ASME PCC-2S:2015 pdf free download – Supplement to ASME PCC-2–2015
3.3 Examples of Damage
Figure 2 shows examples of damage that can occur in Cr–Mo pressure vessels with or without stainless steel cladding or weld overlay. The examples are typical of high-temperature, high-pressure (HTHP) pressure ves- sels in refining service.
3.4 Development of Weld Repair Procedures
(a) The selection of weld repair method should be based on the reliability of the repaired area considering the future operation period, as shown in Fig. 3.
(b) Sleeve repair and partial patchrepairmethods (see Table 5) are normally applied temporarily and are not recommended for periods beyond the next upcoming shutdown or outage without appropriate nondestruc- tive examination (NDE) and applicable fitness-for- service assessment.
3.5 Repair Welding Methods
Applicable to Cr–Mo Vessels Some applicable repair welding approaches and alter- natives to postweld heat treatment (PWHT) and the ASME PCC-2 Articles in which they are described are listed in Table 5, along with some additional limitations and considerations.
3.6 Welding and Preheat When the actual aged condition of the component to be repaired cannot be sufficiently evaluated for develop- ment of a repair welding procedure, a bead-on plate test should be used to verify the repair welding procedure.
NOTE: A bead-on plate test is a type of self-restraint weld test used to evaluate the cracking sensitivity of the base materials and arc welding consumables. Refer to Kayano et al. and Yamamoto et al. (see section 7, References).
4.6 Dehydrogenation Heat Treatment
The preheat temperature should be maintained until PWHT or DHT is performed. When the materials are required to cool to ambient temperature after repair welding, dehydrogenation heating shall be carried out at a minimum of 300°C (570°F) for a minimum of 1 h, or for a duration to be agreed upon between the pur- chaser and fabricator, to prevent cold cracking.
4.7 Postweld Heat Treatment
(a) PWHT should be performed when required per applicable construction codes or standards.
(b) Temper bead and other welding methods as detailed in ASME PCC-2, Article 2.9 may be applicable to some low-chrome steels when corresponding WPSs or procedure qualification records (PQRs) are developed specifically for the welding repair considering welding position and welding circumstances.
(c) Temper bead methods are usually not appropriate for 2 1 ⁄ 4 Cr–1Mo and higher-chrome materials used for hydrogen service because of the high weld-metal and heat-affected zone (HAZ) hardnesses generated by the welding process.
(d) In case of local PWHT, the PWHT procedure developed shall include the arrangement of thermocou- ples and insulation to minimize the thermal stresses generated during the PWHToperation. AWS D10.10 and WRC Bulletin 452 provide guidelines for developing a PWHT plan with specific band widths (soak band, heated band, and gradient control band) to ensure that thermal gradients are not harmful.
5 EXAMINATION
(a) NDE, as indicated in Table 6, shall be considered at each appropriate step of repair welding work. The appropriate NDE procedure(s) for the applicable repair shall be selected to meet the requirements ofthe applica- ble code of construction and to provide the level of examination necessary for the repair.
(b) NDE procedures shall be in accordance with ASME BPVC Section V and applicable construction codes and standards.
(c) NDE before repair welding of pressure boundary shall include the following:
(1) The entire area of the pressure vessel that is to be repair welded shall be examined by means of visual examination (VT) or other NDE methods as may be applicable to ensure that the area is free of any defect harmful to the repair operation, which may include welding, PWHT, and pressure testing.
(2) The need for carrying out pressure testing after repairs as well as the pressure used in pressure testing shall be evaluated inconsideration ofservice conditions.