What flange surface finishes can a flange facer produce?

A flange facer can produce several surface finishes depending on the application and gasket type. The most common is a serrated (phonographic) finish — concentric grooves at a controlled pitch — which is the standard finish for raised-face flanges per ASME B16.5. Typical finish values range from 125 to 250 microinches Ra (3.2 to 6.3 µm) for standard gaskets, and 63 to 125 microinches Ra for spiral-wound and ring-type joint gaskets. The Flange Hog® 110 produces a phonographic finish that meets ASME PCC-1 guidelines for gasket seating.

What size flanges can the Flange Hog handle?

The Flange Hog® 110 covers flanges from 1.0″ I.D. to 14.0″ O.D. (25.4mm to 355.6mm). This range covers the majority of process piping flange sizes encountered in refinery, power plant, chemical processing, and marine applications — from 1″ NPS through 12″ NPS raised-face flanges in ASME B16.5 pressure classes 150 through 2500.

What is the difference between a flange facer and a flange facing lathe?

A flange facing lathe is a large, often fixed-position machine used in fabrication shops to machine new flanges or perform heavy-duty resurfacing. A portable flange facer is a lightweight, field-deployable tool designed for in-situ repair of flanges that are already installed in a piping system. The Flange Hog® 110 weighs a fraction of a shop lathe and can be set up by a single operator directly on the flange — making it the preferred tool for turnaround, outage, and emergency repair work where shop access is not practical.

On-Site Flange Repair

Flange Facing Tools & Flange Resurfacing

Q: What is a flange facer?

A flange facer (also called a flange facing tool or flange facing machine) is a portable machining tool that restores damaged flange gasket sealing surfaces to their original flatness and finish — on-site, without removing the flange from the piping system. The tool clamps to the flange bore or bolts, and a cutting head rotates across the flange face to machine it back to the required surface finish. This eliminates the need to cut out the damaged flange, weld in a new one, and re-qualify the weld — saving days of downtime and thousands of dollars per repair.

Q: When do you need to resurface a flange?

Flange resurfacing is required when the gasket seating surface is damaged by corrosion, erosion, steam cutting, chemical attack, improper gasket removal, or mechanical damage from overtorquing. Symptoms include persistent flange leaks after re-gasketing, visible scoring or pitting on the flange face, and flanges that fail hydrostatic pressure testing. If the damage is within the machining capacity of the flange facer (typically 0.060″ to 0.125″ of material removal), resurfacing is faster and less expensive than flange replacement.

Q: Can you face a flange in the field without removing it?

Yes. Portable flange facing tools like the Flange Hog® 110 are designed specifically for in-situ flange repair. The tool clamps directly to the flange and machines the seating surface while the flange remains welded to the piping system. This eliminates cutting, re-welding, post-weld heat treatment, NDE inspection, and pressure testing — work that can add days to a turnaround schedule and cost thousands per flange joint.

Restore damaged flange gasket seats in the field — no cutting, no welding, no flange replacement. The Flange Hog® 110 machines a phonographic finish on flanges from 1.0″ to 14.0″ OD in a single setup.

See Flange Hog® 110 → Get a Quote

1–14″ OD

Flange size range

No Weld

Eliminates cutting & welding

ASME

PCC-1 compliant finish

Flange Hog® 110

Made in USA

Phonographic Finish

Single-Operator Setup

Rental Available

Flange Facing Explained

What Is a Flange Facer?

A flange facer (also called a flange facing tool or flange facing machine) is a portable machining tool that restores damaged flange gasket sealing surfaces to their original flatness and surface finish — on-site, without removing the flange from the piping system.

The tool clamps to the flange bore and a cutting head rotates across the flange face, machining it back to the required serrated phonographic finish specified by ASME B16.5 and ASME PCC-1. This eliminates the traditional repair approach of cutting out the damaged flange, welding in a replacement, performing post-weld heat treatment, NDE inspection, and hydrostatic testing.

The Esco Tool Flange Hog® 110 covers flanges from 1.0″ I.D. to 14.0″ O.D. (25.4mm to 355.6mm) — spanning 1″ NPS through 12″ NPS raised-face flanges across all ASME B16.5 pressure classes from 150 to 2500. It’s manually operated, requires no external power source, and can be set up and run by a single operator.

Without a Flange Facer

Cut out damaged flange
Weld in new flange
Post-weld heat treatment (PWHT)
NDE / radiography inspection
Hydrostatic pressure test
2–5 days per flange joint

With the Flange Hog®

Mount tool on existing flange
Machine gasket surface in place
Install new gasket
Bolt up and torque
Back in service
Hours, not days

Common Flange Damage

When to Resurface a Flange

Flange gasket seats degrade over time from corrosion, erosion, steam cutting, and mechanical damage. When re-gasketing alone can’t stop the leak, flange resurfacing is the repair.

Persistent Leaks

Flange continues leaking after new gasket installation and proper bolt torque. The gasket seating surface is too damaged or uneven to form a seal — resurfacing restores the contact geometry.

Visible Scoring & Pitting

Corrosion pits, radial scoring from steam cutting, and erosion channels on the gasket face. If damage depth is within 0.060″ to 0.125″, flange facing can machine the surface flat without replacing the flange.

Mechanical Damage

Gouges from improper gasket removal (screwdrivers, chisels), dents from dropped bolt heads, or warping from overtorquing. The Flange Hog machines past the damage to restore a flat, true surface.

Chemical Attack

Acid, caustic, and solvent exposure erodes the gasket seating surface over time. Common in chemical processing, refinery acid service, and pulp & paper plants.

Failed Hydrotest

Flange joint fails hydrostatic or pneumatic pressure testing during commissioning or re-commissioning. Resurfacing the gasket seat and re-gasketing often avoids a full flange replacement.

Turnaround & Outage Scope

Planned inspection reveals flange face degradation during a scheduled outage. In-situ facing saves days compared to flange replacement — critical when the turnaround schedule is compressed.

Surface Finish Standards

Flange Face Finishes & Gasket Compatibility

The gasket seating surface finish on a flange must match the gasket type being used. Too smooth and the gasket won’t grip. Too rough and the gasket can’t seal. The Flange Hog® 110 produces a controlled serrated (phonographic) finish — concentric grooves at a consistent pitch — that is the standard for raised-face flanges per ASME B16.5.

ASME PCC-1 (Guidelines for Pressure Boundary Bolted Flange Joint Assembly) specifies the surface finish requirements for different gasket types. The table below shows the most common combinations.

Gasket Type	Finish (Ra)	AARH (µin)	Notes
Compressed fiber / non-metallic	3.2–6.3 µm	125–250	Standard serrated finish
Spiral-wound (with inner ring)	3.2–6.3 µm	125–250	Most common in process piping
Spiral-wound (without inner ring)	1.6–3.2 µm	63–125	Smoother finish required
Kammprofile / grooved metal	1.6–3.2 µm	63–125	High-pressure, high-temp
Ring-type joint (RTJ)	0.8–1.6 µm	32–63	Machined groove required
PTFE envelope / filled PTFE	3.2–6.3 µm	125–250	Chemical service

How It Works

Four Steps to a Restored Flange Face

Clean & Inspect

Remove old gasket material. Inspect flange face for damage depth, type, and extent. Verify damage is within machining capacity.

Mount Flange Hog®

Insert the tool into the flange bore and engage the clamping mechanism. The tool self-centers on the flange — no external alignment fixtures needed.

Machine the Face

Rotate the cutting head across the flange face. The Flange Hog produces a controlled phonographic finish in a single pass — serrated grooves at a consistent pitch.

Gasket & Bolt-Up

Verify finish with a surface comparator. Install new gasket, torque bolts per ASME PCC-1 sequence. Joint is ready for service.

Industries & Applications

Where Flange Facing Tools Are Used

Any industry with bolted flange joints encounters gasket seat damage. Portable flange facing eliminates the most expensive repair in piping maintenance.

Refinery & Petrochemical

Process piping flanges in acid service, high-temperature hydrogen, and hydrocracker units. Flange facing during turnarounds avoids the 3–5 day penalty of flange replacement and PWHT.

Power Generation

Main steam, feedwater, and extraction line flanges. High-pressure flanges (Class 600–2500) in P91 and P22 service where welding a new flange triggers mandatory PWHT and extended NDE.

Chemical Processing

Acid-resistant alloy flanges (Hastelloy, Monel, 20Cb-3) where chemical attack erodes the gasket face. Resurfacing preserves the expensive alloy flange — replacement cost can exceed $5,000 per flange.

Pulp & Paper

Digester and bleach plant piping flanges exposed to caustic and chlorine compounds. Persistent corrosion of gasket surfaces makes flange facing a routine maintenance activity.

Offshore & Marine

Platform piping and shipboard flange joints where salt-water corrosion and limited crane access make flange replacement impractical. Portable, manual operation — no external power required.

Water & Wastewater

Large-diameter pump flanges, valve body flanges, and pipeline flanges. Corrosion pitting from raw water service is the most common damage mode — flange facing restores the seat faster than replacement.

Common Questions

Flange Facing FAQ

What is a flange facer?

A flange facer is a portable machining tool that restores damaged flange gasket sealing surfaces to their original flatness and finish — on-site, without removing the flange. The tool clamps to the flange bore and a cutting head rotates across the face to machine it back to the required surface finish. This eliminates cutting out the old flange, welding a replacement, PWHT, NDE, and pressure testing.

When do you need to resurface a flange?

When the gasket seat is damaged by corrosion, erosion, steam cutting, chemical attack, or mechanical damage from improper gasket removal. If the flange leaks after re-gasketing with proper torque, has visible scoring or pitting, or fails hydrostatic testing — and the damage depth is within 0.060″ to 0.125″ — resurfacing with a flange facer is faster and cheaper than replacement.

What surface finish does the Flange Hog produce?

The Flange Hog® 110 produces a serrated (phonographic) finish — concentric grooves at a controlled pitch — which is the standard for raised-face flanges per ASME B16.5. Typical finish values are 125–250 microinches Ra (3.2–6.3 µm) for standard and spiral-wound gaskets. The finish meets ASME PCC-1 guidelines for gasket seating.

What flange sizes can the Flange Hog handle?

The Flange Hog® 110 covers 1.0″ I.D. to 14.0″ O.D. (25.4mm to 355.6mm). This spans 1″ NPS through 12″ NPS raised-face flanges across all ASME B16.5 pressure classes from 150 through 2500.

Can you face a flange without removing it from the pipe?

Yes. The Flange Hog® 110 is designed for in-situ flange repair. It clamps directly to the installed flange and machines the gasket surface while the flange remains welded to the piping system. No cutting, no re-welding, no PWHT, no NDE — the flange stays in place and the repaired surface is ready for a new gasket and bolt-up.

Is the Flange Hog available for rent?

Yes. Esco Tool offers the Flange Hog® 110 for short-term and long-term rental. Rental is ideal for turnaround work, outage projects, or evaluating the tool before purchase. Contact Esco Tool for availability and pricing.

Leaking Flange? Let’s Fix It — Not Replace It.

Tell us your flange size, pressure class, and damage type. We’ll confirm the Flange Hog can handle it.

Get a Flange Facing Quote →