Tri Clamp Size Chart: Ferrule Flange OD, Gasket and Clamp by Tube Size

A tri clamp size chart is a chart of ferrule flange diameters, not tube diameters. The hygienic clamp connection standardized in ISO 2852 and as Type A in ASME BPE seats two identical ferrules against a gasket and closes a clamp around the pair, and the clamp only cares about the flange it grips. Because several tube sizes share one flange, the tube size printed on a fitting does not tell you which clamp or gasket it takes. This page lists the tri clamp ferrule dimensions by tube size, shows which sizes share a flange, and explains how to identify a clamp in the field.

Tri clamp sizes: ferrule flange OD by tube size

Flange OD is the diameter of the ferrule face that the clamp closes on. The nominal clamp size in the last column is how the clamp and gasket are usually labelled by distributors; it is the useful ordering number.

Two shared flanges do most of the damage in a stockroom. A 1/2 inch and a 3/4 inch ferrule are both 0.984 inch across the face, and a 1 inch and a 1-1/2 inch ferrule are both 1.984 inch. The clamp is identical within each pair; only the bore of the ferrule and the bore of the gasket differ. From 2 inch upward every tube size has its own flange. For the tube dimensions behind this chart, see the sanitary tube size chart.

Mini and standard flanges on 1/2 and 3/4 inch ferrules

The small sizes carry a historical complication. Before the 0.984 inch flange was standardized as the ASME BPE Type A dimension, 1/2 inch and 3/4 inch ferrules were commonly made on the 1.984 inch flange shared with 1 inch and 1-1/2 inch tube, and many installed systems still have them. Those are called standard or full-size small ferrules; the 0.984 inch versions are called mini. The two do not mate. A plant that has both, which is common when a newer skid arrives at an older line, needs to stock two clamps and two gasket bores for the same tube size and needs the difference marked on the P&ID. When ordering replacement parts for a 1/2 inch or 3/4 inch connection, measure the flange before ordering, because the tube size alone is ambiguous in exactly these two sizes.

Gasket sizes and why the bore matters

Gaskets are sold by the same nominal clamp size as the ferrule, and within a shared flange the gasket outer bead is the same. The bore is not. A 3/4 inch gasket in a 1/2 inch joint leaves a recessed ring between the gasket and the tube wall; a 1/2 inch gasket in a 3/4 inch joint intrudes into the flow path. Both are cleanability defects, and both pass a visual check from outside because the flanges close normally.

Gasket material is a separate selection from size: EPDM, silicone, fluoroelastomer, PTFE and PTFE-enveloped elastomers each have a temperature and chemical range, and a gasket that hardens or swells in service changes the joint geometry as surely as a wrong bore. Some designs, including screen gaskets and orifice gaskets, are made in the same nominal sizes and are counted on a bill of materials like any other gasket.

Clamp styles compared

Four clamp styles cover nearly all hygienic joints, and the choice is set by size, pressure, vibration and how often the joint is opened.

The style does not change the ferrule or the gasket. A 2 inch joint takes the same 2.516 inch flange and the same 2 inch gasket whether the clamp is a wing nut or a bolted high-pressure type, which is why upgrading a leaking joint from hand-tight to bolted is a one-part change.

Pressure ratings depend on clamp, size and gasket

There is no single pressure rating for a tri clamp connection, and ASME BPE does not assign one. The rating is published by the clamp manufacturer for a specific clamp style, size and gasket material at a stated temperature, and it falls as the size goes up because the same closure has to hold a larger area. In general terms: wing-nut clamps carry the lowest rating and drop off quickly above 2 inch; bolted high-pressure clamps carry the highest; elevated temperature reduces every rating because the elastomer softens. For a rated system, take the value from the catalog of the clamp actually installed and put it in the specification. A rating quoted for a different manufacturer’s clamp of the same nominal size is not transferable.

How to identify a tri clamp size in the field

• Measure the ferrule flange, not the tube. Read the outside diameter of the flange face with a caliper and match it to the chart. 0.98 inch is mini 1/2 or 3/4; 1.98 inch is 1 or 1-1/2 (or a legacy 1/2 or 3/4); 2.52 is 2 inch; 3.05 is 2-1/2; 3.58 is 3 inch; 4.68 is 4 inch; 6.57 is 6 inch.
• Then measure the tube OD to resolve a shared flange, and for a 1/2 or 3/4 inch tube on a 1.98 inch flange, order the legacy standard gasket rather than the mini.
• Check for a metric ferrule. DIN 32676 and ISO 2852 metric flanges are close to, but not the same as, the inch series at some sizes. A clamp that closes but leaves the gasket bead visibly offset is usually a metric-to-inch mismatch.
• Read the gasket bore after the joint is opened. A gasket that shows a witness ring on one side only was the wrong bore or was over-compressed.

Tightening: hand-tight or torqued, and why over-tightening fails

A wing-nut clamp is designed to be closed by hand. The ferrule faces have a raised lip that bottoms against the gasket’s outer bead, and once the faces are seated the joint is sealed; additional force goes into the gasket, not into the seal. Over-tightening squeezes the elastomer inward past the ferrule bore, producing gasket intrusion: a ring of rubber standing into the product stream that traps soil, resists CIP flow and eventually tears. The same joint opened repeatedly with a wrench on the wing nut will also distort the clamp ears and stop pulling evenly. Bolted clamps are the exception: they should be tightened to the manufacturer’s torque value with a calibrated tool, and that value belongs on the installation checklist for every SIP and high-pressure joint. The principle is the same for both styles, seat the faces and stop.

What to require on a clamp fitting order or specification

• Ferrule dimension standard named: ASME BPE Type A, ISO 2852 or DIN 32676, with the tube OD and wall the ferrule is made for.
• Mini or standard flange stated for every 1/2 inch and 3/4 inch ferrule.
• Ferrule material 316L with a mill certificate, and the sulfur range matched to the tube where the ferrule will be orbital welded.
• Product-contact surface finish as an ASME BPE SF designation, since ferrule faces and bores are polished separately from tube.
• Gasket material, size by nominal clamp size and bore, with a certificate of conformance and, for pharmaceutical work, USP Class VI or equivalent biocompatibility data.
• Clamp style by joint, with the published pressure and temperature rating for that style and size attached.
• Torque values for every bolted clamp and a note that wing-nut clamps are hand-tight only.
• A count of spare gaskets by size, since gasket replacement is the most frequent maintenance act on a hygienic line.

What Paul Industries does

Paul Industries builds and installs hygienic clamp piping in every size on this chart, selects the ferrule series and clamp style for each joint against the pressure, temperature and cleaning regime of the line, and matches ferrules, gaskets and tube so that shared flanges never produce a mismatched bore. Installation includes seating and torque control, a joint list on the drawings, and a gasket schedule for the owner’s maintenance program. Sanitary valves, instruments and fittings are covered on the sanitary components and instrumentation page, the full set of connection types on the sanitary pipe connections guide, and the dead-leg consequences of instrument tees on the dead-leg L/D guide. Quotes go through the request-a-quote form or 201-450-8280.

Standards referenced: ASME BPE · ASTM A270 · 3-A · ASME B46.1 · 21 CFR 117

Frequently asked questions

What tri clamp size fits 1 inch tube?

A 1 inch tri clamp ferrule has a 1.984 inch (50.5 mm) flange, and the clamp that fits it is the same clamp that fits 1-1/2 inch tube. Order the clamp by the 1.984 inch flange and order the gasket specifically as 1 inch so the bore matches the 0.870 inch tube ID rather than the 1.370 inch bore of the 1-1/2 inch gasket.

Why do 1/2 inch and 3/4 inch tri clamp fittings use the same clamp?

Both ferrules are made on the same 0.984 inch (25.0 mm) flange in the ASME BPE Type A series, so one clamp closes on either. The economy of a shared flange at small sizes outweighs the risk of a wrong gasket, but only if the gasket bore is chosen by tube size. The ferrule bores differ by a quarter inch.

How do I tell a mini tri clamp from a standard one?

Measure the flange. A mini 1/2 inch or 3/4 inch ferrule has a 0.984 inch flange; a standard or legacy one for the same tube sizes has a 1.984 inch flange, the same as 1 inch and 1-1/2 inch tube. Many older installations use the larger flange, so the tube size stamped on a fitting does not settle which clamp it takes.

Is a 2 inch tri clamp the same as a 2 inch pipe clamp?

No. A 2 inch tri clamp closes on a 2.516 inch ferrule flange attached to 2.000 inch OD sanitary tube. A 2 inch pipe is 2.375 inch OD and uses grooved, flanged or threaded connections with entirely different dimensions. Pipe couplings do not fit sanitary ferrules and sanitary clamps do not fit pipe.

What is the flange diameter of a 3 inch tri clamp ferrule?

3.579 inch, or 91.0 mm, in the ASME BPE Type A and ISO 2852 series. A 3 inch joint uses a 3 inch gasket with a bore matched to the 2.870 inch tube ID and a clamp sized for the 3.579 inch flange. It does not share its flange with any other tube size.

Do tri clamp sizes match between inch and DIN 32676 fittings?

Not reliably. DIN 32676 and ISO 2852 metric ferrules are dimensioned for metric tube and several flange diameters differ from the inch series by enough to offset the gasket bead. Some sizes appear to close, which is worse than an obvious mismatch because the joint leaks or harbours soil only after cleaning cycles.

How tight should a wing nut tri clamp be?

Hand-tight, until the ferrule faces seat against the gasket bead and resistance rises sharply, then no further. Using a wrench or pliers on a wing nut drives the gasket inward into the flow path and bends the clamp ears so they no longer pull evenly. If hand-tight will not hold the joint, the answer is a bolted clamp, not more force.

When does a joint need a high-pressure bolted clamp instead of a wing nut?

When the line sees pressure beyond the wing-nut rating for that size, pulsation from a positive displacement pump, repeated steam-in-place cycles, vibration from nearby equipment, or thermal cycling that relaxes elastomer gaskets. Bolted clamps hold a defined torque and keep clamping force through the cycle; wing nuts rely on hand force that fades.

What is a three-segment tri clamp used for?

Large diameters, typically 6 inch and above and sometimes 4 inch, where a two-piece clamp cannot draw the flanges together evenly around the whole circumference. Three hinged segments distribute the load and are usually closed with a bolt rather than a wing nut. They are common on tank outlets, large transfer headers and manway-sized connections.

Where do tri clamp connections belong in a hygienic system, and where should they not be used?

They belong where a joint must be opened for inspection, cleaning verification, instrument removal or gasket change: at pumps, valves, filter housings, sample points and spool ends. They do not belong in long runs of purified water or WFI distribution, which are welded to avoid the gasket crevice and the maintenance burden of hundreds of joints.

Can tri clamp ferrules be welded to sanitary tube by orbital welding?

Yes, when the ferrule tangent has the same OD and wall as the tube and its sulfur content falls in the same ASME BPE range. Short-tangent ferrules may need a manual weld or a special collet because the weld head cannot grip the flange. Match the wall exactly; a ferrule with a heavier tangent creates an inside step.

What does a witness ring on a used gasket mean?

A witness ring is the compression mark the ferrule lip leaves on the gasket bead. Even rings on both faces mean the joint was seated correctly. A ring on one side only points to misaligned ferrules, a wrong-bore gasket or a metric-to-inch mismatch. A ring displaced toward the bore usually means the joint was over-tightened.

Which gasket sizes should a plant keep in stock for tri clamp joints?

One bore for every tube size installed, not one for every flange. A plant with 1/2, 3/4, 1, 1-1/2 and 2 inch tube on 0.984, 1.984 and 2.516 inch flanges needs five gasket bores in each material used, plus the legacy 1/2 and 3/4 inch bores on 1.984 inch flanges if any older ferrules remain.

Are tri clamp sizes the same as Tri-Clover sizes?

Tri-Clover was the manufacturer whose clamp fitting became the generic hygienic clamp, and the inch-series ferrule flanges in this chart trace back to that design. Current parts sold as tri clamp, hygienic clamp or ASME BPE Type A fittings are interchangeable within the inch series when they are made to the BPE dimensions. Check legacy small-size flanges as described above.

How do I count clamps and gaskets from a piping isometric?

Every clamp joint on the isometric is one clamp, one gasket and two ferrules, and the count must be made by flange size, not tube size. Merge the 1/2 and 3/4 inch mini joints into one clamp size and the 1 and 1-1/2 inch joints into another, then keep the gasket count separate by tube size so the bores are right.

Related: Types of Sanitary Pipe Connections · Sanitary Tube Size Chart · Sanitary Components & Process Instrumentation · Sanitary Process Piping Installation (ASME BPE) · Dead Legs in Hygienic Piping: The L/D Rule Explained (2D vs 3D vs 6D) · Dead-Leg L/D Calculator (ASME BPE Limit of 2) · Request a quote