A dash number fixes the size of an O-ring and stops there. What the ring is made of is a second decision, and the dash-number guide says so and hands the compound over to this database. This page takes the 5 elastomers it holds and reads their service windows against each other.
A window is two numbers, sold as one
| Compound | Lowest (°C) | Highest (°C) | Span (°C) | Midpoint (°C) |
|---|---|---|---|---|
| EPDM | -57 | 150 | 207 | 46.5 |
| VMQ | -54 | 204 | 258 | 75.0 |
| NR | -50 | 70 | 120 | 10.0 |
| NBR | -34 | 100 | 134 | 33.0 |
| FKM | -26 | 204 | 230 | 89.0 |
A rubber's temperature range is always quoted as a single fact and is always two. Nothing in the table ties the floor to the ceiling: a compound can be narrow and high, or wide and centred, and both get called good temperature resistance. The span column is the distance between the ends; the midpoint column says where the window sits. Those are the two facts a single number hides.
The cold end separates them, in an order that surprises
Sorted by floor, the order is EPDM at -57 °C, VMQ at -54 °C, NR at -50 °C, NBR at -34 °C, FKM at -26 °C. The distance from the first to the last is 31 °C, and the last of them is FKM — the compound a print reaches for when the medium would destroy everything else on this page, and the one with the least room at the cold end.
FKM is not a narrow window — 230 °C wide, the second widest here — it is an offset one. Wide, and pushed up the scale, which is exactly what the midpoint column measures. Sort them by midpoint instead and the order has nothing to do with the order by floor: the highest midpoint is FKM at 89.0 °C and the lowest is NR at 10.0 °C.
Span and position are two different facts
The widest window belongs to VMQ at 258 °C; the narrowest to NR at 120 °C. The gap between them is 138 °C — wider than the whole of the narrowest window — so "good temperature resistance" is a spread of more than two to one in this table, and says nothing on its own.
NBR is the case worth carrying away. It is the second narrowest of them at 134 °C, its window sits at 33.0 °C, and it is still the family the NBR page calls the default dynamic seal. It is chosen for its media, not for its range.
The band where temperature decides nothing
Put them all together and the common ground is short. From -26 °C — the highest floor, FKM's — to 70 °C — the lowest ceiling, NR's — every one of them is inside its family window. That band is 96 °C wide, and anywhere inside it temperature cannot choose the compound. The medium has to, and the second table is where that column is.
NR at 70 °C, NBR at 100 °C, EPDM at 150 °C, VMQ at 204 °C, FKM at 204 °C
The ladder's last two steps are one step: VMQ and FKM leave together at 204 °C, so the ceiling cannot separate them. The floor can — -54 °C against -26 °C, 28 °C apart — and the media column above says which of the two is for dry heat and which for fuels.
| Compound | Media it is chosen for | ASTM D2000 | Basis and source |
|---|---|---|---|
| EPDM | Water, steam, glycol, brake fluid, ozone; never petroleum oil | AA, BA | family range · Parker O-Ring Handbook ORD 5700, §2.2 |
| VMQ | Dry heat and cold, air, static service; some fuels and solvents | FE | family range · Parker O-Ring Handbook ORD 5700, §2.2 |
| NR | Water, alcohols, organic acids, refrigerants | AA | family range · Apple Rubber standard compound figure (dry heat) |
| NBR | Mineral oils, hydraulic fluid, grease, water | BF | family range · Parker O-Ring Handbook ORD 5700, §2.2 |
| FKM | Fuels, hot oils, acids, aggressive chemistry | HK | family range · Parker O-Ring Handbook ORD 5700, §2.2 |
What the print has to carry
The D2000 column reads NBR BF; EPDM AA, BA; VMQ FE; NR AA; FKM HK — a type and a class per compound, not a family name. A family name is a screening label; the D2000 line is what a drawing can hold a supplier to, and that is the line to put on the print when the seal matters.
The O-ring tables go the other way. They are indexed by dash number, and those records carry no compound column at all — size and material are separate lookups in this database, as they are in the joint.
What the window is not
Every row carries the same basis — family range — and the sources are not one document: 4 of the 5 name Parker O-Ring Handbook ORD 5700, §2.2; 1 of the 5 name Apple Rubber standard compound figure (dry heat).
A family range is a screening number, not a specification. Rubber is a recipe: the same polymer is compounded to different durometers, fillers and cure systems, and the window above is where the family is normally used rather than a limit any particular compound is guaranteed to hold.
All 5 are listed at 70 Shore A here, so hardness does not separate them. That is this database's record rather than a property of the material — compounds of one family are sold softer and harder than this, and durometer moves compression set and extrusion resistance without changing which chemistry the window belongs to.
Where this stops
- How long it lasts. A window says where a family is normally used, not how fast it ages there. No ageing rate is in this database for any of them.
- Swell and compression set. The media column is descriptive prose. There are no percentage swell figures here, so selection by fluid still needs the compound data sheet.
- Pressure and extrusion. None of the numbers above involve pressure, gap or surface finish, and a seal that extrudes fails inside its temperature window.
- Dynamic service. The window does not know whether the joint moves. Some of them carry an explicit warning on their own page — one tears, one is for clamped static joints only.
- Price. Not a column here.
- Which one to use. This page orders windows and prints sources. It does not know your fluid, your cycle or your joint, and it makes no recommendation.
The compound pages are NBR, EPDM, VMQ, NR, FKM, and the rubber family lists what else the database holds.