Standard Recommended Practice Field-Applied Underground Wax Coating Systems for Underground Pipelines: Application, Performance, and Quality Control

Transcription

1 NACE Standard RP Item No Standard Recommended Practice Field-Applied Underground Wax Coating Systems for Underground Pipelines: Application, Performance, and Quality Control This NACE International standard represents a consensus of those individual members who have reviewed this document, its scope, and provisions. Its acceptance does not in any respect preclude anyone, whether he or she has adopted the standard or not, from manufacturing, marketing, purchasing, or using products, processes, or procedures not in conformance with this standard. Nothing contained in this NACE International standard is to be construed as granting any right, by implication or otherwise, to manufacture, sell, or use in connection with any method, apparatus, or product covered by Letters Patent, or as indemnifying or protecting anyone against liability for infringement of Letters Patent. This standard represents minimum requirements and should in no way be interpreted as a restriction on the use of better procedures or materials. Neither is this standard intended to apply in all cases relating to the subject. Unpredictable circumstances may negate the usefulness of this standard in specific instances. NACE International assumes no responsibility for the interpretation or use of this standard by other parties and accepts responsibility for only those official NACE International interpretations issued by NACE International in accordance with its governing procedures and policies which preclude the issuance of interpretations by individual volunteers. Users of this NACE International standard are responsible for reviewing appropriate health, safety, environmental, and regulatory documents and for determining their applicability in relation to this standard prior to its use. This NACE International standard may not necessarily address all potential health and safety problems or environmental hazards associated with the use of materials, equipment, and/or operations detailed or referred to within this standard. Users of this NACE International standard are also responsible for establishing appropriate health, safety, and environmental protection practices, in consultation with appropriate regulatory authorities if necessary, to achieve compliance with any existing applicable regulatory requirements prior to the use of this standard. CAUTIONARY NOTICE: NACE International standards are subject to periodic review, and may be revised or withdrawn at any time. NACE International requires that action be taken to reaffirm, revise, or withdraw this standard no later than five years from the date of initial publication. The user is cautioned to obtain the latest edition. Purchasers of NACE International standards may receive current information on all standards and other NACE International publications by contacting the NACE International FirstService Department, 1440 South Creek Drive, Houston, Texas (telephone / ). Revised Reaffirmed Revised October 1994 Approved March 1975 NACE International 1440 South Creek Drive Houston, Texas / ISBN , NACE International

2 Foreword Wax coating systems are designed to provide underground pipes with protection against corrosive environments. This standard recommended practice covers surface preparation, material requirements, application, and handling of hot- and cold-applied wax and component wrappers and wax-tape coating systems for the protection of underground pipe, fittings, and valves. This standard is intended for use by corrosion control personnel, design engineers, project managers, purchasers, and construction engineers and managers. This standard was originally prepared in 1975 by Task Group T-10D-16, a component of NACE International Unit Committee T-10D on Protective Coating Systems. It superseded NACE Publication 2L The scope of the original NACE Standard RP0375 included only the application of hot- and cold-applied wax coatings. When this standard was revised by the task group in 1994, the section on wax-tape coatings was added. In 1999 this standard was reviewed by Task Group (TG) T-10D-17/T-6A-63 and reaffirmed with editorial changes. In 2005 it was revised by TG 296, which is administered by Specific Technology Group (STG) 03 on Protective Coatings and Linings Immersion/Buried. It is also sponsored by STG 04 on Protective Coatings and Linings Surface Preparation, and STG 35 on Pipelines, Tanks, and Well Casings. This standard is issued by NACE International under the auspices of STG 03. In NACE standards, the terms shall, must, should, and may are used in accordance with the definitions of these terms in the NACE Publications Style Manual, 4th ed., Paragraph Shall and must are used to state mandatory requirements. The term should is used to state something good and is recommended but is not mandatory. The term may is used to state something considered optional. NACE International i

3 NACE International Standard Recommended Practice Field-Applied Underground Wax Coating Systems for Underground Pipelines: Application, Performance, and Quality Control Contents 1. General Hot-Applied Wax Systems Cold-Applied Wax Systems Cold-Applied Wax-Tape Coating Systems Handling of Wax-Coating Piping Cathodic Protection of Wax-Coated Pipelines, Valves, and Fittings... 6 References... 7 Table 1: Requirements for Hot-Applied Wax... 1 Table 2: Property Values of Component Wrappers... 2 Table 3: Requirements for Cold-Applied Wax... 4 Table 4: Requirements for Wax Tape and Primer... 5 ii NACE International

4 Section 1: General RP This standard covers hot- and cold-applied wax and component wrappers and wax-tape coating systems for the protection of underground metallic pipe, fittings, and valves. It outlines material requirements for hot-applied waxes, cold-applied waxes, component wrappers, and wax tapes as well as proper methods of surface preparation, coating application, and handling of the coated pipe. 1.2 Tables 1 through 4 provide material requirements and give references to ASTM (1) standard test methods for the various coating materials discussed. 1.3 Any reference made to wax tape and wax primer in this standard also applies to petrolatum tape and petrolatum primer. 1.4 Hot-applied wax coatings may be applied by machine as a line-travel operation in the field or by hand. Coldapplied wax and wax-tape coatings are applied only by hand. These coatings may be used on new piping or for coating rehabilitation. 1.5 The surface preparation required for hot-applied wax coatings differs from the surface preparation required for cold-applied wax and wax-tape coatings. Section 2: Hot-Applied Wax Systems 2.1 Hot-applied wax coating systems for underground pipes usually consist of a microcrystalline wax coating applied directly to the surface followed by an overwrap of component wrapper. 2.2 Hot-applied wax coating materials shall have the following characteristics: Microcrystalline Wax Microcrystalline wax shall be inert, flexible, waterproof, adhesive, and have good wetting characteristics Microcrystalline wax shall be capable of being blended with suitable wetting agents and rust inhibitors Microcrystalline wax shall meet the requirements given in Table 1 when tested in accordance with the test methods listed therein Microcrystalline wax shall be heated or may be reheated in a clean kettle or a kettle that has been previously used for microcrystalline wax pipe coating Microcrystalline wax shall have servicetemperature capability up to 52 C (125 F). Service-temperature properties shall be determined by the hot-applied wax conforming to properties listed in Table 1. TABLE 1 Requirements for Hot-Applied Wax Properties Physical Requirements Test Method Specific Gravity at 25 C (77 F) 0.85 to 0.92 ASTM D 70 2 Needle Penetration at 25 C (77 F) 26 to 50 ASTM D Melting Point 71 to 79 C (160 to 175 F) ASTM D Flash Point 260 C (500 F) minimum ASTM D 92 5 Dielectric Strength 4 V/µm (100 V/mil) minimum ASTM D Component Wrappers Component wrappers shall consist of a wax-laminated plastic film, a wax-saturated mat, or extruded polyethylene on glass mesh that is compatible with the microcrystalline wax coating. (1) ASTM International, 100 Barr Harbor Dr., West Conshohocken, PA Component wrappers shall be used over fittings and valves and have the ability to conform to the contours of the surface Component wrappers shall meet the requirements in Table 2 when tested in accordance with the test methods listed therein. NACE International 1

5 2.2.3 Additional outerwraps or rockshields may consist of suitable material such as kraft paper, glass cloth, or synthetic fiber mat, and may be used to assist in the prevention of handling or backfill damage and to help with visual detection of physical damage to the coating system. TABLE 2 Property Values of Component Wrappers Properties Physical Requirements Test Method Supported Wrapper Wax-Laminated Plastic Film on Spun-Bonded Plastic Mat Plastic Film Thickness 13 to 25 µm (0.5 to 1.0 mil) ASTM D Wax Melt Point 71 to 99 C (160 to 210 F) ASTM D 127 Average Thickness 300 µm (12 mil) ASTM D 1000 Dielectric Strength 14 V/µm (350 V/mil) minimum ASTM D 149 Supported Wrapper Wax-Saturated Spun-Bonded Plastic Mat Wax Melt Point 71 to 99 C (160 to 210 F) ASTM D 127 Total Thickness 250 to 640 µm (10 to 25 mil) ASTM D 1000 Dielectric Strength 14 V/µm (350 V/mil) minimum ASTM D 149 Supported Wrapper Extruded Polyethylene on Glass Mesh Polyethylene Film Thickness 50 to 150 µm (2 to 6.0 mil) ASTM D 1000 Total Thickness 150 to 250 µm (6.0 to 10 mil) ASTM D 1000 Dielectric Strength 28 V/µm (710 V/mil) minimum ASTM D Suggested Application Systems Traveling machine application (1) One coat of hot-applied wax coating; (2) One wrap of component wrapper; and (3) One wrap of suitable outerwrap (if specified) Hand application (1) One coat of hot-applied wax coating; (2) One wrap of component wrapper; and (3) An additional overcoat of hot-applied wax (if specified). the coating. The pipe surface temperature shall be more than 3 C (5 F) above the dewpoint temperature. The pipe shall be heated to remove moisture. Coating application should follow immediately after preheating The prepared surface shall be visually inspected to determine whether foreign material has been removed in accordance with the degree of cleanliness specified. 2.5 Coating Application Hot wax shall be flooded directly on the surface at the temperature recommended by the manufacturer and approved by the engineer in charge or a representative of the owner. The application temperature range is based on ambient conditions and pipe temperature. 2.4 Surface Preparation The surface shall be free from oil and grease and, if necessary, shall be solvent cleaned in accordance with SSPC (2) -SP Unless otherwise specified, the surface shall be hand-tool cleaned in accordance with SSPC-SP The surface shall be dry prior to application of (2) Society for Protective Coatings (SSPC), th St., 6 th Floor, Pittsburgh, PA The temperature of the wax applied to the pipe surface shall be sufficiently hot to produce a continuous film of 500-µm (20-mil) minimum thickness and adhere well to the surface. An infrared temperature gun or bulb thermometer may be used to measure the temperature of the wax and to ensure proper heating of the wax. A wet-film thickness gauge shall be used to measure thickness at the 12, 3, and 6 o clock positions on the pipe. 2 NACE International

6 2.5.3 Before starting to coat a full section of pipe, a 1-m (3-ft) section of pipe shall be coated and inspected for adhesion at the 12, 3, and 6 o clock positions. Using a field knife, the inspector shall attempt to remove a 50- x 25-mm (2.0- x 1.0-in.) strip, consisting of a continuous and clean layer of wax, from the pipe surface. If the wax layer can be removed from the pipe surface in a continuous film with no visual evidence of a wax layer remaining on the pipe surface, then proper adhesion was not achieved. If proper adhesion is not apparent, the temperature of the heating vessel containing the wax shall be raised 11 C (20ºF) and the adhesion test shall be attempted again. The temperature shall continue to be increased in 11 C (20ºF) increments until the wax adheres properly to the surface. When the proper heating temperature of the coating has been achieved, coating of the pipe section may commence. At no time during the heating shall the temperature meet or exceed the flash point of the wax as shown in the manufacturer s material safety data sheet (MSDS). Note: If proper adhesion is not achieved on the test section, the wax shall be removed in accordance with the manufacturer s recommendation and reapplied to the test section at a higher temperature, as stated above. In addition, the operator may implement operational workarounds in conditions in which pipe may have moisture on the surface due to pressure differentials (e.g., reduce product flow through the section of pipe to be coated in order to raise the pipe temperature) The wrappers shall be applied in a uniform, snug-fitting, and overlapping pattern following the application of the hot wax coating Component wrappers are normally applied using a spiral wrap. Component wrappers may also be applied using a cigarette wrap technique as specified by the manufacturer Wrapper tension shall be sufficient to ensure tight application over the coating Overlap at the edges of the wrapper shall be maintained as recommended by the manufacturer and approved by the engineer in charge or a representative of the owner. Usually a minimum of 25 mm (1.0 in.) of overlap and 76 mm (3 in.) of existing coating is required Application of the wax coating and wrapper shall be visually inspected to determine that the application conforms to contract specifications and is free from holidays or other coating irregularities. Flood coating the pipe with a method specified by the coating manufacturer shall be used to ensure adequate coverage The entire hot-applied microcrystalline wax system of each field application area may, at the purchaser s option, be inspected with a holiday detector in accordance with NACE Standard RP and set at the voltages indicated in Paragraph If the pipe is inspected, the holiday detector voltage shall be set at 4 V/µm (100 V/mil) of hot wax coating thickness plus the additional voltage recommended for the outerwrap used Defects in the coating shall be repaired in accordance with Paragraphs 2.4 and Pipe shall be handled in accordance with Section 5 of this standard. Section 3: Cold-Applied Wax Systems 3.1 Cold-applied wax coating systems for underground piping systems consist of a wax coating that is hand applied to the surface without primer and overwrapped with a component wrapper. 3.2 Materials for Cold-Applied Wax Coating Systems Cold-Applied Wax Coating Cold-applied wax coatings shall be composed of petroleum wax and plasticizers and may contain fillers, inhibitors, and additives Cold-applied wax coatings shall be of a consistency that allows build-up of coating thickness Cold-applied wax coatings shall be inert, flexible, waterproof, and adhesive, and shall have good wetting characteristics, and have dielectric strength in accordance with values in Table Cold-applied wax coatings shall meet the requirements in Table 3 when tested in accordance with the test methods listed therein. NACE International 3

7 TABLE 3 Requirements for Cold-Applied Wax Properties Physical Requirements Test Method Congeal Point 66 C (150 F) minimum ASTM D Specific Gravity at 25 C (77 F) 0.88 to 0.94 ASTM D 70 Cone Penetration at 25 C (77 F) 160 to 290 ASTM D Flash Point 93 C (200 F) minimum ASTM D 92 Dielectric Strength 4 V/µm (100 V/mil) ASTM D Component Wrapper The component wrapper shall consist of a plastic film (supported or unsupported) that is compatible with the cold-applied wax The component wrapper shall have the ability to conform to the contours of the irregular surface if used over fittings and valves The component wrapper shall meet the requirements in Table 2 when tested in accordance with the test methods listed therein. 3.3 Surface Preparation Loose rust, mill scale, old coating, and dirt shall be removed in accordance with SSPC-SP 2. 9 Wet surfaces shall be wiped until they are as dry as possible. If ice is present, it shall be removed by heating the pipe The prepared surface shall be visually inspected prior to application of the wax coating system. 3.4 Application A thin film of cold-applied wax shall be applied by hand or brush. An additional build-up of coating shall be applied If moisture is present, the cold-applied coating shall be rubbed and pressed onto the surface until the coating adheres to the surface. If adhesion is not sufficient as evidenced by primer rolling off, floating, or otherwise not adhering to the pipe surface, then the manufacturer shall be consulted for recommended procedures for wet pipe primer application. or curing time, and the component wrapper shall be applied immediately after coating in order to avoid contamination or abrasion of the coated surface A wrapper shall be applied using a spiral wrap, a cigarette wrap, or precut pieces formed over irregular surfaces, with a minimum 25-mm (1.0-in.) overlap The cold-applied wax may be used to fill the voids in irregular surfaces of fittings and valves. The wrapper shall be applied so that it does not bridge over irregular surface configurations. 3.5 Inspection and Repair The completed application of the cold-applied coating shall be visually inspected to determine whether it complies with contract specifications and is free from holidays or other coating irregularities Holiday Inspection: The cold-applied wax coating system of each field application may, at the purchaser s option, be inspected with a holiday detector that does not physically damage the coating, in accordance with NACE Standard RP and set at a voltage in conformance with the specifications in Paragraph If the pipe is inspected, holiday detector voltage shall be set at 4 V/µm (100 V/mil) of coldapplied wax coating thickness plus the additional voltage recommended for the outerwrap used Defects in the coating shall be repaired in accordance with Paragraphs 3.3, 3.4, and Pipe shall be handled in accordance with Section 5 of this standard The cold-applied wax does not require drying Section 4: Cold-Applied Wax-Tape Coating Systems 4.1 Wax-tape coating systems shall consist of a petroleum wax primer applied to the surface and then overwrapped with a petroleum wax tape. If extraordinary construction or backfill conditions exist that could result in mechanical damage, a double thickness of wax tape or an additional outerwrap may be used. 4.2 Materials for Wax-Tape Coating Systems 4 NACE International

8 4.2.1 Primer The primer shall be composed of petroleum waxes and plasticizers The primer may contain fillers, inhibitors, and additives that are compatible with the waxtape system The primer may be used as a surface conditioner to wet the surface, displace moisture, arrest active corrosion, and ensure adhesion of the wax tape The primer shall meet the requirements in Table 4 when tested in accordance with the test methods listed therein Wax-Tape Coating The wax-tape coating shall be composed of a synthetic fiber fabric saturated with a petroleum wax blend The wax saturant shall be composed of petroleum wax and plasticizers and may contain fillers, inhibitors, and additives The plasticizers may be of a solvent or nonsolvent type, and the tape may either become firm or remain pliable over a period of time The coating shall meet the requirements in Table 4 when tested in accordance with the test methods listed therein The wax tape and primer shall have maximum service-temperature capability of at least 43 C (110 F) and a minimum servicetemperature capability of -40 C (-40 F). Servicetemperature properties shall be determined by the wax tape and wax tape primer conforming to properties listed in Table 4. TABLE 4 Requirements for Wax Tape and Primer Properties Physical Requirements Test Method Primer Congeal Point 57 to 68 C (135 to 155 F) ASTM D 938 Flash Point 66 C (150 F) minimum ASTM D 92 Specific Gravity at 25 C (77 F) 0.88 to 1.25 ASTM D 70 Cone Penetration at 25 C (77 F) 74 to 224 ASTM D 937 Dielectric Strength 4 V/µm (100 V/mil) minimum ASTM D 149 Tape Congeal Point of Saturant 63 to 71 C (145 to 160 F) ASTM D 938 Flash Point of Saturant 60 C (140 F) minimum ASTM D 92 Thickness 1,000 µm (40 mil) minimum ASTM D 1000 Dielectric Strength 6.7 V/µm (170 V/mil) minimum ASTM D An outerwrap that consists of suitable material such as plastic film, glass mesh, or synthetic fiber mat may be used for additional mechanical protection. 4.3 Surface Preparation Loose rust, mill scale, old coating, and dirt shall be removed by hand-tool cleaning in accordance with SSPC-SP 2. 9 Wet surfaces shall be wiped until they are as dry as possible. If ice is present, it shall be removed by heating the pipe Surface preparation shall be visually inspected prior to application of the wax-tape coating system. 4.4 Application A thin film of primer shall be applied by hand or brush to the surface If moisture is present, the primer shall be rubbed and pressed onto the surface until it adheres to the surface. The manufacturer shall be consulted for recommended procedures Because the primer does not require drying or curing time, the wax tape may be applied immediately after priming The wax tape may be applied using a spiral wrap, a cigarette wrap, or precut pieces formed over irregular surfaces with a minimum 25-mm (1.0-in.) overlap The wax tape shall be applied by pressing and molding the tape into conformity with the surface so that it does not bridge over irregular surface NACE International 5

9 configurations. Wrapping shall begin approximately 76 mm (3.0 in.) behind the cutback area to be wrapped. On straight piping, the tape shall be spiral wrapped around the pipe with a minimum 25-mm (1.0-in.) overlap at the seam. If starting at a straight edge, the tape shall be wrapped entirely around the pipe while touching the end edge before starting to angle to begin the spiral. If the previous roll is headed in a downward direction, the next roll shall be tucked under the previous roll. To avoid air bubbles, each roll shall be stretched tight as wrapping continues After application, the overlap seams of the wax tape shall be sealed by hand by tapering and pressing (rubbing) the seam, attempting to create a continuous appearance. There should be no air pockets underneath the tape, and it should have direct, intimate contact with the pipe surface On vertical sections, such as pipe soil-to-air transitions, the pipe must be wrapped starting from the bottom and going upward to ensure that downwardflowing water and backfill do not catch in a seam. These vertical sections shall be wrapped with a 50% overlap Wax tapes used for pipe soil-to-air transition areas shall be ultraviolet (UV)-light stable so as not to degrade in the presence of sunlight. The pipe owner may require reasonable proof from the manufacturer that their product meets UVstability requirements. 4.5 Inspection and Repair The completed application of the wax-tape coating shall be visually inspected to determine whether it complies with contract specifications and is free from holidays or other coating irregularities Holiday Inspection: The cold-applied wax coating system of each field application may, at the purchaser s option, be inspected with a holiday detector that does not damage the coating, in accordance with NACE Standard RP and set at a voltage in conformance with the specifications in Paragraph If inspected, holiday detector voltage shall be set at 6.7 V/µm (170 V/mil) of wax-tape coating thickness plus the additional voltage recommended if an outerwrap is used Defects in the coating shall be repaired in accordance with Paragraphs 4.3, 4.4, and Pipe shall be handled in accordance with Section 5 of this standard. Section 5: Handling of Wax-Coated Piping 5.1 The coated and wrapped pipe shall be handled in such a manner as to minimize damage to the coating. 5.2 All supported areas of the coated pipe shall be inspected, and damaged areas shall be repaired before installation. (3) 5.3 The pipeline ditch shall be graded and free of rocks, foreign matter, and projections that could cause damage to the coating system. 5.4 A rockshield, additional layers of coating and wrapping material, padding of the ditch bottom, or selected backfill materials may be used to prevent coating damage. 5.5 All equipment used for the handling of coated pipe shall be designed to minimize damage to the protective coating system and shall be approved by the engineer in charge or a representative of the owner. 5.6 If weights, supports, or anchoring devices are used on the coated pipe, they should be attached or applied without damaging the coating system. Such damage can be minimized by protecting the coating system with protective padding such as rockshields. 5.7 When excavations are made for repairs, tie-ins, lateral connections, or any other purpose, all damaged or deteriorated coating shall be repaired. Section 6: Cathodic Protection of Wax-Coated Pipelines, Valves, and Fittings 6.1 If required, cathodic protection shall be installed in accordance with NACE Standard RP (3) NACE Publication 10D contains additional information on the subject. 6 NACE International

10 References RP NACE Publication 2L161 (withdrawn), Tentative Recommended Minimum Requirements for Hot-Applied Wax-Type Protective Coatings and Wrappers for Underground Pipelines (Houston, TX: NACE). Available from NACE as a historical document only. 2. ASTM D 70 (latest revision), Standard Test Method for Density of Semi-Solid Bituminous Materials (Pyncnometer Method) (West Conshohocken, PA: ASTM). 3. ASTM D 1321 (latest revision), Standard Test Method for Needle Penetration of Petroleum Waxes (West Conshohocken, PA: ASTM). 4. ASTM D 127 (latest revision), Standard Test Method for Drop Melting Point of Petroleum Wax Including Petrolatum (West Conshohocken, PA: ASTM). 5. ASTM D 92 (latest revision), Standard Test Method for Flash and Fire Points by Cleveland Open Cup Tester (West Conshohocken, PA: ASTM). 6. ASTM D 149 (latest revision), Standard Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at Commercial Power Frequencies (West Conshohocken, PA: ASTM). 8. SSPC-SP 1 (latest revision), Solvent Cleaning (Pittsburgh, PA: SSPC). 9. SSPC-SP 2 (latest revision), Hand Tool Cleaning (Pittsburgh, PA: SSPC). 10. NACE Standard RP0274 (latest revision), High Voltage Electrical Inspection of Pipeline Coatings (Houston, TX: NACE). 11. ASTM D 938 (latest revision), Standard Test Method for Congealing Point of Petroleum Waxes, Including Petrolatum (West Conshohocken, PA: ASTM). 12. ASTM D 937 (latest revision), Standard Test Method for Cone Penetration of Petrolatum (West Conshohocken, PA: ASTM). 13. NACE Publication 10D194 (withdrawn), State-of-the- Art Report on Rockshielding (Houston, TX: NACE). Available from NACE as a historical document only. 14. NACE Standard RP0169 (latest revision), Control of External Corrosion on Underground or Submerged Metallic Piping Systems (Houston, TX: NACE). 7. ASTM D 1000 (latest revision), Standard Test Method for Pressure-Sensitive Adhesive-Coated Tapes Used for Electrical and Electronic Applications (West Conshohocken, PA: ASTM). NACE International 7