EDMH Double Cartridge Mechanical Seal: The Economical Double for Centrifugal Pumps

Hot, pressurized, metal-eating fluid in the pump is exactly where a single seal stops being safe. That is the job the EDMH was built for. Rotary pusher, back-to-back double cartridge, sized for the Sulzer APP and similar centrifugal pumps. Two faces, barrier fluid between them. Rated 15 bar, 120 °C. Covers the moderate hazardous duty most plants run every day, without paying for a heavy-duty rating nobody needs.

Why a double seal, and why this one

A single seal is one wall. On a toxic line that wall is the only thing standing between the product and the atmosphere. A double seal stacks two faces in series with clean barrier fluid between them, so a worn face only bleeds buffer, never product. The EDMH is the economical double in the range. Same two-barrier safety, rated for moderate duty at 15 bar and 120 °C. Nobody pays for the 25 bar, 160 °C rating of the GDMH when those numbers never show up on the job. For fluid nasty enough to need two barriers but otherwise a calm duty, the EDMH is the sensible pick.

Balanced faces, springs kept clear of the media

Heat kills more seals than anything else, double or single. An unbalanced face makes more of it, the rubber bakes, then it leaks. The EDMH runs hydraulically balanced faces, runs cooler, draws less power. The multi-spring set sits outside the product stream. Sounds minor. It is not. Slurry, crystallizing stuff, anything that settles, clogs a spring sitting in the flow. Seated outside the stream, the springs stay clean. Load stays even, seal lasts. Balanced doubles on this exact duty routinely outlive unbalanced ones by years. Spring position is most of the reason.

Modular cartridge, fast to fit

It is a cartridge. Slide it on, set the clips, done. No hand-stacking faces and springs, no guessing the stack length in the field. Every unit ships with the impeller spacer ring. Sizes 30, 40, 50, 60, 80, 90 mm. The barrier chamber between the faces runs on the usual plans 52, 53A, 53B, 53C or 54, so the buffer loop is already a layout the plant knows how to run.

Materials that match the fluid

The metal is not the place to save money. The whole wetted side is 316SS. Sleeve, seats, gland, clamp, spring, screws, the intermediate sleeve. Faces are SSIC or tungsten carbide, both sides. O-rings in EPR, Viton, Aflas or Kalrez, with PTFE, FKM, FEP, EPDM also on the list, plus an AF1 or PTFE gasket. Match the elastomer to the fluid, not the other way around. On a mild barrier fluid, EPR is the usual choice and it is left at that. At the edge of the range, that one choice is what keeps the seal alive.

Where the EDMH runs

The EDMH turns up on chemical and petrochem lines, oil and gas, water treatment, pharma, food, hazardous handling, marine decks. Anywhere a Sulzer APP or a standard centrifugal pump needs two barriers without paying for a heavy-duty double. Built in China by FBU SEALS.

Technical specifications

Frequently Asked Questions (FAQ)

Q: What is a double mechanical seal and when is one needed?

A: A double mechanical seal runs two faces in series with barrier fluid between them. If the inboard face wears, only clean buffer comes out, never product. The EDMH is a back-to-back double cartridge for centrifugal pumps like the Sulzer APP. A double is needed whenever the fluid is toxic, flammable or simply unsafe to breathe. That is the duty this seal was built for.

Q: What is the difference between a single seal and a double seal?

A: One barrier versus two. A single seal has one face between product and air. A double has two, split by barrier fluid, so one face failing never dumps product. EDMH is the double. ESMH is the single, meant for benign fluid. Nasty fluid, go double. Clean fluid, the single saves the money.

Q: Which pumps does the FBU SEALS EDMH double seal fit?

A: The EDMH fits the Sulzer APP and other standard centrifugal seal chambers. Each unit ships with the impeller spacer ring. Shaft sizes 30, 40, 50, 60, 80, 90 mm. An APP or a close clone drops right in.

Q: What pressure and temperature can the EDMH centrifugal pump double seal handle?

A: Rated 15 bar, -20 to 120 °C, sliding speed to 20 m/s. That is the moderate hazardous duty most plants run day to day. Figures in that band make the EDMH the right-priced double. Past 120 °C or 25 bar, the GDMH is the one to look at.

Q: What piping plan does the EDMH double seal use?

A: Barrier plans 52, 53A, 53B, 53C or 54 between the faces. These are the standard double-seal arrangements. Most plants already run one of them, so there is nothing new to plumb. On these applications 53A or 54 is what shows up most often.

Q: What are EDMH seal faces and springs made of?

A: Faces are SSIC or tungsten carbide, both rotary and stationary. The wetted structure is all 316SS, including the multi-spring set, and the springs sit outside the product. O-rings in EPR, Viton, Aflas or Kalrez, with PTFE, FKM, FEP, EPDM also available, plus an AF1 or PTFE gasket. Match the elastomer to the fluid. That is the whole game.