NPTF Tube Fittings: Dryseal (ASME B1.20.3) Pipe-Thread Ends in Stainless & High-Nickel Alloys

An NPTF tube fitting connects instrumentation tubing to pipe. Its pipe-thread end is cut to the NPTF (Dryseal) American National Standard Taper Pipe Thread form specified in ASME B1.20.3. That thread form seals metal-to-metal through controlled crest-and-root interference, no sealant needed. The other end grips the tubing with a single- or double-ferrule compression connection.

Crestflo machines these Dryseal ends on stainless and high-nickel instrumentation fittings in-house. The tube-gripping end is qualified to ASTM F1387, and every part gets a heat number stamped on it. Delivery runs on a 6-8 week program: standard items ship from ready stock, while specials are made to order.

Reviewed by the Crestflo Engineering Team

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NPTF, in this context, refers to the Dryseal, sealant-free taper pipe thread built to ASME B1.20.3, meant for fluid-system instrumentation fittings. It isn't a hose or plumbing part, and it's not interchangeable with a plain NPT thread. The two forms look nearly identical and will physically thread together, but they seal in completely different ways.

Also Known As: NPTF, Dryseal & ASME B1.20.3 Designations

This thread goes by several names on specifiers' drawings. Most people write it as NPTF, NPTF thread, NPTF connector or NPTF fitting, though its formal title is the Dryseal American National Standard Taper Pipe Thread of ANSI/ASME B1.20.3. Older paperwork sometimes calls it "National Pipe Taper Fuel," or just the dry-seal pipe thread. Within the Dryseal family, you'll also come across the internal designations F-NPTF, PTF-SAE SHORT, NPSF and NPSI. Instrumentation drawings favor reversed, spaced forms: tube fittings NPTF, NPTF male connector, NPTF female connector, NPTF adapter, NPTF x tube. Each one points to the same sealant-free taper pipe thread supplied here.

What Is an NPTF (Dryseal) Fitting?

An NPTF fitting uses a Dryseal taper pipe thread built to ASME B1.20.3. It seals metal-to-metal, crushing the mating thread crests and roots into controlled interference, so the joint doesn't need tape or dope in the thread clearance. The letter "F" once stood for "Fuel," since the form was developed for automotive and aero fuel systems, and today it marks the Dryseal interference-seal thread. Sixty degrees. That's the included angle, paired with a 3⁄4-in-per-foot (1⁄16-in-per-inch) taper and the same pitch series as NPT. Internal ports get cut with matching NPTF taps, and every end is checked against L1 plug and ring gages to ASME B1.20.5. On a Crestflo fitting, this NPTF pipe end pairs with a ferrule tube-gripping end, so one component alone connects tubing to a threaded instrument port.

NPTF Thread Quick-Spec

Values per applicable standard; customizable to requirement.

NPTF vs NPT: What Changes for Your Fitting

NPTF and NPT share the same 60° angle, taper and pitch series, so the two forms will physically thread together. The difference is the seal: NPTF is machined so the thread crests and roots interfere and seal dry, whereas NPT relies on tape or pipe dope filling the spiral clearance. If your application requires a validated sealant-free seal, specify NPTF on both the fitting and the mating port and do not mix forms. Because the forms mate mechanically but not always sealing-wise, thread identification matters before you order. For the full head-to-head, including whether NPT and NPTF are interchangeable and when a thread sealant is still advisable, see the NPT vs NPTF guide and the thread identification guide. For a plain sealant-dependent thread, see NPT tube fittings.

NPTF Configurations & End Connections: Male, Female, Adapter, Tee & Bulkhead

Every Crestflo NPTF compression fitting joins an NPTF pipe-thread end to a ferrule compression tube end. Here, "compression" refers to the tube-gripping side; the NPTF thread itself seals metal-to-metal. Standard forms include:

• NPTF male connector, male NPTF pipe end to tube.
• NPTF female connector, female NPTF pipe end to tube.
• NPTF male / female adapter and reducing adapter, thread-to-thread and stepped-size transitions.
• NPTF branch and run tee / elbow ends, flow-direction fittings with an NPTF port.
• Bulkhead NPTF and port connector, panel-through and gauge-port connections.

Explore the underlying shapes: check out the male connector, the female connector, the adapter, the bulkhead union, and the port connector. Crestflo builds each one to hold up under real working pressure.

NPTF Sizes (1⁄16″–1″) & Thread Dimensions

NPTF pipe-thread sizes span 1⁄16, 1⁄8, 1⁄4, 3⁄8, 1⁄2, 3⁄4 and 1 in, following the standard NPTF series. The 1⁄4 NPTF fitting gets requested more than any other. Tube ends run up to 2 in (50 mm) OD, offered in both imperial fractional and metric across every fitting. NPTF is an inch NPT thread. The tube side doesn't have to match, though; it can follow either measurement system. Crest, root and pitch dimensions follow ASME B1.20.3 exactly. Before ordering, check the Crestflo thread identification guide and the tube fitting size chart to confirm the size.

Tube ends come in the full range of imperial and metric sizes. Values follow the applicable standard, and they can be adjusted to whatever the job calls for.

NPTF Fitting Materials: 316/316L Stainless, 904L, Duplex & High-Nickel Alloys

Crestflo machines NPTF ends on stainless and other corrosion-resistant alloys, brass and carbon steel don't touch the US instrumentation line. 316/316L is the default when you're unsure which grade to specify. Step up from there for chloride exposure, sour service, or high temperatures.

The NPTF joint seals metal-to-metal, with no elastomer in the thread, so its temperature ceiling comes from the alloy chosen, not from a seal element. Working pressure depends on tube OD and wall thickness, alloy, and thread size per the applicable standard. The rating that fits your configuration, whether NPTF or NPT, gets confirmed on the quote.

Standards, Certifications & Testing for NPTF Instrumentation Fittings

NPTF threads meet ASME B1.20.3. The compression tube-gripping end is qualified to ASTM F1387, the interchange performance standard most competitors don't publish. Crestflo holds ISO 9001, 14001, 45001, and PED certification, with certificates available at quality. Fittings come in NACE MR0175 and ISO 15156 compliant versions, built from alloys suited to sour service, with tube and bar to ASTM A269, A276, and A479. Oxygen and ultra-high-purity cleaning are available on request.

Testing under the program covers a wide range: hydraulic proof, burst and impulse, pneumatic, flexure and rotary-flex fatigue, vibration, thermal cycling, pull-out and vacuum. Positive material identification and in-house NDT round out the routine. Destructive testing takes place at labs accredited to ISO/IEC 17025. There's also third-party inspection, available on request. Every part carries a heat or lot number.

Why Crestflo for NPTF Tube Fittings

Crestflo manufactures and supplies NPTF fittings to customers across the United States. It's the instrumentation division of an export house that the Government of India has recognized for four decades, one with a proven record of deliveries into the Middle East. That heritage backs the newer manufacturing brand.

Drop-in interchange, proven. These are dimensional equivalents for Swagelok®, Parker®, Hoke® and Hy-Lok®, backed by ASTM F1387 performance qualification.

6-8 week delivery. Standard items ship from ready stock, specials are made to order, and both beat the 20+ weeks typical for the majors.

• In-house thread machining, national, international and custom threads cut on CNC, VMC and EDM equipment.
• Full traceability, heat number on every part with EN 10204 MTC 3.1 (3.2 on request).
• Small MOQ and private label, flexible volumes and OEM branding.

Honest origin: the material is Indian in origin, with US or European melt available on request and full material traceability included. See US-origin & compliance for details.

Order NPTF Tube Fittings: Request a Quote

Send over your NPTF thread size, tube OD, alloy, and configuration, and Crestflo's engineering team will send back a quote. For competitor equivalents, skip the part-number lookup. Ask for a Swagelok®/Parker® cross-reference instead, starting at the cross-reference hub. Datasheets and CAD files are available to customers on request.

• Request an NPTF quote
• Request a sample
• Private-label program
• Become a distributor

For US inquiries, reach our sales team at sales@crestflousa.com or call +1 346 594 9005. Crestflo's office is based in Houston, TX.

NPTF Tube Fittings FAQ

Related Pages

• NPT tube fittings
• NPT vs NPTF guide
• Thread identification guide
• Tube fittings hub
• ASTM F1387
• 316/316L material
• Cross-reference

Swagelok® belongs to Swagelok Company as a registered trademark. Parker® is held by Parker Hannifin Corporation, Hoke® by Hoke Incorporated, and Hy-Lok® by Hy-Lok Corporation. Crestflo operates independently of these companies. There's no affiliation, no authorization, no endorsement. The brand names appear here for one reason: to identify which part a given Crestflo interchange equivalent replaces.