Investment Cast Aerospace-Grade Stainless Steel Chain Links

and Chain Pins

Benefit: Precipitation Hardening Martensitic (PHM) stainless steels were first developed for NASA and the aerospace industry. Cast PHM stainless steel alloys are heat-treatable, and offer superior strength, abrasion and corrosion resistance when compared to all other available chain materials, including cast and fabricated carbon steel, 304 and 316 stainless steel, 403 and 410 series stainless steels, and unfilled and reinforced acetal plastics.

Heat-treated PHM stainless steel alloys offer superior abrasion resistance, and are twice as hard on the Brinnell scale (425 BHN vs. 200 BHN) than conventional cast steel chains, and fabricated chains made from 304/316 stainless steels.

PHM stainless steel alloys offer superior corrosion resistance to all of the major physical, chemical and biological elements and compounds normally found in water and wastewater. Such typical elements include silica sand, grit, hydrogen sulfide, ammonia, chlorine, ferric and ferrous chlorides, sodium and calcium chlorides, anoxic (septic) wastes, high and low pH wastes, including unconcentrated solutions found in nitric, hydrochloric and sulfuric acid wastes, and sodium hydroxide solutions.

Note: All cast stainless steels have some surface ferrite in them as part of the casting process, and are slightly ferromagnetic, unlike wrought austenitic stainless steel alloys, such as rolled plate 304 stainless steel. However, the DuraMax casting process does not change the reactive and non-reactive properties of stainless steel alloys.

When requested for specialty extreme-duty, high-load and/or corrosive and abrasive applications, DuraMax Chain links can also be cast from other custom alloys, including the full range of 300 series austenitic, 400 series martensitic, austenitic-martensitic, nickel, and titanium alloys.

The DuraMax casting process yields a very uniform, tight grain, isotropic tool-grade material structure. and the greatest ultimate tensile strength, the highest corrosion and abrasion resistance, and the highest ASME rated working load versus ANY OTHER cast, welded, fabricated or plastic chain in their class. DuraMax one-piece cast stainless steel chain links eliminate the stress fractures, stress risers, material carburization and corrosive attack common in welded and fabricated chain link designs.

For example, DuraMax CS720S chain (5.8#/ft.), has an ultimate tensile strength of over 80,000 pounds, and a ASME rated working load of 8,000 pounds per strand. DuraMax CS715SS cast stainless steel chain (only 3.2#/ft.) has an ultimate tensile strength of over 50,000 pounds, and a ASME rated working load of 4,200 pounds per strand.

By comparison, standard cast and welded steel 720S/730S chains (5.4#/ft.) have a maximum pull strength of 42,000 to 45,000 pounds, and an ASME rated working load of 4,250 to 4,500 pounds. Low-grade fabricated 400 series stainless steel chains, like SAV715 and SS715 chains, have a maximum ultimate strength less than 30,000 pounds, and an ASME rated working load of less than 2,500 pounds.

Benefit: DuraMax investment cast chain links offer very precise and uniform dimensional tolerances throughout each and every link cast, within +/- .010". Conventional sand cast chain links have an average dimensional variation of +/- .01875. Previously, only injection molded plastic chain links offered a comparable uniform dimensional tolerance. These close dimensional tolerances eliminate
the need for match-marking and shipping chain strands in matched sets, and assure perfect side-to-side equipment alignment even when used in very long strands.

Benefit: The tight tolerances between the barrel and chain pin, and between the pin boss and chain pin help preclude the entry of grit, sand and other abrasive particles within the chain joint, reducing the rate of wear and extending chain life.

Benefit: Investment cast chain links yield a very smooth, uniform surface and tight-grain structure that is suitable and compatible for operation on conventional polymeric, cast or fabricated stainless steel sprockets, and reduces the rate of sprocket wear. In most applications, DuraMax stainless steel chains are ideally suited for operation with 75 Shore D polyurethane and Nylon-6 sprockets.
Conventional sand cast chain links have a rough, grainy surface, and a porous, course and generally impure molecular structure that make them abrasive on polymeric sprockets, and which accelerates the rate of wear when operated on cast or fabricated sprockets. Conventional welded chain links have weld splatter and pitting that can make them abrasive on polymeric sprockets, and often accelerates the rate of wear on cast or fabricated sprockets.

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Full-length Lateral 3/8" x 3/8" Reinforcing Rib

Benefit: A T-shaped sidebar cross section runs the full length of DuraMax chain link sidebars, from the pin bosses (open end of the link) to the chain barrel (closed end of the link). This provides a consistent and uniform cross sectional mass throughout the "x" and "y" axis, yielding exceptional strength throughout the chain link. This feature eliminates the concentration of stress risers that traditionally form at the pin bosses and link barrel, and cause premature failure when high working loads and/or shock loads are applied to conventional cast, welded or fabricated chain. In all DuraMax Chains this unique design results in a 50% to 100% greater ultimate pull strength than all other chains, whether cast or fabricated. Conventional cast chains only offer small reinforcements (1" in length or less) at the pin bosses and barrel ends of the chain link. Fabricated chain links do not have sidebar reinforcing ribs.

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Install-by-Hand Non-locking Chain Pin and Pin Boss Design

Benefit: Allows the chain pin to be inserted in the chain link from either side of the link for ease of assembly in close dimensional quarters. This design allows the chain pin to be inserted quickly into the chain sidebar, by hand, and by one person. The DuraMax Chain pin design does not require the application of mechanical force when installing the pin into the chain side bars during assembly.

All other current chain designs have a locking T-shaped pin head that fits in a T-head pin boss that exists only on one side of the chain link. The chain pin cannot be installed from the opposite direction. On all other conventional chain designs, both the T-head and of the chain pin, and the opposite (cottered) end of the chain pin have an interference fit, and must be pressed into the chain side bars by mechanical means. This requires the use of substantial mechanical force for inserting the pin, and some mechanical method for preventing the sidebars from bending and spreading as the chain pin is forced into the sidebars. This requires the use of two people to complete the assembly task, and a substantial amount of additional time and labor for chain assembly.

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DuraMax Rotating Chain Pin and Pin Boss Design

Benefit: Allows the load and rotating wear of the chain as it articulates around sprockets to be distributed evenly between the chain pin, pin bosses (open end of the chain) and chain link barrel. This distributes the load and wear across the entire available chain link contact surface area, and prevents the concentration of load and wear on only one side of the chain pin, pin boss and link barrel.

Conventional chain pin designs have chain pins that are mechanically locked in place. This causes the load and wear to always be concentrated only on one side of the chain pin outside diameter (O.D.) and only on one side of the chain barrel inside diameter (I.D.) as the chains articulate around sprockets. None of the rotating wear is distributed to the chain pin bosses at the open end of the link. In
conventional chain designs, the higher concentration of wear and load over a smaller surface areas promotes accelerated and one-sided premature failure of the chain pin O.D. and chain link barrel I.D.

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20-year Design Life and 10-year Warranty on Certified Applications

Benefit: When paired with high-grade polymeric sprocket materials like 70-75 Shore D polyurethane, or Nylon-6/6, or with heat-treated stainless steel sprockets, all DuraMax Chains are designed to operate up to a full 20-year continuous duty service cycle without replacement of either the chain or the sprockets. They will require substantially less routine and preventive maintenance as well. When evaluated on a 20-year life cycle basis including replacement chain, replacement sprockets, and installation labor, DuraMax Chains are substantially less expensive to operate and maintain than any other cast, fabricated steel, or 400 series stainless steel chain and sprocket system. All DuraMax Chains have a standard 10-year warranty when operated on high-grade polymeric or stainless steel sprockets, and applied, installed, and maintained within chain design parameters and traditional industry standards.

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DuraMax Chain and Equipment Products are a "Green World" Technology

Benefit: The cast stainless steel alloys in DuraMax Chains are fully recyclable at the end of their life-cycle, and have significant value as a recyclable material, unlike rusty, worn out cast iron chains. Typically, DuraMax Chains do use some recycled content as part of the casting process. The long life-span of DuraMax Chains also provides significant waste reduction and reduces the waste-to-landfill stream generated by the frequent replacement of cast iron chain and sprocket systems.

The long life-span of the DuraMax Chains, and much lower maintenance requirements significantly reduce plant energy consumption. Equipment tanks and basins do not have to be drained and cleaned every few months for tensioning adjustments, or to repair chain failures, or to replace worn out cast iron chains, thus reducing Plant power consumption by reducing the operation of high horsepower de-watering pumps.

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