How Do You Manifold Bolted Steel Tanks: Header Sizing and Isolation
Created on 09.08
How Do You Manifold Bolted Steel Tanks: Header Sizing and Isolation
Manifolded bolted steel tanks are piped as a common header system, with the header sized for the combined peak flow, each tank isolated by its own valve set, and equalisation or level control so that no single tank is asked to absorb the whole swing. Keep the piping material compatible with the tank interior and the fluid, hold the header free of dead legs where solids can settle, and verify torque records and gasket compatibility before first fill. The manifold is what turns several bolted shells into one reliable storage bank.
A bank of bolted tanks works well right up to the point where the piping has to join them. The shells arrive, the panels are bolted, the foundation is cured, and then the manifold design turns into an argument between the process engineer, who wants equalisation, and the piping designer, who wants isolation. Both are right, and reconciling them is the whole job. Get it wrong and the symptoms are familiar: one tank cycling while the others sit idle, a header that never balances, solids settling in a dead leg, or a gasket incompatibility that only shows at the first hot day. Manifold design ought to start with the flow diagram and the fluid, not with the header diameter already chosen.
What the Manifold Has to Do
Isolate, equalise and control are three separate jobs. Isolation gives you the ability to take one tank out of service for inspection while the rest hold the plant; equalisation lets the bank share the level swing so the peak does not land on a single vessel; and control keeps the bank within its operating envelope with a level instrument feeding the fill and draw valves. A manifold that only does the first of these will be retrofitted within a year. The usual arrangement is a common header with a valve set at each tank outlet and inlet, a bypass or cross-connect between adjacent tanks for equalisation, and a level control that distributes the flow rather than dumping it into whichever tank happens to be lowest. Each of those three functions should be visible on the piping and isometric, because a manifold drawn as a single line is a manifold that will be modified on site.
Fluid Compatibility and Interior-Safe Piping
Nothing in the wetted path should be more aggressive than the tank interior. A bolted shell may be glass fused to steel, fusion bonded epoxy to AWWA C550, hot-dip galvanized to GB/T 13912-2020, or 304 or 316L stainless, and the piping, valves and gaskets inside the manifold have to match that duty. Enamel tolerates pH 1–14 and is smooth below 0.8 µm Ra; epoxy coatings at 180–280 µm handle the milder services the standard refers to; galvanized is for the clean, non-food-contact duties; and stainless is for chloride and high-purity service. If the header runs through the tank farm and the fluid is aggressive, specify the interior wetted parts to the same standard as the shell rather than relying on the external piping specification to cover it.
Physical Layout: Slopes, Dead Legs and Access
A manifold that cannot be drained or surveyed is a maintenance liability. Lay the header with a slope and a drain point at the low end so the line can be emptied; avoid dead legs where a slow-moving or settled stream can harden and block the branch; keep the valve sets inside reach of the tank walkway rather than over the roof; and leave access around each tank for the annual bolt torque check and the internal inspection. Bolted panels are roughly 1.2 m wide and the tank is assembled on a ring beam, so the nozzle elevation and the platform level should be fixed together in the assembly drawing, because a valve set that sits at knee height on a 12 m tank is a valve nobody maintains.
Technical Specification
Parameter | Typical Value / Range | Note |
Panel width | approx. 1.2 m | bolted shell assembly module |
Fasteners | 8.8-grade bolts | torque recorded at assembly |
Gasket | EPDM, fluid compatible | joint seal on the shell and nozzles |
Enamel shell data | fused at 820–930 °C, 0.25–0.45 mm | inert across pH 1–14, Ra < 0.8 µm |
Epoxy shell data | 180–280 µm, AWWA C550 | fusion bonded epoxy alternative |
Galvanized shell | HDG, GB/T 13912-2020 | clean water and dry materials |
Manifold header | sized for combined peak flow | with isolation at each tank |
Commissioning check | torque, level, isolation test | before first fill |
Commissioning and the Inspection Routine
Verify the manifold before the bank is filled. Confirm the bolt torque records for every panel, check that the valve set at each tank actually isolates that tank alone, test the level instrument against a known level, and confirm the equalisation path opens in the intended sequence. Then run the bank: fill, distribute, draw down one tank while the equalisation is active, and watch whether the level control hands the flow over correctly. After that, the inspection routine is short — torque check after first fill and after the first year, a check of the gasket tracks and the nozzle seals, and an internal visual check of each tank at its shutdown, which is also when the manifold valves are exercised.
Project Case
Project | Location | Product | Capacity | Scope |
Big-diameter water tank | Namibia | GFS tank | 44,900 m³ | supply + installation supervision |
Firewater series | Sichuan, China | GFS tank | 8,930 m³ (φ19.87 m × 14.4 m × 2) | supply + erection assistance |
Potable water series | Indonesia | GFS tank | 21,099 m³ (φ42.04 m × 15.2 m) | supply + commissioning support |
Industrial wastewater series | Xinjiang, China | GFS tank | 30,469 m³ in 27 tanks | supply + installation supervision |
Center Enamel Engineering Capability
Center Enamel (Shijiazhuang Zhengzhong Technology Co., Ltd) has designed and fabricated bolted storage tanks since 2008. As the first glass-fused-to-steel (GFS) tank manufacturer in China, the company holds close to 200 enamel-related patents, produces roughly 300,000 enamel-coated steel plates a year, has completed more than 30,000 installed projects and supplies its tanks to over 100 countries. The new 150,000 m² production base was added to raise output capacity, and single tanks are supplied up to 60,000 m³. Manufacturing runs under ISO 9001 and ISO 45001, with product certification including NSF/ANSI 61, WRAS, FDA, LFGB, CE (EN 1090), ISO 28765, FM, BSCI and EUROCODE, and design referenced to AWWA D103-09, AWWA C550 and NFPA where the application requires it.
For multi-tank banks the capability lands as nozzles and manifolds positioned on the assembly drawing with the platform level, a single-scope shell and joint standard across enamel, epoxy and galvanized, and torque and gasket records that make the manifold commissioning and inspection routine straightforward.
Frequently Asked Questions
Q1: Should the header be shared or should each tank have its own line?
A1: A common header with an individual valve set at each tank is normally the right compromise: it gives isolation and equalisation without doubling the pipe runs. Size the header for the combined peak flow, not for the average.
Q2: How do I stop one tank from absorbing the whole swing?
A2: With equalisation and level control. Cross-connect adjacent tanks and let the level control distribute inflow across the bank instead of letting the lowest tank take everything, then verify the sequence during commissioning.
Q3: Can one tank be taken out of service while the bank runs?
A3: Yes, which is the main operational argument for a manifold. Close that tank's inlet and outlet valves, verify the isolation by level test, and the remaining tanks hold the plant while the isolated one is inspected internally.
Q4: What gasket works across enamel, epoxy and galvanized shells?
A4: EPDM is the standard joint gasket for bolted shells, with the compound chosen for the fluid and the temperature. Keep one gasket standard across the bank so that spare parts and torque values are consistent.
Q5: What causes a manifold to fail first?
A5: Dead legs where solids settle, and low points that cannot be drained. Both are layout problems, and both are preventable in the isometric review rather than in the field.
Q6: Does the manifold affect the tank foundation?
A6: Indirectly. Nozzle loads and the valve set weight are carried by the tank and its ring beam, so the nozzle elevations and the access level belong in the assembly drawing before the foundation is poured.
Q7: How often is the manifold inspected?
A7: Exercise the valves at each tank inspection, check the gasket tracks and nozzle seals, verify torque after first fill and after the first year, and drain and flush any header section that can hold sediment.
A manifold converts a group of bolted shells into a storage bank that can be maintained, equalised and controlled. Size the header for the combined peak, isolate every tank with its own valve set, provide cross-connection for equalisation, keep the piping wetted-material compatible with the shell, eliminate dead legs and low points, and verify the whole arrangement before the first fill. Those six decisions determine whether the bank behaves as designed through a thirty-year life. Send the flow diagram, the number and size of tanks, the fluid and its chemistry, and the plot, and the manifold design follows directly.
Talk to an Engineer
Send the flow diagram with peak and average flow, the number and size of tanks, the fluid and its chemistry, the required level control and equalisation, available plot and access, and the commissioning date. The engineering team will return a manifold arrangement with header sizing, a valve set and isolation scheme, nozzle elevations and access level, gasket and interior piping material recommendation, a commissioning test list, and the inspection routine. Where a different shell material fits the fluid better, that option is stated alongside rather than replacing it.
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