A pipe spool RFQ that is missing critical technical information is the most common cause of delivery delays, fabrication errors, and site rejection. Suppliers quote what they understand — if your RFQ is ambiguous, you will receive spools that don't fit, don't meet the weld standard, or can't be accepted by your QC team. This guide covers the 12 data points that every buyer of prefabricated duplex or stainless steel pipe spools must include in their RFQ.
What is a Pipe Spool?
A pipe spool is a pre-fabricated assembly of straight pipe runs, elbows, tees, reducers, and flanges — joined by welding or threaded connections — ready for installation at site. Spools reduce site welding time, improve quality control (shop-welded spools are easier to inspect than field welds), and allow parallel fabrication while site construction is ongoing. For offshore and desalination projects, spools are typically transported in shipping containers and lifted into position by crane.
The 12 RFQ Data Points
1
Isometric Drawings (Isos)
Issue the latest revision of fabrication isometric drawings (P&ID derived isos) showing all spool dimensions, material specs, weld joints, flange ratings, and component lists. Without isos, the fabricator cannot produce the spools. Isos must carry a document revision status — never send "for reference" drawings without confirming they are the current-for-construction (CFC) issue.
Issue the latest revision of fabrication isometric drawings (P&ID derived isos) showing all spool dimensions, material specs, weld joints, flange ratings, and component lists. Without isos, the fabricator cannot produce the spools. Isos must carry a document revision status — never send "for reference" drawings without confirming they are the current-for-construction (CFC) issue.
2
Pipe Material Grade and Standard
Specify the exact grade and product standard: e.g., "ASTM A790 UNS S32205 seamless pipe, Schedule 40S." Include both the material grade (2205, 2507, 316L) and the applicable ASTM/ASME standard. Ambiguous specs like "duplex pipe" without a standard or grade lead to incorrect material procurement.
Specify the exact grade and product standard: e.g., "ASTM A790 UNS S32205 seamless pipe, Schedule 40S." Include both the material grade (2205, 2507, 316L) and the applicable ASTM/ASME standard. Ambiguous specs like "duplex pipe" without a standard or grade lead to incorrect material procurement.
3
Fitting and Flange Specifications
List standards for all fittings (ASTM A815) and flanges (ASTM A182, ASME B16.5 class). For flanges: face type (RF, RTJ, FF), pressure class, and bore size. For fittings: radius type (LR, SR), schedule, and end connection. Components must match pipe schedule and end prep (BE, PE, flanged).
List standards for all fittings (ASTM A815) and flanges (ASTM A182, ASME B16.5 class). For flanges: face type (RF, RTJ, FF), pressure class, and bore size. For fittings: radius type (LR, SR), schedule, and end connection. Components must match pipe schedule and end prep (BE, PE, flanged).
4
Applicable Piping Code
State which design code governs: ASME B31.1 (Power Piping), ASME B31.3 (Process Piping), B31.4 (Liquid Transport), B31.8 (Gas Distribution), or NORSOK / EN 13480. The code determines allowable stress, weld category, examination extent, and hydrostatic test pressure.
State which design code governs: ASME B31.1 (Power Piping), ASME B31.3 (Process Piping), B31.4 (Liquid Transport), B31.8 (Gas Distribution), or NORSOK / EN 13480. The code determines allowable stress, weld category, examination extent, and hydrostatic test pressure.
5
Welding Procedure Specification (WPS) Requirements
State whether the fabricator must use: (a) your approved WPS, (b) their own approved WPS (provide approval body, e.g., ASME IX), or (c) whether you require WPS/PQR submittal for your review before fabrication. For duplex and super duplex, WPS must control preheat, interpass temperature, heat input and filler metal (e.g., 2209 for duplex 2205 welds).
State whether the fabricator must use: (a) your approved WPS, (b) their own approved WPS (provide approval body, e.g., ASME IX), or (c) whether you require WPS/PQR submittal for your review before fabrication. For duplex and super duplex, WPS must control preheat, interpass temperature, heat input and filler metal (e.g., 2209 for duplex 2205 welds).
6
Non-Destructive Examination (NDE) Requirements
Specify examination type and percentage: e.g., "100% RT on all butt welds; 10% PT on all socket welds." Common NDE methods for pipe spools: Radiographic Testing (RT), Ultrasonic Testing (UT), Dye Penetrant Testing (PT), Magnetic Particle Testing (MT — not applicable to austenitic/duplex grades). For ASME B31.3 Category M or high-pressure, 100% examination is mandatory. Confirm acceptance criteria: ASME B31.3 Table 341.3.2 or project-specific.
Specify examination type and percentage: e.g., "100% RT on all butt welds; 10% PT on all socket welds." Common NDE methods for pipe spools: Radiographic Testing (RT), Ultrasonic Testing (UT), Dye Penetrant Testing (PT), Magnetic Particle Testing (MT — not applicable to austenitic/duplex grades). For ASME B31.3 Category M or high-pressure, 100% examination is mandatory. Confirm acceptance criteria: ASME B31.3 Table 341.3.2 or project-specific.
7
Dimensional Tolerances and Fit-Up Requirements
State the allowable dimensional tolerance for each spool: face-to-face dimensions, bolt hole orientation (clock position for flanges), flange squareness, and overall spool envelope. Industry standard is typically ±3mm on face-to-face, ±1.5° on flange rotation — but offshore and compact plant designs often require tighter tolerances. State whether you require 3D dimensional reporting.
State the allowable dimensional tolerance for each spool: face-to-face dimensions, bolt hole orientation (clock position for flanges), flange squareness, and overall spool envelope. Industry standard is typically ±3mm on face-to-face, ±1.5° on flange rotation — but offshore and compact plant designs often require tighter tolerances. State whether you require 3D dimensional reporting.
8
Hydrostatic or Pneumatic Test Requirements
State whether shop pressure testing is required, the test medium (water or air), test pressure (typically 1.5× MAWP for hydro, 1.1× for pneumatic), duration, and acceptance criteria. For duplex spools, ensure any residual chlorinated water is fully flushed and dried before packaging — chloride contamination on internally tested duplex spools in laydown storage is a known risk.
State whether shop pressure testing is required, the test medium (water or air), test pressure (typically 1.5× MAWP for hydro, 1.1× for pneumatic), duration, and acceptance criteria. For duplex spools, ensure any residual chlorinated water is fully flushed and dried before packaging — chloride contamination on internally tested duplex spools in laydown storage is a known risk.
9
Pickling and Passivation Requirements
For stainless steel and duplex spools: specify whether pickling and passivation is required after welding. Welding produces heat tint and oxidation that must be removed to restore corrosion resistance. Specify the method (paste, spray, or bath) and the passivation standard (ASTM A380 or ASTM A967). PMI testing should be specified here if required.
For stainless steel and duplex spools: specify whether pickling and passivation is required after welding. Welding produces heat tint and oxidation that must be removed to restore corrosion resistance. Specify the method (paste, spray, or bath) and the passivation standard (ASTM A380 or ASTM A967). PMI testing should be specified here if required.
10
Coating or Insulation Requirements
If flanges or external pipe surfaces require coating: specify the paint system (primer, intermediate, topcoat), DFT (dry film thickness), and colour coding. For offshore spools: confirm if insulation or flange protection (flange guards) are required and who supplies them. Stainless and duplex spools typically do not require external corrosion coating but may need insulation for thermal or personnel protection.
If flanges or external pipe surfaces require coating: specify the paint system (primer, intermediate, topcoat), DFT (dry film thickness), and colour coding. For offshore spools: confirm if insulation or flange protection (flange guards) are required and who supplies them. Stainless and duplex spools typically do not require external corrosion coating but may need insulation for thermal or personnel protection.
11
Material Test Certificate (MTC) and Traceability Requirements
State: EN 10204 3.1 or 3.2 for pipe, fittings and flanges. Heat number traceability is required for all components — the MTC heat number must be traceable to physical material markings. For NACE service, specify hardness test results and heat/lot compliance.
State: EN 10204 3.1 or 3.2 for pipe, fittings and flanges. Heat number traceability is required for all components — the MTC heat number must be traceable to physical material markings. For NACE service, specify hardness test results and heat/lot compliance.
12
Packing, Marking, and Shipping Requirements
Specify spool marking requirements (spool number per iso, size, material, heat number, project number). State packing method: flange face protection (plywood or plastic blank flange covers), pipe end caps, moisture-absorbing bags for sea freight, and any special packaging for crevice-sensitive duplex grades. State shipping destination, port of loading, and preferred Incoterms.
Specify spool marking requirements (spool number per iso, size, material, heat number, project number). State packing method: flange face protection (plywood or plastic blank flange covers), pipe end caps, moisture-absorbing bags for sea freight, and any special packaging for crevice-sensitive duplex grades. State shipping destination, port of loading, and preferred Incoterms.
Summary checklist: Before issuing your pipe spool RFQ, verify it includes: (1) Isos, (2) Material grade + standard, (3) Fitting/flange specs, (4) Piping code, (5) WPS requirements, (6) NDE scope, (7) Dimensional tolerances, (8) Pressure test requirements, (9) Pickling/passivation, (10) Coating, (11) MTC requirements, (12) Packing/marking. Missing any one of these will delay your enquiry cycle and increase the risk of delivery rejection.
Typical Documentation Package for Spool Delivery
| Document | Provided By |
|---|---|
| As-built isometric drawings | Fabricator |
| Material Test Certificates (EN 10204 3.1/3.2) | Mill / Fabricator |
| Weld Map (showing weld numbers, welder IDs, WPS referenced) | Fabricator |
| NDE Reports (RT films / UT / PT records) | Fabricator / TPI Agency |
| Hydrostatic Test Report | Fabricator |
| Dimensional Inspection Report | Fabricator |
| PMI Test Report (if specified) | Fabricator / TPI Agency |
| Pickling/Passivation Record | Fabricator |
| Heat Treatment Records (if applicable) | Fabricator |
| Packing List and Shipping Documents | Exporter |