GDMA Stationary Double Mechanical Seal — The Standard Cartridge Solution for ANSI Chemical Pumps

The GDMA stationary double mechanical seal is FBU SEALS' standardized, modular cartridge seal built for ANSI/ASME B73.1 and B73.2 chemical pumps. It is a true double seal — two sealing faces arranged in a face-to-back (back-to-back) configuration with a buffer or barrier fluid circulating in between. That second line of defense is exactly what makes it the right choice for toxic, flammable or hazardous media where a single seal would leave too much risk on the table. When the inboard face eventually wears, the outboard face still holds the process line, so you get a controlled, planned shutdown instead of an unexpected leak.

What sets the GDMA apart mechanically is its stationary pusher design. The spring compensation sits on the stationary side rather than spinning with the shaft, which avoids the dynamic imbalance and end-face displacement you sometimes see in inlay-type rotating designs. FBU SEALS points out that the GDMA has no ring shedding and no face displacement caused by the inlay process, and it holds stable at a higher temperature limit of up to 160°C. Combined with the double balanced integral ring design, the seal resists pressure fluctuations inside the sealing chamber without the faces lifting or chattering — a common failure mode on aggressive chemical services.

On paper, the GDMA is rated to 25 bar, operates from -20°C to +160°C, handles sliding velocities up to 20 m/s, and covers shaft diameters from 34.9 to 66.67 mm (1.375" to 3.625"). That operating envelope covers the majority of standard ANSI process pumps in the field, so it slots into an existing B73.1 or B73.2 pump without a custom chamber redesign. The modular cartridge format also means the seal arrives pre-assembled and preset — install it, remove the setting clips, and it is running, which cuts commissioning time and removes the alignment errors that come with field-built seal stacks.

Material selection is where the GDMA earns its place on corrosive services. The structural parts are 316SS, including the shaft sleeve, gland, drive rings and deflector. The rotating and stationary faces use silicon carbide (SSIC) or tungsten carbide (TC), with carbon, SSIC or TC options on the stationary side depending on the media. The spring is Alloy 276, and the secondary seals are EPR, Viton, Aflas or Kalrez O-rings backed by a PTFE gasket — so you can spec the exact elastomer and face pairing your fluid demands, from mild solvents up to aggressive acids and hazardous chemicals.

Compatibility is squarely in the ANSI world. The GDMA fits ANSI standard seal chambers and complies with ASME B73.1 and B73.2 pump chamber dimensions, and it is offered specifically as a double cartridge seal for the Durco® Mark 3 pump. It carries dedicated buffer and barrier fluid in/out environmental ports, and it supports the between-seals piping plans 52, 53A, 53B, 53C and 54 — the standard arrangements for feeding and circulating barrier fluid in a double-seal loop. The integrated bidirectional flow path and the unique pump-efficiency ring give a strong, passive barrier-liquid circulation effect without relying on an external pump, which keeps the buffer loop stable and the faces cool.

Because it is a double seal, the GDMA shows up wherever leakage is not an option. Typical applications span the chemical and petrochemical industry, oil, gas and energy, water treatment and environmental engineering, pharmaceutical and food & beverage lines, hazardous chemical and specialized processes, and marine and offshore engineering. In any of these, the seal's job is the same: keep the product in, keep the atmosphere out, and give the plant a predictable, serviceable boundary.

FBU SEALS manufactures the GDMA in China and backs it with a 3-year warranty. If you are qualifying a double seal for an ANSI/ASME B73 chemical pump — especially a Durco Mark 3 — the GDMA gives you a standardized, face-to-back cartridge option with verified materials and a documented piping plan. Reach out with your pump model and media, and we will confirm the chamber fit, face and elastomer selection, and the right piping plan for your barrier system.

FAQ

Q1: What is a GDMA stationary double mechanical seal? A: The GDMA stationary double mechanical seal is FBU SEALS' cartridge-type double mechanical seal for ANSI/ASME B73 chemical pumps. It uses a face-to-back (back-to-back) configuration with two sealing faces and a buffer/barrier fluid in between, rated to 25 bar, -20~160°C and 20 m/s, covering shaft sizes 34.9–66.67 mm, with a 3-year warranty.

Q2: What is the difference between the GDMA double seal and a single seal like the GSMA? A: The GDMA is a double (face-to-back) seal with a buffer/barrier fluid gap, built for hazardous or toxic media; the GSMA is a single seal for less critical services. Both are stationary pusher cartridge seals for ANSI/ASME B73 pumps, but the GDMA adds a second sealing line and supports piping plans 52/53A/53B/53C/54.

Q3: Which pumps is the GDMA double seal compatible with? A: The GDMA fits ANSI standard seal chambers and complies with ASME B73.1 and B73.2 dimensions. It is offered as a double cartridge seal for the Durco® Mark 3 pump and covers shaft diameters from 34.9 to 66.67 mm (1.375"–3.625").

Q4: What piping plans does the GDMA double seal support? A: The GDMA supports the between-seals piping plans 52, 53A, 53B, 53C and 54, which are the standard arrangements for feeding and circulating barrier fluid in a double-seal loop.

Q5: What media can the GDMA double seal handle? A: With 316SS structure, SSIC/TC faces, an Alloy 276 spring and EPR/Viton/Aflas/Kalrez secondary seals, the GDMA handles corrosive chemicals, solvents, flammable liquids and hazardous media across chemical, petrochemical, oil & gas, pharma, water treatment and marine services.

Q6: What materials are used in the GDMA seal? A: Structural parts are 316SS; rotating and stationary faces are SSIC or TC (stationary side also carbon); the spring is Alloy 276; secondary seals are EPR/Viton/Aflas/Kalrez O-rings with a PTFE gasket.

Q7: What is the warranty on the FBU SEALS GDMA seal? A: FBU SEALS provides a 3-year warranty on the GDMA stationary double mechanical seal.