Views: 0 Author: Site Editor Publish Time: 2026-08-19 Origin: Site
Picking a seal for a chemical pump is rarely about the seal alone. It is about keeping a fluid that is often hot, pressurized and corrosive exactly where it belongs. Inside the pump. Not turning every maintenance window into a gamble. The FBU SEALS GDMH is a stationary, cartridge-mounted double seal we built for exactly that, with the Sulzer® APP pump as its reference platform.
A single seal is one barrier between the process fluid and the atmosphere. On a chemical pump, that single line is all that separates a clean run from a toxic or flammable release the moment the face wears. A double seal puts two faces in series and packs the gap with clean barrier fluid. So even a worn face vents harmless buffer. Never product. The GDMH goes further and makes the seal stationary. The faces and spring assembly stay put in the gland, and the shaft turns inside them. We like this on bigger shafts and higher speeds, because a rotating assembly spends its energy fighting centrifugal load. The payoff is boring in the best way: the seal keeps its alignment through pressure swings instead of creeping out of position.
The GDMH runs a face-to-back double arrangement, with both seal faces mounted back-to-back so the barrier chamber sits between them. That chamber is fed by the standard plans (52, 53A, 53B, 53C or 54), and this is where the GDMH earns its keep. An integrated bidirectional flow path and a purpose-designed pump-efficiency ring keep the barrier liquid moving on its own, with no external circulation pump required. Both faces are hydraulically balanced and integrally formed rather than inlaid, which is exactly why we do not see the ring-shedding or face-walk that plagues bonded designs once the temperature climbs. The double balanced integral ring also resists the pressure fluctuations common inside a chemical seal chamber, so the faces stay seated when the process breathes.
Most off-the-shelf double seals top out around 120 °C. The GDMH is rated to 160 °C and 25 bar, with sliding velocity to 20 m/s. That headroom is not a spec-sheet vanity number. It is what lets the same seal survive steam-out, hot transfers and pressure spikes that would cook a conventional face. We have put it on hot caustic where every 120 °C seal before it was a quarterly tear-down, and the 160 °C ceiling is the difference between a seal that quietly does its job and one that becomes the reason for the next unplanned shutdown.
It is a modular cartridge, so installation is a matter of sliding it on and setting the clips. No field stacking of faces and springs, no guesswork on stack length. We ship the impeller spacer ring with every unit, and the GDMH covers shaft diameters 30, 40, 50, 60, 80 and 90 mm. Beyond the Sulzer APP it handles general chemical-pump chambers, which makes it a sensible stock item for plants running a mixed fleet. Structurally the wetted frame is all 316SS: sleeve, drive ring, gland, thrust ring, clamp ring, deflector and holders. Springs are Hastelloy C276, which will not pit in corrosive service. Faces come in SSIC or tungsten carbide (TC), and the inboard face can also be carbon depending on what you are pumping. O-rings are offered in EPR, Viton, Aflas or Kalrez so the elastomer matches the fluid rather than forcing you to change the fluid to suit the seal.
You will find the GDMH on chemical and petrochemical lines, oil and gas, water treatment and environmental duty, pharma and food, hazardous-solids handling and marine decks. If your pump moves something you would rather not smell, taste or explain to an inspector, a stationary double seal is the right call. At three weeks lead and three years warranty, the GDMH is an easy one to justify to procurement.
Need a GDMH stationary double seal for your Sulzer APP or chemical pump? Contact FBU SEALS for a quote →
Configuration | Stationary pusher cartridge, face-to-back double seal |
|---|---|
Shaft diameter | 30, 40, 50, 60, 80, 90 mm |
Pressure | ≤ 25 bar |
Temperature | -20 °C ~ +160 °C |
Sliding velocity | ≤ 20 m/s |
Seal chamber | Sulzer® APP pump and general chemical-pump chambers |
Recommended piping plans | Between seals: 52, 53A, 53B, 53C, 54 |
Faces | SSIC / TC (inboard face also carbon) |
Structural parts | 316SS; springs Hastelloy C276 |
O-rings | EPR / Viton / Aflas / Kalrez; PTFE option |
Lead time / warranty | ~3 weeks / 3 years |
Q: What is a stationary double mechanical seal and how is it different from a rotating one?
A: A stationary double mechanical seal holds the seal faces and spring assembly fixed in the gland while the shaft rotates inside them. A rotating seal spins that whole assembly with the shaft. On larger shafts and higher speeds the stationary layout avoids fighting centrifugal load, so the FBU SEALS GDMH stays aligned through pressure swings instead of creeping out of position.
Q: Which pumps does the FBU SEALS GDMH double seal fit?
A: The GDMH is built for the Sulzer APP pump and other general chemical-pump seal chambers. FBU SEALS ships each unit with the impeller spacer ring and covers shaft sizes 30, 40, 50, 60, 80 and 90 mm.
Q: What temperature and pressure can the GDMH chemical pump seal handle?
A: FBU SEALS rates the GDMH stationary double seal for up to 25 bar and -20 °C to +160 °C, with sliding velocity up to 20 m/s. Its 160 °C ceiling comes from the integrally formed, hydraulically balanced ring design rather than an inlaid face.
Q: What barrier fluid piping plan does the GDMH double seal need?
A: The GDMH runs on standard API plans 52, 53A, 53B, 53C or 54 between the two faces. Its integrated bidirectional flow path and pump-efficiency ring circulate the barrier fluid on their own, so you do not need an external barrier-fluid pump.
Q: What are the GDMH seal faces and O-rings made of?
A: GDMH seal faces are SSIC or tungsten carbide (TC); the inboard face can also be carbon. Structural parts are 316SS, springs are Hastelloy C276, and O-rings come in EPR, Viton, Aflas or Kalrez to match the pumped fluid.
Q: How long is the lead time and warranty on the GDMH double seal?
A: FBU SEALS builds the GDMH in China with a typical lead time of about 3 weeks and backs it with a 3-year warranty.
Q: What does face-to-back double seal configuration mean?
A: In a face-to-back double seal the two seal faces are mounted back-to-back so the barrier fluid chamber sits between them. The barrier liquid is fed by an API plan and flushed across both faces, so a worn face only ever vents clean buffer fluid instead of process media.
