Immersion Requirements Rev 2.0, First Amended (Revision 2.10, August 18, 2023)

Overview

The document is the checklist used to qualify OCP immersion contributions; it was published as Rev 1.00 (20 May 2019), Rev 2.00 (21 January 2022) and the amended Rev 2.10 (18 August 2023). Requirements are tagged Specification Requirements (SR, for the solution vendor), Customer Requirements (CR, for owners and operators) and optional requirements (OR). The qualification process requires a filled-in checklist and presentation to be shared at least one week before the review, with a quorum of at least 5 votes. Among the Rev 2.10 changes, the minimum auto-ignition point rose from 250 C to 300 C.

The quality and safety chapter requires that horizontal busbars are not load-bearing, that conductors are protected against shorting by dropped conductive objects of at least 6 mm length, that a grounding interface is provided, that electrostatic generation in dielectric fluids is managed and that no aerosol is dispersed. For spills, containment must hold at least 100% of the volume of any single system, open baths need a well-ventilated room, fluid must be kept out of sewers and at least one person must be present during service. Two-phase and volatile systems must contain vapour losses by enclosure and condensation.

The fluids chapter tabulates minimum dielectric limits: lifetime dielectric strength of at least 6 kV/mm at 1 mm, volume resistivity of at least 2.00 GOhm-m unused and 0.20 GOhm-m lifetime, Cleveland closed-cup flash point of at least 150 C, auto-ignition of at least 300 C, sulphur below 10 ppm and acidity of at most 0.01 mg KOH/g for hydrocarbons. Mineral oils are to be avoided in favour of synthetic oils and esters. Suppliers report data-sheet properties such as density, specific heat, thermal conductivity, viscosity and vapour pressure across 20-70 C.

The specification-sheet chapter standardises units and metrics so solutions can be compared: density at ASHRAE facility-water classes W17, W27, W32, W45 and W55, footprint at W32, full-solution static floor load in kN/m2, ceiling clearance, non-IT power per kW of IT and a thermal-loss test. The facility-interface chapter covers flow-direction marking, partial vacuum down to 50 kPa, glycol mixtures up to 50%, a corrosion strategy for galvanic potential differences above 0.15 V and Redfish-based management with Modbus, SNMP or BACnet output for legacy systems.

Three feature classes are defined: thermal optimised, high safety and high availability. High availability allows N+1 to be supplemented with ride-through giving at least 30 minutes of operation without cooling. The ride-through chapter defines dielectric, partial dielectric and facility-water buffering but leaves quantification open. This is a requirements catalogue rather than a design guide and is meant to be read alongside the ACS immersion design guidelines.

Key points

1. Requirements are tagged SR (vendor), CR (customer/operator) and OR (optional); the qualification panel quorum is at least 5 votes.
2. Rev 2.10 raised the minimum auto-ignition point from 250 C to 300 C and restated dielectric strength in kV/mm.
3. Busbar conductors in tanks must be protected so a dropped conductive object of at least 6 mm length cannot short them; horizontal busbars must not be load-bearing.
4. Containment must hold at least 100% of the fluid volume of any single system without breach.
5. Minimum fluid limits: dielectric strength at least 6 kV/mm at 1 mm, volume resistivity at least 2.00 GOhm-m unused and 0.20 GOhm-m lifetime, flash point at least 150 C, auto-ignition at least 300 C, sulphur below 10 ppm.
6. Acidity limits are 0.01 (hydrocarbons), 0.06 (natural esters), 0.03 (synthetic esters) and 0.001 (fluorocarbons) mg KOH/g; mineral oils are to be avoided.
7. Specification sheets report density at W17/W27/W32/W45/W55 facility-water classes; the W32 solution footprint is mandatory.
8. Public data sheets must include full-solution static floor load (kN/m2), ceiling height clearance and non-IT power per kW of IT.
9. The facility-water interface must tolerate partial vacuum down to 50 kPa and glycol mixtures up to 50%, and needs a galvanic corrosion strategy above 0.15 V difference.
10. High-availability systems may supplement N+1 with ride-through of at least 30 minutes without cooling; ride-through is not yet quantified in the document.

Using it in design

• Compare vendor offers on the same template: request W32 footprint density (kW/m2), full-solution static floor load, ceiling clearance and non-IT power per kW of IT in writing.
• Check the fluid data sheet against the minimum table (6 kV/mm, 150 C flash, 300 C ignition, sulphur below 10 ppm) and obtain the supplier's monitoring tests and intervals for the lifetime limits.
• Size room containment to at least 100% of the largest connected container; for open baths write ventilation, absorbent, no-sewer and disposal procedures into operating documents.
• At the facility-water connection, check vacuum rating, glycol fraction, galvanic compatibility and flow-direction marking, noting that quick disconnects are not recommended.
• Specify in the technical requirements a Redfish-compliant management system with liquid temperature at two or more locations, two warning levels and Modbus, SNMP or BACnet output for the BMS.
• If high availability is targeted, have the vendor demonstrate any 30-minute no-cooling ride-through claim with measured data.

Who should read it

Immersion solution vendors, facility mechanical designers and operators who qualify or select immersion cooling.

Document contents

1. Table of amendments
2. Introduction
3. Technology definitions (single- and two-phase, enclosed chassis, open bath, hybrid)
4. Quality and safety requirements
5. Immersion Fluids
6. Minimum dielectric fluid requirements
7. Dielectric fluid quality management guidelines
8. Feature classifications (minimum management, thermal optimized, high safety, high availability)
9. General standards and solution specification items
10. Required available documentation
11. Datacenter interface requirements (FWS compatibility, water quality, galvanic properties)
12. DCIM interfaces and Redfish definitions
13. Immersion related uptime factors (ride through, thermal design)
14. Requirements catalogue
15. Glossary
16. References

Read the document

Publication details

Authors

Rolf Brink; Jessica Gullbrand; John Bean; Nigel Gore; Rick Payne; Jimil Shah; Rick Margerison

Publisher

Open Compute Project Foundation

Year

2023

Document language

English

Source type

Industry body

Access

Open licence — downloadable

Licence

CC BY-SA 4.0 — share with attribution under the same licence

Licence evidence

www.opencompute.org

Citation