OS-C501

Recommendations

Info

Offshore Standard DNV-OS-C501, November 2013 Sec.11 Fabrication – Page 168 SECTION 11 FABRICATION 1 Introduction 1.1 Objective 1.1.1 The objective of this section is to provide guidelines to ensure that the structure is built as planned and that the material properties are of consistent quality with the same properties as used in the design analysis. It is not the intention here to give advise on how to operate particular processing equipment. 1.2 Quality system 1.2.1 This standard does not specify how requirements are controlled, it specifies what should be controlled. 1.2.2 A quality system, like ISO 9001, shall be in place to specify how production activities are controlled. All requirements given in this section shall be addressed in the quality system for components with normal and high safety class. 2 Link of process parameters to production machine parameters 2.1 Introduction 2.1.1 Composite laminate and sandwich structures are normally produced as the component is built. This is a special situation compared to other materials like metals that are purchased as a finished material and subsequently assembled, joined, and maybe modified. 2.1.2 The material properties depend not only on the raw materials but also on the specific way they are laid up. 2.1.3 The main quality principle when building composite structures is to ensure that the laminates and sandwich structures are built with a consistent quality. 2.2 Process parameters 2.2.1 The following process parameters shall be controlled as a minimum for laminates, as described in Sec.4 [6]: — temperate and pressure over time in production and post-cure — void content — fibre content (volume fraction) / good local wet-out — fibre orientation — fibre tension — number of layers and thickness. 2.2.2 For sandwich structures the requirements for laminates apply ([2.2.1]). In addition a good bond between skins and core shall be ensured at all places, see also Sec.5 [6]. If sections of core materials are joined by adhesives good filling of all joints shall be ensured at all places. 2.3 Production machine parameters 2.3.1 Production machine parameters are defined here in a wide sense as all physical parameters that may have an influence on the process, since no specific production process is addressed in this standard. Guidance note: A production machine parameter can be an electrical current that produces a certain temperature in a curing chamber in a pultrusion process; it can be rolling pressure when compacting reinforcements in a hand lay-up process. ---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e--- 2.3.2 All production machine parameters shall be identified that may influence the process parameters in B200. 2.3.3 Ideally a link between the dependence of processing parameters on machine parameters should be established. If such a link cannot be established, the parameters should be kept constant or within well defined tolerances. 2.3.4 Material properties should be established as a function of the process parameters and it shall be shown that the design values (mean and standard deviation) can be achieved under all conditions. Alternatively, material properties shall be measured and used in the design for the worst possible variation of machine parameters. DET NORSKE VERITAS AS
Offshore Standard DNV-OS-C501, November 2013 Sec.11 Fabrication – Page 169 3 Processing steps 3.1 General 3.1.1 Bending of composites shall be avoided. A minimum bending radius shall be defined if the process requires bending of materials. 3.1.2 Materials and components shall not be exposed to point-loads. All possible point loads shall be evaluated and it shall be ensured that they will not damage the material. 3.1.3 The working conditions are important when producing composite parts. Ambient temperature ranges shall be defined and production areas should be well ventilated. Dust, fumes, chemicals etc. may influence curing conditions or may attack the material later during service. The working conditions shall be defined. 3.1.4 Humidity shall be controlled at places where chemical reactions occur. If humidity cannot be controlled its effect shall be evaluated. 3.2 Raw materials 3.2.1 All raw materials shall be traceable for applications with normal and high safety class. 3.3 Storage of materials 3.3.1 The manufactures recommended storage conditions should be followed. All materials shall be stored in clean and dry environments. 3.3.2 Fibres should be stored in a clean environment, preferably wrapped up. 3.3.3 Resins and other chemicals should be stored in tight containers or tanks. 3.3.4 All resins and chemicals shall not be used after their shelf life has expired. 3.3.5 Some foam cores have internal gases from the production process that diffuse out with time. Such cores shall be stored long enough to allow the gases to diffuse out. Core skin delaminations may be the result if the gases remain in the core. 3.3.6 When taking materials out of storage it is important that they reach the same temperature as in the production facility while inside their sealed storage bag or container. This step prevents the formation of humidity on the materials. 3.4 Mould construction 3.4.1 The word moulds is interpreted in this section in a wide sense, covering many processes. Laying tables, mandrels and vacuum bags are considered as moulds or parts of moulds. 3.4.2 Moulds should match all tolerances required by the design. 3.4.3 Sharp corners and discontinuities at joining points should be avoided. 3.4.4 The surface finish shall be as specified. It shall be demonstrated that the mould surface finish can produce components with the required surface finish of the component. 3.4.5 Compatibility of mould release agents with the material and further operations should be considered. Especially adhesive joining or re-lamination may be effected by residues of mould release agents on the surface of the component. This applies for mould release agents that were applied to the mould and for mould release agents that were added to the resin. 3.4.6 The structural stability of moulds or mandrels should be ensured. 3.4.7 Possible deformations of the moulds should be considered in the design. The structure should be able to withstand all resulting loads and strains. 3.4.8 If moulds are heated a controlled distribution of temperature shall be ensured. 3.4.9 If a vacuum is applied inside the mould (or some bag), it shall be ensured that no leaks exist. The vacuum shall be measured far away from the point where the vacuum is pulled. Large moulds may require more than one measurement point. 3.4.10 When removing the part from the mould large stresses and deformations may be induced, especially if the component got stuck somewhere. These effects should be avoided or at least carefully controlled. Possible stresses or strains due to these operations should be considered in the design. If such a situation occurs accidentally the loads shall be estimated and the component shall be reanalysed. DET NORSKE VERITAS AS
Page 1 and 2:
OFFSHORE STANDARD DNV-OS-C501 Compo
Page 3 and 4:
Offshore Standard DNV-OS-C501, Nove
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 69 and 70:
Page 71 and 72:
Page 73 and 74:
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118: Offshore Standard DNV-OS-C501, Nove
Page 167: Offshore Standard DNV-OS-C501, Nove
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
show all

OS-C501

Create successful ePaper yourself

Delete template?

Save as template?