---

Key

er > 2 mm; see C.4.2.2 a) a-, + аг > s

1. fin

2. tube

Figure C.2 — Weld requirements for fin to tube welds

Key

A<2 mm

Key

- Z>2 = A < 3 mm

a) Linear misalignment

b) Angular misalignment

Figure C.3 — Allowable misalignment for fin to tube welds

Figure C.4 — Allowable excessive convexity for fin to tube welds

Annex D
(normative)

Coiled boilers and coiled superheaters

D.1 General

This annex gives the special requirements applicable to the design, manufacture and inspection of coiled boilers and coiled superheaters. Except for these special requirements, all the requirements of this European Standard shall apply.

D.2 Special requirements

Circumferential butt welds in the coiled length of the tubing shall be acceptable, subject to the following conditions:

1. the rJd₀ ratio should preferably be not less than 6

where r_b is the mean radius of the coil;

and d₀ is the nominal outside diameter of the tube;

2. the maximum departure from circularity of the tube diameter in the bent condition shall not exceed 5 %;

3. backing rings shall not be used with the butt welds;

4. the oxy-acetylene welding process shall not be used.

For coils constructed from steel group 1.1, 1.2 or austenitic steels, where the r_b/d₀ ratio is less than 6, or for other steels of any r_b/d₀ ratio, the ability to bend the tube without detrimental effect on the weld metal shall be demonstrated. This shall be by means of a welding procedure approval test involving the butt welding of a coil, then bending to the minimum r_b/d₀ ratio to be used in production for a given thickness of tube and then subjecting the test weld to destructive and non-destructive tests. The nature of the tests carried out in this procedure test shall be in accordance with the manufacturer's own proven procedures which shall ensure that, by their use, the safety of the boiler is not impaired.Annex E
(normative)

Special requirements for composite tubes

E.1 General

This annex gives special requirements applicable to the specific rules for workmanship and construction of chemical recovery boilers (black liquor boilers) as defined in E.2. These special requirements are additional to all the other requirements of this European Standard which shall continue to apply.

E.2 Definition

The chemical recovery boiler is primarily a pulping chemical recovery process unit where the organic materials are burned while the recovered chemicals are reduced and drained as molten smelt from the furnace bottom. The heat released is used for steam generation.

E.3 Special requirements for forming of composite tube bends

E.3.1 General

The general rules of EN 12952-5, mainly 7.3 and Annex A, shall be supplemented by application of the specific rules in E.3.2.

E.3.2 Application of forming rules to composite tubing

E.3.2.1 Range of tube bending procedure test approval

Only an approval obtained with composite tubes shall be valid for forming composite tubes. When calculating a tube forming ratio (TFR), the nominal tube wall thickness e shall be the total nominal wall thickness of a composite tube. The tube outside diameter d₀ shall be the total nominal diameter of a composite tube. A bending procedure test shall cover only that material combination including also the base material/cladding thickness relation of the composite tube it represents.

E.3.2.2 Additional tests required for composite tubes

E.3.2.2.1 Ultrasonic testing of a composite tube bend concerning the metallurgical bonding

A tube bend shall be tested for the total length of the bend with ultrasonic inspection in accordance with EN 12952-2:2011, C.2.7.1. Acceptance criteria shall be the same as in EN 12952-2:2011, C.2.7.1.3.

E.3.2.2.2 Hardness test

At hardness tests in accordance with A.2.4.5, the hardness shall be measured from a macro specimen at the extrados of both materials.

E.3.2.2.3 Macro examination

The macrosections shall be taken from the longitudinal bend centre plane. Any cavities or structural abnormalities, especially on the bonding, shall not be permitted.

E.4 Special requirements for manufacture of welded tubewalls from composite tubes

E.4.1 General

The general rules in Annex C shall be supplemented by the specific rules in E.4.2.

E.4.2 Fins

Fins for composite tubing shall be made from a plain austenitic or ferritic steel plate or strip. Fins can also be made from a composite plate or strip.

E.4.3 Fin-to-tube attachment welds on composite tubes

Fin welds shall not penetrate essentially below the surface of the ferritic pressure retaining inner core material. Unpenetrated minimum calculation thickness shall always be maintained.

E.5 Material marking

Marking method in accordance with EN 12952-2:2011, C.2.3.1, shall be allowed for austenitic or composite tubes.

E.6 Flash butt welding

Water containing tubes or composite tubes in chemical recovery boilers where leak could result in smelt-water explosion shall not be welded by flash welding. It is, however, permitted to use flash welding for superheater tubes of these boilers provided that the manufacturer can show that the welds do not increase any risk to safe operation of the boiler.Annex F
(informative)

Guidelines for the determination of the competency of boiler
manufacturers

F.1 General

The basis of this European Standard is that a manufacturer of a boiler should ensure that the requirements of the specification for the boiler are competently executed in the design and subsequent manufacturing operations. The guidelines contained in this annex identify criteria whereby a judgement can be made as to the competency of a boiler manufacturer's organisation and controls.

The principles of EN ISO 9001 and EN ISO 3834-2 have been utilised as a basis for forming this judgment and the information requested provides guidance on the potential competency of a manufacturer and his available controls.

The guidelines include criteria embracing design, materials, fabrication, erection, commissioning, examination and inspections.

F.2 Responsibility of the purchaser

It is the responsibility of the boiler purchaser (owner, user or operator) to place the order for a boiler plant with a competent boiler manufacturer to ensure that adequate quality is obtained when the boiler is put into operation in accordance with the manufacturer instructions. The guidelines indicate how such a judgement may be made by the boiler purchaser if he so requires.

F.3 Responsibility of the manufacturer

It is the responsibility of the boiler manufacturer to ensure that the requirements of the specification are competently executed by applying appropriate techniques and relevant procedures during all stages of the design, manufacture and subsequent commissioning of a boiler and to ensure that all work performed complies with the applicable requirements of this European Standard.

It is permitted for parts of the work in a contract, such as design, forming, welding, heat treatment, non­destructive testing, etc. to be subcontracted by the manufacturer responsible for the overall boiler plant. It is then the responsibility of the manufacturer to place the order for such work with a competent subcontractor or part manufacturer.

The offices, workshops and sites associated with design and manufacture (see EN 12952-3 and EN 12952-5) should be properly equipped and have suitable provisions for all the inspections and testing specified in EN 12952-6. It is important that manufacturing and other procedures are adequate and that manufacturing and testing personnel and equipments are competent and properly qualified for their assigned tasks, respectively. Reference should be made to EN ISO 3834-2 for additional guidance.

F.4 Requirements concerning the manufacturer's competency

This Annex F provides guidelines as to how judgement can be made regarding the competency of a manufac­turer and the manufacturer should confirm that he can meet all the requirements of this European Standard.

Basic requirements are given in EN ISO 9001 and EN ISO 3834-2 and EN ISO 3834-3.

Specific requirements are contained in EN 12952-3, EN 12952-4 and EN 12952-6.

Table F.1 provides a cross reference between the quality elements and processes concerned and the source of the requirements.

In some cases, in order to provide an overall picture of the manufacturing operation, additional data are requested concerning plant capacity and personnel involved, etc.

F.5 Manufacturer's competency declaration

The "Manufacturer's competency declaration" (Table F.2) has been designed to enable a manufacturer to be able to assess that he has made appropriate provisions for all the requirements of this European Standard. The form provides only the essential content of a declaration. If a sub-contractor or manufacturer of a part of a boiler is only providing limited components, processes or services, the declaration may be modified to suit the particular circumstances. It can therefore be enlarged or shortened to properly reflect the operations to be provided.

The manufacturer having overall responsibility for the boiler, sub-contractors and those providing services should ensure that an up to date, completed form (see Table F.2), is available to any involved or authorized persons at the boiler manufacturer's office. The completed forms should be available over the total period of manufacturing up to the take over of the boiler.

Table F.1 — Schedule concerning topics for competency declaration of boiler manufacturers

Table F.1 (continued)

Table F.1 (continued)