20 psig, so the highest permitted pressure is 220 psig.

Question 9Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which ASME Manufacturer's Data Report form is used for a new Section I power boiler?

  1. Form R-1
  2. Form H-2
  3. Form P-2 Correct answer.
  4. Form U-1

Explanation

A new power boiler constructed to Section I is documented on Manufacturer's Data Report Form P-2. Form H-2 applies to heating boilers, Form U-1 to pressure vessels, and Form R-1 to repairs.

Question 10Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What is the minimum size permitted for a handhole inspection opening in a Section I boiler?

  1. 1 in. by 2 in.
  2. 2 in. by 3 in. Correct answer.
  3. 3 in. by 4 in.
  4. 4 in. by 6 in.

Explanation

Section I sets the minimum handhole opening at 2 in. by 3 in. so that the opening is large enough for inspection while remaining smaller than a manhole. Larger openings are acceptable, but smaller dimensions do not meet the Code minimum.

Question 11Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A boiler is designed for a maximum allowable working pressure of 15 psig steam. Under the ASME Boiler and Pressure Vessel Code, which Section contains the construction requirements that apply to this boiler?

  1. Section VIII
  2. Section IV Correct answer.
  3. Section I
  4. Section IX

Explanation

Section IV applies to heating boilers limited to 15 psig steam, 160 psig water, and 250°F. Section I applies to power boilers that exceed those heating-boiler limits. The 15 psig steam design therefore falls under Section IV construction rules.

Question 12Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which ASME Boiler and Pressure Vessel Code Section establishes the rules for qualifying welding procedures and welders used in boiler construction?

  1. Section II
  2. Section V
  3. Section VIII
  4. Section IX Correct answer.

Explanation

Section IX contains the qualification requirements for welding, brazing, and fusing procedures and personnel. Boiler construction under Section I references Section IX for those qualifications. Section II addresses materials and Section V addresses nondestructive examination.

Question 13Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which ASME Boiler and Pressure Vessel Code Section contains the material specifications, such as tensile requirements and allowable stress values, used in boiler construction?

  1. Section I
  2. Section IV
  3. Section II Correct answer.
  4. Section IX

Explanation

Section II, Materials, contains the specifications and properties for materials permitted in code construction. Section I gives boiler construction rules and references Section II for material data. This separation keeps material requirements in a single referenced section.

Question 14Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A Section I power boiler has a maximum allowable working pressure of 200 psig. Its safety valve capacity must prevent the pressure from rising more than 6% above the MAWP during full steam generation. What is the maximum pressure allowed during that accumulation?

  1. 220 psig
  2. 210 psig
  3. 212 psig Correct answer.
  4. 206 psig

Explanation

Section I limits safety valve accumulation to 6% above the maximum allowable working pressure. Six percent of 200 psig is 12 psig, so the maximum allowed pressure is 200 plus 12, or 212 psig. The safety valve capacity must be adequate to hold the boiler at or below that pressure.

Question 15Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What is the minimum size permitted for a manhole opening in a Section I boiler?

  1. 11 in × 15 in oval or 11 in diameter
  2. 10 in × 16 in oval or 12 in diameter Correct answer.
  3. 12 in × 16 in oval or 14 in diameter
  4. 8 in × 12 in oval or 10 in diameter

Explanation

Section I sets the minimum manhole size at 10 in × 16 in oval or 12 in diameter. Handhole openings are permitted to be smaller because they are intended for inspection and cleaning access rather than entry. A manhole below that minimum would not satisfy the code inspection-opening requirement.

Question 16Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Before a new Section I power boiler receives its Code symbol stamp, who must certify the Manufacturer's Data Report?

  1. Owner, manufacturer, and inspector jointly
  2. Manufacturer and inspector Correct answer.
  3. Inspector only
  4. Manufacturer only

Explanation

The Manufacturer's Data Report for a Section I boiler requires certification by the manufacturer and by the Authorized Inspector. The inspector's signature confirms that the required inspections and tests were performed and accepted. The owner is not a required certifying party on the manufacturer's report.

Question 17Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A Section I steam boiler has a maximum allowable working pressure of 150 psig. Which pressure gauge range satisfies the Code requirement?

  1. 0 to 300 psig Correct answer.
  2. 0 to 200 psig
  3. 0 to 150 psig
  4. 0 to 500 psig

Explanation

Section I requires the pressure gauge range to be at least 1.5 times the maximum allowable working pressure and not more than 2 times that pressure. For 150 psig, the acceptable range is therefore from 225 psig to 300 psig at the top of the scale. A 0 to 300 psig gauge meets that requirement.

Question 18Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A steam line is connected to the main steam outlet of a Section I power boiler and extends beyond the boiler external piping boundary. Which ASME code governs the design of that steam line?

  1. ASME B31.1 Correct answer.
  2. ASME Section I
  3. ASME Section IV
  4. ASME Section VIII

Explanation

ASME B31.1, Power Piping, governs power piping beyond the boiler external piping boundary defined by Section I. Section I covers the boiler and its boiler external piping up to that boundary. Once the steam line is beyond that boundary, B31.1 design rules apply.

Question 19Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A circular opening is cut in the shell of a Section I boiler and no additional reinforcing material is added. What does the Code require for this opening?

  1. The strength removed by the opening must be replaced Correct answer.
  2. The opening diameter must be limited to half the shell thickness
  3. The entire shell course must be thickened
  4. The opening must be closed with a blank flange

Explanation

Section I requires openings in boiler shells to be reinforced so that the strength removed by the opening is replaced. This compensation may be provided by extra thickness in the shell, the nozzle, or a reinforcing pad. Without compensation, the opening would create an unacceptable weak point in the pressure-retaining shell.

Question 20Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Section I requires post-weld heat treatment for certain carbon steel boiler welds. What is the primary purpose of this treatment?

  1. To increase the hardness of the weld metal
  2. To improve penetration of the weld root
  3. To relieve residual welding stresses Correct answer.
  4. To prevent galvanic corrosion at the weld joint

Explanation

Post-weld heat treatment raises the weldment to a controlled temperature and cools it slowly to relax residual stresses. Reducing those stresses lowers the risk of cracking and distortion in the completed boiler. Hardness control may be a secondary effect, but stress relief is the primary Code purpose.

Question 21Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which ASME Boiler and Pressure Vessel Code Section contains the requirements for nondestructive examination methods such as radiography and ultrasonic examination?

  1. Section II, Materials
  2. Section V, Nondestructive Examination Correct answer.
  3. Section IX, Welding, Brazing, and Fusing Qualifications
  4. Section I, Power Boilers

Explanation

Section V is the Code section that describes nondestructive examination methods and their performance requirements. Section I invokes those methods for power boiler construction and supplies the applicable acceptance criteria. Section II and Section IX address materials and qualification, respectively, not NDE method requirements.

Question 22Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A heating boiler is constructed to ASME Section IV. Which Code symbol stamp is applied to its nameplate?

  1. U
  2. H Correct answer.
  3. V
  4. S

Explanation

Section IV heating boilers use the H Code symbol stamp. The S stamp is used for Section I power boilers, and the U stamp is used for Section VIII pressure vessels. A V stamp is associated with pressure relief valves, not with the complete Section IV heating boiler.

Question 23Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Who performs the required Code inspections during construction of a Section I power boiler at the manufacturer's shop?

  1. The manufacturer's quality control manager
  2. An Authorized Inspector Correct answer.
  3. The owner's boiler operator
  4. The purchaser's insurance broker

Explanation

Section I construction inspections are performed by an Authorized Inspector who acts for an ASME-accredited Authorized Inspection Agency. The manufacturer's quality control personnel support construction but do not replace the Code inspector. The purchaser, broker, and owner's operator do not perform the required shop Code inspections.

Question 24Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

In the Section I formula for minimum thickness of a cylindrical shell under internal pressure, what does the symbol E represent?

  1. Joint or ligament efficiency Correct answer.
  2. Modulus of elasticity
  3. Thermal expansion coefficient
  4. Corrosion allowance

Explanation

In the Section I shell thickness formula, E is the efficiency of the welded joint or ligament that reduces the shell's effective strength. It is not a material elastic property or a corrosion allowance. The designer uses the applicable joint efficiency together with allowable stress and pressure to determine minimum thickness.

Question 25Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Where must a safety valve for a Section I power boiler be connected?

  1. On the main steam line outside the boiler proper
  2. On the feedwater line before the check valve
  3. Directly to the boiler shell or drum Correct answer.
  4. At the superheater inlet header

Explanation

Section I requires the boiler safety valve to be connected directly to the boiler shell or drum so it senses true boiler pressure. The connection must be independent of other steam or water connections and must not include a shutoff valve. Mounting the valve on external piping can prevent it from protecting the boiler properly.

Question 26Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A Section I power boiler is equipped with a superheater. Where must at least one safety valve be located?

  1. On the boiler drum only
  2. On the main steam line after the stop valve
  3. At the superheater inlet
  4. At the superheater outlet Correct answer.

Explanation

Section I requires at least one safety valve at the superheater outlet so the superheater is protected against overpressure. Drum safety valves protect the boiler drum but do not ensure protection of the superheater. A valve downstream of the main stop valve cannot protect the superheater when the stop valve is closed.

Question 27Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What is required for the discharge piping of a Section I boiler safety valve?

  1. Into the boiler blowoff line below the valve
  2. Through an isolation valve to permit maintenance
  3. Into the feedwater tank to recover waste heat
  4. Open to atmosphere, with no valve and drainage Correct answer.

Explanation

Safety valve discharge piping must be arranged so the valve can relieve freely, usually open to a safe atmosphere location with no shutoff valve. It must also drain condensate so water cannot collect and obstruct relief. Connecting the discharge to other piping can create backpressure or isolation that defeats the valve.

Question 28Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What is the primary function of a water column installed on a boiler?

  1. To drain sludge from the boiler bottom
  2. To separate steam before the superheater
  3. To prevent feedwater backflow
  4. To steady the water level indication Correct answer.

Explanation

A water column provides a calmer, more representative water level for the gauge glass by dampening the turbulence and surging inside the boiler. It does not separate steam for the superheater, act as a feedwater check valve, or serve as a bottom blowoff. Its purpose is reliable water level indication for safe operation.

Question 29Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A hot-water boiler is designed for a maximum allowable working pressure of 150 psig and a maximum temperature of 260°F. Which ASME Boiler and Pressure Vessel Code Section governs its construction?

  1. Section VIII, Division 1, Pressure Vessels
  2. Section I, Power Boilers Correct answer.
  3. Section IV, Heating Boilers
  4. Section II, Materials

Explanation

Section I applies to hot-water boilers that exceed either 160 psig or 250°F, so the 260°F design temperature brings this boiler under Section I even though its pressure is below 160 psig. Section IV is limited to heating boilers at or below both of those thresholds. Section VIII and Section II do not govern boiler construction in this case.

Question 30Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A jurisdiction has adopted the 2021 edition of the ASME Boiler and Pressure Vessel Code. A manufacturer begins a new Section I boiler after that adoption but holds a certificate of authorization issued under the 2019 edition. Which Code edition governs the boiler's construction?

  1. Either edition, at the manufacturer's option
  2. The 2021 edition adopted by the jurisdiction Correct answer.
  3. The 2019 edition, because the manufacturer's certificate references it
  4. The edition in effect when the boiler was ordered

Explanation

When a jurisdiction has adopted a Code edition, new boiler construction within that jurisdiction must meet the adopted edition. The manufacturer's certificate authorizes the manufacturer's scope of activity but does not freeze construction at the edition referenced when the certificate was issued. The adopted edition controls unless the jurisdiction grants a specific alternative.

Question 31Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which Code symbol stamp is applied to the nameplate of a boiler constructed to ASME Section I?

  1. S Correct answer.
  2. A
  3. H
  4. U

Explanation

Section I power boilers receive the S symbol stamp. The H stamp is for Section IV heating boilers, U is for Section VIII pressure vessels, and A is for assembly of power boilers.

Question 32Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What is the minimum size permitted for a handhole opening in a Section I boiler?

  1. 2 in × 3 in Correct answer.
  2. 6 in × 8 in
  3. 4 in × 6 in
  4. 3 in × 4 in

Explanation

Section I requires handhole openings to be at least 2 in. by 3 in. This minimum gives access for inspection and cleaning while preserving the required opening reinforcement.

Question 33Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What type of safety valve is conventionally used for a Section I steam boiler, excluding special Code Case provisions?

  1. Weighted-lever valve
  2. Rupture disk
  3. Pilot-operated valve
  4. Direct spring-loaded valve Correct answer.

Explanation

A direct spring-loaded safety valve is the conventional choice under the stated exclusion of special Code Case provisions. Steam pressure acts against the spring to open the valve at its set pressure, and the valve recloses as pressure falls. Approved pilot-operated designs may be permitted under applicable Code Case provisions.

Question 34Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A new Section I boiler has a MAWP of 250 psig. What is the minimum hydrostatic test pressure?

  1. 375 psig Correct answer.
  2. 250 psig
  3. 500 psig
  4. 312.5 psig

Explanation

Section I requires the hydrostatic test to be conducted at 1.5 times the maximum allowable working pressure. For a 250 psig MAWP, the minimum test pressure is 375 psig.

Question 35Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

A Section I boiler has a MAWP of 200 psig. What is the maximum allowable set pressure for its safety valve?

  1. 240 psig
  2. 220 psig
  3. 180 psig
  4. 200 psig Correct answer.

Explanation

The safety valve set pressure may not exceed the boiler's maximum allowable working pressure. Therefore the highest permitted set pressure is 200 psig.

Question 36Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which ASME document establishes requirements for controls and safety devices on automatically fired boilers?

  1. QAI-1
  2. NBIC
  3. Section VII
  4. CSD-1 Correct answer.

Explanation

ASME CSD-1 covers controls and safety devices for automatically fired boilers. It addresses items such as flame safeguards, low-water cutoffs, and operating controls.

Question 37Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

In Section I, what joint efficiency is used for a double-welded butt joint that receives full radiographic examination?

  1. 0.90
  2. 1.00 Correct answer.
  3. 0.70
  4. 0.85

Explanation

Section I assigns a joint efficiency of 1.00 to a double-welded butt joint when full radiographic examination is performed. Lower efficiencies apply when examination is less complete.

Question 38Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

What safety device is required on an automatically fired steam heating boiler under Section IV?

  1. Manual reset high-limit control
  2. Water column
  3. Low-water cutoff Correct answer.
  4. Pressure relief valve

Explanation

Section IV requires an automatically fired steam heating boiler to have a low-water fuel cutoff. This device stops fuel input when the water level falls below a safe point.

Question 39Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which ASME standard establishes qualification requirements for authorized inspectors who perform Code inspections?

  1. CSD-1
  2. NBIC
  3. Section IX
  4. QAI-1 Correct answer.

Explanation

ASME QAI-1 sets the qualification and certification requirements for authorized inspectors. These inspectors perform the Code inspections required during construction.

Question 40Boiler Construction, Design, and Code Requirements (ASME and adopted code editions)

Which document governs repairs and alterations to boilers after they have been placed in service?

  1. NBIC Correct answer.
  2. Section I
  3. CSD-1
  4. Section IV

Explanation

The National Board Inspection Code, NBIC, governs in-service repairs and alterations to boilers and pressure vessels. Section I and Section IV are construction codes, not the repair code.

Question 41Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

What is the primary function of the low-water fuel cutoff on a steam boiler?

  1. It opens to relieve pressure once the set point is reached.
  2. It stops the burner below the lowest safe level. Correct answer.
  3. It sounds an alarm but allows firing to continue.
  4. It starts the feedwater pump as the level drops.

Explanation

The low-water fuel cutoff is a safety interlock whose only duty is to stop combustion before the water level drops far enough to expose heated surfaces. It does not feed the boiler, relieve pressure, or merely alarm, because allowing continued firing without water would overheat and eventually rupture the metal.

Question 42Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

Why must the furnace of a gas-fired boiler be purged before the burner is lighted off?

  1. It proves that the low-water cutoff is working.
  2. It raises drum pressure above the light-off set point.
  3. It cools the refractory so that light-off is gradual.
  4. It clears combustible gases from the furnace before ignition. Correct answer.

Explanation

Air is forced through the furnace for a set time and volume before any attempt at ignition, which removes gas or vapour left from a previous trip, a leaking fuel valve, or an incomplete burn. Without that purge, a spark can ignite the accumulated mixture and produce a furnace explosion.

Question 43Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

A steam boiler safety valve is set to lift at 150 psig. What does the valve do when drum pressure reaches that point?

  1. It trips and locks out the burner until manually reset.
  2. It signals the pressuretrol to reduce firing rate.
  3. It opens and discharges steam until pressure drops. Correct answer.
  4. It throttles feedwater to hold drum level.

Explanation

The safety valve is the last line of overpressure protection and must open at its set pressure without any operator or control action. It stays open until pressure has fallen enough for it to reseat, and it is not used as a routine pressure control device.

Question 44Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

A cold fire-tube boiler is being placed in service. Which practice best protects the drum and tube sheets from thermal stress?

  1. Keep the main steam stop closed and omit any warm-up period to save time.
  2. Fill with cold water to the top of the glass and bring the burner to high fire.
  3. Fire at the maximum rate at once so the boiler reaches pressure before uneven heating can occur.
  4. Warm slowly at low fire with the vent open, then raise pressure gradually. Correct answer.

Explanation

Uneven heating between the hot gas side and the cooler water side creates differential expansion that can overstress tube sheets and rolled joints. A slow warm-up at low firing rate, with air vented so the shell heats evenly and no vacuum forms, keeps those temperature differences small.

Question 45Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

Which procedure is correct for a routine bottom blowdown of an operating steam boiler?

  1. Open the near-boiler valve, then the downstream valve, and close both after a short blowdown. Correct answer.
  2. Open the downstream valve first, then the boiler valve, and blow down continuously for several minutes.
  3. Blow down at maximum firing rate with the water level at the top of the glass.
  4. Leave both valves open after the blowdown so the line drains freely.

Explanation

The valve nearest the boiler is opened first so the line is pressurised only briefly, and the downstream valve is used to throttle the flow and take the wear. The blowdown is kept short so drum level is not lost, and both valves are closed, near-boiler valve last, when the operation is finished.

Question 46Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

Sharp banging is heard in a steam main shortly after startup. What is the most likely cause and the right response?

  1. Air trapped in the main; open the air vents only after the line is fully hot.
  2. Condensate in the line; drain the low points and warm the main slowly. Correct answer.
  3. Loose pipe hangers; tighten them while the line is hot and expanded.
  4. An undersized header; permanently reduce the firing rate to lower steam velocity.

Explanation

Water hammer in a steam main comes from slugs of condensate being driven by high-velocity steam into fittings, valves, and bends. Warming the main slowly with drains and traps in service keeps the line dry so condensate leaves before steam velocity can pick it up and slam it downstream.

Question 47Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

A hot water heating boiler's relief valve starts to weep soon after the system reaches design temperature. Which fault best explains it?

  1. The aquastat is set below the design temperature.
  2. The circulating pump is running at too low a speed.
  3. The expansion tank is waterlogged or its bladder failed. Correct answer.
  4. There is excess air in the upper-floor radiators.

Explanation

In a closed hot water system the expansion tank absorbs the volume increase as the water heats. If the tank is waterlogged or its bladder has ruptured, that volume has nowhere to go, so system pressure climbs until the relief valve lifts and discharges.

Question 48Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

A steam boiler will be idle for several hours in warm standby. Which shutdown sequence is appropriate?

  1. Stop firing, close all vents and drains, then open the blowdown valves to cool the boiler.
  2. Trip the burner, close the main steam stop, and open the safety valve to speed cooling.
  3. Reduce load, stop firing, close the main steam stop, and keep the boiler full. Correct answer.
  4. Stop firing, open the main steam stop fully, and drain the drum to the bottom of the glass.

Explanation

The boiler is brought off load gradually so the shell cools evenly, then the main steam stop is closed to isolate it from the header and the shell is left full of water for the standby period. Draining or force-cooling a hot boiler causes thermal stress and can bake scale onto heated surfaces.

Question 49Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

While firing, the water level drops out of sight in the gauge glass and does not return after the glass is blown down. What is the safest next step?

  1. Open the bottom blowdown valve slowly to see whether water is drawn back up into the gauge glass.
  2. Start the feedwater pump at once and refill the drum to the normal operating level as quickly as possible.
  3. Hold the burner off, verify with the trycocks, and add water only after heated surfaces are checked. Correct answer.
  4. Restart the burner at low fire as soon as water becomes visible again in the gauge glass.

Explanation

A confirmed low-water condition means heated surfaces may be far above the waterline and already overheated. Feeding water into that metal can flash violently into steam and warp or rupture tubes and drum, so firing stays off, the level is confirmed with the trycocks, and water is added only after the surfaces have been inspected and cooled.

Question 50Boiler Operation, Startup, Shutdown, and Steam/ Hot Water System Fundamentals

A boiler is firing hard with the drum level riding near the top of the glass, and wet steam with an erratic level shows up in the main. What is happening?

  1. Attemperator over-spray; the desuperheater is flooding the main steam line.
  2. Shrinkage; the drum level will fall sharply and the low-water cutoff will trip the burner.
  3. Priming; water and dissolved solids are carrying over into the steam lines. Correct answer.
  4. Foaming caused by low dissolved solids; steam quality improves as the bubbles break.

Explanation

A high water level combined with a sudden heavy steam demand lets the steam space fill with droplets and foam that leave with the steam. That carryover can foul a superheater, erode turbine blades, and lay down solids in the steam mains, so drum level and boiler water dissolved solids must be brought back under control.