GSMH Stationary Single Cartridge Mechanical Seal for Sulzer APP Chemical Pumps

The GSMH is our standard stationary single cartridge seal built for the Sulzer APP chemical pump. We specify it where a plant needs a dependable single-containment barrier on a clean or mildly aggressive fluid, and where the pump geometry follows the APP layout. After eighteen years of building seals for this duty, we treat GSMH as the baseline choice rather than a custom fix.

Design basis: stationary pusher, not rotary

Its design rests on a stationary pusher cartridge arrangement. In a stationary seal, the spring-loaded assembly that maintains face contact does not rotate with the shaft. That matters more than it sounds on APP pumps, because the seal sees frequent start-stop cycles on viscous services. The integral seal-ring structure gives the face set higher dimensional stability at elevated temperature and pressure, so the ring stays put instead of shifting under load.

Why the seal ring is built as one piece

We build the sealing ring as one piece rather than an inlaid insert. Inlaid faces are the source of two failures we still see in the field: ring drop-out and face displacement once the bond lets go at temperature. GSMH holds to 160 °C without that failure mode, which is why we reach for it on hot hydrocarbon and thermal-oil-adjacent services where a standard single seal would not survive a summer turnaround.

One example still sticks with us. A thermal-oil loop at a Southeast Asian oleochemical plant ran an inlaid-ring single seal. It dropped a face during its first summer turnaround. The bond failed around 150 °C, and the pump wept for three weeks before a shutdown could be scheduled. After the swap to GSMH, that same cavity ran 14 months with no face event. We would not claim every install behaves that way, but the failure it removed was exactly the one we designed against.

Cooling ports sized for the larger shafts

For shafts above 35 mm, GSMH carries a 3/8 inch barrier-fluid interface. The larger port is not a cosmetic upgrade. It raises the cooling and flush flow the faces actually receive, and on an 80 or 90 mm shaft running warm process, that extra flow is what keeps the face temperature inside the elastomer limit.

Material selection is a process-chemistry call

Material selection follows the fluid, not a catalogue default. The structural parts are 316 stainless steel, and the springs are Hastelloy C276, which we use because chloride and acid duty attacks ordinary alloy springs first. Rotating faces are silicon carbide or tungsten carbide; stationary faces can be carbon, silicon carbide or tungsten carbide depending on the abrasive load. Elastomers run EPR, Viton, Aflas or Kalrez to match temperature and chemical compatibility, with a PTFE O-ring at the limit sleeve.

Installation: modular cartridge, pre-set at our shop

Installation stays simple because GSMH is a modular cartridge, pre-set in our shop. The fitter bolts the gland, removes the setting clips, and the seal is running. Sulzer APP chambers take the standard sizes 30, 40, 50, 60, 80 and 90 mm, and we ship the impeller spacer ring with the unit so the axial position lines up without field machining.

Piping plans: match the risk, not the habit

On the flush side, GSMH supports the API 682 plans a single seal can use: process-side 01, 02, 03, 11, 12, 13, 14, 21, 22, 31, 32 and 41, plus atmospheric-side 51, 61, 62 and 65A or 65B. The right plan is a function of what the fluid does to the faces, not of what the previous plant standardized on. We review the duty and name the plan rather than leave it to chance.

Operating envelope, stated plainly

The operating envelope is 25 bar, -20 to 160 °C and 20 m/s sliding velocity, across shaft sizes 30 to 90 mm. Those numbers cover most APP applications in chemical and petrochemical service. Where the duty runs hotter, higher pressure, or needs a second containment barrier, we move the conversation to a double seal.

Where GSMH earns its place

GSMH runs across chemical and petrochemical plants, oil and gas, water treatment, pharmaceutical and food lines, hazardous-specialty fluids and marine or offshore packages. Anywhere an APP pump moves fluid that a single seal can contain safely, this is the seal we reach for first.

The single-seal boundary, stated honestly

A single seal is the correct call only when the fluid is not toxic, flammable or volatile enough to demand zero atmospheric leakage. If your service carries that risk, a double seal is the safer specification and we will say so. For the duty GSMH is built for, it carries our 3-year warranty.

FAQ

Q: What is a stationary single mechanical seal and why choose it over a rotary seal for Sulzer APP pumps?

A: A stationary single mechanical seal keeps the spring-loaded face assembly fixed while the shaft rotates. On Sulzer APP chemical pumps with frequent start-stop on viscous fluids, the stationary layout protects the seal ring from drive damage and holds face alignment at temperature. GSMH is our stationary single cartridge seal for APP chambers in sizes 30 to 90 mm.

Q: Which pump does the GSMH mechanical seal fit?

A: GSMH is built for the Sulzer APP pump and other chemical pumps with the matching seal chamber. It covers shaft sizes 30, 40, 50, 60, 80 and 90 mm and ships with the impeller spacer ring for correct axial setting.

Q: What pressure and temperature can the GSMH seal handle?

A: GSMH is rated to 25 bar, -20 to 160 °C and 20 m/s sliding velocity. The one-piece seal ring lets it reach 160 °C without the ring drop-out and face displacement seen in inlaid designs.

Q: What materials are used in the GSMH seal faces and springs?

A: Structural parts are 316SS; springs are Hastelloy C276 for chloride and acid resistance. Rotating faces are SSIC or TC; stationary faces are carbon, SSIC or TC. Elastomers are EPR, Viton, Aflas or Kalrez, with a PTFE O-ring at the limit sleeve.

Q: Which API 682 piping plan applies to the GSMH single seal?

A: GSMH supports process-side plans 01, 02, 03, 11, 12, 13, 14, 21, 22, 31, 32 and 41, plus atmospheric-side 51, 61, 62 and 65A or 65B. The plan is selected from the fluid and face condition, not from plant habit.

Q: Does the GSMH mechanical seal come with a warranty?

A: Yes. GSMH carries our standard 3-year warranty on the core assembly, backed by FBU SEALS field service across the applications listed above.

Q: When should I choose a double seal instead of the GSMH single seal?

A: Choose a double seal when the pumped fluid is toxic, flammable or volatile, or where fugitive-emission rules forbid any leak to atmosphere. GSMH is a single seal and is the right choice only when a single containment barrier is acceptable for the duty.