Are dry gas seals mechanical seals? Yes, technically — but if you came to that question from a pump problem, the taxonomy is not what will help you. The useful question is whether the device on your search results was engineered for a centrifugal compressor or a centrifugal pump, because those are two different worlds with two different standards. For almost every pump application a maintenance or reliability engineer is likely to face, the correct answer is a pump mechanical seal, and the dry-gas-seal trail leads back to compressor turbomachinery where it belongs.
Are Dry Gas Seals Mechanical Seals?
Yes — a dry gas seal is formally a non-contacting, dry-running mechanical face seal, with rotating and stationary rings just like any other mechanical seal. The first patent went to Kaydon Ring & Seal in 1951, with field deployment in 1952, followed by a competing John Crane patent in 1968. The defining trait is not the rings but the lubricating film: dry gas seals run on a gas film roughly 0.003 mm thick, generated by hydrodynamic lift profiles machined into one face. Standard pump mechanical seals run on a thin liquid film instead.
So the textbook answer to the People-Also-Ask question is “yes.” The honest follow-up is that this classification does not tell a pump owner anything they can act on. A jet turbine and a passenger-car diesel are both internal combustion engines, and that fact will not help anyone pick which one to put under their hood. The decisive question is what process fluid the seal is sitting in and how fast the shaft is turning, and that is where pumps and compressors part company.
The Application Split: Pumps vs Compressors
The pump-versus-compressor divide is anchored in two separate API standards. API 682 covers pump mechanical seals — the contacting, liquid-film face seals built for centrifugal pumps in petroleum, chemical, and gas-processing service. API 692, first published in June 2018, covers dry gas sealing systems for axial, centrifugal, and rotary screw compressors, written to sit alongside the API 617 and API 619 compressor specifications. The fact that the compressor world needed its own dedicated sealing standard, separate from the pump-side API 682 universe, is itself the strongest evidence that these are not interchangeable devices.
The physics drives the standards. Process pumps move liquids at 1,200 to 3,600 rpm, where a thin liquid film between the faces is the lubricant. Centrifugal compressors move gas at speeds from under 3,000 rpm to well above 10,000 rpm, where there is no liquid available and the only viable film is the process gas itself, rendered usable by hydrodynamic groove geometry and a filtered seal-gas supply. API 692 mandates 99.9% filtration down to one micron and seal-gas boosters as standard equipment — a level of support-system complexity that has no analog in pump mechanical seal practice. The plain-language version field engineers use is shorter: for liquids, you do not need a dry gas seal; for gas compressors, you do.
Three Products Buyers Keep Confusing
Three different devices share enough name overlap to derail a search. Naming them cleanly is the single most useful thing an article on this topic can do.
- Compressor dry gas seal. The API 692 device. Lives on centrifugal and rotary compressors running from under 3,000 rpm to well above 10,000 rpm. Runs on a pressurized gas film with a 0.003 mm face gap. Not a pump device.
- Process pump gas seal. A specialized pump seal — same gas-film operating principle, but a fundamentally different design tuned for 1,200–3,600 rpm pump speeds with reduced spring loads, regulated nitrogen barrier gas at 30–50 psi above process pressure, and service capability up to 800°F. Roughly 105,000 units have been sold into pump markets since the first polymer-plant installation in 1992, with about a six-year average operating life. A real but specialized niche, used in pharmaceutical, food, petrochemical zero-emissions, and big-bore solids-handling applications.
- Dry-running mechanical seal. A pump mechanical seal designed to survive intermittent loss of liquid — vapor service, frequent start-stop, vertical cryogenic pumps with cofferdams. Not gas-film lubricated; engineered to handle no-lubrication transients without face damage. This is the device a pump engineer usually wants when they search “dry gas seal” with a dry-running symptom in mind.
The Pumps & Systems “3 Considerations” article actively conflates the first and third of these categories, which is how the confusion ends up in published trade press. Calling the three apart is the precondition for choosing correctly.
When to Choose Which
The decision collapses cleanly once the application is named. Use this table as a 60-second classifier.
| Dimension | Pump Mechanical Seal | Compressor Dry Gas Seal |
|---|---|---|
| Equipment | Centrifugal pump | Centrifugal / rotary compressor |
| Process fluid phase | Liquid | Gas |
| Shaft speed | 1,200–3,600 rpm | Under 3,000 to about 20,000 rpm |
| Lubricating film | Liquid film | Gas film, ~0.003 mm |
| Governing standard | API 682 | API 692 |
| Support system | Flush plan (API Plan 11, 32, 53, etc.) | Filtered seal-gas panel, booster |
| Emission profile | Liquid-side fugitive | Compressor methane/process-gas |
The narrow middle column — process pump gas seal — fits a real but specialized niche of zero-emissions, high-purity, frequent dry-running, or vapor-service pump duty. For routine water, chemical, hydrocarbon, HVAC, and general industrial liquid transport, the pump mechanical seal column is the answer for the same reasons it has always been the answer: the physics fits, the standard fits, and the support infrastructure already exists in plant maintenance shops.
The Verdict for Pump Operators
For pump applications, the correct device is a pump mechanical seal. Compressor dry gas seal hype bleeds into pump conversations through trade press, conference talks, and SEO-driven blog content, but the engineering case for swapping a standard pump seal for a compressor device almost never holds. Pump engineers searching this comparison should be looking at Type 1, Type 2, or Type 21 mechanical seals and cartridge variants, with seal selection driven by process chemistry, temperature, and shaft size. For high-pressure pump duty, the selection logic shifts toward balanced seals and engineered cartridge configurations, but the device family is still the pump mechanical seal.
Bottom Line
If a pump is involved, the answer is a mechanical seal — and if the original concern was dry running rather than dry gas, the device to ask about is a dry-running mechanical seal, not a compressor dry gas seal. Two products, similar names, completely different equipment. Compressor engineers belong on OEM dry-gas-seal channels. Pump engineers belong on the pump mechanical seal selection path, starting with type and arrangement rather than with a category that was never built for their machine.