Double Tube Sheet Design: Importance and Applications

Shell and tube heat exchangers stand out as one of the most popular types of heat exchangers used in industry today. Renowned for their versatility, ease of maintenance, and availability in a range of sizes, they cater to diverse applications.

In the process of choosing the ideal configuration for a shell and tube heat exchanger, factors such as temperature, pressure, and the nature of the processing fluid come into play. Design considerations encompass choices like straight or U-tube arrangements, single or double tube sheets, as well as options between fabricated or machined channels. In the following discussion, we’ll delve into the nuances of tube sheet selections.

The Function of a Tube Sheet

Enerquip Tubesheet

Tube sheets are round, flat plates made from a variety of materials including stainless steel, duplex, AL6XN and Hastelloy. Their primary function is to support and isolate the tubing. Since tube sheets are in contact with both fluids on the shell side and the tube side, they must have corrosion resistance and be sealed tightly to prevent fluids from gaining contact.

At Enerquip, each tube is roller-expanded into grooved tube sheets. Typically, tube sheets less than 1.5” thick receive single sealing grooves and those thicker are double-grooved. The tube-to-tube sheet joints can also include seal welding or strength welding when requested.

Once the tubes are in place, the tube sheet face is polished (if required) to the specified finish for enhanced stability and contamination prevention.

Single Tube Sheet vs. Double Tube Sheet

Every exchanger will have the option of a single tube sheet or double tube sheets.

In a single tube sheet design, the tubes are expanded and sometimes seal welded into one tube sheet that is held between the bonnet and shell flange. If there is a leak between the tube sheet and the tubes, cross-contamination of the process and utility fluids could occur.

In a double tube sheet design, a second outer tube sheet is added to further seal and separate the tubes and the shell. The gap between the tube sheets allows for differential radial thermal expansion, minimizing stress on the tube-to-tube sheet expansions. In the event of a leak in a tube-to-tube sheet joint, shell-side or tube-side fluids would flow out into the gap between the two tube sheets, instead of the leak causing cross-contamination issues. Leaks can also be easily detected and fixed sooner.

Single Tube Sheet and Double Tube Sheet

Enerquip exchangers are fabricated using multiple measures to ensure proper hygienic design and production. As a standard, pharma-grade exchangers are designed with double tube sheets to minimize the risk of cross-contamination of process fluids between the shell and tubes.

Pharmaceutical units also include roller expanding and seal welding of the tube-to-tube sheet joints on the face of the outer tube sheet per ASME BPE. The roller-expanded and seal-welded surfaces are then polished to the specified finish for all the wetted surfaces.

Double Tube Sheet Design Applications

Double tube sheets are crucial for the safe operation of many heat exchanger applications. In recent years, power plant condensers have even made use of double tube sheet designs. And water treatment facilities use double tube sheets to prevent contamination of their treated and demineralized water from the raw water they used in their condenser steam space.

Both straight tube and U-tube style heat exchangers can utilize the double tube sheet design for added safety and security.

Straight Tube

This type of heat exchanger uses tube sheets that are either welded directly to the shell or floating inside the shell. In a welded construction, an expansion joint may be necessary to allow for differential thermal expansion between the tubes and shell.

Enerquip Straight Tube Heat Exchanger


As the name indicates, the tubes inside the shell are U-shaped. The tubes start at the top of the tube sheet, make a U-shaped bend, then come back to the bottom. The U-tube design does not require an expansion joint because the tube bundle is free to expand or contract.

Enerquip U-Tube Heat Exchanger

The ability of thermal regulating equipment like heat exchangers, condensers, and immersion heaters to heat and cool substances efficiently and safely, make them an indispensable tool in industrial processes. Choosing the right equipment to fit your production operations will help greatly in ensuring your process and product quality.

In the market for a custom thermal solution? Our team of experts can design and engineer customized solutions specific to your production needs. Contact us today.

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