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Pressure Ratings for Stainless Steel

All Penflex working pressure ratings use minimum 4 to 1 safety factors.

To print this chart, please click here.

Size Braids P3
Standard & Compressed Pitch
Standard & Compressed Pitch
700 800 900 1400
1/4 1 2360 2500 2116 2562 2754
2 2832 3375 3125 4099 4406
5/16 1 1647 2300
2 1976 3680
3/8 1 1639 1680 1501 1501 1921
2 1967 2700 2401 2401 3073
1/2 1 1225 1240 1075 2194 2194
2 1470 1980 1720 3510 3510
3 4000
5/8 1 1200
2 1440
3/4 1 1034 940 792 1311 1994
2 1241 1500 1267 2098 3192
3 5000
1 1 796 630 571 1069 1599
2 955 1000 914 1710 2558
3 4200
1-1/4 1 600 575 531 1110 1317
2 720 920 850 1776 2107
1-1/2 1 557 500 472 868 1062
2 668 800 755 1388 1698
3 2750
2 1 570 532 516 810 842
2 684 850 826 1296 1346
3 2180
2-1/2 1 500 387 578
2 700 619 925
3 1 400 316 540
2 600 506 864
3 1250
3-1/2 1 297
2 475
4 1 300 232 333
2 444 371 533
3 1250
5 1 191
2 306
6 1 165 266
2 264 425
3 640
8 1 234 234
2 374 450
3 550
10 1 230
2 367
12 1 161
2 257
14 1 119
2 190

With inside diameters (I.D.) spanning 14” – 24”, P5 Series is typically used in low pressure applications where absorbing vibration is a primary concern. For P5 pressure ratings, please click here. 

Metal Hose for Tank Terminals

A Guide to Alloy Selection and Corrosion Prevention

Tank terminals play an important role in today’s global economy. Their ubiquity across continents supports a supply chain that ensures consumers and companies receive the products and raw materials on which they depend without interruption.

Critical to the operation of a tank farm is its piping system, and flexible components like metal hose assemblies and expansion joints are needed to support the transfer of media between tanks and ships, barges, pipelines, trucks and rail cars.

Like the storage tanks themselves, piping is susceptible to corrosion which can lead to leaks that then, in turn, become safety hazards. Fires, groundwater contamination and increasing toxicity levels in the air are just a few of the associated risks with a release.

To protect a facility’s assets, its people and the surrounding environment, steps can be taken in the design and handling of terminal hose assemblies to guard against corrosion and the potential for leaks.

Design Considerations for Terminal Hoses

Flashlight reveals pinholes caused by pitting corrosion on hose for tank terminals.

Flashlight reveals pinholes caused by pitting corrosion.

Ensuring the proper alloy for metal hose assemblies is important as—depending on their chemical composition —some are better suited to resist corrosion from certain compounds. This, of course, depends on the media passing through the hose.

Chemical Compatibility

For instance, in the case of sour gas, rich in highly corrosive hydrogen sulfide (H2S), 316 SS is a suitable option due to its molybdenum (Mo) content. However, if price is a secondary concern, then using AL-6XN which has twice as much Mo than 316 SS or one of the exotic alloys such as Inconel 625 or Hastelloy C-276—with significantly greater amounts of Mo (as much as four to eight times the amount compared with 316 SS)—is preferable.

Stress Corrosion Cracking

High chloride levels, often found in crude oil, can lead to pitting and subsequently stress cracking corrosion (SCC). Chlorides react with chromium in the passive layer, leaving the active iron exposed. Chlorides can then bore into the stainless steel surface, creating spherical, smooth wall pits which become stress concentrators. Similarly, alloying elements like—again— molybdenum (Mo) and or nitrogen (N) are added to improve resistance chloride attack.

It is important to note that many forms of corrosion do not happen solely because of the media passing through the hose but happen in concert with other environmental and operating conditions.

With regard to stress corrosion cracking, the application of tensile stress above critical values is another prerequisite. When flow velocity exceeds the maximum recommended rate, using an interlocked hose liner or a larger diameter hose with reducers at each end will reduce velocity. Residual stresses introduced during manufacturing might also need to be checked when the likelihood for SCC is high. To this end, engineers may suggest various heat treatments.

Sketch of metal hose assembly with interlocked liner, used in terminal operations.

Sketch of metal hose assembly with interlocked liner.

Other means of controlling SCC include using corrosion inhibitors during cleaning operations, employing a closed system to control the environment, and coating the material to isolate it from the environment.

There are many considerations that go into making a terminal hoses and selecting the right alloy, the proper design and the appropriate manufacturing process will ensure a longer life in service by staving off corrosion as long as possible.

Positive Material Identification (PMI)

The right materials are important to any design. In selecting the appropriate alloy for a metal hose assembly, engineers consider the temperature, pressure, movement and rates of corrosion anticipated within the given application.

PMI analyzer reveals flange is 304 SS

PMI analyzer reveals flange is 304 SS

It’s a careful calculation with many variables and selecting a less-than-ideal material could lead to faster rates of corrosion, decreased efficacy as a transfer medium, and premature hose failure.

While Penflex does specify the chemical and physical properties for our stainless steel, Hastelloy, Monel, Inconel and Bronze hoses with Material Test Results (MTR) from our raw material suppliers, some end users want additional assurance in the form of a final verification.

This final verification is Positive Material Identification (PMI, carried out before hose assemblies are shipped to the final destination. PMI testing analyzes the composition of a component by reading quantities of its constituent parts, often delivered in percentages.

Penflex uses an alloy analyzer that leverages X-ray fluorescence technology for its PMI testing.

Proper Installation

Regardless of design and manufacturing decisions, if hoses are not installed and handled properly, they become susceptible to fatigue, corrosion, and—ultimately— premature failure. Follow the recommendations below for correct installation of a metal hose assembly.

Avoid torque

Do not twist the hose assembly during installation when aligning the bolt holes in a flange or in making up pipe threads. Using lap joint flanges or pipe unions will minimize this condition. Penflex recommends using two wrenches to make the union connection; one to prevent the hose from twisting and the other to tighten the coupling.

In plane lateral offset installation

Prevent out-of-plane flexing in an installation. Always install the hose so that the flexing takes place in only one plane. This plane must be the plane in which the bending occurs.

Avoid over bending

The repetitive bending of a hose to a radius smaller than the radius listed in the specification tables for corrugated hose will result in premature hose failure. Always provide sufficient length to prevent over bending and to eliminate strain on the hose.

Avoid sharp bends

Utilize sound geometric configurations that avoid sharp bends, especially near the end fittings of the assembly.

Provide support

When installing the assembly in a horizontal loop, provide support for the arms to prevent the hose from sagging.

Do not extend or compress axially

A piping system which utilizes metal hose to absorb movement must be properly anchored and/or guided. Always support the piping to prevent excessive weight from compressing the hose and relaxing the braid tension.

Correct Handling for Terminal Hoses

Once in service, the most common causes of failure stem from careless handling.

Extreme over bending

When hoses are bent beyond the recommended Minimum Bend Radius, the hose beneath the braid can be damaged, fatigue cracks may appear in the hose, potential for leak failures increases and there is a higher likelihood for braid bagging. As a general rule, do not bend hose 90 degrees at fitting. Instead, use 45- or 90-degree elbows where tight bends are required.

Hose stacking

Stacking hose on top of hose can create damage under the braid to the hose tube that cannot be seen. As the case with extreme over bending, damage to the hose can shorten its life. In addition to ushering in premature hose failure, hose stacking contributes to braid bulging and braid wire damage. Avoid stacking hoses wherever possible.

Braid bulging at a terminal facility that is likely caused by mishandling.

Braid bulging likely caused by mishandling

Braid wear

Metal hose grows longitudinally under pressure and contracts when pressure decreases. The braid is the “pressure carrier” and supports this movement. Damage it and working pressures will be affected and, if the wear is significant, hose failure can result. Braid wear can occur by dragging the assembly, improper or undersized lifting support or snagging the braid on another object. Hose stacking also contributes to braid wear, as often evidenced by braid bulging. Prevent dragging exposed braid and consider using hose buns instead of undersized lifting straps. Always lift or carry hose to prevent abrasion damage.

Too tight protective covering

Using protective covers provides protection from braid wear. However, over tightening the clamps that hold the cover restricts the natural movement of the hose and braid. As the hose elongates under pressure, the braid stretches. If the clamps are too tight, the hose will shrink when pressure decreased but the braid will not be able to contract. This causes braids to bulge, reducing the efficacy of the assembly as a pressure carrier.


If storing hoses not in use, keep them away from areas subject to spillage, corrosive fumes or sprays, weld splatter, etc.

Preventative Maintenance for Terminal Hoses

Periodically inspect terminal hoses in order to recognize features which lead to failure in order to schedule replacement before actual failures occur. Here is what to look for.

  • Loose, broken, bulged, frayed or worn braid
  • Deformation of the hose, including braid wear, twisting, kinking, denting, flat spots
  • Coupling slippage, cracks, severe dents or excess corrosion
  • Traces of media on or around the assembly
  • Loose or damaged guard or covers
  • Indications of corrosion of the hose or braid
  • Loose fitting attachments
  • Hose assembly rubbing or making contact with adjacent machinery or piping
  • Unreadable or missing identification or tag

To print this guide as a PDF, please click here.

Video Library

Meet our Team

Hose Design & Manufacture

Expansion Joints

Welding at Penflex


Leak Testing & Hose Cleaning


Installation & Service


Corrosion Analysis

Photo Gallery



Expansion Joints


Cryogenic Transfer Hose and Braid Solutions

Metal hose is the sole means of transferring cryogenic liquids with minimal evaporation and without significant changes in temperature or pressure. Penflex has thus consistently refined its manufacturing and leak testing processes to best serve this market.

Helium Mass Spectrometer Testing for Cryogenic Hose

Ronit Patil, Penflex Inside Sales/Application Engineer, discusses the step-by-step process for testing cryogenic hose assemblies using a mass spectrometer.

Welder Training Program

Dave Gregor, Penflex Certified Weld Educator, explains what welders can expect during our one-week ASME Section IX certified program designed to improve their welding technique. Upon completion of the program, welders receive weld performance coupons, a Penflex Certification of Completion and ASME Section IX Certificates.

A few words from our satisfied customers…

“Thank you for the training and instruction we received. The qualifications and information we received are invaluable.  After welding metal hose for twelve years we assumed everything was right.  The best way I could explain to you is that “we didn’t know what we didn’t know.”

— Owner, Leading Supplier and Manufacturer in Fluid Transfer and Sealing Industry

“Worth every penny.”

— President, Fabricating Distributor Organization

To learn more about the Welder Training Program, please click here.

Non-Standard Alloys and High Pressures

Here we look at how mechanical properties of austenitic steels are influenced by cryogenic temperatures and what types of stainless steel alloys are best suited for low temperature applications.

In additional to 304, 304L, 316, 316L and 321, we also offer non-standard alloys Monel 400, Hastelloy C276, Inconel 600 and Inconel 625.

Mechanical Properties of 304, 321 and 316 Stainless Steels at Cryogenic Temperatures

Alloy Temperature Yield Strength Tensile Strength Elongation in 2″
°F °C ksi MPa ksi MPa %
304 -40 -40 34 234 155 1069 47
-80 -62 34 234 170 1172 39
-320 -196 39 269 221 1524 40
-423 -252 50 344 243 1675 40
316 -40 -40 41 283 104 717 59
-80 -62 44 303 118 814 57
-320 -196 75 517 185 1276 59
-423 -252 84 579 210 1448 52
321 -40 -40 45 310 120 828 55
-80 -62 50 345 138 952 52
-320 -196 60 414 211 1455 23
-423 -252 68 469 248 1710 34