the age of boiler tubes 3

[hyl]

Hello members
I want to arise aquestion about the age of boiler tubes .it depend on the operation houers or on the testing report .we have boiler works more than 100,000, houers .What is the advice to make complete retubing or according to the testing report .the boiler pressure 127kg/cm^2 &the capacity is 6,600 ton/houer.for urgent mantaninace we can change the firing zone tubes only.
thank very much and god bless.

jamil a alshahed nama
hartha power station

 

[metengr]

hyl;
Replacement of boiler tubing is not necessarily based on operating hours. This is only one part of the equation. For example, if tubes are suffering from wastage (erosion and/or corrosion) this damage mechanism would decide on when to re-tube. If creep is the damage mechanism, you need to evaluate the tubes by removing samples and performing a metallurgical evaluation to determine the condition of the tubing. Here replacement is based on test results, not operating hours.

I have seen boiler tubes have upwards of 250,000 operating hours with no sign of needing replacement. Other boiler tube circuits we have installed have been replaced after 150,000 operating hours because of poor material choice from the beginning.

 

[ApC2Kp]

hyl,

The IBR Code has a table of values for de-rating the allowable pressure of a boiler, perhaps down to 30% of the original design pressure atfer 50 years of service.

The ASME Code does not use a table for de-rating a boiler over its life. The ASME pressure design rules are set up to avoid exceeding the selected proportional values of yield stress and creep deformation. The piping design has rules and values for its allowable pressure and cycles.

You have to comply with your jurisdiction authority - IBR.

 

[metengr]

Most codes of construction do not deal with in-service equipment condition because this is accounted for in design margin by establishing allowable stresses used in design. ASME Boiler and Pressure Vessel Code does not deal with in-service inspection, repair or alterations because this is the domain of the National Board Inspection Code.

Simply derating a piece of equipment because of age makes no sense.

 

[rmw]

Derating is as condition based decision, not an age related one. A relatively new piece of equipment that has suffered rapid tube wall thickness loss might have to be derated accordingly while some old dinasour boiler nearby with no tube wastage wouldn't have to be at all.

In fact, with some of the conservatism built into the older units (we were designing units with slide rules way back when) I'd trust them more than some modern units designed to a knats a$$ with FEA and CFD.

I'm with metengr on this one.

rmw

 

[ApC2Kp]

hyl,

I must apologize for my lack of geographical knowledge. The simple Google search for "hartha power station" showed that it is in Iraq - not India as I had assumed. So my comment about the IBR Code does not apply to Hartha, unless the Owner has selected the IBR Code for design.

What design Codes are accepted for boilers and pressure vessels in that location? There is more provision for the use of other international design codes and fabricators in many countries, including India and US. It is another matter about differences for continuing exam and test of the equipment.

 

[0707]

Estimation of remaining life.

Do some replicas of representative zones of boiler tubes.

Cut a piece section of a tube more subjected to cyclic stress.

Make a destructive test of accelerated fluency with the tube.

luis marques