ASTM A333 Grade 8 Pipes

Amardeep Steel supplies ASTM A333 Grade 8 pipes in seamless and welded form for plants that handle liquefied gases at cryogenic temperatures. Grade 8 is a 9% nickel steel and it sits at the cold end of our low temperature range, well below the limit of our ASTM A333 Grade 6 pipes. For small bore heat exchanger work in the same service you can look at our ASTM A334 tubes, and our full range of alloy steel pipes and tubes covers other critical grades.

Every length we supply comes with mill test certificates, Charpy impact results at minus 195 degrees Celsius and full heat traceability, so your inspection team has what it needs before the pipe reaches site.

What Are ASTM A333 Grade 8 Pipes?

ASTM A333 is the standard specification for seamless and welded steel pipe meant for low temperature service and other uses where notch toughness has to be proven by test. The specification lists several grades and each one is tied to a minimum impact test temperature. Grade 8 has the lowest of them all. It is tested at minus 195 degrees Celsius (minus 320 degrees Fahrenheit), which is close to the boiling point of liquid nitrogen.

The grade gets this toughness from a nickel content of 8.40 to 9.60 percent, which is why engineers also call it 9% nickel steel pipe or 9Ni pipe. It is a ferritic alloy steel rather than an austenitic stainless steel. That gives it a far higher yield strength than 304L stainless pipe, so designers can often use thinner walls on large cryogenic lines and save weight and cost.

Why 9% Nickel Steel Pipe Works at Cryogenic Temperatures

Ordinary carbon steel turns brittle as it gets colder. Below a certain point it can crack suddenly under impact or thermal shock. Nickel pushes that ductile to brittle transition much lower. In 9% nickel steel, a controlled heat treatment produces a fine tempered martensite structure with a small amount of stable austenite spread through it. This mix keeps the pipe tough at temperatures where carbon steel would shatter.

Heat Treatment of ASTM A333 Grade 8 Pipes

The standard allows two heat treatment routes for Grade 8 pipe and the manufacturer must follow one of them.

• Quenched and tempered: the pipe is heated to about 800 degrees Celsius, quenched in water and then tempered between 565 and 605 degrees Celsius.
• Double normalized and tempered: the pipe is normalized at about 900 degrees Celsius, normalized again at about 790 degrees Celsius and then tempered between 565 and 605 degrees Celsius.

After tempering the pipe is cooled in air or water quenched at a controlled rate. Grade 8 pipe that is cold bent after heat treatment is stress relieved in the range of 550 to 585 degrees Celsius.

Seamless and Welded A333 Grade 8 Pipes

Applications of 9% Nickel Low Temperature Pipes

• LNG liquefaction trains, import terminals and regasification units
• LNG storage tank piping and boil off gas lines
• Liquid nitrogen, oxygen and argon lines in air separation plants, including feed lines to nitrogen storage tanks and liquid argon storage tanks
• Ethylene and other cryogenic petrochemical process lines
• LNG fuel gas systems on ships and bunkering facilities
• Cryogenic transfer lines at industrial gas filling stations

Welding and Handling of SA333 Grade 8 Pipes

SA333 Grade 8 pipe is normally welded with nickel based filler metals, because they keep the weld tough at cryogenic temperatures and handle the difference in thermal expansion well. Nine percent nickel steel can also pick up residual magnetism, which causes arc blow during welding. For this reason we lift and move Grade 8 pipe with nylon slings rather than magnetic lifters, and we can check residual magnetism before dispatch on request.

Matching buttweld pipe fittings and alloy steel flanges can be supplied with the pipe so the complete spool package comes from one source.

Testing and Documentation

Every order of A333 Grade 8 pipe goes through the checks below at our testing facility or approved labs.

• Chemical analysis of heat and product samples
• Tensile test for strength and elongation
• Charpy V-notch impact test at minus 195 degrees Celsius
• Hydrostatic test or nondestructive electric test
• Flattening test, visual inspection and dimensional checks
• Positive material identification and third party inspection on request

Mill test certificates are issued to EN 10204 3.1 and 3.2. You can view our approvals on the certificates page.

Packing and Marking

Each pipe is marked with the specification, grade, size, schedule, heat number and manufacturer name. Pipe ends are fitted with plastic caps, and lengths are bundled or packed in wooden boxes for export. You can read more about our packing and despatch process.