1、PFI Technical Bulletin TB-8 (Reaffirmed December 2013) RECOMMENDED PRACTICE FOR THE FABRICATION OF POLYVINYLIDENE FLUORIDE (PVDF) PIPING Prepared by Pipe Fabrication Institute Engineering Committee All PFI Standards are advisory only. There is no agreement to adhere to any PFI Standard and their use
2、 by anyone is entirely voluntary. Copyright by PIPE FABRICATION INSTITUTE Dedicated to Technical Advancements and Standardization in the Pipe Fabrication Industry Since 1913 USA 511 Avenue of Americas, # 601 New York, NY 10011 CANADA 655, 32ndAvenue, # 201 Lachine, QC H8T 3G6 WEB SITE www.pfi-instit
3、ute.orgPFI Technical Bulletin TB-8 (Reaffirmed December 2013) Recommended Practice for the Fabrication of Polyvinylidene Fluoride (PVDF) Piping 1. Scope 1.1 The purpose of this recommended practice is to provide methods for purchasing, material receiving, welder qualification, fabrication and instal
4、lation, inspection and documentation for Polyvinylidene Fluoride (PVDF) piping systems. 2. General 2.1 This recommended practice applies to Industrial applications and provides additional requirements where high levels of cleanliness and high purity are necessary. Additional measures for high purity
5、 applications are delineated in Section 8. of this practice. 2.2 Fabrication of PVDF should be pre-planned to minimize the amount the quantity of field fabrication required. 2.3 Precautions should be taken to maintain cleanliness for all pipe and components. 2.3.1 Materials should be handled only wi
6、th latex gloves. Gloves should be changed if they become soiled or torn. 2.3.2 Hand tools that will come in contact with fabrication materials should be pre-cleaned with Iso Propyl Alcohol. 2.4 Completed fabrication should be stored out of direct ultraviolet light. 3. Purchasing, Receiving and Inspe
7、ction 3.1 All materials should be purchased in accordance with known standards and appropriately specified quality standards. 3.2 Material should be received in accordance with established Quality Control procedures and methods that provide for proper identification and segregation. 3.3 Vendor docum
8、entation should be verified for any specified certifications, manuals, etc. accompany the shipment and should be legible and complete. 3.4 A representative sample from each lot of incoming material should be randomly segregated for detailed inspection. The randomly selected material should be moved
9、into a clean area where QC personnel can perform the required inspections. 3.4.1 Any material received contaminated should be rejected immediately. 3.4.2 Verify inner and outer legs should be verified for integrity of primary and secondary seals. 3.4.3 End-protection film and end caps should be veri
10、fied to be in place per specifications. 3.4.4 A detailed dimensional and surface cleanliness inspection of randomly selected material should be performed to ensure customer requirements are met. 4. Welder Qualification 4.1 The fabricator or installer of PVDF piping materials should qualify all weldi
11、ng technicians in accordance with the PVDF manufacturers established welding procedures for each size and thickness of tube and fittings to be used. A representative of the PVDF manufacturer may be appointed to oversee the qualifications. (Special arrangements must be made when systems of mixed PVDF
12、 materials are being joined.) 4.2 Each welder shall demonstrate his skill in welding techniques by making (two) pipe-to-pipe horizontal (SG) welds for each type of welding process that the welder will be using. PFI Technical Bulletin TB-8 (Reaffirmed December 2013) 4.2.1 Qualification coupons shall
13、be identified with the craftsmans name or ID number. 4.3 Welders coupons shall be inspected for insufficient or excessive bead, cleanliness, and general craftsmanship criteria as listed in Section 7.0 of this bulletin. 5. Fabrication and Installation All welding shall be performed in accordance with
14、 both the material manufacturer and equipment manufacturer joining equipment recommendations, unless directed otherwise by the customer. 5.2 All cutting, facing, and welding operations shall be performed in a clean environment, whenever possible. 5.3 Piping, fittings, and components should only be r
15、e-cleaned if contaminated at the job site (see 3.4). 5.4 All equipment and tools shall be dedicated for use only on PVDF material, kept clean and in good working order. Tools should be identified for PVDF use only. 5.5 Grease, oil, or other lubricants should not be used when pipe must be cut to size
16、 for fabrication. 5.6 Tube ends should be verified for square after cutting and prior to fitup. The manufacturers normal allowable wall offset at a joint is 10% of wall thickness. 5.7 Before any material is entered into the fusion machine and before any joining is performed, materials should be veri
17、fied for the proper type and size. 5.8 All joining operations should be performed in accordance with the equipment manufacturers recommendations and the fabricators established joining procedure. 5.9 Care should be taken to eliminate any airflow at both the ID and OD of the weld joint during the wel
18、ding process. Airflow could adversely affect the quality of the finished weld. 5.10 Pre-fabricated spool pieces should have adequate end protection prior to shipment and/or installation 5.11 After the piping system is completed and inspected (see Sec 6.0), but prior to pressure test, a system walk d
19、own should be performed to ensure the following: 5.11.1 All piping supports, guides, and anchors as per specification are installed. 5.11.2 Pipe is in good condition with no visible cracks, gouges, deformations, or other evidence of abuse. 5.11.3 Pipe flanges are aligned and correct system slope is
20、maintained as specified. 5.11.4 Manufacturers recommended torque sequence for all flange connections must be marked and followed. 5.11.5 Correct bolts, washers, and gaskets were used as per specification. 6. Visual Inspection 6.1 Weld bead geometry should be consistent and symmetrical for the entire
21、 circumference. Small irregularities are acceptable as long as the bead size is not smaller than half the average bead size of the remaining circumference. 6.2 A double weld bead is the most desirable geometry (see Fig 1). A double bead that converges to a single bead is rejectable. A uniform width,
22、 height, and form to the I.R. weld bead should be apparent. 6.3 Acceptance criteria shall be as stated in the customer specifications. Welds should meet the requirements of Table 1. PFI Technical Bulletin TB-8 (Reaffirmed December 2013) 6.4 If inspection reveals any rejectable conditions as defined
23、above, the unacceptable welds shall be removed and replaced. 7. Documentation 7.1 Documentation requirements shall be in accordance with customer requirements or the fabricators Quality Control program. The following may be used as a guide: 7.1.1 The Isometric Drawing (ISO) may be used for weld numb
24、er identification, welder, and inspection documentation. 7.1.2 The back of the ISO may include the following information, as a minimum: A. Welder identification number B. Date the weld joint was made C. Weld joint number D. Weld parameter sheet E. Quality Assurance approval sign-off. 7.1.3 Each weld
25、er should be responsible for documenting his production welds on the ISO each day. 7.1.4 After completion of the welding and cooling process, some equipment automatically prints out a parameter report. The weld number and ISO number may be noted on this report, and retained with the corresponding IS
26、O. 7.1.5 Production personnel should control ISOs until all work is completed. The ISO should then be turned over to Quality personnel for inspection and retention. 7.1.6 Quality personnel should be responsible for documenting all his weld inspections on the ISO each day. 8. Additional High Purity R
27、equirements 8.1 All cutting, facing, and welding operations should be performed in a controlled environment, (class 1,000 or better), whenever possible. Field operations should be under a portable HEPA- filtered environment, whenever possible. 8.2 Welders coupon may require analytical testing as def
28、ined in the customer specifications. 8.3 Fabricated spool pieces should be bagged for protection prior to shipment and/or installation: 8.3.1 Ends of each tube should be covered with 6 mil polyethylene bag and sealed to the tube with tape. A second 6 mil bag should be placed over the first and exten
29、d 2“ beyond the first bag, and securely taped to the tube. This ensures a tight double seal. 8.4 Pre-fabricated spools should be in-place and aligned for installation prior to removing end protection to minimize possible contamination. 8.5 A filtered gas purge should be maintained on the system when
30、ever it is not under construction (approx. 10 PSI nitrogen). PFI Technical Bulletin TB-8 (Reaffirmed December 2013) Table 1 Acceptance Criteria for Welds in PVDF Piping Condition Probable Cause Acceptance Criteria Any line or chain of bubbles Too quick on joint makeup None allowed Wall offset Poor f
31、it up or out of round Greater than 10% wall offset is rejectable Cracks in the fusion seam or base material None allowed Bead notches, continuous or locally restricted, that extend into the base material Inadequate joining pressure or overheating None allowed Notches and scoring in the base material
32、 Caused by clamping tools or improper handling None allowed Angular or alignment deviation Improper end preparation None allowed Incomplete fusion at the joining faces Contaminated end faces or excessively long change-over time from the heating to the joining processes None allowed Voids or pores in
33、 the pipe wall or weld bead Contaminated end faces or incorrect fusion parameters None allowed Fig. 1: Double Weld Bead CURRENT INDEX OF 2014-2015 PFI STANDARDS A complete list of PFI members and available membership CHARTER MEMBERS CONTRACTOR MEMBERS ASSOCIATE MEMBERS AFFILIATE MEMBERS HONORARY MEM
34、BERS Associate and Affiliate member contributors Walter Sperko Sperko Engineering Services, Inc. Greensboro, NC Thomas Warrelmann Victaulic Company of America Easton, PA Sheryl Michalak Welding Outlets, Inc. Houston, TX PFI Standards and Technical Bulletins are published to serve proven needs of the
35、 pipe fabricating industry at the design level and in actual shop operations. Hence, such needs are continually considered and reviewed by the Engineering Committee of the Pipe Fabrication Institute to provide recommended procedures, which have been demonstrated by collective experiences to fulfill requirements in a manner for Code compliance. However, as the PFI Standards are for minimum requirements the designer or fabricator always has the option of specifying supplementary conditions in the form of requirements beyond the scope of the PFI publications.
