Pressure vessels

Piping

Remarks

Scope of

application¹

The API regulations (API 510) relating to the inspection of pressure vessels apply to pressure vessels in the chemical and petrochemical industries.

Exclusions comprise:

§     Movable pressure vessels and containers

§     Pressure vessels where V £ 5 ft³ (0.141 m³) and
PS £ 250 lb/in² (1723.1 kPa) or V £ 1.5 ft³ (0.042 m³) and PS £ 600 lb/in² (4136.9 kPa)

§     Pressure vessels in the context of natural gas/petroleum extraction (“E&P” è Exploration and Production)

§     Steam boilers

Piping in the chemical and petrochemical industries. Classification into classes according to the potential threat. The following list provides reference points for the classification:

Class 1

Piping with the greatest danger potential. Leaks can result in immediate damage².

Class 2

Piping that are not assigned to one of Classes 1 or 3³.

Class 3

Piping with flammable products, which scarcely evolve gas in the case of pressure relief and which are not installed in threatened zones (“high activity areas”). Piping for substances that are harmful to health in remote areas⁴.

¹ Steam boilers are not covered by the API regulations

² Flammable and explosive fluids (e.g. C2-C4-streams), gases with marked generation of cold in the case of pressure-relief (risk of brittle fracture), HCl and HF, piping over/under traffic routes or in the vicinity of waterways/rivers, etc.

³ Hydrocarbons that evaporate slowly in the case of pressure-relief, hydrogen, heating/natural gas, strong acids/alkalis within the system, etc.

⁴ e.g. product pipe from/to tank farms and loading facilities

Responsibility

The operator is responsible for the production of inspection programs, maintenance, the observance of the inspection intervals and documentation.

Official

supervision

Non-existent

Implementation of inspection

Authorized pressure vessel or pipe Inspectors - certified under API 510 or 570; the Inspectors are normally employees of test organizations of local authorities or insurance companies for pressure vessel issues.
There are also operator test organizations.

“Examiners” assist the pipe Inspector in the implementation of NDTs.

Documentation

Construction and design principles. Operating and inspection history (esp. operating malfunctions with an effect on pressure vessel/pipe material, inspection reports, records of special measuring procedures).

An inspection program (based on RBI evaluations¹) produced by the operator is the basis for carrying out the Recurring Inspections.

The inspection certificate should contain various items including the date of inspection, the date of the next inspection, the name of the person carrying out the inspection, the ID no. of the pressure vessel/pipe, a description of the examination, and the inspection results.

¹ RBI = Risk Based Inspection

Inspections

Initial insp.

At installation

External inspection

Every 5 years (or as Internal Inspection or OSI¹).

§     Inspection of insulation, hangers, leaks, corrosion underneath insulation. Where appropriate, removal of insulation on a random sample basis (e.g. in the case of -4°C<TS<120°C)

§     Special regulations for earth-covered containers

§     Inspection intervals for safety valves dependent on conditions of use, but not > 5 years (with the exception that longer intervals are possible where corresponding experience exists). Safety valve inspection by technical companies with corresponding experience and quality assurance system.

                      Wall-thickn. meas.       Ext. Examination

Class 1              Every 5 years               Every 5 years

Class 2              Every 10 years             Every 5 years

Class 3              Every 10 years             Every 10 years

The intervals stated are guide values. Inspection intervals can be extended, but also shortened, depending on anticipated damage mechanisms.

Alongside the classification, the criteria for defining inspection intervals comprise corrosion rates, calculations of residual lifetime, official orders, and also requirements of the Inspector or other specialists on the basis of operating conditions, inspection history, and current inspection results.

Changes to intervals should be effected on the basis of RBI evaluations (retrospective assessments of RBIs required).

External Examinations comprise inspection for corrosion under insulation (CUI). The piping to be inspected and the scope of the inspection are defined in API 570³. The scope of inspection can be expanded if damage is found. CUI inspections are not required in the case of residual lifetimes > 10 years and specially protected piping.

Definition of the inspection intervals by the operator or Inspector

In the case of damage to the insulating material, more extensive inspections with a defined scope are prescribed.

Specific inspection programs and intervals for injection points⁴ and earth-covered piping.

¹ OSI = On-Stream Inspection

² In determining the residual lifetime, account must be taken of the results of corrosion rate calculations that go into wall-thickness measurements (determined by NDT).

³ The following apply as possible NDTs:
ultrasound wall-thickness measurements, X-ray inspections, etc.

⁴ e.g. for inhibitors

Internal

inspection

Inspection intervals depend on the calculated lifetime of the container ²:

Inspection interval = 0.5 x calculated container lifetime

                                   (min. 10 years)

RBI evaluation as the basis for extension (and also shortening where appropriate) of the 10-year inspection intervals.

If the residual lifetime is < 4 years, the inspection interval must be set to the same as the residual lifetime, but with a maximum of 2 years. In the case of pressure vessels that are not in continuous operation, the inspection interval can be defined as 10 years referred to the time of actual operation.

Internal Inspections are used to determine corrosion and other damage. They must be supplemented by NDTs³. A representative number of wall-thickness measurements must be plotted for the determination of local corrosion rates.

At the discretion of the Test Inspector, Internal Inspections can be replaced by inspections during ongoing operations (OSI) given the presence of defined preconditions (e.g. lack of accessibility and corrosion rates < 0.125 mm/a).

Pressure test

At the request of the Test Inspector, especially after repairs, changes to the pressure vessel or changes to the design conditions.

Level of the test pressure in agreement with the calculation method for determining the max. possible working pressure.

Gas pressure test only if a water pressure test is impossible.

At the request of the Test Inspector, especially after repairs, changes to the pipe or changes to the design conditions.

Gas pressure test only if a water pressure test is impossible.

Insp. in spec. cases

After repairs and changes to apparatus and piping

Pressure vessels

Steam boilers

Piping

Remarks

Scope of

application

§          The inspection group classification is based on the Pressure Equipment Directive (PED).

§          Inspection levels and inspections must be regarded as supplementary to the data given in the operating instructions from the manufacturer.

§          The breakdown is effected by module category and fluid categorization according to the PED.

¹In concrete terms:
pressure-bearing equipment that is fired or heated in some other way

Responsibility

No details

Official

supervision

No details

Implementation of inspection

§          Authorized companies for inspections at Level A¹

§          Authorized test organization - OCA (for inspections at Levels B and C)

¹Without further details relating to qualification

Documentation

No details

Inspections¹

Initial inspection

No details

¹The module categories and fluid groups are according to the nomenclature in the PED.

Special features

Portable fire extinguishers should only be inspected at Level C with an inspection interval of 5 years.

Refrigerant containers should be inspected by authorized specialists in refrigerant systems engineering. Inspections at Level C are only required in the case of

§     damage

§     containers that have been out of service for more than 2 years

§     following repairs

§     if the refrigerant is changed.

External inspection

Complete visual inspection of all pressure-bearing parts and safety-related fittings (Level A)

Module category/fluid group: I-2, II-2

     Every 4 years

Module category/fluid group: I-1, II-1, III-2,
                                                IV-2

     Every 3 years

Module category/fluid group: III-1, IV-1

     Every 2 years

for pressure-bearing equipment as per charts 1, 2, 3, and 4 in Annex II of the Pressure Equipment Directive (PED)

Module category: I, II, III

     Every 3 years

Module category: IV

     Every 2 years

for pressure-bearing equipment as per chart 5 in Annex II of the Pressure Equipment Directive (PED)

Internal

inspection

Visual inspection of parts at risk from corrosion and under mechanical stress, wall-thickness inspection, functional inspection of safety-related fittings, NDT (Level B)

Module category/fluid group: I-2, II-2

     Every 8 years

Module category/fluid group: I-1, II-1, III-2,
                                                IV-2

     Every 6 years

Module category/fluid group: III-1, IV-1

     Every 4 years

for pressure-bearing equipment as per charts 1, 2, 3, and 4 in Annex II of the PED

Module category: I, II, III

     Every 6 years

Module category: IV

     Every 4 years

for pressure-bearing equipment as per chart 5 in Annex II of the PED

Inspection scope according to Level B, can be carried out with the pipeline in operation.

Module category I, II:

     Every 12 years

Module category: III

     Every 6 years

for piping as per charts 6, 7, 8, and 9 in Annex II of the PED

Pressure test

Pressure test under the same conditions and with the same test pressure as in the initial inspection. Where appropriate, the test pressure is as given on the data plate as per item 3.3, Annex I of the PED. The pressure test can be replaced by a simulated test if this is expressly indicated by the manufacturer or the locally acting authorities have consented to a simulated test in advance due to constructional circumstances. The pressure test is always carried out in conjunction with an inspection according to Level B.

Module category/fluid group: I-2, II-2

     Every 16 years

Module category/fluid group: I-1, II-1, III-2, IV-2

     Every 12 years

Module category/fluid group: III-1, IV-1

     Every 12 years

for pressure-bearing equipment as per charts 1, 2, 3, and 4 in Annex II of the PED

Module category: I, II, III

     Every 12 years

Module category: IV

     Every 8 years

for pressure-bearing equipment as per chart 5 in Annex II of the PED

Insp. in spec. cases

No details