ASTM A312 TP316L Studded Tube With 11-13Cr Stud Fins For Refinery Heaters

ASTM A312 TP316L Studded Tube With 11-13Cr Stud Fins For Refinery Heaters

This is a high-performance heat exchanger tube. It consists of a core pipe made of a corrosion-resistant stainless steel (TP316L) with small, stud-like fins (made of 11-13% Chromium steel) welded onto its outer surface. The primary purpose is to greatly increase the heat transfer surface area in demanding environments, particularly in high-temperature and corrosive applications like refinery heaters and boilers.

Detailed Breakdown

1. Base Tube Material: ASTM A312 TP316L

(1). Chemical Composition (Weight %)

The composition is specified in Table 1 of ASTM A312. The values for TP316L are shown below.

Note: The standard also requires that the material must contain at least 5 × %C to a maximum of 0.10% Copper (Cu) for seamless pipe. This is a less commonly cited but important detail for product verification.

(2). Mechanical Properties

The mechanical properties are specified in Table 2 of ASTM A312. These are the minimum required values.

2. Studded Tube

This describes the physical form and construction.

It is a bare tube (the core pipe) that has studs (short, rod-like pins) attached to its external surface. These studs are not merely glued on; they are resistance welded using a specialized automated process. This creates a metallurgical bond that is very strong and efficient at transferring heat.

3. 11-13Cr Stud Fins

This specifies the material of the studs (fins) themselves.

11-13Cr means the studs are made of a steel alloy containing 11% to 13% Chromium.

Why a different material? While the 316L base tube is chosen for corrosion resistance, the studs are chosen for different reasons:

• High Temperature Strength: 11-13% Chromium steel (often similar to grades like SA 213 T11) retains its strength and resists oxidation (scaling) at very high temperatures better than a stainless steel like 316L would.
• Cost Effectiveness: This material is typically less expensive than 316L stainless steel. Since the studs are numerous, using a fit-for-purpose material optimizes performance and cost.
• Compatibility: The thermal expansion rate of 11-13Cr steel is closer to carbon steel than austenitic stainless steel is, which can be a design consideration in certain assemblies. The weldability between the two materials is well-established.

How It Works (Function)

The entire purpose of this component is enhanced heat transfer:

• The core tube carries a fluid inside (e.g., water, oil, process fluid).
• Hot combustion gases or another heat source flow over the outside of the tube and the studs.
• The studs dramatically increase the surface area of the tube exposed to the heat source (by 3 to 8 times or more).
• This allows heat to be absorbed or dissipated much more efficiently than a bare, smooth tube could.

Primary Application: Fired Heaters in Refineries & Petrochemical Plants

This is the most classic and critical application. These tubes are the core component in the radiant section or convection section of large industrial furnaces, often called fired heaters.

How it works:

• The TP316L core tube carries the process fluid that needs to be heated (e.g., crude oil, hydrocarbons, chemical feedstocks) under high pressure.
• The exterior of the tube bank is exposed to intense radiant heat and hot, corrosive combustion gases (over 1000°C / 1800°F) from burners.
• The 11-13Cr studs absorb this intense heat and efficiently transfer it to the fluid inside the tube.

Why this specific material combination is perfect:

• Internal Corrosion Resistance (TP316L): The process fluid inside can be corrosive. TP316L's excellent corrosion resistance protects the internal surface of the tube from attack, ensuring integrity and preventing contamination of the process fluid.
• External High-Temperature Strength (11-13Cr Studs): The studs are made of a material that retains its strength and resists oxidation (scaling) at the extreme temperatures on the outside of the tube. Austenitic stainless steel like 316L would be weaker and could succumb to "hot corrosion" or oxidation in this environment.
• Enhanced Heat Transfer: The studs increase the external surface area of the tube by 3 to 8 times, dramatically improving the efficiency of heat capture from the flue gases.

Other Key Applications

The same principle applies to other demanding heat transfer scenarios:

• Power Generation Boilers:
  • Used in sections like the economizer (to pre-heat feedwater) or the superheater (to heat steam beyond its saturation point).
  • They handle high-pressure water/steam inside (corrosion-resistant by 316L) and are exposed to hot flue gases from coal, gas, or oil combustion on the outside (handled by the studs).
• Waste Heat Recovery Units (WHRUs):
  • These systems capture thermal energy from hot exhaust streams of gas turbines, incinerators, or other industrial processes that would otherwise be wasted.
  • The studded tubes are ideal for efficiently extracting heat from these often dirty and corrosive exhaust gases.
• Chemical Process Industries:
  • In high-temperature reactors, reformers, and cracker furnaces where a chemical process requires precise and efficient heating in a corrosive environment.
• Air Heaters / Combustion Air Pre-heaters:
  • Used to pre-heat combustion air being fed into a furnace. The hot exhaust flue gas passes over the studded tubes, transferring its residual heat to the incoming air, which significantly improves the overall fuel efficiency of the furnace