Garage Door Springs
Oil Tempered Wire vs. Galvanized
By Walt Weller
I had the good fortune of becoming involved in the garage door industry in 2003 when my partner and I acquired General Spring LLC. It didn’t take long before we began to hear about—and field—questions regarding oil tempered wire vs. galvanized wire relative to the manufacture of garage door torsion springs. This topic inspires much discussion, and there seems to be two definite and distinct camps in this ongoing debate. My purpose here is not to take one side or the other, but to present information which allows you, the reader, to make your own decision.
Although my partner and I are newcomers to the garage door industry, General Spring certainly is not. The company has a long history of manufacturing garage door springs and is, in fact, one of the few spring manufacturers in the industry to have mass-produced springs from both types of wire. This places us in the unique position of being able to speak from experience. Additionally, information has been provided by the Coalition of Oil Tempered Wire Producers (COTWP), a group of oil tempered wire producers, as well as from Sivaco, a galvanized wire supplier, to provide the reader with both perspectives.
In the mid-1990s, General Spring began manufacturing galvanized garage door torsion springs from wire manufactured by Sivaco Wire, called 9000 series spring wire, under an exclusive test marketing agreement between the two companies. It was the result of this test market agreement that apparently convinced Canadian-based Sivaco Wire Group the product had a future.
Both types of wire, oil tempered (OT) and galvanized hard drawn (GHD), are made from the same basic raw material: a high-carbon steel rod which is “drawn” down to a specific wire diameter. The simple explanation of the drawing process is that the wire is “stretched” to a specific wire diameter by running the rod through a series of progressively smaller dies, coated with a lubricant until the required diameter is achieved.
Galvanizing is the process of applying/ bonding a zinc coating to the surface of the wire. In the case of galvanized wire for garage door springs, the galvanizing process is done prior to drawing. You may have heard the term “drawn after galvanizing” or DAG. This is the process currently used to manufacture galvanized spring wire for garage doors. Sivaco offers a “lead-patented” hard drawn galvanized wire. It is this process, according to a Sivaco representative, that gives GHD its “superior” performance characteristics for garage door torsion springs.
Oil tempering is an additional step in the process after the wire is drawn in which oil is used to heat-treat the wire to give it certain properties. The wire is heated to a very high temperature—in excess of 1500 degrees Fahrenheit—then cooled rapidly or quenched using oil, and then reheated again to a very high temperature. This process is intended for wire used in springs “that are subjected to static loads or relatively infrequent stress applications,” according to ASTM. This is meant to distinguish garage door spring applications with relatively low cycles from valve spring wire for automotive applications, which are very highstress, high-cycle springs for example.
Historically, the garage door industry used torsion springs made of oil tempered wire that conformed to ASTM 229 standards which detail, among other things, tensile strength ranges by wire size. This wire falls into two categories: Class I and Class II. The difference is that Class II has higher tensile ranges than Class I in the same wire size.
At one time, the garage door industry had a unique classification called Overhead Door (OHD) Quality oil tempered wire. It was a hybrid between Class I and Class II. Although some wire mills still supply OHD Quality oil tempered wire, today the vast majority of the industry uses Class II.
Information courtesy of Sivaco Wire Group.
OT wire has excellent performance properties for garage door torsion springs. A significant negative aspect of OT material is the oil residue from the oil tempering process. This residue stays with the wire even after the spring has been coiled and heat-treated. This requires the installer to be very careful not to leave handprints on the garage door and walls after installation or else face an unhappy homeowner. This oil residue has no rust-inhibitive benefits, therefore OT springs, as any unprotected steel product, will rust rather quickly, presenting yet another challenge to the hard-working door installer carrying springs in his service truck.
Some door manufacturers began to require the application of a painted finish to their residential torsion springs, thereby providing a clean spring surface as well as some degree of rust protection. As the average residential torsion spring weighs about 10 pounds, this process was, at that time, very laborintensive. The timing was perfect to present a product that provided the benefits of a clean, rust-inhibitive coating without the additional labor. Galvanized wire appeared to be the perfect solution.
In the early to mid-90s, Sivaco began promoting its 9000 series wire for garage door torsion springs. This wire was a lead-patented hard drawn wire, galvanized to solve the residue and appearance issues. As an added benefit, according to press releases from that time, it also provided superior cycle life in comparison to springs made from OT wire.
Interestingly, superior life cycles is a claim made today by the supporters of both types of wire. A major door manufacturer even touts the superior lifecycle performance—50 percent more—of galvanized wire in their door advertising. They promote their springs manufactured from galvanized wire as “longerlasting springs.” Not to be out done, the COTWP recently launched a series of advertisements in which third-party testing established that springs made from OT wire had an increase in cycle life of more than 20 percent when compared to springs made from GHD wire.
Can both positions be supported technically? The answer to that question is a definite maybe. It depends on the wording used and how one chooses to interpret the test results. Both camps have presented independent testing and technical explanations to support their claims and positions. Regardless of how those issues are positioned in the minds of the competing sides of this argument, several significant differences exist between the two materials relative to appearance and performance.
GHD springs look great and usually are nice and shiny when installed. Springs manufactured from OT wire and coated after coiling look great as well, thanks to the development of rustinhibitor coatings that offer a clean, nonoily surface and a brilliant shiny, black finish. It’s important to mention that GHD wire has a limited shelf life. Over time, the finish on the GHD wire will begin to dull, and a white, powder-like substance will appear on the surface. This is known as white rust and is oxidation of the zinc coating. Springs made from GHD wire will exhibit this characteristic over time and will not maintain their shiny appearance indefinitely. Springs manufactured from OT wire, even with the newest coatings available to the market, will also oxidize over time, although the appearance of the oxidation does not seem to be as apparent as that of the GHD.
Fact or Fiction?
The COTWP claim in its advertising that GHD springs must be installed “hot” to avoid service callbacks. This is due to a certain amount of spring relaxation which occurs in the first few weeks of operation. A hot installation is the practice of adding additional turns to the spring in excess of the number normally called for by the weight of the door and the IPPT of the spring. OT wire springs do specify GHD for their doors are located in the West.
Any market-share gains of GHD springs that did occur would have come from the growth of the group of door manufacturers that specify them for their doors. At least two of these manufacturers are door industry heavyweights with dominant positions in the market. But beyond these manufacturers why hasn’t the market position of GHD grown? Why, if GHD springs are technically superior, has their penetration in the market been exclusively in residential sizes? Why not commercial, industrial and rolling-steel sizes as well?
GHD is offered exclusively in residential sizes of .192 to .375 wire diameters, which could explain why it has no position in the commercial, industrial and rolling-steel markets.
Another explanation could be the limited availability of GHD wire. Back in the 90s, Sivaco was the only manufacturer to offer it. Sometime after GHD was introduced to the market by Sivaco, Davis Wire also began to offer GHD. As a result of the recent acquisition of Sivaco Wire by the Heico Co., parent of Davis Wire, we are back in a position where there is really only one wire manufacturer that offers GHD in garage door wire sizes.
General Spring marketed GHD material for a few years in the 1990s. The product was discontinued for reasons which had nothing to do with the performance of the springs, and everything to do with managing raw material inventory. General Spring was selling the galvanized springs to a significant number of accounts, but they were unable to convince a sufficient number of OEM accounts to make the conversion to galvanized springs.
Because General Spring was unable to increase the demand for the galvanized wire, which would have in turn increased the number of inventory turns, it became difficult to efficiently manage the process. As I mentioned, galvanized wire has a limited shelf life. One must purchase and maintain the material in a controlled environment as well as turn inventory frequently to maintain the appearance of the material. Further, there was only one manufacturer of the wire at that time, which made it very challenging to procure the raw material at a competitive price. A decision was made to discontinue selling the galvanized material and invest in a Thermadep painting process to more economically satisfy the need in the marketplace for a spring with a clean, rust-inhibitive finish.
From years of experience, we can confidently say that Oil Tempered wire is “tried and true” when it comes to the manufacture of garage door torsion springs. We are also able to say from experience that torsion springs manufactured from galvanized material perform at a level which is at a minimum comparable to that of oil tempered springs.
Walt Weller is the managing director for General Spring, LLC, a Harsville, Tenn., manufacturer of galvanized and oil tempered springs. For more information, call 800.497.3545; visit www.generalspring.com