Data Center Cooling & Liquid Infrastructure: CDU, RDHx & Coolant-Loop Sealing and Insulation
H-O Products die-cuts and converts EPDM foam, flame-rated silicone sponge, fluorosilicone sponge, aerogel blanket insulation, microcellular urethane vibration pads, expanded PTFE (ePTFE) vent membrane, and fluoroelastomer sheet into sealing and insulation parts for coolant distribution units, rear-door heat exchangers, coolant piping, aisle containment, and immersion cooling systems, built to your drawing.
Built for: CDU door and access-panel gaskets, coolant manifold penetration seals, RDHx frame-to-rack gaskets, below-dew-point chilled-line insulation, hot-return line insulation, containment panel perimeter gaskets, and immersion tank lid and feedthrough seals.
To seal or insulate liquid-cooling infrastructure, pick the material from the fluid and the location. Dry-side CDU doors and containment panels default to EPDM foam (RE41E–RE45E), stepping up to UL 94 V-0 kSil V-0 or RS-series silicone sponge where a flame class is called out. Glycol-exposed manifold penetrations use fluorosilicone sponge; RDHx frame-to-rack seals use BISCO silicone foam.
Coolant pipe insulation splits by line temperature: Cryogel Z below the dew point, ArmaGel HT / HTL on warm runs, Pyrogel XTE on the hottest returns. Immersion fluid contact uses FKM, stepping up to FFKM.
See the list at right for the full when-to-spec-what map.
Fluid compatibility is qualitative here — confirm each elastomer against the fluid maker's compatibility data for the specific coolant; the seal is one variable. Compression-deflection per ASTM D1056, thermal conductivity per ASTM C177; values per the TDS on file.
ASTM D1056 · UL 94 · ASTM C177 · ASTM E84 · ASTM E96 · ASTM D3574 · ASTM C447 · AMS 3323 · ASHRAE TC 9.9 datacom · NFPA 75 · TDS on file for per-grade values
- CDU door / access panel, dry side: EPDM foam RE-series
- Fire-rated enclosure gasket: kSil V-0 or RS-series silicone sponge
- Glycol-exposed manifold penetration: Fluorosilicone sponge
- Sealed CDU pressure equalization: ePTFE vent membrane
- CDU pump vibration pads: Microcellular urethane foam
- RDHx frame-to-rack gasket: BISCO silicone foam
- Below-dew-point chilled line: Cryogel Z
- Warm supply / return run: ArmaGel HT / HTL
- Hottest return / reclaim line: Pyrogel XTE
- Containment panel perimeter: Neoprene foam SCE-series or EPDM
- Immersion fluid contact: FKM, step up to FFKM
Where are you in the spec process?
This page serves cooling-hardware engineers who already know the material they want and engineers still mapping fluid, fire, and condensation constraints. Pick the path that matches where you are; you don't have to read the rest.
Send a drawing, get a quote
EPDM foam, kSil V-0 or RS-series silicone sponge, fluorosilicone sponge, BISCO silicone foam, ArmaGel / Cryogel Z / Pyrogel XTE, microcellular urethane, ePTFE vent membrane, or a fluoroelastomer grade on your drawing.
Skip to the quote form →Walk through the selection factors
Six selection factors (fluid chemistry, fire rating, line temperature, compression set, pressure equalization, vibration), a coolant-loop seal picker, a pipe-insulation lookup, and twelve material families with TDS-cited test methods.
Start with selection factors →
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1Send drawingUpload a DXF, STEP, or PDF, or describe the assembly. A sample part works too.
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2Material reviewEngineering reviews the seal location against the vendor TDS: the fluid in the loop, fire-rating need, line temperature, compression range, and whether the part sees coolant contact or stays dry-side.
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3PrototypeSamples typically ship in 3–5 business days for common die-cut configurations on materials we commonly convert. Made-to-order; MOQ varies by material and part.
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4ProductionStandard production runs ship about 2 weeks after drawing approval, including kiss-cut-on-liner and laminated configurations. Expedited service available. Ongoing parts run with material traceability and lot-code TDS records.
What are you sealing or insulating?
Application Zones
Five distinct material problems hide inside a liquid-cooled data center build: the CDU enclosure, where door gaskets, glycol-exposed penetration seals, a breathing vent, and pump isolation pads all live in one cabinet; the rear-door heat exchanger, where a compliant gasket has to seal the door to the rack frame through thousands of open-close cycles; the coolant piping, where the insulation grade follows the line temperature and the dew point; the aisle containment system, with long runs of panel and door gasket; and the immersion cooling tank, where every seal touches a dielectric fluid.
Click a tab to see the joint, the fluid and fire considerations, and the material families H-O converts for that zone.
CDU enclosure sealing, venting, and pump isolation
The coolant distribution unit is the heart of a liquid-cooled facility, and one cabinet carries four different sealing jobs. Door and access-panel gaskets on the dry side are a classic closed-cell foam application: EPDM foam covers the general case, and a UL 94 V-0 rated silicone sponge takes over where the enclosure specification calls a flame rating. At coolant manifold penetrations, where glycol mist or a weep can reach the seal, a fluorosilicone sponge is the cautious choice; the dossier maps it specifically to glycol-exposed manifold seals.
A sealed CDU also breathes with thermal cycles, so an ePTFE vent membrane equalizes pressure without opening a water path. And the pump skid sits on microcellular urethane pads that keep pump vibration out of the cabinet panels. Compression-deflection is reported per ASTM D1056; flame ratings and per-grade values are per the TDS on file.
Rear-door heat exchanger (RDHx) interface sealing
A rear-door heat exchanger replaces the rack's rear door with a coolant coil, and the gasket between the RDHx frame and the rack frame is what keeps the hot exhaust air going through the coil instead of around it.
The seal is long, sees thousands of open-close cycles, and follows the frame's tolerance stack, which is exactly the duty profile of a soft closed-cell silicone foam: BISCO BF-1000 and BF-2000 are the extra-soft and ultra-soft grades for low-closure-force doors, and the HT-800 series steps up in firmness where the frame provides more compression.
The same cabinet uses microcellular urethane pads at the mounting points to keep coil and fan vibration out of the rack, and ArmaGel blanket on the hot-side coolant connections where a technician could contact the line. Compression-deflection is per ASTM D1056; flammability ratings per grade are on the TDS. [9]
Coolant pipe & manifold insulation
Pipe insulation in a liquid-cooled facility is really three different jobs separated by line temperature. Below-dew-point chilled lines are a condensation-control problem first and a heat-loss problem second: the insulation has to keep the jacket surface above the room dew point and resist water-vapor drive, which is why Cryogel Z, the aerogel blanket grade built for sub-ambient and chilled service, is the dossier's mapping for these lines, with water-vapor behavior characterized per ASTM E96 on the TDS.
Warm supply and return runs in the W-class bands the ASHRAE datacom liquid-cooling guidance describes are the general case, where ArmaGel HT and HTL give a thin, flexible, low-conductivity wrap that cleanly into fitted sleeves, saddles, and manifold blankets. The hottest return and heat-reclaim lines step up to Pyrogel XTE, the high-temperature industrial grade; the dossier rates the family for service to 650 °C, far above any coolant loop, so the margin is in the material, not the installation.
Thermal conductivity is reported per ASTM C177 and surface burning per ASTM E84; per-grade values are on the TDS. [3] [8]
Hot / cold aisle containment sealing
Aisle containment lives or dies on the small leaks: every panel-to-panel joint, door perimeter, and roof-section seam that passes air is bypass airflow the cooling plant has to make up. The materials are straightforward and the quantities are large, which makes this a converting-economics zone: long or slit perimeter strips in closed-cell EPDM foam for the general case, and neoprene foam (SCE-series) as the lower-cost alternative the dossier maps for containment seals, with UL 94 HF-1 flame data on the SCE TDS.
The discipline is dimensional: measure the real joint gaps, pick the foam firmness so panels and doors still close, and cut strip widths to the extrusion or panel system on the drawing rather than defaulting to a catalog width. Compression-deflection is per ASTM D1056 and resilience per ASTM D2632; per-grade values are per the TDS on file. [1]
Immersion cooling system sealing
Immersion cooling changes the sealing question: the gasket is no longer keeping water out of an electrical box, it is living in continuous contact with a dielectric fluid, a synthetic ester, hydrocarbon, or fluorinated chemistry chosen by the tank maker. Elastomer selection follows the fluid, not the fixture.
The dossier maps FKM as the working fluid-side family for tank lid gaskets, sight-glass seals, and feedthrough grommets, with Viton sponge where a conformable closed-cell form is needed at low closure force, and holds FFKM for the most aggressive chemistries where FKM's compatibility margin is in question.
The honest engineering position is that compatibility is confirmed against the fluid maker's elastomer compatibility data for the specific fluid, not assumed from the family name; swelling, hardness change, and extractables matter more than any single headline number. H-O both families from sheet to drawing; durometer and mechanical values are per the elastomer TDS on file. [10]
Six decisions that drive your cooling-infrastructure material spec
Liquid-cooling material selection is not a single-property choice. The right gasket or insulation satisfies six independent constraints at once, and missing one produces a part that installs cleanly, passes commissioning, and fails in service when glycol reaches the wrong elastomer, a chilled line sweats through its insulation, or a door gasket takes a set and the aisle starts leaking air.
Match the material to the fluid and the location, not to the catalog. The firmest foam will not save a seal that the loop chemistry attacks, and a premium aerogel will not stop condensation if the grade was picked for the wrong line temperature. Read the six factors below before reaching for a part number.
Cryogel Z (below-dew-point chilled lines), ArmaGel HT / HTL (warm supply and return), and Pyrogel XTE (hottest returns; rated to 650 °C service per the dossier) are all "aerogel blanket" on a data sheet. Specifying the warm-line grade on a chilled line is a condensation problem, not a heat-loss problem. Match the grade to the actual line temperature against the dew point.
Read the six factors below in order. Each one constrains the others: the loop fluid narrows the elastomer family, the fire specification overrides the economics, and the line temperature picks the insulation grade before thickness even comes up. Selecting one factor at a time and re-checking the others is the discipline.
Show all 6 selection factors tap to expand
Fluid chemistry decides the elastomer family
Rule — Name the fluid and how it reaches the seal first; dry-side faces take EPDM or neoprene economics, glycol-exposed penetrations take fluorosilicone, and immersed seals take FKM (stepping up to FFKM), each confirmed against the fluid maker's compatibility data.
The single most consequential question on this page: what fluid can reach the seal? A dry-side cabinet gasket never wets, so EPDM or neoprene foam economics win. A coolant manifold penetration sees glycol mist and occasional weeps, which is why the dossier maps fluorosilicone sponge there rather than standard silicone. An immersion tank seal lives in the dielectric fluid itself, which points to FKM, with FFKM held for the most aggressive chemistries.
Name the fluid, its concentration, and the exposure mode (continuous, mist, or none) on the drawing, and confirm the pairing against the fluid maker's elastomer compatibility data; this page frames compatibility qualitatively per the dossier and TDS, not as a guarantee. [10]
Fire rating: V-0 sponge where the enclosure spec demands it
Rule — If the enclosure spec or the authority having jurisdiction (AHJ) calls a flammability class, pick a grade whose TDS shows UL 94 V-0 and name that grade on the drawing; an unrated foam is not rated by sitting inside a rated assembly.
Data center electrical rooms and cooling cabinets inherit fire-safety requirements from the facility specification, and the practical material question is whether the gasket needs a UL 94 V-0 rating. The kSil V-0 silicone sponge range and the RS-series silicone sponge grades carry V-0 ratings on their TDS; SCE-series neoprene foam carries HF-1. The fire requirement overrides cost: when the enclosure standard or the AHJ asks for V-0, an unrated foam is not a candidate at any price.
State the required flammability class on the drawing and let the material TDS, not the family name, carry the rating. [2]
Line temperature against dew point picks the insulation grade
Rule — Put the line temperature and room design dew point on the drawing; below the dew point specify Cryogel Z with vapor control, warm runs take ArmaGel HT / HTL, and the hottest returns take Pyrogel XTE.
Pipe insulation is bought by the degree. Below the room dew point, the job is condensation control: Cryogel Z is the aerogel grade engineered for sub-ambient and chilled-water service, with water-vapor behavior characterized per ASTM E96. Above ambient but in the normal facility-water bands the ASHRAE datacom guidance describes, ArmaGel HT / HTL is the thin flexible default. The hottest return and reclaim lines step to Pyrogel XTE.
The conductivity numbers that drive thickness come from the TDS per ASTM C177. Put the line temperature and the room design dew point on the drawing; the grade falls out of those two numbers. [3] [8]
Compression set decides who survives the door
Rule — For high-cycle, warm doors specify silicone foam or sponge (its compression-set recovery holds across temperature); reserve EPDM and neoprene foam for panels that close once and stay closed, and match firmness to the real closure force.
A gasket that takes a permanent set stops sealing long before it visibly fails. RDHx doors and CDU access panels cycle constantly, and silicone's flat compression-set behavior across temperature is why BISCO silicone foam and silicone sponge own the high-cycle, warm-exhaust locations, while EPDM and neoprene foam cover panels that close once and stay closed. Match firmness to the real closure force: BF-2000 ultra-soft for light doors, the HT-800 ladder where the frame compresses harder.
Compression-deflection and compression-set values are reported per ASTM D1056 on each TDS. State open-close frequency and service temperature at the seal, and pick the chemistry before the firmness. [1]
Sealed enclosures breathe: plan the pressure path
Rule — Give any tightly sealed, thermal-cycling enclosure one deliberate pressure path — a ePTFE vent membrane patch equalizes pressure while blocking liquid water; size it from the membrane maker's airflow data for the enclosure volume.
Seal a CDU cabinet well and it starts breathing through whatever you left open: every thermal cycle swings internal pressure, pumping humid air past the gaskets and condensing moisture inside. The fix is to give the cabinet a deliberate pressure path: a ePTFE vent membrane patch equalizes pressure while its hydrophobic pore structure blocks liquid water. The vent is not a substitute for the gasket; it is what lets the gasket do its job without the enclosure fighting its own pressure differential.
Specify a vent location on any tightly sealed enclosure that thermal-cycles, and size it with the maker's airflow data for the enclosure volume.
Vibration isolation keeps the pump out of the rack
Rule — Treat the isolation pad as a spring: state the supported mass and footprint on the drawing so the microcellular-urethane firmness grade loads into its working deflection range rather than bottoming out.
CDU pumps and RDHx fans inject structure-borne vibration into cabinets that share floors, and sometimes frames, with running servers. Die-cut microcellular urethane pads (PORON Industrial) under pump skids and at RDHx mounting points isolate that energy, and their low compression set per the maker's TDS (tested per ASTM D3574) is what keeps the isolation working years in, where a cheap open-cell foam would collapse and couple the vibration straight through.
Treat the pad as a spring: state the supported mass and footprint on the drawing so the firmness grade loads the pad into its working range rather than bottoming it out. [6]
Specification Tools
Three tools to take you from "I have a liquid-cooling sealing problem" to here's what to put on the drawing: a coolant-loop seal picker that maps your fluid and seal location to an elastomer family, a side-by-side comparison matrix of every material family on this page, and a pipe-insulation lookup that pairs your line temperature with the right aerogel grade.
1. Coolant-loop seal picker by fluid and location
Pick the fluid in the loop and where the seal lives. The picker maps them to a recommended elastomer or membrane family with the reason. Qualitative, per the dossier mapping and the material TDS; confirm the pairing against the fluid maker's elastomer compatibility data for your specific fluid.
Pick a fluid, a location, and a fire requirement to see a recommendation
The result returns a recommended material family, the reason it fits your fluid and location, and a one-click path to its entry in the material reference below.
2. Side-by-side: cooling-infrastructure material matrix
Every material family called out on this page, with its construction, service role, flame data as reported on its TDS, and the zone it fits. Click a column header to sort. Click any material name to jump to its accordion entry and full TDS reference.
| Material | Construction | Flame data (TDS) | Key test methods | Form factor | Suited to | |
|---|---|---|---|---|---|---|
| Enclosure & containment gaskets | ||||||
| EPDM Foam (RE41E–RE45E, 553, 563)Closed-cell EPDM, soft to firm | Closed-cell foam | Per grade TDS | ASTM D1056, D2632 | CDU doors, containment | ||
| kSil V-0 Silicone SpongeFlame-resistant, super-soft to firm | Closed-cell sponge | UL 94 V-0 (TDS) | ASTM D1056, UL 94 | Fire-rated gaskets | ||
| RS-Series Silicone Sponge (RS-800/820/840/870)General-purpose FR sponge | Closed-cell sponge | UL 94 V-0 (TDS) | ASTM D1056, D746 | Electrical compartments | ||
| Fluorosilicone SpongeFuel / chemical-resistant sponge | Closed-cell sponge | Per TDS | AMS 3323, ASTM D1056 | Glycol-exposed penetrations | ||
| BISCO Silicone Foam (BF-1000/2000, HT-800 series)Ultra-soft to medium | Closed-cell foam | Per grade TDS (E162/E662 data) | ASTM D1056, E162 | RDHx door gaskets | ||
| Neoprene Foam (SCE41B–SCE45B)Lower-cost containment seal | Closed-cell foam | UL 94 HF-1 (TDS) | ASTM D1056, D2632 | Aisle containment | ||
| Microcellular Urethane (PORON Industrial 4701/4790)Low-compression-set pads | Microcellular foam | Per grade TDS (40V0 = V-0) | ASTM D3574, UL 94 | Pump / fan isolation | ||
| Pipe & manifold insulation | ||||||
| Cryogel ZSub-ambient / chilled aerogel | Aerogel blanket | ASTM E84 data (TDS) | ASTM C177, E96 | Below-dew-point lines | ||
| ArmaGel HT / HTLThin flexible blanket | Aerogel blanket | ASTM E84 data (TDS) | ASTM C177, C1728 | Warm supply / return | ||
| Pyrogel XTEHigh-temp industrial blanket | Aerogel blanket | ASTM E84 data (TDS) | ASTM C177, C447 | Hottest return lines | ||
| Fluid-side & venting | ||||||
| FKM Fluoroelastomer (75D solid + Viton Sponge 1628)Working immersion-seal family | Solid sheet / sponge | Per TDS | ASTM D2240, D412 | Immersion tank seals | ||
| FFKM Perfluoroelastomer (GP 70/75D, Steam 75D)Step-up chemistry | Solid sheet | Per TDS | Per maker TDS | Aggressive fluid chemistries | ||
| ePTFE Vent MembraneHydrophobic pressure equalization | Expanded PTFE membrane | Per maker datasheet | Per maker datasheet | Sealed CDU breathing | ||
3. Pipe-insulation lookup by line temperature (qualitative)
Pick where your line runs relative to room conditions; the lookup returns the aerogel blanket grade the dossier maps to that band and why. Qualitative guidance only; thickness and conductivity design values come from the grade's TDS per ASTM C177.
line temp vs dew point → grade; thickness per TDSGrade mapping per the H-O dossier; conductivity design values per ASTM C177 on each grade's TDS.
Skip ahead and request your engineering review now
If your drawing already calls out an EPDM, silicone-sponge, fluorosilicone, aerogel, urethane, ePTFE, or fluoroelastomer grade, send it over for engineering review.
Cooling-infrastructure failures you can prevent at spec
Liquid-cooling material failures rarely show at commissioning. The cabinet seals, the loop holds pressure, the aisle reads tight. Then months later a manifold gasket softens under glycol exposure, a chilled line sweats through its insulation onto a cable tray, or a rear door stops sealing because its gasket took a set. Five patterns cover most of what fails in this zone, and each is a specification decision made before the first rack powers on.
Coolant-loop seal failures are chemistry failures on a delay. An elastomer the fluid attacks does not leak on day one; it swells, softens, or hardens over weeks until the sealing force is gone. The fix is at spec, against the fluid maker's compatibility data, not at the leak.
Show all 5 failure modes tap to expand
1. Standard silicone sponge at a glycol-exposed penetration
Fix — Classify every seal by what fluid can reach it: dry-side doors stay on standard silicone or EPDM, mist- or weep-exposed penetrations move to fluorosilicone sponge, and immersed seals move to the fluoroelastomer families — each confirmed against the fluid maker's compatibility data.
A silicone sponge gasket goes in at a coolant manifold penetration because it sealed the door beautifully. Months later the gasket near the manifold has softened and swollen where glycol mist and the occasional weep reach it, and the seal force is gone. Silicone elastomers are a poor match for sustained glycol exposure; that is exactly why the dossier maps fluorosilicone sponge, the fuel- and chemical-resistant sibling, to CDU manifold penetrations.
The fix: classify every seal location by what can reach it. Dry-side doors can stay on standard silicone sponge or EPDM economics; anything in the mist or weep path of the loop moves to fluorosilicone, and anything immersed moves to the fluoroelastomer families. Confirm the pairing against the fluid maker's elastomer compatibility data. [7]
2. Warm-line aerogel on a below-dew-point chilled line
Fix — Put the line temperature and room design dew point on the drawing; if the line runs below the dew point, specify the sub-ambient grade (Cryogel Z) and detail the vapor-control jacket and seam sealing, not just the blanket.
An aerogel blanket grade that performs perfectly on a warm return gets specified on a chilled supply running below the room dew point. The line sweats: water vapor drives through and condenses at the cold pipe wall, the insulation wets, conductivity climbs, and water finds the cable tray below. Sub-ambient lines are a condensation-control problem first, which is why Cryogel Z, with water-vapor behavior characterized per ASTM E96 on its TDS, is the dossier's grade for below-dew-point service.
The fix: put the line temperature and the room design dew point on the drawing; if the line runs below the dew point, specify the sub-ambient grade and detail the vapor-control jacket and seam sealing, not just the blanket. [5]
3. Door gasket compression set on a high-cycle RDHx
Fix — For high-cycle, warm-side doors specify a silicone foam or sponge with compression-set data per ASTM D1056 on the TDS, and match firmness to the door's real closure force so the gasket works in its design deflection range.
A rear-door heat exchanger door opens and closes thousands of times over its life, much of it warm. An organic foam gasket that tested fine at commissioning gradually takes a permanent set, the door stops sealing against the rack frame, and hot exhaust starts bypassing the coil; rack inlet temperatures drift up with no visible fault. Silicone foam holds its compression-set behavior across temperature far better than organic foams, which is why BISCO BF / HT-series silicone foam owns this location.
The fix: for high-cycle, warm-side doors, specify a silicone foam or sponge grade with compression-set data per ASTM D1056 on the TDS, and match firmness to the door's real closure force so the gasket works in its design deflection range. [1]
4. Sealed CDU breathes through its gaskets and condenses inside
Fix — Give every sealed, thermal-cycling enclosure a deliberate pressure path: a ePTFE vent membrane patch equalizes the swing while blocking liquid water; size the vent from the maker's airflow data and keep the gasket spec unchanged.
A tightly gasketed CDU cabinet thermal-cycles with the loop. Every cycle swings the internal pressure, and with no engineered vent the cabinet inhales humid room air through whatever path yields first, usually a corner of the gasket, then condenses that moisture on the coldest internal surface. Electronics and instrument bays corrode in a cabinet that was sealed too well. The fix: give every sealed, thermal-cycling enclosure a deliberate pressure path: a ePTFE vent membrane patch equalizes the swing while blocking liquid water.
Size the vent area from the membrane maker's airflow data for the enclosure volume and cycle profile, and keep the gasket spec unchanged; the vent and the gasket are partners, not alternatives.
5. Pump vibration couples into the racks because the pad bottomed out
Fix — Treat the pad as a spring: put supported mass and footprint on the drawing, pick the microcellular-urethane firmness grade so bearing pressure lands in its working range per the TDS, and re-check after any pump or skid change.
A CDU pump skid gets set on a generic foam pad that felt right by hand. Loaded, the pad compresses to near-solid, the isolation vanishes, and pump vibration travels through the floor and frames into racks of spinning media and connectors. Isolation only happens when the pad operates in its working deflection range, which is a function of supported mass, pad footprint, and the grade's compression-deflection curve.
The fix: treat the pad as a spring. Put the supported mass and footprint on the drawing, pick the microcellular urethane firmness grade so the bearing pressure lands in the grade's working range per the TDS (tested per ASTM D3574), and re-check after any pump or skid change. Low compression set is what keeps the isolation working in year five.
Material reference
Detailed reference for the thirteen material families on this page: the enclosure and containment gaskets (EPDM foam, kSil V-0 and RS-series flame-rated silicone sponge, fluorosilicone sponge, BISCO silicone foam, SCE-series neoprene foam); the vibration pads (microcellular urethane); the pipe-insulation grades (Cryogel Z, ArmaGel HT / HTL, Pyrogel XTE); the fluid-side seal families (FKM with Viton Sponge, FFKM); and the ePTFE vent membrane.
Compression-deflection is tested per ASTM D1056, urethane properties per ASTM D3574, thermal conductivity per ASTM C177, and flame ratings per UL 94 as listed on each TDS. H-O and converts all of them to drawing; per-grade values are per the TDS on file, not headline numbers.
EPDM Foam (RE41E–RE45E, 553, 563)Closed-cell EPDM · CDU doors, containment panels · soft-to-firm ASTM D1056 ladder
EPDM foam is the general-economics gasket on this page: specify it wherever the seal stays dry-side and no V-0 flame rating is called out. Where the enclosure specification requires UL 94 V-0, move to the kSil V-0 or RS-series silicone sponge; where glycol can reach the seal, move to fluorosilicone sponge. Per-grade compression-deflection values are per the TDS on file.
kSil V-0 Flame-Resistant Silicone SpongeUL 94 V-0 per TDS · fire-rated CDU & compartment gaskets · super-soft to firm
The fire requirement is the gate: when V-0 is called out, unrated foams leave the candidate list regardless of cost. kSil V-0 carries the rating on its TDS across a super-soft-to-firm range; the RS-series below is the general-purpose alternative with the same rating class. Values are per the TDS on file.
RS-Series Silicone Sponge (RS-800 / 820 / 840 / 870)General-purpose FR sponge · UL 94 V-0 per TDS · medium / firm / very firm / soft
RS-800 is the medium default; step softer (RS-870) for low-closure-force covers and firmer (RS-820 / RS-840) for bolted or firmly latched panels. The V-0 listing is per the TDS; verify the rating at your specified thickness during drawing review.
Fluorosilicone SpongeGlycol / fuel / chemical-resistant · coolant manifold penetrations · AMS 3323 family
Fluorosilicone buys chemical resistance at a price premium over standard silicone sponge, so spec it where the exposure actually is: the dossier maps it specifically to glycol-exposed penetrations, not to every gasket on the cabinet. Confirm fluid pairing against the fluid maker's compatibility data; cellular values are per the TDS on file.
BISCO Silicone Foam (BF-1000 / BF-2000, HT-800 / 820 / 840 / 870)Ultra-soft to medium · RDHx frame & high-cycle door gaskets · ASTM D1056 per TDS
Specify silicone foam where the door cycles and runs warm: its compression-set behavior across temperature is the property that keeps the seal alive. Match the grade to the real closure force so the gasket operates at mid-deflection. Per-grade values are per the BISCO TDS on file.
Neoprene Foam (SCE41B–SCE45B)Lower-cost containment seals · UL 94 HF-1 per TDS · soft-to-firm ladder
Neoprene foam wins on converting economics for long containment runs; EPDM takes over where UV/ozone exposure or outdoor-adjacent service appears, and silicone sponge takes over where a V-0 rating or high-cycle warm service is called out. HF-1 listings are per the TDS at specific thicknesses.
Microcellular Urethane Foam (PORON Industrial 4701 / 4790 Series)Pump & RDHx vibration pads · low compression set · ASTM D3574 per TDS
Isolation is a sizing exercise, not a material brand: state the supported mass and pad footprint on the drawing so the firmness grade loads into its working range instead of bottoming out. Low compression set per the TDS is what keeps that working range stable for years. The V-0 grade (4701-40V0) covers flame-rated locations.
Cryogel Z Aerogel BlanketBelow-dew-point & chilled lines · vapor control · ASTM C177 / E96 per TDS
On a sub-ambient line the failure mode is sweating, not heat gain: specify the sub-ambient grade and detail the vapor-control jacket and seam sealing on the drawing. Size thickness from the TDS conductivity values for your line and ambient; this page keeps the numbers on the TDS where they belong.
ArmaGel HT / HTL Aerogel BlanketWarm supply & return runs · thin flexible wrap · ASTM C177 per TDS
ArmaGel HT / HTL is the default once a line runs above ambient: thin, flexible, and die-cuttable into fitted parts that install repeatably, with conductivity and surface-burning data on the TDS. Below the dew point, switch to Cryogel Z; on the hottest reclaim lines, step up to Pyrogel XTE.
Pyrogel XTE Aerogel BlanketHottest return & reclaim lines · max use temp 650 °C (1200 °F) per the Pyrogel XTE TDS (ASTM C447) · ASTM C177 per TDS
Pyrogel XTE brings industrial high-temperature headroom to lines that will never approach its rating, which makes the margin a property of the material rather than the installation. Specify it where the return or reclaim line runs hottest, and size thickness from the TDS conductivity values.
ePTFE Protective Vent MembranePressure equalization on sealed CDUs · hydrophobic · vent patches
The vent complements the gasket; it never replaces it. Specify a vent on any tightly sealed enclosure that thermal-cycles, locate it away from spray paths, and size the open area from the maker's airflow data. H-O membrane sheet into patches and disks to drawing.
FKM Fluoroelastomer (75 Durometer Solid + Viton Sponge 1628)Immersion tank seals · dielectric-fluid contact · values per TDS
Elastomer selection in immersion systems follows the fluid, not the fixture: swelling, hardness change, and extractables against your specific fluid decide the family. FKM is the working default per the dossier; confirm against the fluid maker's elastomer compatibility tables, and step up to FFKM where the margin is in question.
FFKM Perfluoroelastomer (GP 70 / 75D, Steam 75D)Step-up chemistry for aggressive fluids · near-universal resistance per dossier
FFKM is the premium answer, so reserve it for where the chemistry demands it; FKM covers the common ester and hydrocarbon fluids at a fraction of the material cost. State the fluid, temperature, and exposure on the drawing and let the compatibility data make the call.
Data center liquid cooling: engineer-grade FAQ
Twelve of the questions we hear most from cooling-hardware engineers, facility teams, and OEM purchasing. If your question isn't here, send a drawing or call, engineering picks up.
Which gasket material do I use on a CDU door?
For a dry-side CDU door or access panel, closed-cell EPDM foam (RE41E–RE45E) is the economics default, with the grade picked so the door closes and the gasket works at mid-deflection. If the enclosure specification calls a UL 94 V-0 seal material, move to kSil V-0 or RS-series silicone sponge, both of which carry V-0 listings on their TDS. If the door cycles frequently or runs warm, silicone foam or sponge also wins on compression set. Compression-deflection values are per ASTM D1056 on the TDS on file. [1]
What seals a coolant manifold penetration where glycol can reach the gasket?
A fluorosilicone sponge. Standard silicone sponge is a poor match for sustained glycol exposure, so where mist, drips, or a weep can reach the seal at a manifold or pipe penetration, the dossier maps the fuel- and chemical-resistant fluorosilicone sibling (AMS 3323 family). Keep the standard silicone or EPDM grades for the dry-side gaskets on the same cabinet, and confirm the pairing against the fluid maker's elastomer compatibility data for your specific coolant and concentration. [7]
Which elastomer works in an immersion cooling tank?
Selection follows the fluid, not the fixture. For the common synthetic-ester and hydrocarbon dielectric fluids, FKM (75 durometer solid, with Viton Sponge 1628 for conformable lids) is the working family per the dossier. For the most aggressive chemistries, including some fluorinated fluids and hot spots near heaters, FFKM (GP 70/75D, Steam 75D) is the step-up with near-universal chemical resistance. In every case, confirm swelling, hardness change, and extractables against the fluid maker's elastomer compatibility tables before freezing the spec. [10]
Which insulation goes on a chilled line that runs below the dew point?
Cryogel Z, the aerogel blanket grade engineered for sub-ambient and chilled service. Below the dew point the problem is condensation control: the insulation must hold its jacket surface above the room dew point and resist water-vapor drive toward the cold pipe, behavior characterized per ASTM E96 on the TDS. Detail the vapor-control jacket and seam sealing on the drawing along with the blanket, and size thickness from the TDS conductivity values (ASTM C177) for your line temperature and ambient. [5]
ArmaGel vs Pyrogel vs Cryogel: how do the aerogel grades split?
By line temperature. Cryogel Z covers below-dew-point and chilled lines (sub-ambient engineering, vapor control). ArmaGel HT / HTL covers the warm supply and return runs that make up most of the loop, as a thin flexible wrap. Pyrogel XTE covers the hottest return and heat-reclaim lines; the dossier rates the family for service to 650 °C, so coolant temperatures sit deep inside its envelope.
All three report conductivity per ASTM C177 and surface burning per ASTM E84 on their TDS; pick the grade from the line temperature against the dew point, then size thickness from the TDS. [3]
What gaskets seal hot/cold aisle containment panels?
Closed-cell EPDM foam or SCE-series neoprene foam, cut as long perimeter strips and door seals. The duty is indoor, dry, and high-quantity, so converting economics dominate: neoprene foam (UL 94 HF-1 data per TDS) is the lower-cost mapping in the dossier, with EPDM beside it for ozone/UV-adjacent service. Measure the real panel and door gaps, pick a firmness that still lets panels latch, and cut strip widths to the panel system on the drawing. Every joint that leaks is bypass airflow the plant pays for. [1]
Do I need a UL 94 V-0 rated gasket in a data center cooling cabinet?
When the enclosure specification, the facility fire engineering, or the authority having jurisdiction calls for it, yes, and the requirement then overrides material economics. The kSil V-0 range and the RS-series silicone sponge carry UL 94 V-0 listings on their TDS; SCE neoprene foam carries HF-1. Two cautions: ratings are per grade and per thickness, so verify the listing at your specified gauge, and the fire-protection framing for IT spaces sits in standards like NFPA 75, which your facility engineer maps to the equipment level.
State the required class on the drawing and let the TDS carry the rating. [2]
Why does my sealed CDU cabinet collect moisture inside?
Because it breathes. A tightly gasketed cabinet thermal-cycles with the loop, and every cycle swings internal pressure; with no engineered vent, the cabinet inhales humid room air through whatever path yields first and condenses that moisture on the coldest internal surface. The fix is a ePTFE vent membrane patch: its hydrophobic pore structure equalizes pressure while blocking liquid water. Size the vent open area from the membrane maker's airflow data for the enclosure volume and cycle profile, and keep the gasket spec unchanged.
What pad goes under a CDU pump to keep vibration out of the racks?
A microcellular urethane pad (PORON Industrial 4701 / 4790 series), sized so the supported mass loads the pad into its working deflection range. The grade's low compression set per the maker's TDS (tested per ASTM D3574) is what keeps the isolation working over years of service; a generic foam that bottoms out couples the vibration straight through. Put the supported mass and footprint on the drawing and let the firmness grade follow. The 4701-40V0 grade carries a UL 94 V-0 listing where the location demands it. [6]
What does ASHRAE's liquid-cooling guidance mean for gasket and insulation specs?
The ASHRAE datacom liquid-cooling guidance defines facility-water temperature classes (the W classes) that frame how warm a loop is allowed to run. For materials, the class sets the service temperature your seals and insulation see: warmer classes push more locations toward silicone-chemistry seals (compression set at temperature) and confirm that warm-line insulation grades like ArmaGel HT / HTL are operating well inside their envelope.
This page cites the guidance qualitatively, by designation; your thermal engineer owns the class selection, and the material TDS owns the temperature limits. [8]
Can H-O cut these materials to our drawing, and how do orders run?
Yes. H-O Products is a precision converter: we die-cut, kiss-cut on liner, slit, and laminate gasket, foam, sponge, aerogel, membrane, and elastomer sheet stock to your drawing as an ISO 9001:2015 certified organization in Winsted, Connecticut. Everything is made-to-order against the drawing, with material traceability and lot-code TDS records; MOQ varies by material and part.
H-O does not extrude or mold raw material in-house; extruded or molded profiles are coordinated through a partner network. Lead-time details are on the process strip above and in the quote form below.
Why frame strength and compatibility values as "per the TDS on file"?
Because the honest number depends on grade, thickness, compression, temperature, and, for fluid contact, the exact fluid and concentration. A single headline figure flatters one condition and misleads the rest.
This page names the governing test methods (ASTM D1056 compression-deflection, ASTM C177 thermal conductivity, ASTM E96 vapor transmission, UL 94 flammability, ASTM D3574 cellular urethane) and keeps per-grade values on the manufacturer TDS, which H-O reviews against your drawing during quoting. Fluid compatibility is confirmed against the fluid maker's data, not assumed from a family name.
We're between rear-door heat exchangers and full liquid loops. Does the material set change?
Less than you'd expect, which is good news for standardization. RDHx deployments use the silicone-foam door gasket, urethane mounting pads, and warm-line aerogel set; full CDU-based loops add the manifold-penetration fluorosilicone, the ePTFE vent, and more pipe insulation; immersion adds the fluoroelastomer fluid-side seals. The families repeat across stages, so a drawing package standardized on this page's material set carries from the first RDHx retrofit through a full liquid build-out, with the same TDS layer and the same converter behind it.
Glossary: terms used on this page
Quick reference for the liquid-cooling, gasket, and insulation terminology used throughout. Each entry links to the relevant test method or section where applicable.
CDU (coolant distribution unit)
The cabinet that joins the facility water system to the technology cooling loop serving the racks: heat exchanger, pumps, controls, and manifolds in one enclosure. On this page it is four sealing jobs in one box: dry-side door gaskets, glycol-exposed penetration seals, a pressure-equalization vent, and pump isolation pads.
RDHx (rear-door heat exchanger)
A liquid-cooled coil that replaces a server rack's rear door, removing heat from the exhaust air before it enters the room. The frame-to-rack gasket is the critical converted part: a soft closed-cell silicone foam that seals through thousands of door cycles so exhaust air goes through the coil, not around it.
Dew point / below-dew-point line
The air temperature at which room moisture condenses. A coolant line running below the room dew point will sweat unless its insulation holds the jacket surface above dew point and resists vapor drive; that condensation-control duty is what separates the sub-ambient insulation grade (Cryogel Z, vapor behavior per ASTM E96 [5]) from the warm-line grades.
Hot / cold aisle containment
Physical separation of supply and exhaust air in the white space using panels, doors, and roof sections over the aisles. Every unsealed joint is bypass airflow the cooling plant must make up, so the converted parts are long perimeter gasket runs in EPDM or neoprene foam, cut to the panel system.
Immersion cooling (single-phase)
Cooling servers by submerging them in a tank of non-conductive (dielectric) fluid that carries heat to an exchanger. Every tank seal lives in continuous fluid contact, so elastomer choice follows the fluid chemistry: FKM as the working family, FFKM for the most aggressive fluids, confirmed against the fluid maker's compatibility data.
Dielectric fluid
An electrically non-conductive heat-transfer fluid, typically a synthetic ester, hydrocarbon, or fluorinated chemistry, used in immersion cooling. For seals, the fluid is the specification: swelling, hardness change, and extractables against the specific fluid decide the elastomer family before any mechanical property does.
Compression set
The permanent deflection a foam or sponge retains after sustained compression, the property that quietly kills door gaskets. A gasket with high set stops pushing back and stops sealing. Silicone foams and sponges hold low set across temperature, which is why they own high-cycle, warm-side doors; set data is reported per ASTM D1056 [1] on each TDS.
UL 94 V-0 / HF-1
Flammability classifications under UL 94 [2], the standard for flammability of plastic materials in devices and appliances. V-0 is a vertical-burn rating; HF-1 is a horizontal-burn rating for cellular foams. Ratings are listed per grade and per thickness on each material TDS; verify the listing at your specified gauge, not just the family name.
Closed-cell vs open-cell foam
Closed-cell foams trap gas in discrete cells, so they resist water and air transmission and make environmental seals; open-cell foams interconnect and breathe, suiting acoustics and filtration. Every perimeter gasket on this page (EPDM, neoprene, silicone foam and sponge, fluorosilicone) is closed-cell; classification and grading follow ASTM D1056 [1].
Aerogel blanket
Flexible insulation made by reinforcing silica aerogel, among the lowest-conductivity solid insulations, with a fiber batt. It delivers a given thermal resistance in a fraction of conventional thickness, which matters in cable-dense plant galleries. Conductivity is tested per ASTM C177 [3]; this page's grades are Cryogel Z, ArmaGel HT / HTL, and Pyrogel XTE.
ePTFE vent membrane
Expanded PTFE: a micro-porous, hydrophobic membrane that passes air but blocks liquid water. Die-cut into vent patches, it gives sealed enclosures a deliberate pressure-equalization path so thermal cycling doesn't pump humid air past the gaskets. Airflow sizing comes from the membrane maker's datasheet.
Facility water / ASHRAE W classes
The ASHRAE datacom liquid-cooling guidance defines facility-water temperature classes (the W classes) that frame how warm the loop runs. For converted parts, the class sets the service temperature at seals and insulation: warmer classes favor silicone-chemistry gaskets and confirm warm-line aerogel grades operate inside their envelope. Cited qualitatively on this page. [8]
Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
Standards, test methods & technical references
The standards, test methods, and vendor technical data sheets cited throughout this page. Standards editions current as of June 2026; verify against the publishing body before final spec. H-O converts materials that are tested to these methods on the source manufacturer's TDS; H-O does not independently certify materials unless explicitly stated on the quote.
ASTM D1056
Standard Specification for Flexible Cellular Materials, Sponge or Expanded Rubber. The compression-deflection classification system behind the EPDM, neoprene, silicone sponge, silicone foam, and fluorosilicone grades on this page. astm.org/d1056
UL 94
Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances. The V-0 and HF-1 ratings cited on the silicone-sponge, neoprene-foam, and urethane TDS; listings are per grade and thickness. shopulstandards.com (UL 94)
ASTM C177
Standard Test Method for Steady-State Heat Flux Measurements and Thermal Transmission Properties by Means of the Guarded-Hot-Plate Apparatus. The conductivity method behind the aerogel-blanket thermal values on the TDS. astm.org/c0177
ASTM E84
Standard Test Method for Surface Burning Characteristics of Building Materials. The flame-spread / smoke-developed method cited on the aerogel-blanket TDS for plant-space installation. astm.org/e0084
ASTM E96
Standard Test Methods for Water Vapor Transmission of Materials. The vapor-drive characterization relevant to below-dew-point insulation; cited on the sub-ambient aerogel TDS. astm.org/e0096
ASTM D3574
Standard Test Methods for Flexible Cellular Materials, Slab, Bonded, and Molded Urethane Foams. The property methods behind the microcellular-urethane pad values, including the compression-set behavior that keeps isolation pads working. astm.org/d3574
AMS 3323
SAE Aerospace Material Specification for fluorosilicone sponge. Cited on the fluorosilicone sponge TDS; the family this page maps to glycol-exposed manifold penetration seals. sae.org (AMS 3323)
ASHRAE datacom liquid-cooling guidance (TC 9.9)
The ASHRAE Technical Committee 9.9 datacom series on liquid cooling, which defines the facility-water temperature classes (the W classes) referenced qualitatively on this page. Class selection belongs to the facility thermal design; material temperature limits stay on each TDS. Refer to the ASHRAE datacom series for the W-class definitions.
BISCO & PORON technical data sheets
Manufacturer TDS for the BISCO BF / HT silicone foams and PORON industrial urethanes cited on this page: compression-deflection per ASTM D1056, urethane properties per ASTM D3574, UL 94 listings, and E162 / E662 flame and smoke data per grade.
Aerogel blanket technical data sheets (ArmaGel; Cryogel Z / Pyrogel XTE)
Manufacturer TDS for the three aerogel grades on this page: thermal conductivity per ASTM C177, surface burning per ASTM E84, water-vapor behavior per ASTM E96 (Cryogel Z), and the C-series insulation test methods listed per grade. Per the Pyrogel XTE TDS, Pyrogel XTE carries a maximum use temperature of 1200 °F (650 °C) determined per ASTM C447 (Estimation of Maximum Use Temperature).
Fluoroelastomer (FKM / FFKM) technical data, TDS on file
Per-grade TDS on file with H-O for the 75-durometer FKM solid, Viton Sponge 1628, and the FFKM GP / Steam grades: durometer per ASTM D2240, tensile per ASTM D412. Fluid compatibility for immersion service is confirmed against the fluid maker's elastomer compatibility data for the specific fluid, not assumed from the family.
NFPA 75
Standard for the Fire Protection of Information Technology Equipment. The facility-level fire-protection framing within which enclosure and gasket flammability requirements (UL 94 classes) are set; cited by designation, mapping to the equipment level belongs to the facility fire engineer. nfpa.org (NFPA 75)
Updated . Standards editions and links current at publication; verify against the publishing body before final spec. H-O converts materials tested to the methods cited; lot-specific documentation available on request.
Get a liquid-cooling materials engineering quote
Send a drawing, BOM, or spec sheet. We typically respond within one business day with a material-family recommendation, prototype lead time, and TDS verification against your fluid, fire rating, line temperature, and seal locations.
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Material data & standards. All material properties and ratings referenced on this page are taken from the source manufacturer's technical data sheets and the cited standards: compression-deflection per ASTM D1056, cellular-urethane properties per ASTM D3574, thermal conductivity per ASTM C177, water-vapor transmission per ASTM E96, surface burning per ASTM E84, and flammability classifications per UL 94 as listed per grade and thickness.
This page frames performance qualitatively and keeps per-grade values on the TDS, where they belong; fluid compatibility is confirmed against the fluid maker's elastomer compatibility data for the specific fluid. H-O converts materials tested to these methods; H-O does not independently certify materials against the standards unless explicitly stated on the quote. Verify against the vendor TDS for your specific application.
Conversion scope. H-O and converts sheet, roll, and blanket stock to drawing in Winsted, Connecticut: die-cut and kiss-cut-on-liner gaskets, slit strip, fitted insulation sleeves and wraps, and multi-layer laminations, with material traceability and lot-code TDS records, as an ISO 9001:2015 certified organization. H-O does not extrude or mold raw material in-house; extruded or molded profiles are coordinated through a partner network. Lead-time and MOQ details are on the process strip and in the quote form above.