Understanding Finish Requirements for Shell and Tube Heat Exchangers

Sanitary Finish

Enerquip Industrial Heat Exchanger
Mill FinishEnerquip Electropolish Finish

When hiking, it is important to understand the terrain before setting out. Scaling the Rocky Mountains is far different than taking a leisurely stroll around the block. And the physical endurance required for each will provide drastically different results.

This is just as true in stainless-steel manufacturing and finishing procedures.

Metals are not completely flat, as they appear. When looked at under a microscope, there are peaks and valleys over the entire surface, much like the peaks and valleys of a mountain range. The average of those peaks and valleys is referred to as the Ra value. The higher those peaks and valleys, the duller of a finish. The lower the peaks and valleys, the shinier the finish.

The Ra and grit (size of the abrasive) will result in different internal and external design features and function of Enerquip’s thermal designs. Finishes can be optional but are often required for different applications and industries. We can help you determine the best option for your solution.

Let’s look into the different types of finishes at Enerquip, and what each entail.

USA Finish #1(125 – 250Ra): Mill Finish

Mill finish surfaces are “as-machined” with an unpolished, matte appearance. This is the standard, basic supply condition for all stainless steel. The welds are cleaned to remove discoloration where accessible.

This type of finish does not meet sanitary finish requirements and cannot be used in food contact. Threaded connections can be used on the tube side for non-sanitary applications such as hot water sets.

USA Finish #4 (29 – 40Ra): Sanitary Finish

This sanitary finish uses a 150-grit abrasive and appears as a semi-polished, brushed surface.

Enerquip’s product contact surfaces are 32Ra or better, except for the tubes which are ASME SA-249 bright annealed. Our exterior finish is 40Ra or better.

This finish is acceptable for food, beverage and CIP.

USA Finish #4A (32Ra): 3A Sanitary Finish

The 4A dairy finish uses a 180-grit abrasive and meets the 3-A Dairy Sanitary standard 12-08 finish requirements of 32Ra or better, including SA-213 seamless tubing. Our exterior finish is 40Ra or better.

This is the finish requirement for dairy applications.

BPE Standard

The BPE standard was created to instill continuity and standardization in the pharmaceutical industry. Our Biopharmaceutical designs meet ASME BPE-2019 standards. Enerquip’s double (gap-type) tubesheets feature SA-213 seamless tubing and sloped foot supports for draining. Units are bright polished, and process or surface roughness can be specified, including:

  • SF1 20Ra, SF2 25Ra, SF3 30Ra (mechanically polished)
  • SF4 15Ra, SF5 20Ra, SF6 25Ra (mechanically and electropolished)


This finish is uniform, highly reflective, and smooth. The process of electropolish involves immersing the stainless steel in an electrolyte bath in which the metal acts as an anode, removing a layer of metal and smoothing the surface.

If you’re looking for a thermal solution, leave the design specifics to us. Call 715-748-5888 or email sales@enerquip.com today.