The PED pressure test requirements are contain in the essential requirements in Annex I section 7.4. The hydrostatic pressure test is part of the final inspection in acc. to PED Annex I sect. 3.2 and is the required for all pressure equipments as pressure vessel, piping, pressure accessories, safety accessories and assemblies. This pressure test Pt is intended to test the aspect of the required compressive strength. The proof test demonstrate the integrity of the finished product.
1. Calculation of the test pressure for standard pressure test
The test pressure must be calculated in accordance with PED Annex I section 7.4 (also EN 13445-3 sect. 10.2.3.3 a) using the formulae below:
(1) Pt = Ps * 1,43
or
(2) Pt = Pd * 1,25 * ƒa / ƒTd
The higher of the two calculated test pressures Pt is decisive and must not be exceeded.
The test pressure factor 1,25 * ƒa / ƒTd in the above formula (2) takes into account the temperature-dependent strength characteristics.
Note: For testing load cases during final assessment the corrosion allowance may be ignored.
where:
| Pt | the test pressure measured at the highest point of the chamber of the vessel in the test position |
| Pd | the coincident design pressure values for the maximum pressure load case; |
| Td | the coincident design temperature values for the maximum pressure load case; |
| Ps | the maximum allowable pressure of the vessel; |
| ƒa | the nominal design stress for normal operating load cases of the material of the part under consideration at the test temperature; |
| ƒTd | the nominal design stress for normal operating load cases of the material of the part under consideration at design temperature Td |
The test pressure factor 1,43 in formula (1) means that a stress level of 95% of the yield strength corresponding to a residual safety factor of 1,05 is achieved in the test condition.
With other words: The nominal design stress for testing conditions ƒ shall not exceed ƒtest (the minimum yield strength or 0,2 % proof strength at test temperature, as given in the technical specification for the material, divided by the safety factor 1,05).
Since the ratio ƒa / ƒTd depends on the material of the part under consideration, the value ƒa / ƒTd to be used for calculation of Pt shall not be less than the smallest ratio obtained considering the different materials of the main pressure bearing parts (e.g. shells, ends, tubesheets of heat exchangers, tube bundles, main flanges but ignoring bolting associated to main flanges). Main pressure bearing parts do not include pressure rated standard flanges and bolting designed without calculation.
2. Calculation of the modified test pressure for pressure equipment with hydrostatic pressure (Liquid column) during operation which exceeds 3 % of the design pressure
This modified test pressure is decisive only when the hydrostatic pressure (Liquid column) during operation is higher than the hydrostatic pressure during test. This is possible if the vessel in operation contains liquid with specific gravity higher than the specific gravity of the test medium or if a vertical vessel is tested in the horizontal position.
The modified test pressure must be calculated in accordance with EN 13445-3 sect. 10.2.3.3.1 b) using the formulae below:
(3) Pt,mod = Pt + (Phyd,ope – Phyd,test )
but always: Pt,mod ≥ Pt
where:
| Pt,mod | modified test pressure |
| Pt | as determined in formula (1) or (2) above |
| Phyd,ope | the maximum hydrostatic pressure (liquid column) during operation |
| Phyd,test | the maximum hydrostatic pressure (liquid column) during hydrostatic test |
3. Substitute tests for the hydrostatic pressure test
The PED expressly permits substitute tests if the above-mentioned hydrostatic test is disadvantageous or not feasible:
a) a pneumatic pressure test
b) other test pressures
c) testing on a statistical basis;
3.1 The pneumatic pressure test
The pneumatic pressure test should only be used in exceptional cases, e.g. if the hydrostatic pressure test is disadvantageous or not possible. If a lower test pressure is used for safety reasons, additional measures must be taken, e.g. non-destructive testing, to achieve an equivalent level of safety.
3.2 Other test pressures
The test pressure level must be selected so that the hydrostatic pressure test, with due regard to the safety factors, ensures that no damage occurs to the pressure equipment.
3.3 Testing on a statistical basis
This type of test can only be used for category I pressure equipment manufactured in series.
4. Other requirements of the Design Code EN 13445 for pressure test
When carrying out the hydrostatic pressure test, additional aspects must be taken into account which are not explicitly stated in the PED, but which can be derived from the specifications. The following table takes into account the essential aspects in the EN 13445 series:
| Requirements | EN 13445-5 Unfired Pressure vessels | EN 13445-6 (Pressure Vessel of spheroidal graphite cast iron) | EN 13445-8 (Pressure Vessel of Aluminium and Aluminium alloys) |
|---|---|---|---|
| Definition test pressure | a) Internal pressure at the highest point of the chamber of the vessel for either horizontal or vertical test positions; b) Modified pressure test for vessels with hydrostatic pressure during operation which exceeds 3 % of the design pressure | – | – |
| Test pressure calculation (Pt) | Calculation of the test pressure factor in EN 13445-5 section 10.2.3.3 a; Special calculation specifications for pressure equipment of test group 4 | PT ≥ 1,43* Pd/CT*CQ (see also EN 13445-6 section 7.2.2.1 and 7.2.2.2) | EN 13445-5 section 10.2.3.3 is applicable, but test pressure min. EN 13445-5 section 10.2.3.3.1; EN 13445-5 section 10.2.3.3.2 not applicable for test group 4; |
| Testing of pressure equipment with multiple pressure chambers | EN 13445-5 section 10.2.3.3.3 | – | – |
| Pressure test at jacketed vessels | EN 13445-5 section 10.2.3.3.4 and Section 10.2.3.6 | – | – |
| Timing of the pressure test | After completely manufacture and testing; Before lining, coating etc.; EN 13445-5 section 10.2.3.2.2 | – | – |
| Consideration of the static liquid pressure column during operation and during the pressure test | The static pressure only needs to be taken into account if the stress of the pressure vessel wall is increased by more than 5%. Specifications for taking static pressure into account in EN 13445-5 section 10.2.3.3.1 | – | – |
| Pressure test of pressure equipment with single-pass welded seams | EN 13445-5 Section 10.2.3.3.1 c) | – | – |
| Pressure test for pressure equipments that are operated in the creep range | EN 13445-5 Section 10.2.3.3.1 d) | – | – |
| Test pressure for group 4 vessels | EN 13445-5 Section 10.2.3.3.2 | – | – |
| Test pressures over 100 bar | EN 13445-5 Section 10.2.3.8 | – | – |
| Testing as a pneumatic pressure test | only allowed, if not practicable; see also EN 13445-5 sections 10.2.3.1 and 10.2.3.4 | – | EN 13445-5 section 10.2.3.4.1 is applicable; additional requirements see EN 13445-8 section 8.7; |
| Testing on a statistical basis | EN 13445-5 Annex A.11 | – | – |
| Testing of enamelled or coated pressure equipment | EN 13445-5 Section 10.2.3.2.2 | – | – |
| Water quality | EN 13445-5 Section 10.2.3.2.5 | – | – |
| Information on the pressure gauge used | EN 13445-5 Table 9.2.2.1 and Section 10.2.3.11 | – | – |
| Acceptance criteria | EN 13445-5 Section 10.2.3.9 | – | – |
| Test records | EN 13445-5 Section 10.2.3.10 | – | – |
| Post pressure test inspection | EN 13445-5 Section 10.2.4 | – | – |
