Stainless Steel & Alloy Hydraulic Tubing

Hydraulic tubing, as we use the term, is rigid, fully-annealed stainless-steel or corrosion-resistant-alloy tube. It carries pressurized fluid through high-pressure fluid-power and hydraulic control lines and seals into instrumentation compression fittings by ferrule bite. Here, that means rigid instrument-grade tube only, not rubber or thermoplastic hydraulic hose, and not carbon-steel DOM hydraulic-cylinder tubing. Crestflo supplies it in stainless through exotic nickel and CRA alloys, sized to seal in the same compression fittings we manufacture. It's heat-number traceable and ships to the US market on a 6-8 week delivery.

Reviewed by the Crestflo Engineering Team

Buyers and specifiers label this line item in a dozen different ways. Some call it hydraulic tube, others hydraulic steel tubing or hydraulic metal tubing. You'll also see stainless steel hydraulic tubing, hydraulic instrument tubing, hydraulic control line tubing, seamless or welded hydraulic tubing, high-pressure hydraulic tubing, cold-drawn seamless hydraulic tube, and annealed stainless hydraulic tube. That holds true whether the size is given in imperial fractional or metric OD. Three standards govern the product: ASTM A269 covers austenitic stainless tube, ASTM A213 covers seamless ferritic/austenitic alloy tube, and ASTM A789 covers duplex tube. All three ship with EN 10204 material traceability.

Hydraulic Tubing Materials: 316L, 304L, 904L, Duplex & Nickel Alloys

Crestflo picks the right alloy for the fluid, the chloride and sour-service exposure, and the line temperature, not for pressure alone. 316/316L is the default choice for general hydraulic and instrument service. Step up to 904L, duplex, super duplex, or a nickel alloy when chlorides, seawater, sour gas, or high temperature attack standard austenitic grades like 316. Each grade below links to its material page, which covers the grade in depth and shows it in Crestflo instrumentation forms.

Titanium Gr2 and the rest of the exotic-alloy range sit on our alloy tubing page at Crestflo. Each grade's composition and mechanical properties follow the applicable ASTM specification, and we'll customize to whatever the job calls for.

Seamless vs Welded Hydraulic Tubing: Cold-Drawn & Bright-Annealed Construction

Both seamless and welded constructions are available, and each ships fully annealed so fittings go together without a fight. Cold-drawn seamless tube remains the standard pick for higher-pressure hydraulic lines. Welded-and-drawn tube, made from strip and drawn to final size, is the cheaper route wherever the spec allows it. Bright annealing under a controlled atmosphere gives a clean, oxide-free surface that suits instrument service well.

Crestflo customers who need construction only, without the tubing itself pre-selected, can browse seamless tubing or welded tubing directly. High-purity applications call for a different path: electropolished tubing.

Why Fully-Annealed Hydraulic Tubing Seals in Compression Fittings

Instrument-grade hydraulic tube ships fully annealed, or soft-annealed, so the ferrule can bite into the tube wall and swage it into a leak-tight, gas-tight seal. Too hard, and the tube pushes back against the ferrule; it can leak. Soften it correctly, though, and the seal holds up every time. ASTM A269 sets a hardness ceiling of 90 HRB, but experienced fitters have long aimed lower, roughly 80 HRB or softer, for 316 tube paired with compression fittings; the exact figure depends on the applicable standard and can be adjusted to the job. That gap between a hard tube and a properly softened one is what separates a joint that holds from one that weeps. It's why Crestflo keeps tight control over hardness on the tube it supplies alongside its fittings.

Hydraulic Tubing Sizes & Wall Thickness: Imperial (1/4″–2″) & Metric (6–50 mm)

Hydraulic tubing comes stocked in imperial fractional and metric OD sizes, made to match compression fittings up to 2 inch (50 mm) OD. You don't choose wall thickness on its own. It's selected alongside the working pressure, the alloy, and the fitting the tube must seat in. The sizes below are representative examples only. You'll find the full OD, wall, and matching-fitting matrix on the size chart.

OD and wall combinations follow standard published tube dimensions and are customizable to requirement. See the hydraulic tubing size & pressure chart for the full matrix.

High-Pressure Hydraulic Tubing Ratings: How Working Pressure Is Calculated

Allowable working pressure comes from the tube's geometry and its alloy together, not from the grade alone. You derive it from the outside diameter, the wall thickness, the material's allowable stress, and a safety factor, following ASME B31.3 and the classic Barlow relationship P = 2 · S · t / D, where S is the allowable stress for the alloy at temperature, t is the wall, and D is the outside diameter. Allowable-stress values come straight from the code for each grade. Derating applies as temperature climbs. The correct rating depends on the exact OD × wall × alloy you specify, so published values follow the applicable standard and can be tailored to what you need. Rated-pressure figures per size are tabulated on the size & pressure chart, courtesy of Crestflo.

Matching Hydraulic Tubing to Compression Tube Fittings

A hydraulic line is only as good as its tube-and-fitting joint. That's why tube and fitting need to be qualified as a pair. Crestflo single- and double-ferrule compression tube fittings are tested to ASTM F1387, the performance standard for compression tube fittings, and the tube we supply is annealed to exactly the hardness those ferrules need to seat properly. Buy both from one manufacturer, and you skip the guesswork of matching a random tube to a random fitting. For bite-type connections, DIN 2353 hydraulic fittings sit within the tube fittings range. The nut-and-ferrule components that terminate the tube, meanwhile, are sold separately.

Hydraulic Tubing Standards & Traceability: ASTM A269, A213, A789 & EN 10204 MTC

Crestflo builds hydraulic tubing to the standard that fits each construction and alloy. Every length carries a heat-number mark, so it can be traced back in full.

Traceability comes from heat- and lot-number marking stamped right on the tube, and every batch ships with an EN 10204 3.1 material test certificate as standard. Need 3.2 instead? Just ask. Crestflo holds ISO 9001, 14001, 45001 and PED certification. Datasheets and CAD files are available to customers on request.

Hydraulic Tubing Applications: Hydraulic Power Units, Control Lines & Subsea

Rigid stainless and alloy hydraulic tubing handles the high-integrity lines where hose won't cut it. It plumbs hydraulic power units and control lines, offshore and subsea umbilicals, and chemical, oil-and-gas, and power installations that call for a permanent, low-maintenance, high-pressure joint. Alloy selection follows the service conditions: austenitic stainless for general lines, duplex and super duplex where chloride and seawater exposure come into play, nickel alloys for sour and high-temperature media. Crestflo's oil and gas, offshore, and subsea pages cover the sector detail: oil and gas, offshore, and subsea.

Hydraulic Tubing Supplier: Why Buy from Crestflo

Crestflo is a US-serving hydraulic tubing manufacturer and supplier, the instrumentation arm of an export house that's been recognized by the Government of India for four decades, with a long track record of delivery across the Middle East. Where most hydraulic tubing suppliers resell only 304 and 316 SS tube, and a typical hydraulic tube supplier sits a step removed from whoever makes the mating fitting, Crestflo does it differently: tube and fitting come from a single source, engineered together as a system. That means fully-annealed tube in stainless, exotic nickel alloys, and CRA grades, all sized to seal properly in Crestflo compression fittings tested to ASTM F1387.

Standard items ship from ready stock. Specials are made to order, with delivery running 6 to 8 weeks. Minimum order quantities stay small, and private-label programs are available for those who want them. The tube itself is of Indian origin, though US or European melt can be arranged on request, and full material traceability comes standard. When you're ready to convert a spec into a quote, just provide the alloy, OD by wall, length, temper, end and finish, and the MTC level you need. Request a quote at request a quote, or reach the US sales desk directly at sales@crestflousa.com or +1 346 594 9005 in Houston, TX. For more detail, see lead time, private label, testing & inspection, and why Crestflo.

Hydraulic Tubing FAQ

Related Tubing, Materials & Standards

Browse the full stainless steel & alloy tubing hub on Crestflo's site. Or head to a related page: instrumentation tubing, seamless tubing, welded tubing, coiled tubing, alloy tubing, the tubing size chart, the compression tube fittings that seal this tube, and the ASTM A269 standard.