You’ve installed the replacement seal, followed the torque specs, and yet, six months later, the pump is leaking again. For maintenance teams operating Sulzer® APP or Ahlstar pumps, repetitive seal failure is more than an inconvenience—it’s a drain on the plant’s profitability and a risk to operational safety.

At FBU Sealing Technology (Suzhou), we’ve analyzed thousands of failed seals from global processing sites. The reality is that the seal itself is rarely "bad" by design; rather, it is often the victim of the invisible conditions inside the stuffing box.

As your technical partner, we’ve identified the three most common "hidden killers" of mechanical seals in Sulzer® equipment and how to fix them.

1. The Barrier Fluid Gap: A Pressure Battle

In double seals (like the JCS2 or our FBU 2240/2285), the barrier fluid is the lifeblood of the seal faces. A common mistake is assuming that simply having fluid in the tank is enough.

• The Problem: If the barrier fluid pressure isn't maintained at 1.5 to 2 bar above the stuffing box pressure, the process media (abrasive pulp or chemicals) will force its way between the faces.

• The FBU Solution: We don't just provide the seal; we provide the engineering support to audit your API Plan 53/54 setup. Our cartridge designs are optimized for fluid circulation, ensuring a stable, pressurized film that keeps contaminants out.

 

2. The "Silent Killer": Micro-Vibrations and Shaft Misalignment

Sulzer® pumps are incredibly robust, but as equipment ages, bearing wear or slight piping strain leads to micro-vibrations. Standard seals are brittle; these vibrations cause the faces to "chatter," leading to chipped edges and heat checking. 

• The Problem: Rigid seal designs cannot absorb the shock of a shaft that isn't running perfectly true.

• The FBU Solution: Our 2200 series utilizes a specialized stationary spring configuration. By placing the springs on the stationary side of the seal, they act as a shock absorber, allowing the seal to maintain face contact even during moderate vibration or misalignment.

 

3. The Clogging Trap: When Pulp Becomes Concrete

In the pulp and paper industry, "Medium Consistency" (MC) is where seals go to die. Fibers tend to pack into the spring pockets of a seal, eventually "solidifying" the mechanism.

• The Problem: Once the springs are clogged, they can no longer compensate for normal face wear or thermal expansion, leading to immediate leakage.

• The FBU Solution: For Sulzer® MCA and MCE pumps, we recommend the FBU 222M. Its smooth-profile, open-face design uses centrifugal force to throw fibers away from the sealing area, preventing the buildup that kills standard OEM designs.

   

Stop Buying Spares. Start Buying Uptime.

At FBU Sealing Technology, we believe our role is to act as your Engineering Arm. We provide the factory-direct value you expect from a Suzhou-based manufacturer, combined with the technical depth of an OEM partner.

• Failure Analysis: Send us a photo of your failed seal, and our engineers will provide a technical report on why it failed.

• Customization: If standard materials aren't lasting, we can upgrade you to diamond-coated faces or FFKM elastomers to handle your specific media.

• Rapid Logistics: We keep common Sulzer® sizes (30mm–90mm) in stock to ensure that troubleshooting is followed by an immediate solution. 

FAQ

1.My seal faces show heavy wear but no cracking. What does this mean? 

This usually indicates "Abrasive Wear." The media is likely too aggressive for the current face material. We recommend upgrading from Carbon to SSiC (Sintered Silicon Carbide) or Tungsten Carbide.

2.Why does my seal leak only during pump startup? 

This is often a sign of "Compression Set" in the O-rings or a lack of initial lubrication. Our FBU 2210/2220 cartridge seals are pre-lubricated and pressure-tested to prevent (leak on startup) issues.

3.Can FBU cross-reference my old Sulzer® part numbers? 

Absolutely. Even if the part number is obsolete, our technical support team uses dimensional re-engineering to match an FBU 2200 series seal to your pump housing perfectly.