In the domestic and international water markets there is a flood of “poor quality” bolted tank designs and products being promoted in the industry today, even by major suppliers. The simple facts are that manufacturers of bolted water tanks are trying to make their products as cheap as possible, to increase margins. This has led to a hodgepodge of tank construction and promotion rhetoric that simply “doesn’t hold water”. Many of today’s bolted steel storage tanks are being designed like today’s household appliances. They will provide a short, finite service life and then require replacement.
At Tank Connection, we receive continuous calls from new clients with horror stories on a “brand x” tank product that was installed in the past. In most cases, they selected a name brand product, but ended up with an installed product that did not meet their expectations.
In municipal water storage, subscribing to AWWA D103 “bolted water tank specification” is a good start, but even this specification includes a few bad ideas that have not been corrected.
In developing a water tank specification, can you protect yourself by utilizing a consultant? The answer is both “yes and no”. In the municipal water market, many consultants are tied to specific products, so objective reviews are in short supply. At TC, we recommend that you conduct your own product review. A little common sense and asking the right questions will go a long way in determining whether or not a storage tank product and service will fulfill your expectations.
As previously noted, AWWA D103 is a good start in developing a bolted tank specification tailored for your application. There are a few deficiencies in the AWWA D103 specification that should be addressed and answered to your satisfaction.
AWWA D103 “Factory Coated Bolted Tanks for Water Storage”
- Allows the use of .094” minimum thickness in tank sidewall.Commentary: It is interesting to note that AWWA D100 (the welded water tank specification) allows a minimum thickness of .1875” for the tank sidewall, but D103 allows a minimum thickness of .094” for the tank sidewall (basically, half the thickness). To be specific, the use of .094” material will fulfill design parameters. Since it is allowed, .094” or common 12 gauge (.1046”) material will be utilized by all bolted tank manufacturers.Fact: If you specify AWWA D103 without a minimum design thickness, you will receive .094” material on select tank sizes.TC Position: A design minimum of .094” is too light for a municipal water tank application. Municipal water storage should be installed as a major infrastructure investment. The minimum material thickness should be 10 gauge (.1345”) material.
Customer Question: Is the use of .094” material acceptable for your application and will it fulfill the expectations of your client for decades to come?
- Allows the use of web stiffeners, also called web supports, web truss and/or webbies. Webbies are an “erectors set” of bolted together stiffeners that go on the outside of a bolted tank.Commentary: Again, it is interesting to note that AWWA D100 does not allow the use of web stiffeners. Webbies are utilized on the cheapest water storage tank designs offered in the global market place today including corrugated.Fact: The usage of web stiffeners in previous years was limited to a few horizontal web stiffeners on larger tank sizes. The use of web stiffeners is currently out of control in the industry. Some tank manufacturers are utilizing web stiffeners on every ring.TC Position: For “A” quality storage, web stiffeners should not be allowed, except for use on 304 or 316 stainless steel tanks. You can’t replace plate thickness with stiffeners and call it high quality storage containment.
Customer Question: Are web stiffeners acceptable for your application or is increased plate thickness preferred?
- Allows the use of 5/16” plate in API 12B flanged panel tank construction.Fact: The original API 12B specification never intended the use of 5/16” plate material, but rather was limited to 3/16” plate material. The problem created with the use of 5/16” material is that the panel flange break has a history of inconsistency (i.e., over and under break). If the flange break is not precision at 90 degrees, a leak proof tank cannot be guaranteed.TC Position: API 12B flanged panels should be limited to ¼” plate material. The use of this product is outdated with today’s precision RTP (rolled, tapered panel) bolted tank technology.Customer Question: Is API 12B tank construction acceptable for your application?
- Allows the use of API 12B flanged panel tanks for standpipe applications.Fact: Flanged panel tanks have a history of continuous leaking due to hydrostat loads and excessive head pressure in standpipe applications.TC Position: API 12B tanks utilized in water standpipe applications are a misapplication. It is being phased out by API 12B tank manufacturers. The only reason it is still offered in standpipe applications, is that it allows subcontracted field installation crews to use archaic field construction equipment (gin pole and scaffolding) to erect the tank. There is no merit in the selection of an outdated product for a water standpipe application.Customer Question: Is API 12B tank construction acceptable for your application?
Bolted Steel Water Tanks — The Correct Equation!
To install a quality bolted steel water tank, there are three major component assemblies to review. This includes the DECK (top of tank), TANK SIDEWALL and TANK BOTTOM. The correct selection of these major components will determine the level of “component quality” available for field construction.
- Specify latest revision AWWA D103 specification
- Specify BSR (base setting ring) in concrete or steel bottom
- Specify aluminum dome cover or conical sloped steel deck design
- Specify 10 ga. minimum design or default to .094” minimum (per AWWA)
- Specify that no web stiffeners will be allowed
- Specify “factory certified” field installation crews
Specify the level of “component quality” required for your project:
- A product quality — RTP (rolled, tapered panel) design, LIQ Fusion 7000 FBE, no webbies & aluminum dome
- A product quality — RTP design, stainless steel, minimal webbies & aluminum dome
- B product quality — RTP design, LIQ Fusion 7000 FBE, minimal webbies, aluminum dome or steel conical sloped deck
- B product quality — Glass tanks with 2 fire process, no webbies & aluminum dome
- C product quality — Glass tanks with minimal webbies & aluminum dome or steel conical sloped deck
- C product quality — API flanged panel design, factory epoxy coated & aluminum dome or steel conical sloped deck
- D product quality — API flanged panel design, galvanized, steel conical sloped deck
- D product quality — Glass tanks with 1 fire process, excessive webbies and other stiffeners, steel conical sloped deck
Today’s product quality consists of an unlimited list of steel panel designs and available coating systems. Although the “component quality” review may be considered subjective, it is based on factual data. Additionally, there is an entire spectrum of alternative products that offer even lower quality standards than those shown. This includes trough roof designs, membrane covers, corrugated tanks and the list continues.
Based on proper maintenance, “A” product quality can provide unlimited service life. “B” product quality can provide a 30-40 year service life. “C” product quality can provide a 20-30 year service life. “D” product quality will provide a questionable service life.
In water storage applications, come to Tank Connection for the facts and correct specifications for factory coated, bolted steel tanks. We always welcome the opportunity to specify a storage tank of unmatched quality that will “stand the test of time”. Get it right the first time!