A leaking flange joint at high pressure isn’t just a maintenance headache; it’s a safety incident waiting to happen. And nine times out of ten, the cause isn’t a faulty gasket. It’s the way it was installed.
Spiral wound gasket installation looks straightforward on paper: clean the flange, drop in the gasket, tighten the bolts. But the difference between a joint that holds for years and one that fails in weeks comes down to small details; things like flange surface finish, torque sequence, bolt load distribution, and the discipline to follow each step in order.
This guide walks through the proper installation process used by reliability engineers and maintenance teams, with the specific values and references you need to get it right the first time.
Key Takeaways:
Inspect both the gasket and flange faces before installation; any damage, scoring, or contamination on either component will compromise the seal.
Spiral-wound gaskets require a flange surface finish of 3.2-6.3 μm Ra (125–250 μin) for proper sealing.
Always tighten bolts in a star (cross) pattern using at least three torque passes: roughly 30%, 60%, and 100% of the final torque value.
Never reuse a spiral wound gasket; once compressed, the windings have permanently deformed and won’t reseal reliably.
For systems with thermal cycling, plan a hot bolting re-torque after the first heat-up to compensate for gasket relaxation.
What Is a Spiral Wound Gasket?
A spiral wound gasket is a semi-metallic seal made by alternately winding a V-shaped metal strip with a soft non-metallic filler, usually flexible graphite or PTFE. The metal provides recovery and resilience under load cycling, while the filler conforms to flange surface imperfections and creates the actual seal.
Most spiral wound gaskets you’ll encounter on raised face flanges include an outer centring ring, and ASME B16.20 has required inner rings on most sizes since 2008 to prevent inward buckling of the windings under pressure. The outer ring also acts as a compression limiter, stopping the windings from being crushed during bolt-up.
These gaskets are the standard choice for high-pressure, high-temperature flange joints in oil and gas, chemical processing, power generation, and refinery service. They handle pressures well above 100 bar and temperatures from cryogenic up to around 650°C with graphite filler, well beyond the range of most soft-cut gaskets.
Why Spiral Wound Gasket Installation Matters
Spiral wound gaskets are engineered components with specific compression requirements. The sealing element typically needs around 30% compression to seat properly; too little and the joint leaks, too much and the windings buckle, or the filler extrudes.
Get the installation wrong, and you’ll see one of several failure modes: blow-out under pressure, slow weeping leaks, inward buckling of the windings, or accelerated relaxation under thermal cycling. Each of these traces back to the same root causes: contaminated sealing surfaces, uneven bolt load, incorrect torque, or an out-of-spec flange face.
Fortunately, these issues are easy to avoid. They just require following the steps in the right order, with the right tools.
What You’ll Need Before Starting
Before you touch the flange, gather the following:
The correct gasket, verified against the P&ID, flange standard (ASME B16.5, B16.47, etc.), pressure class, and material specification.
A calibrated torque wrench rated for your bolt size.
Bolt thread lubricant (anti-seize or the lubricant specified by your bolting procedure).
Hardened flat washers to ensure even load transfer.
A wire brush, a scraper, and clean rags for flange-face cleaning.
A surface roughness comparator if flange finish is in question.
Safety equipment: gloves, safety glasses, and any PPE required for the system being worked on.
Manufacturer torque specifications or an ASME PCC-1 bolting procedure for reference.
Confirm the system is isolated, depressurised, drained, and locked out before starting. This is non-negotiable.
Step-by-Step Spiral Wound Gasket Installation
Step 1: Inspect the New Gasket
Check the gasket under good light for dents in the winding, displaced filler, or distortion in the centring ring. Cross-check the markings on the outer ring against your specification: manufacturer, size, pressure class, and material grade per ASME B16.20.
A 304 stainless winding in a service that requires 316L will fail. Verify before installing. If anything looks off, set the gasket aside and grab another. Spiral wound gaskets are not field-repairable.
Step 2: Prepare the Flange Faces
Remove the old gasket with a brass scraper or wire brush. Never use a steel chisel, hammer, or angle grinder on the sealing surface.
Insect for radial scoring, pitting, corrosion, or warpage. Radial scratches across the sealing face are the enemy and create a direct leak path that bolt torque can’t close. Light circumferential marks are usually acceptable.
Check the surface finish. ASME B16.5 raised face flanges should have a serrated finish of 3.2 to 6.3 μm Ra (125 to 250 μin). Use a surface comparator if in doubt. Flanges outside this range need re-matching.
Wipe both faces clean with a lint-free rag. Don’t apply grease, anti-seize, or sealant to the sealing surfaces.
Step 3: Check Flange Alignment
Flanges must be parallel and concentric before the gasket goes in. Bolt holes should line up freely without forcing the flanges together.
A small flex in the pipework to bring flanges parallel is acceptable. Significant force isn’t. Sort the pipe support or alignment first. Never use the flange bolts to drag misaligned flanges into position.
Step 4: Centre the Gasket
Set the gasket between the flange faces so the outer centring ring rests hard against the inside of the bolt circle. The centring ring keeps the sealing element concentric with the bore.
If the gasket isn’t sitting flat by hand, stop. Either the size is wrong, the centring ring is damaged, or the flange has issues. Don’t use the bolts to pull it into position.
Step 5: Lubricate and Install the Bolts
Apply thread lubricant to the bolt threads and to the nut bearing face. The bearing face matters as much as the threads: it determines how much applied torque becomes actual bolt tension.
Run all nuts on hand-tight. If a nut won’t run the full length of the bolt by hand, replace the bolt or chase the threads. Always use hardened flat washers under the nuts to distribute load and prevent galling.
Step 6: Tighten in Multiple Passes Using a Star Pattern
This is the step that makes or breaks the seal. The star pattern compresses the gasket evenly around its full circumference, rather than squeezing one side and prying open the other.
Run at least three torque passes:
First pass: 30% of final torque
Second pass: 60% of final torque
Final pass: 100% of specified torque
For an 8-bolt flange, the star pattern goes 1, 5, 3, 7, 2, 6, 4, 8. Always cross to the opposite side before working around. The same principle applies to 12, 16, and 20-bolt flanges.
Finish with a full rotational pass at 100% torque (1, 2, 3, 4…) to pick up bolts that have lost tension as the gasket compressed. ASME PCC-1 is the recognised reference for this procedure.
Step 7: Verify Even Compression
Check the flange gap around the full circumference. A uniform gap means even compression. A wedge-shaped gap means uneven load. Stop and investigate before pressurising.
Document the torque values applied to each bolt. It’s a useful record if the joint is ever investigated for leakage or audited under a mechanical integrity programme.
Common Spiral Wound Gasket Installation Mistakes
Even experienced teams slip up on these:
Reusing a gasket. Once compressed, the windings have permanently deformed and won’t reseal.
Skipping the surface finish check. A flange that’s been re-faced too many times often falls outside the 3.2-6.3 μm Ra range.
Lubricating the gasket faces. This reduces friction with the flange, increases the risk of blowout, and can contaminate the system.
Using uncalibrated torque tools. A wrench that hasn’t been calibrated in two years is a guessing tool.
Single-pass tightening. Going straight to the final torque crushes one side before the other has seated, creating a leak path.
Substituting gasket types. A spiral wound gasket cannot replace a sheet gasket without verifying flange type, surface finish, and bolt load capacity.
Hot Bolting and Thermal Cycling
Systems that operate well above ambient) steam lines, hot oil, refinery service) will relax during the first heat-up as the filler settles and the bolts expand. This is normal.
The fix is a hot bolting procedure: re-torque the bolts to the original spec once the system has reached operating temperature and stabilised. Live hot bolting requires specialist tooling and trained personnel due to safety risks. Where it isn’t practical, plan a re-torque at the next shutdown.
When to Use Other Gasket Materials
Spiral wound gaskets aren’t universal. Flat-face flanges, low-pressure water or air systems, and applications with limited bolt load are better suited to soft-cut rubber, fibre, or PTFE gaskets. Below 80 bar with chemical resistance requirements, ePTFE or CNAF often performs better. For ring joint and kammprofile alternatives, see our metallic gaskets.
Get the Right Gasket for the Job
A perfect installation can’t compensate for the wrong gasket. Industrial Experts supply spiral wound gaskets for demanding industrial applications, with options available to suit ASME B16.20 requirements and a range of material, filler and configuration needs. As an authorised Garlock supplier with in-house CNC oscillating knife cutting, milling and routing capability, Industrial Experts can supply both premium sealing products and precision-cut soft gaskets to match. If you’re not sure which gasket suits your service conditions, our team can help you specify the right material based on pressure, temperature, media and flange type. Explore our industrial gaskets and sealing products, or get in touch for advice and a quote.
28 Oct, 2025
5 Nov, 2025