Snyder Industries 10,000 Gallon HDLPE Captor Double Wall Liquid Storage Tank

The pad under an eighteen foot double wall tank

Everything about buying this tank starts at the pad, because a double wall tank is a heavy circle that puts its whole load on one plane and then stands eighteen feet ten inches in the air above it. The footprint is 142 inches across, just under twelve feet, and the pad has to extend past that circle on every side, be flat within the tolerance your engineer specifies, and be level. Not nearly level. A tall cylinder out of plumb loads one side of the base for its whole life, and at 83,400 pounds full of water, or 158,460 pounds at the specific gravity of 1.9 the sheet rates it to, there is no forgiveness in that load for a pad that was poured by eye. Get the concrete designed and inspected: the concrete pad sizing guide for above-ground polyethylene tanks works through the framework properly and shows where a slab-on-grade design stops and a structural one begins. The second site question is the outer tank. A Captor is one delivery, one set of anchors and one footprint that contains itself, which is why plants buy it instead of building a concrete bund around an open tank, and the trade is that everything you want to inspect lives inside the outer shell. The Captor double wall SPCC walkthrough is the piece to read before the design is fixed, because it works through what a plant actually has to demonstrate rather than assuming a second wall closes the question. The third is usable volume, which is never the nameplate. The Captor freeboard sizing article takes thermal expansion, chemistry and density into account and lands on the volume you can really fill to; run the answer through the tank sizing calculator against your delivery size, and take the rest of the sizing discipline from the tank sizing guide. A tank this large is usually sized to the tanker, and getting that wrong costs a partial delivery every time for twenty years.

The 10,000 gallon Captor shells, the 8,700 below and the 12,500 above

Four listings share this exact 142 by 226 inch envelope and 10,000 gallons, and the sheet separates them by wall and by weight rather than by size: this part and 1006600N30 are listed at 7,400 pounds, while 1006600N40 and 1006600N46 are listed at 6,400 pounds in the same shell. The sheet gives both weights and explains nothing further, so neither does this page. What it means for a buyer is practical rather than mysterious: the pad, the anchors and the crane are sized on the heaviest figure, and the shipping weight you are quoted is the one for the part number you actually order. The reason to buy this listing in particular is that it is the high density linear wall of the group at the 7,400 pound weight, with its own 3 year warranty and its own 1.9 rating; the cross-linked listings are specified where a chemistry or a duty asks for that wall. Change the diameter and nothing changes, which is the useful thing here: 1006400N46 gives up 8,700 gallons in the same 142 inch circle at 197 inches tall and 5,000 pounds, and 1031100N30 goes to 12,500 gallons at 274 inches and 9,500 pounds. All three heights sit on the same pad diameter, so a site that pours for one can grow or shrink the volume later without repouring, provided the ceiling or the skyline allows the height. That is worth knowing before the concrete is ordered.

Need the taller or the wider one? Every row links to its page with freight to your ZIP on each; 866-418-1777 will check the ceiling and the pad.

An 18 inch threaded vented manway, and the outlet the sheet does not give

• Outlet and valve: this sheet lists no outlet fitting and no inlet. On a double wall tank that is not a detail to guess at, because every penetration has to pass through two shells and stay sealed at both, so name the chemical, the fill method and the draw rate when you order and the fitting schedule for your part is confirmed in writing before anything is built.
• Top access: an 18 inch threaded vented manway, which is the only opening the sheet publishes, at the top of a tank 226 inches tall. Everything about working there is a fall protection and confined space question before it is a tank question. Plan the ladder, the platform and the permit at design time, not on the morning of the first inspection.
• Venting: the manway the sheet names is a vented one. Whatever the final arrangement, the tank has to be able to take air in as fast as the pump takes liquid out. Fast pump, restricted vent, polyethylene wall is the classic way a large tank is damaged, and it happens on a first fill as often as on a draw.
• The interstitial space: the volume between the inner tank and the outer containment is the whole point of the purchase, so decide at design time how it will be monitored and who looks at it. A leak detector that nobody reads is a decoration, and the Captor SPCC walkthrough sets out what inspection actually looks like.
• Service limit and term: 120 F / 48 C, and a 3 year warranty as the sheet gives it. Ask us for the current written terms rather than relying on a number in a listing.

The other thing worth designing deliberately is where the wall is thinnest in service, which is not the bottom. The vapour-saturated headspace at the top of a tall polyethylene tank is where premature failures start, and liquid-side inspection walks straight past them. The article on wall thickness at the vapour-saturated headspace explains the sizing logic behind that and what an operator should be looking at. On a tank this tall it is the single most useful piece of maintenance knowledge on this page.

Bulk chemical storage where a second wall is the reason for the purchase

Ten thousand gallons of double wall storage goes in where a spill would be expensive in more than product: water and wastewater treatment chemical storage, municipal and industrial bulk chemistry, agricultural chemical and fertilizer storage at a hub, mining reagents, pulp and paper, food processing, and any plant whose containment plan would otherwise mean pouring and maintaining a concrete bund around an open tank. The buyers who choose it are usually deciding between one vessel that contains itself and a civil works project, and the comparison is rarely about the tank price alone once the concrete, the drainage, the rainwater in the bund and the inspection regime are counted. Size it against the tanker delivery rather than the annual usage, and give the interstitial space an owner and a cadence in writing before it is commissioned.

Lincoln, Nebraska, oversize, and 7,400 pounds on the ground

This tank is molded at Lincoln, Nebraska, and the sheet gives the freight class as OVS, which is a mode rather than a numeric class; it publishes no NMFC for this part. A 142 inch circle standing 226 inches tall does not ride on an ordinary flatbed with ordinary paperwork, so treat the delivery as a project: route survey, overhead clearances, the gate and the yard turn, and a set-down plan agreed before the truck leaves. Price the lane with the freight cost estimator to your ZIP, and note that the listed price is before freight. At 7,400 pounds empty it is a crane or a large telehandler lift with a rigging plan, lifted by the points Snyder specifies and never by the manway. Have the pad cured, surveyed level and swept before the truck is scheduled, because an oversize load waiting on concrete is the most expensive hour on the job. Fill it with water first, in stages, and walk the base, the outer shell and the manway at each stage before the chemical is ordered. Keep the survey sheet from that first fill in the plant file; on a twenty year asset it is the only baseline anybody will ever have. A strap that is checked once a season is a strap that holds; put it on the same calendar as the gutters.