Cost
Another attractive feature of carbon steel tubes is cost. Carbon steel tubes are less expensive when compared to other metals. Since a large portion of a tube bundle cost is the tubes, this can lead to steel bundles being half the cost of a stainless or brass alloy bundles. This is often attractive because it reduces the cost of a project, which is tempting on lump sum contracts or sites operating on a limited budget. Below are some comparisons of tube material costs at the time this article was written.
Tube Costing
Carbon Steel = $ 1.87 per ft
304SS = $ 3.78 per ft
90/10 CUNI = $ 3.99 per ft
Admiralty Brass = $ 4.21 per ft
316SS = $ 4.54 per ft
(*) Pricing as of September 2022, ¾” 18 bwg
What is often not understood at the time steel tubes are selected is how long the bundle will last in service before reaching its end of life. Most stainless steel or brass alloy bundles will last 10-15 years or more if operated under normal conditions, however most steel-tubed bundles last no more than 18 months based on experience. At roughly this point in time, the bundles begin to fail and the cooling water restricted causing low flow. This is clearly an issue for many facilities as the operating time between turnarounds almost always exceeds 18 months. This means that a carbon steel bundle will need to be replaced far more often. The cost of multiple steel bundles, cranes, labor, and down time dwarfs the cost of a bundle made with tubing that is more expensive. This means that in the end steel bundles actually cost more than the other tube materials.