Chilled Water Storage Tank for Data Center: Technical Specification and Selection Guide
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Chilled Water Storage Tank for Data Center: Technical Specification and Selection Guide
Specify a chilled water storage tank for data center by starting from usable ΔT and usable fraction, then working outward to lining, pressure class, insulation and the nozzle list. Standing chilled water is oxygenated and slowly aggressive, so the lining is a coating question rather than a strength question. Fusion-bonded epoxy and glass-fused-to-steel enamel are both used on large water volumes, and the choice turns on programme and repairability. Pressure class decides wall thickness, openings and relief, and belongs in the specification in writing before the order.
Tank enquiries for a chilled water storage tank for data center usually state a volume and a temperature difference, then leave the rest to the supplier. That leaves the two decisions that change price and service life unstated: what the inside of the vessel is made of, and whether it sits inside the system pressure boundary.
What follows is the structure most owner's engineers find useful: a small set of parameters, each with the value that follows from it.
Usable Temperature Difference and Capacity
Everything starts with two numbers, and volume is derived rather than chosen.
· Set the usable ΔT. Five to seven kelvin is the usual window, arranged as 5 °C charging with 11-12 °C return. A wider span cuts volume but raises return temperature, which both the coils and the chiller have to accept.
· Fix the usable fraction. Obtainable capacity is 70-90% of theoretical once mixing, ambient gain and the thermocline reserve are taken out. Quote gross volume alongside the usable value, or vendor comparisons are meaningless.
· Convert energy to volume. Q = V × ρ × cp × ΔT gives about 1.163 kWh per cubic metre per kelvin for water, so a 4,000 m³ shell at 6 K holds roughly 28,000 kWh before derating.
· Check the flow rate. Discharge flow is load divided by ΔT; the loop pump must deliver it from a cold shell without dropping supply below the IT band.
Reaching the upper end of that usable fraction needs a low inlet velocity and a well-placed diffuser, since both protect the stratification the whole figure rests on.
Lining Selection for Standing Chilled Water
For a chilled water storage tank for data center, the water sits still for hours, holds dissolved oxygen and is treated with biocide and inhibitor. The lining must survive that while staying smooth.
Lining | Characteristic | Suits |
Glass-fused-to-steel panels | Enamel fused at 820-930 °C, 0.25-0.45 mm, pH 3-11 normal and 1-14 special, Ra below 0.8 µm | Large field-erected atmospheric shells inspected panel by panel |
Fusion-bonded epoxy | Resicoat R4-ES 180-280 µm inside with INTERPON D2015 outside, 4000 h salt spray to ISO 9227 and ASTM B117, to AWWA C550 | Large water volumes repairable without a full re-lining |
Hot-dip galvanised | Zinc sacrificial protection to GB/T 13912-2020 practice | Smaller vessels and single-run service water |
Stainless | AISI 304 or 316L, also as a hybrid with enamel on the lower shell | Aggressive treatment or uncertain chloride control |
Two notes. Site programme and repair expectation decide between epoxy and enamel; galvanising spends a finite zinc budget protecting the steel, so it is not the default for a vessel standing for decades.
Pressure Class and the Vessel Boundary
One line changes more engineering than all the others: whether the vessel sits inside the pressure boundary.
· Atmospheric field-erected. Open to atmosphere through a vent or cover, receiving return water only at the inlet nozzle under pump head, so wall thickness stays modest and the shell can be entered for inspection.
· Inside the system pressure boundary. On the pump discharge the tank sees full working pressure, so shell thickness, nozzle reinforcement, flange ratings and a relief device are calculated to the design pressure and design temperature, and the applicable code and design are as agreed in the project specification and contract.
· Foundation and thermal bridges. Insulation carried through the support detail at the shell bottom prevents a cold bridge from freezing and cracking the cladding in an unheated plant room.
Insulation and Interfaces
Insulation thickness is a heat-balance value, not a catalogue line. Standing loss over the hold period, cycles per day and the ambient condition of the location all move it. Interfaces are where late engineering change is generated, so pin them at enquiry.
1. Nozzles. Charge inlet with diffuser, discharge outlet, return connection, fill, vent and drain, plus a flush connection if the loop is washed in place.
2. Instruments. Redundant level, temperature at two depths to watch the thermocline, and a manway sized for a person.
3. Access. Roof access by ladder or platform, and the top enclosure as a weathertight bolted aluminium dome with Batten Bar fixing under AWWA D108, API 650, ADM 2015, ASCE 7-10 and IBC 2012 practice.
4. Strainers and treatment. Strainers on tank connections, plus the biocide, pH and inhibitor schedule the rest of the plant already runs.
The treatment programme deserves a mention because it decides how long the lining lasts. A coating that is compatible on paper can fail early under an oxidising biocide it was never qualified against.
Technical Specification
Line item | Typical value or choice | Why it belongs here |
Usable ΔT | 5-7 K, charging 5 °C, returning 11-12 °C | Sets stored energy per cubic metre |
Rated and usable volume | State both, usable fraction 70-90% | Makes comparisons like for like |
Vessel boundary | Atmospheric field-erected, or inside the pressure boundary | Drives wall thickness and relief |
Design pressure and temperature | Per the project specification and contract | Governs flanges, nozzles and certification |
Lining and thickness | Fusion-bonded epoxy 180-280 µm, or enamel 0.25-0.45 mm | Service life and cleaning regime |
Inlet velocity | 0.5-1 m/s through the diffuser | Protects usable capacity |
Insulation | Mineral wool, weather barrier, cladding continuous at supports | Limits standing heat gain |
Nozzle and instrument list | Per the interface schedule above | Fixes valve and pipework scope |
Project Case
Our delivered reference work in the water and wastewater sector includes large epoxy-lined tanks, including the installation below. The data-center TES scope is engineered to the same standards.
Project Case Summary
Project | Product | Capacity | Dimensions | Completion |
China (Hebei) - pharmaceutical wastewater (P-E) | 02 FBE fusion-bonded epoxy tank | 32,363 m³ | φ36,600 × 24,600 mm plus φ18,340 × 24,600 mm | August 2026 |
Two shells of this size were supplied with a fusion-bonded epoxy lining qualified to AWWA C550 practice with a 4000 h salt spray result to ISO 9227 and ASTM B117. The surface finish and the holiday test record are what carry over to a chilled water storage tank for data center, where the lining also has to hold stratification rather than merely hold water.
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.
Epoxy lining and water chemistry
· Fusion-bonded epoxy shells with an AkzoNobel Resicoat R4-ES internal coating (180-280 µm) and INTERPON D2015 external coating give a corrosion barrier that does not need cathodic protection and can be repaired in situ if the film is damaged.
· Epoxy-lined carbon steel performs well where the stored water carries dissolved salts or aggressive pH, and the coating route is referenced to AWWA C550 with 4000 h salt-spray verification under ISO 9227 / ASTM B117.
· The largest epoxy-coated delivery on record is the Hebei pharmaceutical wastewater scheme of φ36.6 m × 24.6 m plus φ18.34 m × 24.6 m tanks, 32,363 m³, completed 2026-08.
Frequently Asked Questions
Q1: Should the specification ask for a lining or a coating system?
A1: Ask for the lining with its thickness, the standard it is qualified to and the test that proves it. A clause naming a standard, a dry film thickness and a holiday voltage is verifiable at acceptance; an adjective is not.
Q2: How is insulation thickness chosen?
A2: From a heat balance over the hold period: shell area, thickness and conductivity, ambient condition and cycles per day. State a target standing loss in kilowatts rather than only a thickness.
Q3: Must the tank sit inside the pressure boundary?
A3: Only if it sits on the pump discharge and the system relies on it for pressure. Otherwise keep it atmospheric, which is thinner, inspectable and free of a relief device, and any code and design applied will be as agreed in the specification.
Q4: Should the lining be qualified against the water treatment?
A4: Yes, the programme the plant actually runs, including biocide type, pH range and inhibitor. A lining qualified against clean water can fail early under an oxidising biocide.
Q5: Can the lining be repaired during service?
A5: Fusion-bonded epoxy can be patched on site, so require repair procedure documents and the matching resin. Enamel panels are replaced rather than patched, which makes access to the shell a selection criterion.
A well-written chilled water storage tank for data center specification is short: usable ΔT, rated and usable volume, vessel boundary, design pressure and temperature, lining with thickness and test, inlet velocity, insulation target and the interface list. Written at enquiry stage, those lines can be compared between vendors instead of surfacing as change orders after the shell is ordered.
Talk to an Engineer
Send us the load profile, supply and return temperatures, the plot area and the water treatment schedule. We will return a tank specification sheet with rated and usable volume, vessel boundary, lining type and thickness, insulation target, nozzle and instrument list, and the holiday test requirements. For projects still at concept stage, request a lining comparison against your programme and repair expectation before the vessel is sized.
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