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Questions and Answers

EASY What is a common occurrence in boiler tubes due to various operating conditions?

Tube maintenance

Tube failure (correct)

Tube repair

Tube success

What can cause overheating in boiler tubes?

Low water fuel cut-off

Proper water treatment

Over firing (correct)

Good water circulation

What is a sign of slight overheating in boiler tubes?

Tube rupture

Tube collapse

Tube corrosion

Tube drooping (correct)

What can cause tube walls to weaken?

Corrosion Signup and view all the answers

What can cause tube ends to crack?

Uneven expansion Signup and view all the answers

What is a repair in the context of boilers?

Work necessary to restore a boiler to its original design Signup and view all the answers

What must be done when a tube wall is perforated or ruptured?

The tube must be replaced Signup and view all the answers

What is required for both repairs and alterations of boilers?

Approval of the authority with jurisdiction Signup and view all the answers

What is the purpose of plugging a firetube?

To allow the boiler to operate temporarily until a proper repair can be done Signup and view all the answers

What is the length of the steel plugs needed to plug a firetube?

75 mm Signup and view all the answers

What is the purpose of the 16 mm diameter steel rod?

To hold the plugs in place Signup and view all the answers

What is the term used to describe a firetube with minor leakage at its seat?

Weeping firetube Signup and view all the answers

What tool is used to re-expand a weeping firetube?

Three-roller expander Signup and view all the answers

What is the purpose of applying a special paste-style lubricant to the tube expander?

To reduce friction between the tube and the expander Signup and view all the answers

What should be done to the tube end after re-expanding it?

Re-bead the tube end Signup and view all the answers

Why should the tube end not be over-expanded?

It will weaken the tube end Signup and view all the answers

What is the final step in the procedure for re-expanding tubes?

Apply a hydrostatic test Signup and view all the answers

What is the purpose of seal welding the tube end?

To strengthen the tube end Signup and view all the answers

Who should replace the boiler tubes?

An experienced boilermaker Signup and view all the answers

What should be done before replacing a defective tube?

Cool, drain, and open up the boiler Signup and view all the answers

What is required for boiler pressure vessel repairs in all Canadian jurisdictions?

Prior approval and a Repair and Alteration form Signup and view all the answers

What is the purpose of annealing the tube ends?

To soften the tube ends Signup and view all the answers

What is used to check the tightness of the tube ends?

A hydrostatic test Signup and view all the answers

Who can perform welding on a pressure part of a boiler?

A holder of a Pressure Welder's Certificate and a valid Performance Qualification Card Signup and view all the answers

What should be done to the tube sheets after removing the tube?

Clean them with emery cloth Signup and view all the answers

Why should the tube ends be expanded lightly again after beading?

Because the beading process may have loosened them Signup and view all the answers

What tool is used to bead the tube ends?

A beading tool Signup and view all the answers

What is the first step in removing a defective tube?

Cut off the bead at each end of the tube Signup and view all the answers

MEDIUM What is the purpose of plugging a firetube?

To temporarily resume boiler operation until a boiler maker is available Signup and view all the answers

What is the purpose of a three-roller expander?

To expand and flare tube ends in firetube boilers Signup and view all the answers

What should be done to the tube end after re-expanding it?

Re-bead the tube end Signup and view all the answers

Why should the tube end not be over-expanded?

It may weaken the tube end Signup and view all the answers

What is the final step in the procedure for re-expanding tubes?

Apply a hydrostatic test Signup and view all the answers

What is the term used to describe a firetube with minor leakage at its seat?

Weeping firetube Signup and view all the answers

What is the purpose of applying a special paste-style lubricant to the tube expander?

To facilitate expansion Signup and view all the answers

What tool is used to bead the tube ends?

Beading tool Signup and view all the answers

Why should the tube ends be expanded lightly again after beading?

To ensure a tight seal Signup and view all the answers

What is the purpose of seal welding the tube end?

To add additional strength Signup and view all the answers

What is the primary reason for corrosion on the waterside of boiler tubes?

Poor water treatment Signup and view all the answers

What is the consequence of severe overheating in boiler tubes?

The tubes may collapse completely, leading to a serious pressure vessel explosion Signup and view all the answers

What is the definition of a repair in the context of boilers?

The work necessary to restore a boiler or pressure vessel to a safe and satisfactory operating condition, without deviating from the original design Signup and view all the answers

What is the consequence of uneven expansion in boiler tubes?

The tube ends may crack Signup and view all the answers

What is the consequence of heavy scale formation on boiler tubes?

The tube may become more prone to overheating Signup and view all the answers

What must be done when a tube wall is perforated or ruptured?

The tube must be replaced Signup and view all the answers

What is required for all boiler repairs and alterations?

The approval of the authority with jurisdiction Signup and view all the answers

What can cause a tube to collapse completely?

All of the above Signup and view all the answers

Who should be consulted and approved before making repairs affecting the pressure part of a boiler?

An authorized inspector Signup and view all the answers

What is the purpose of annealing the tube ends?

To soften the tube ends to prevent cracking during expansion Signup and view all the answers

What is required for boiler pressure vessel repairs in all Canadian jurisdictions?

Submission and approval of a jurisdictional 'Repair and Alteration' approval form Signup and view all the answers

What tool is used to bead the tube ends?

Beading tool Signup and view all the answers

Why should the tube ends be expanded lightly again after beading?

To ensure the tube ends are securely fastened Signup and view all the answers

Who can perform welding on a pressure part of a boiler?

A holder of a Pressure Welder's Certificate and a valid Performance Qualification Card Signup and view all the answers

What is the purpose of seal welding the tube end?

To ensure the tube end is securely fastened Signup and view all the answers

What should be done to the tube sheets after removing the tube?

Clean off any roughness with emery cloth Signup and view all the answers

What is the first step in removing a defective tube?

Cut off the bead at each end of the tube Signup and view all the answers

What is used to check the tightness of the tube ends?

Hydrostatic test Signup and view all the answers

HARD What is the primary purpose of submitting a jurisdictional “Repair and Alteration” approval form for boiler pressure vessel repairs?

To ensure compliance with local regulations and obtain approval for the repair procedure Signup and view all the answers

What is the primary reason for consulting an authorized inspector before making repairs affecting the pressure part of a boiler?

To ensure compliance with local regulations and obtain approval for the repair procedure Signup and view all the answers

What is the consequence of not annealing the tube ends before replacing a defective tube?

The tube may crack during expansion Signup and view all the answers

What is the purpose of lightly expanding the tube ends again after beading?

To prevent the tube from becoming loose over time Signup and view all the answers

What is the minimum requirement for a repair shop to replace boiler tubes in some jurisdictions?

Approved Quality Assurance program Signup and view all the answers

What is the purpose of using emery cloth to clean the tube sheets after removing a defective tube?

To smooth out any rough surfaces on the tube sheet Signup and view all the answers

What is the primary purpose of using a power impact hammer to drive the beading tool?

To apply additional force to the beading tool Signup and view all the answers

What is the consequence of not consulting an authorized inspector before making repairs affecting the pressure part of a boiler?

It may be unlawful to perform the repair Signup and view all the answers

What is the primary purpose of using a round nosed chisel to cut grooves in the tube ends?

To create a surface for the beading tool Signup and view all the answers

What is the primary reason for using a specific procedure to replace a defective tube?

To ensure the repair is done correctly and safely Signup and view all the answers

What is the primary mechanism by which corrosive and scale-forming waterborne constituents contribute to tube failure?

By weakening tube walls, leading to leakage or collapse Signup and view all the answers

What is the consequence of a tube failure due to severe overheating?

The tube will collapse, causing a serious pressure vessel explosion Signup and view all the answers

What is the key distinction between a repair and an alteration in the context of boiler maintenance?

A repair involves restoring the original design, while an alteration involves deviating from the original design Signup and view all the answers

What is the primary cause of thermal shock in boiler tubes?

Uneven expansion due to poor water circulation Signup and view all the answers

What is the consequence of caustic embrittlement in boiler tubes?

Tube ends may crack due to uneven expansion Signup and view all the answers

What is the purpose of approving repairs and alterations by the authority with jurisdiction?

To guarantee that the boiler is safe and efficient after the repair or alteration Signup and view all the answers

What is the consequence of buckling stress on boiler tubes?

Tubes may collapse, causing a serious pressure vessel explosion Signup and view all the answers

What is the primary reason for plugging a defective firetube?

To prevent further damage to the boiler and ensure safe operation Signup and view all the answers

What is the primary purpose of using a tapered tube expander mandrel in a three-roller expander?

To apply outward force against the tube wall Signup and view all the answers

What is the consequence of not applying a special paste-style lubricant to the tube expander?

The tube expander will not rotate properly Signup and view all the answers

What is the purpose of beading the tube end after re-expanding it?

To provide a secure seal against the tube sheet Signup and view all the answers

What is the advantage of using a three-roller expander to repair a weeping firetube?

It re-expands the tube end to its original diameter Signup and view all the answers

What is the purpose of performing a hydrostatic test after re-expanding a tube?

To check the effectiveness of the repair Signup and view all the answers

What is the consequence of over-expanding a tube end?

The tube end will be weakened Signup and view all the answers

What is the purpose of using a 16 mm diameter steel rod when plugging a firetube?

To connect the two steel plugs together Signup and view all the answers

What is the primary purpose of seal welding the tube end?

To prevent bending loads or sudden temperature changes Signup and view all the answers

What is the consequence of not re-beading the tube end after re-expanding it?

The tube end will not be securely sealed Signup and view all the answers

What is the purpose of using a grommet of high-temperature rope when plugging a firetube?

To seal the tube ends watertight Signup and view all the answers

Study Notes

Boiler Tube Failures

Boiler tubes operate under harsh conditions, experiencing external pressure, buckling stress, tensile stress, corrosive and scale-forming waterborne constituents, and high temperatures.
Tube failures can occur due to:
- Overheating caused by overfiring, poor water circulation, heavy scale formation, or failure of the low water fuel cut-off.
- Corrosion weakening tube walls, leading to leakage or total collapse.
- Tube ends cracking due to uneven expansion, thermal shock, or caustic embrittlement.

Repairing Defective Firetubes

A repair is defined as the work necessary to restore a boiler or pressure vessel to a safe and satisfactory operating condition, without deviating from the original design.
Repairs and alterations are subject to approval by the authority with jurisdiction.
Plugging a defective firetube can be done temporarily to allow boiler operation to resume until a proper repair can be done.
To plug a firetube, two steel plugs with a specific taper are needed, along with a steel rod and a high-temperature rope grommet.

Repairing a Weeping Firetube

A weeping firetube can be repaired by re-expanding the tube end using a three-roller expander.
The expander is used to attach tubes to tube sheets in firetube boilers and to drums of watertube boilers.
The procedure involves cleaning the tube ends, coating the expander with lubricant, and inserting the expander to apply outward force against the tube wall.

Removal and Replacement of Defective Firetubes

If re-expanding the tube does not stop the leak, it will need to be replaced.
An experienced boilermaker should replace the tube, following approved procedures and obtaining necessary jurisdictional approval.
The boiler should be taken out of service, cooled, drained, and opened up before replacement.
Replacement involves cutting off the bead, cutting grooves, breaking away the tube ends, and removing the tube from the boiler.
The new tube should be annealed, cleaned, and polished before installation, and the tube ends should be expanded and beaded.

Boiler Tube Failures

Boiler tubes operate under harsh conditions, experiencing external pressure, buckling stress, tensile stress, corrosive and scale-forming waterborne constituents, and high temperatures.
Tube failures can occur due to:
- Overheating caused by overfiring, poor water circulation, heavy scale formation, or failure of the low water fuel cut-off.
- Corrosion weakening tube walls, leading to leakage or total collapse.
- Tube ends cracking due to uneven expansion, thermal shock, or caustic embrittlement.

Repairing Defective Firetubes

A repair is defined as the work necessary to restore a boiler or pressure vessel to a safe and satisfactory operating condition, without deviating from the original design.
Repairs and alterations are subject to approval by the authority with jurisdiction.
Plugging a defective firetube can be done temporarily to allow boiler operation to resume until a proper repair can be done.
To plug a firetube, two steel plugs with a specific taper are needed, along with a steel rod and a high-temperature rope grommet.

Repairing a Weeping Firetube

A weeping firetube can be repaired by re-expanding the tube end using a three-roller expander.
The expander is used to attach tubes to tube sheets in firetube boilers and to drums of watertube boilers.
The procedure involves cleaning the tube ends, coating the expander with lubricant, and inserting the expander to apply outward force against the tube wall.

Removal and Replacement of Defective Firetubes

If re-expanding the tube does not stop the leak, it will need to be replaced.
An experienced boilermaker should replace the tube, following approved procedures and obtaining necessary jurisdictional approval.
The boiler should be taken out of service, cooled, drained, and opened up before replacement.
Replacement involves cutting off the bead, cutting grooves, breaking away the tube ends, and removing the tube from the boiler.
The new tube should be annealed, cleaned, and polished before installation, and the tube ends should be expanded and beaded.

Boiler Tube Failures

Boiler tubes operate under harsh conditions, experiencing external pressure, buckling stress, tensile stress, corrosive and scale-forming waterborne constituents, and high temperatures.
Tube failures can occur due to:
- Overheating caused by overfiring, poor water circulation, heavy scale formation, or failure of the low water fuel cut-off.
- Corrosion weakening tube walls, leading to leakage or total collapse.
- Tube ends cracking due to uneven expansion, thermal shock, or caustic embrittlement.

Repairing Defective Firetubes

A repair is defined as the work necessary to restore a boiler or pressure vessel to a safe and satisfactory operating condition, without deviating from the original design.
Repairs and alterations are subject to approval by the authority with jurisdiction.
Plugging a defective firetube can be done temporarily to allow boiler operation to resume until a proper repair can be done.
To plug a firetube, two steel plugs with a specific taper are needed, along with a steel rod and a high-temperature rope grommet.

Repairing a Weeping Firetube

A weeping firetube can be repaired by re-expanding the tube end using a three-roller expander.
The expander is used to attach tubes to tube sheets in firetube boilers and to drums of watertube boilers.
The procedure involves cleaning the tube ends, coating the expander with lubricant, and inserting the expander to apply outward force against the tube wall.

Removal and Replacement of Defective Firetubes

If re-expanding the tube does not stop the leak, it will need to be replaced.
An experienced boilermaker should replace the tube, following approved procedures and obtaining necessary jurisdictional approval.
The boiler should be taken out of service, cooled, drained, and opened up before replacement.
Replacement involves cutting off the bead, cutting grooves, breaking away the tube ends, and removing the tube from the boiler.
The new tube should be annealed, cleaned, and polished before installation, and the tube ends should be expanded and beaded.

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Description

This quiz covers the reasons behind boiler tube failures, including overheating, poor water circulation, and more. Learn about the common causes of tube failure and how to prevent them.