Spiral Wound Gasket Installation Guide

Installing a spiral wound gasket correctly is the single most critical factor in achieving a leak-free flange joint. Even the highest-quality metallic gasket will fail prematurely if the seating surface is contaminated, bolt torque is applied unevenly, or the wrong gasket type is selected for the operating conditions. This guide delivers a step-by-step installation procedure, torquing sequence, and pre- and post-installation inspection checklist — grounded in ASME B16.20 gasket standards and real-world refinery and petrochemical field practice.

A spiral wound gasket consists of a V-shaped metal strip — typically 304/316 stainless steel — wound alternately with a soft filler such as flexible graphite gasket material or PTFE gasket filler. The spring-like crown in the metal strip provides exceptional resilience under fluctuating pressures and temperatures, making spiral wound gaskets the preferred sealing solution for high pressure gasket and high temperature gasket applications in oil and gas, refining, power generation, and chemical processing.

Whether you are a maintenance engineer preparing a scheduled turnaround or a procurement manager sourcing from a qualified spiral wound gasket manufacturer, understanding the full installation process protects your assets, ensures regulatory compliance, and extends the service interval of every flanged joint in your facility.

Understanding Spiral Wound Gasket Construction

Before installation, technicians must understand what they are working with. A standard spiral wound gasket has up to four distinct zones, each performing a specific sealing or structural function.

The Four Zones of a Spiral Wound Gasket

• Inner ring (solid metal ring): Prevents the winding from collapsing into the bore under high bolt loads. Mandatory for Class 900 and above per ASME B16.20.
• Winding body: The alternating metal strip and filler material that creates the primary seal. Typical filler density is 1.0–1.4 g/cm³ for flexible graphite.
• Outer centering ring (guide ring): Centers the gasket in the flange bore and limits over-compression of the winding. Color-coded by material per ASME B16.20 standards.
• Filler material: Graphite (up to 450°C), PTFE (chemical service up to 260°C), mica (above 600°C), or ceramic fiber for extreme temperature applications.

The color coding system standardized in ASME B16.20 helps field technicians quickly identify industrial gasket materials on site. For example, a yellow outer ring typically indicates a carbon steel centering ring, while red commonly denotes stainless steel. Always verify with your gasket supplier's documentation rather than relying on color alone, as non-ASME manufacturers may use different conventions.

Pre-Installation Inspection and Preparation

Improper surface preparation is responsible for an estimated 40–60% of all flange joint leaks in process plants. Taking 15 to 30 minutes for thorough pre-installation inspection eliminates the most common root causes of gasket failure before they occur.

Step 1 — Inspect the Gasket Upon Receipt

Before opening the joint, verify the gasket against the purchase order and flange specification. Check the following:

• Correct nominal pipe size (NPS) and pressure class (e.g., ASME Class 150, 300, 600, 900, 1500, or 2500).
• Winding and filler material match the process fluid chemical compatibility requirements.
• No visible damage — dents, loose windings, separated filler, or corrosion on the metal strip.
• Outer ring color matches the specified metal per ASME B16.20 coding.
• Gasket is within its recommended shelf life — graphite-filled gaskets should be stored away from direct sunlight and oxidizing environments.

Step 2 — Clean and Inspect the Flange Faces

Clean flange seating surfaces thoroughly using an appropriate solvent — acetone or isopropyl alcohol for most carbon steel and stainless steel flanges. Remove all traces of the old gasket material, rust, scale, and process residue. Use a wire brush, flange scraper, or abrasive pad only if pitting or heavy oxidation is present; always finish with a lint-free cloth and solvent wipe.

Measure the surface roughness (Ra) of raised-face flanges. For spiral wound gaskets, the recommended surface finish is 125–250 µin Ra (3.2–6.3 µm Ra) — a serrated phonographic finish produced by a 45°/90° tool cutting at a controlled depth. A finish smoother than 125 µin may cause the winding to slip rather than embed; a finish rougher than 500 µin can puncture the filler and create leak paths.

Inspect for radial scratches, pitting, and warping using a straight edge across the flange face diameter. Any radial defect deeper than 0.3 mm that runs continuously from bore to outer diameter is grounds for flange re-machining before re-gasketing.

Step 3 — Inspect Studs, Nuts, and Washers

Stud bolts and heavy hex nuts must be cleaned, inspected for thread damage, and lubricated. Bolt lubrication is critical: unlubricated threads can absorb up to 50% of the applied torque as friction, leaving only 50% available to generate gasket seating stress. Use a molybdenum disulfide (MoS₂) paste or anti-seize compound rated for the operating temperature range. Apply lubricant to the full thread length of the stud and to both nut bearing faces.

Step-by-Step Spiral Wound Gasket Installation

Follow this procedure for every flanged joint. Skipping steps — even seemingly minor ones — can compromise the integrity of a high pressure gasket joint operating at elevated temperature or with hazardous media.

Step 4 — Position the Gasket

Place the spiral wound gasket centrally on the lower flange face. The outer centering ring should contact the flange bolt holes or the pipe bore, depending on the flange type (raised face, flat face, or ring type joint). Never use gasket cement, sealant, or adhesive on spiral wound gaskets — these substances compress unevenly, prevent the winding from seating correctly, and can cause premature failure. Do not re-use a previously installed spiral wound gasket under any circumstances.

Step 5 — Align the Flanges

Bring the mating flange into position without dragging it across the gasket face. Flange misalignment is a leading cause of uneven gasket loading. The gap between flange faces should be parallel within 1.5 mm across any diameter before bolt insertion. Use flange alignment pins in two opposing bolt holes to hold position while remaining bolts are inserted. Never use bolts to pull misaligned flanges together — this can fracture connecting pipework and cause catastrophic joint failure.

Step 6 — Insert and Hand-Tighten All Bolts

Insert all studs and nuts and hand-tighten uniformly. At this stage, every nut should be snug but not torqued. Confirm that the gasket has not shifted — visually verify centering from both sides of the joint. Remove alignment pins once all bolts are in place and hand-tight.

Step 7 — Apply Torque in a Cross Pattern

Torque is applied in multiple passes using a cross (star) pattern — not a sequential clockwise pattern. A sequential pattern applies full load to one side before the opposite side, tilting the gasket and creating leak paths. The recommended procedure is:

1. Pass 1: 20–30% of target torque value, cross pattern.
2. Pass 2: 50–70% of target torque value, cross pattern.
3. Pass 3: 100% of target torque value, cross pattern.
4. Pass 4 (verification): 100% of target torque, clockwise sequence around all bolts. Stop at each bolt only if it is still rotating — if it is already at torque, move on.

For large-bore flanges (NPS 12 and above), consider using hydraulic bolt tensioners rather than torque wrenches. Tensioners apply load axially rather than through torsion, achieving more uniform bolt elongation and reducing scatter in achieved clamp load. Typical scatter with a calibrated torque wrench is ±25–30%; hydraulic tensioners reduce scatter to ±5–10%.

Bolt Torque Values and Gasket Seating Stress

Correct torque is not a single value — it depends on the gasket dimensions, flange class, bolt diameter and grade, lubricant used, and the required minimum gasket seating stress (m and y values per ASME Section VIII). Using too little torque results in insufficient seating stress and leakage; too much torque crushes the winding and destroys the spring-back resilience that makes spiral wound gaskets effective under thermal cycling.

A spiral wound gasket for a flange gasket application typically requires a minimum seating stress (y) of 10,000–15,000 psi (69–103 MPa) and a maintenance factor (m) of 3.0–6.5 depending on filler material and pressure class. These values should be obtained from the gasket manufacturer's technical data sheet rather than generic published tables, since dimensions and winding density vary by manufacturer.

The general torque formula incorporating friction factor (K), bolt diameter (d), and bolt load (F) is: T = K × d × F. For MoS₂-lubricated studs, K is typically 0.14–0.16. For dry, unlubricated studs, K can reach 0.20–0.22, meaning the same torque produces significantly less bolt load — a critical reason for mandating bolt lubrication in all gasket sealing procedures.

Post-Installation Inspection and Hot Bolt Retorque

Installation does not end when the final bolt pass is completed. Two post-installation activities are critical to long-term joint integrity: the initial leak test and the hot bolt retorque.

Pressure Test Before Returning to Service

New gasket joints should be hydrostatically or pneumatically tested before returning to service with process fluid. Hydrostatic testing at 1.5x design pressure is standard for most piping systems per ASME B31.3. During testing, inspect the joint visually for seepage or weeping. Do not re-torque bolts while the joint is under test pressure — this is a safety hazard and may cause sudden bolt fracture.

Hot Bolt Retorque Procedure

When a flanged system reaches operating temperature for the first time, thermal expansion causes bolt elongation and filler material relaxation (particularly with graphite fillers), reducing effective bolt load by 10–25%. A hot retorque — performed at operating temperature within 2–4 hours of initial heat-up — restores target bolt load and compensates for these effects. Hot retorque should be performed in the same cross-pattern sequence as the initial torque procedure.

Safety protocols for hot retorque must address the risk of personnel exposure to hot surfaces (above 60°C) and pressurized systems. Use calibrated torque wrenches with extended handles to keep the operator away from the hot joint. For systems containing hazardous fluids, hot retorque requires a formal permit-to-work. Some operators omit hot retorque on PTFE-filled gaskets due to PTFE's higher creep sensitivity at elevated temperatures — consult your gasket supplier's technical guidance for specific filler materials.

Selecting the Right Spiral Wound Gasket for Your Application

Correct material selection is inseparable from correct installation. A perfectly installed gasket made from the wrong material will fail as surely as a correct material installed improperly. The selection matrix below covers the most critical variables.

Winding Metal Selection

The winding metal must resist corrosion from both the process fluid and the external environment. For most petroleum and chemical applications, 316 stainless steel is the standard choice. For chloride-bearing services above 60°C, Alloy 825 or Hastelloy C-276 windings provide superior resistance to stress corrosion cracking. For high-sulfur crude oil and refinery gas streams, 317L stainless steel or duplex grades are common selections.

Filler Material Selection Guide

• Flexible graphite: Best for steam, hydrocarbons, most acids and alkalis. Not suitable for strong oxidizing acids (nitric, concentrated sulfuric) or liquid oxygen service.
• PTFE: Preferred for strong acids, solvents, pharmaceutical, and food-grade applications. Limited to 260°C and moderate pressure. High creep — requires lower maximum bolt load.
• Mica: For furnace and stack gas applications above 450°C where graphite would oxidize. Less conformable than graphite, requiring smoother flange faces.
• Ceramic fiber: For extreme-temperature service above 700°C in non-corrosive environments. Brittle — requires careful handling during installation.

Common Installation Mistakes and How to Avoid Them

Field experience from petrochemical plant maintenance programs consistently identifies the same installation errors across different sites and operators. Understanding these failure modes is as important as knowing correct procedure.

Re-Using a Previously Compressed Gasket

Once a spiral wound gasket has been compressed between flanges and unloaded, the spring-back in the metal winding is permanently reduced. Filler material — particularly PTFE — has already flowed into surface irregularities and cannot re-conform to a new joint. Never re-use a spiral wound gasket. The cost of a replacement gasket is negligible compared to the cost of a second flange opening or a process leak.

Applying Sealant or Thread Compound to Gasket Faces

Sealant compounds applied to the winding surface create a non-uniform contact layer that causes the gasket to seat eccentrically. Bolt load is then concentrated on the high spots, leading to local over-compression of the winding and potential blow-through at low-stress zones. The only acceptable lubricant in a gasket assembly is on the bolt threads and nut bearing faces — never on the gasket seating surface.

Using a Gasket of Incorrect Pressure Class

A Class 300 gasket installed in a Class 600 flange will be over-compressed and destroyed — its outer ring will not adequately limit compression. Conversely, a Class 600 gasket in a Class 300 joint will be under-compressed, resulting in insufficient seating stress and leakage. Always verify the pressure class marking on the gasket outer ring against the flange rating before installation.

Ignoring Flange Rotation and Pipe Strain

Pipe strain — stress imposed on a flange joint by misaligned or inadequately supported pipework — creates bending moments that unevenly load one side of the gasket. Even a perfectly torqued joint will develop a leak if the pipe experiences significant thermal movement without proper expansion loops or supports. Pipe stress analysis should confirm that flange loads remain within ASME B16.5 allowable limits before a joint is closed.

OEM and Custom Spiral Wound Gasket Manufacturing

For applications where standard catalog gaskets are not suitable — non-standard flange dimensions, extreme media, or special regulatory requirements — working directly with a qualified spiral wound gasket manufacturer offering OEM and ODM services provides significant advantages.

Ningbo Rilson Sealing Material Co., Ltd., founded in 2007 and located in Ningbo, Zhejiang Province, operates a 20,000 m² manufacturing facility dedicated to the design and production of sealing gaskets for the petroleum, chemical, power, shipbuilding, and machinery manufacturing sectors. As a professional gasket supplier and manufacturer, Rilson's product range includes spiral wound gaskets, ring joint gaskets, kammprofile gaskets, corrugated metal gaskets, insulation kit gaskets, and non-asbestos gaskets — covering virtually the complete spectrum of industrial flange sealing requirements.

When engaging a spiral wound gasket manufacturer for custom or OEM development, procurement engineers should request:

• Material traceability certificates for winding strip and filler, including heat number references.
• Dimensional inspection reports confirming ID, OD, and thickness within ASME B16.20 or agreed tolerances.
• Hydrostatic or pneumatic leak test results where applicable.
• Winding density and compression load data for gasket seating stress calculations.
• Chemical compatibility reports or NACE MR0175 compliance documentation for sour service.

Frequently Asked Questions