The temperature on a thread lubricant label is often the limit of a single ingredient, not of the whole compound. This article explains what the number means, what ASME PCC-1-2026 says about it, and how the Moly-B and Nickel 328 ratings are stated. A printable PDF (PB-TD-226) is below. Values are for reference; confirm against the current edition of the governing standard. Send us your bolting list for a quote or call (281) 581-0176.
Related: Thread Lubricants · Moly-B Thread Compound · Nickel 328 Anti-Seize · Nut Factor (K) Guide · How to Lubricate Flange Bolting · All technical docs
What is in a thread lubricant
A thread compound is a mix, not one material. Each part reaches its limit at a different temperature:
- Carrier oil. Makes the compound spreadable and carries the solids into the threads.
- Thickener or binder. Usually a soap. It turns the oil into a paste that stays on the stud.
- Solid lubricants. Molybdenum disulfide (moly), graphite, or metal flakes such as nickel or copper. They separate the thread surfaces under load.
- Additives. Rust inhibitors, tackifiers and fillers. Some of them leave ash once the oil burns off.
All four are there when the nut is tightened, so all four affect the nut factor (K) at assembly.
How headline temperature ratings are often set
Many data sheets show one maximum temperature. Usually it is the melting, oxidation or decomposition point of the ingredient that lasts longest, most often the metal flake. It says nothing about the carrier, the thickener or the other solids, which all fail much sooner (Rocol).
A higher number does not mean a better product at normal flange temperatures. At a few hundred degrees the oil and thickener are still there and control friction, so a 2,400°F rating and a 1,800°F rating can behave the same.
PCC-1-2026 says the same (Appendix K, paraphrased): a lubricant maker’s maximum temperature has not proven to be a reliable sign that a joint will come apart more easily after hot service. The figure is usually the melting or degradation point of the highest-temperature solid. It does not show how the lubricant performs at that temperature. PCC-1 advises users to get test results for materials and conditions like their own.
Where each ingredient reaches its limit
| Ingredient | Where it reaches its limit in air | What happens |
|---|---|---|
| Carrier oil and soap thickener | A few hundred °F. The Nickel 328 carrier has a boiling point above 300°F. | Evaporates or burns off. Only the solids are left. |
| Molybdenum disulfide (moly) | About 750°F (Parker, NASA) | Oxidizes to molybdenum trioxide and sulfur dioxide, and friction rises (Machinery Lubrication). |
| Moly with no air (vacuum or inert gas) | Stable to about 1,706°F (Parker) | A lab figure. A flange joint is open to air. |
| Graphite | Oxidation starts around 570–840°F (SGL Carbon) | Burns away slowly. The rate goes up with temperature. |
| Nickel metal | Melts at 2,651°F (RSC) | The metal itself survives. The rest of the compound is long gone. |
A rating taken from the bottom row tells you nothing about the rows above it. The same applies to moly: the 1,706°F figure holds only without air, so it is not a service limit for a flange in a plant.
Why it matters for torque and disassembly
- Assembly. The nut factor comes from the whole compound with the carrier still in it. PCC-1 App K estimates K at about the friction coefficient plus 0.04. It also reports one lubricant whose K changed by about 50% between 32°F and 100°F. Even small changes in K make large changes in the torque you need.
- The combination counts. The lubricant, stud material and coating each have their own K. Change any one of them and the torque target changes too (App K).
- Start-up retorque. PCC-1 App J-4.2 calls for any hot retorque to be done at 300–450°F, or within 24 hours if the joint runs cooler. This helps avoid problems as the lubricant evaporates. The torque target is adjusted for the nut factor at temperature.
- Disassembly. After hot service the oil and thickener are gone. Whether the nut comes off depends on what is left on the threads at the actual service temperature, plus any ash or residue. The top number on the label does not tell you that.
How the Moly-B and Nickel 328 ratings are stated
Our datasheets give the rating along with what happens to the compound as it gets hotter, so you can see what is left on the threads at your service temperature.
| Moly-B (PB-LD-301) | Nickel 328 (PB-LD-302) | |
|---|---|---|
| Published rating | 750°F, with prorated results to 1,500°F | Cryogenic to 2,500°F |
| What sets the rating | Moly starts to oxidize in air at about 750°F. The rating sits there, not at the 1,706°F no-air figure. | The nickel solids. The datasheet shows how much of the solids reaches its limit at each temperature. |
| Breakdown shown on the datasheet | 67% of the solids decompose at 750°F and 33% at 1,500°F. Most of the 67% is replaced by a byproduct that is also a lubricant and stays intact to 1,200°F. | Melting point of solids: 2% at 350°F, 3% at 1,900–2,000°F, 75% at 2,500°F. Carrier boiling point above 300°F. |
| After the carrier burns off | No ash or silica | No ash or silica. No rust inhibitors, because they turn to ash at the rated temperatures. |
| Nut factor (K) at assembly | 0.100 | 0.172 / 0.144 / 0.120, depending on bolt load |
| Solids content | 74% | 77%, mostly nickel (a blend of three solids) |
Full values are on the Moly-B datasheet and the Nickel 328 datasheet.
Choosing a lubricant for hot service
- Compare products at your actual operating temperature, not by their top ratings.
- Ask what is left on the threads after the carrier burns off, and whether it leaves ash or silica.
- Use the nut factor for that lubricant, bolt material and coating in your torque calculation. See the Nut Factor (K) Guide.
- Where disassembly after hot service matters, ask for test data on similar materials and conditions (PCC-1 App K).
- Check that the lubricant is compatible with the process fluid and the bolting material (PCC-1 Sec. 8). Apply it as described in How to Lubricate Flange Bolting.