Heavy-Duty Double Cylinder Bands and Bolts by Dive Rite

Choose the Appropriate Size Tank Band Set for Your Cylinders
Dive Rite's Heavy-Duty GM1037 bands fit the larger 8.0-inch diameter cylinders such as aluminum 100's or steel LP104's and HP130's. Dive Rite's Heavy-Duty GM1033 bands fit cylinders with diameters between 6.9 and 7.5-inches such as 7.25-inch aluminum 80s or steel HP100's.	Diameter Cylinders 7-¼ Inches AL80, LP80, HP80, HP100, HP120, All E7/X7's 8 Inches AL100, LP95, LP104, HP119, LP120, HP130, All E8/X8's
7.25-Inch Plate and Bolt	8-Inch Plate and Bolt

An often heard debate is the merits of threaded bolt versus all-thread bolt. Corrosion is not an issue because both types are made from high grade stainless steel. Strength is not an issue either, because a 5/16 threaded bolt and a 5/16 all-thread bolt are nearly equal in tensile strength. (The core diameter of both a threaded bolt and an all-thread bolt is where the bolts derive their over 70,000 psi of strength.) As for all-thread bolts being cheaper; they are slightly less expensive but not lower quality. Dive Rite uses all-thread bolts not due to price, but in order to provide customers with the option to adjust their bolt height. Depending on the backplate brand and model, it is possible to have too many threads protruding causing the bolts to abrade and eventually puncture a dry suit or wetsuit. The all-thread bolts allow you to precisely adjust the bolt height to perfectly fit any brand or size of backplate and wing assembly.

Like all very high quality stainless steel products, Dive Rite bands are passivated. Passivation treatments improve the surface condition of stainless steel by dissolving iron that has been imbedded in the surface during forming or machining. If allowed to remain, the iron can corrode and give the appearance of rust spots on the stainless steel. Passivation, which consists of immersing stainless steel components in a special acid solution, will dissolve the imbedded iron and restore the original corrosion-resistant surface by forming a thin, transparent oxide film.

Evolution of Manifolds and Bands

In the early 1980's there were few double tank manifolds available. Divers had a choice of a dual outlet metal-to-metal seal manifold from one manufacturer or a single outlet double barrel o-ring seal manifold from another manufacturer. Manifolds during this period did not have crossbars with isolation valves. The center-to-center spacing on these manifolds was 8.25-inches for aluminum 80s and steel 72s, which was tight for the increasingly popular 8-inch diameter tanks. The tight spacing meant bolts could rub against the tanks and the bands were prone to gapping.

In the late 1980s, more dual outlet manifolds became available with several choices for seal design and centers spacing. Specialty band manufacturers also entered the market and offered a variety of band sizes and types for use with different manifolds and tanks. Some manufacturers used tack welds that would allow the bands to flex in accordance with the size of the tank, rather than manufacture multiple sets of bands. The tack weld approach required care during assembly because the welds would separate if the assembler were to over-torque the bolts.

By the 1990s, valve manufacturers began to standardize manifold centers spacing and isolation valve crossbars became the norm. The double barrel seal manifold became the preferred design, providing better shock absorption and redundancy over the metal-to-metal seal manifolds. Band sizes standardized at 7.25-inches and 8-inches and tack welded bands became obsolete, the tack welds replaced by rigid structural plates.

Today, the new generation adjustable 8.5-inch center-to-center spacing manifolds provide up to 0.25-inches of adjustability so that tank bands fit properly even when there are minor variations in tank dimensions. If you have a recently manufactured manifold with double o-ring seals and adjustable spacing, you should not need a specialized tank band.

Adapted from "The News Reel, Vol 1, Issue IV" © Copyright by Lamartek, Inc.

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