Paper Machine & Stock Preparation
Process Overview
Paper Machine & Stock Preparation — Process Overview
Stock preparation turns pulp, recycled fibre or broke into a uniform furnish: the pulper slushes the fibre, cleaners and screens remove contaminants, refiners develop the fibre, and the blend and machine chests hold the furnish at constant consistency. In the approach flow, the fan pump mixes stock with white water and feeds the headbox; the sheet forms on the wire, is pressed and dried on steam-heated cylinders, and may be coated. White water and broke are recycled continuously.
For digesters, liquor and chemical recovery see Pulp Mill & Chemical Recovery.
Key Sealing Challenges
- Fibre and contaminants: stock wraps around exposed springs and plugs flush orifices; slurry cartridges with external springs and a Plan 32 clean flush are used.
- Abrasive fillers: calcium carbonate and kaolin in white water and coating colour wear carbon faces; SiC vs SiC is standard.
- Coating colour: dries hard in air, so a double seal on a water barrier keeps it off the faces.
- Hot condensate: dryer condensate runs near saturation with little NPSH margin.
What mechanical seal is used on paper machine fan pumps?
Fan pumps typically use a slurry cartridge seal with external springs (e.g. Gipfel HS860) and silicon carbide vs. silicon carbide faces on an API Plan 32 fresh-water flush. The dilute stock still carries fibre and filler, so springs are kept out of the product and the flush keeps the faces clean. Plan 11 is not used on fibrous stock.
Root-Cause Failure Analysis — Field Example
Symptom: Coating colour pump seal leaks after each shift change; white crust on the atmospheric side, faces chipped.
├── Incorrect Response: "Fit a single seal with harder faces."
├── Diagnostic Evidence Required:
│ ├── Is coating colour drying on the atmospheric side when the pump stops?
│ ├── Are calcium carbonate particles reaching a carbon face?
│ └── Is any flush, quench or barrier fitted?
└── Engineered Solution:
├── Double cartridge seal on a Plan 53A water barrier.
├── SiC vs SiC faces on both seals.
└── Flush the pump with water before stopping.
Frequently Asked Questions
Why not use API Plan 11 on stock pumps?
Plan 11 takes liquid from pump discharge, so fibre plugs the orifice and packs the seal chamber. A Plan 32 clean water flush is used instead.
Can gland packing on stock pumps be replaced with mechanical seals?
Yes. Slurry cartridge seals with a controlled Plan 32 flush stop the continuous gland water that dilutes stock, and end sleeve wear.
Related: Pulp Mill & Chemical Recovery · Municipal Water & Sewage · Mining Slurry.
Request a Seal Selection
Send your pump make and model, fluid, temperature, pressure, shaft size and speed to info@gipfelengg.com or use our enquiry form. Gipfel Engineering (ISO 9001:2015, NSIC-registered MSME, Mumbai) designs and manufactures mechanical seals, seal support systems and process pumps.
Equipment solutions: Pulp & MC Stock Pumps · Split-Case Pumps · Specialty Machinery.
Pump Duty & Mechanical Seal Selection Matrix
Typical values for selection guidance only. Final selection is made against the customer duty sheet.
| Pump duty | Fluid | Typical temp. | Typical pressure (bar) | Seal arrangement | Faces / elastomer | API piping plan |
|---|---|---|---|---|---|---|
| Pulper Dump / Stock Transfer Pump | Stock at 3–5 % with contaminants | 30–55 °C | 2–5 bar | Slurry cartridge, external springs (catalogue ref. HS860) | SiC vs SiC / EPDM | API Plan 32 (clean water flush) or Plan 62, per seal design |
| Refiner Feed Pump | Stock at 3–5 % | 40–55 °C | 3–6 bar | Slurry cartridge, external springs (catalogue ref. HS860) | SiC vs SiC / EPDM | API Plan 32 |
| Machine Chest / Blend Chest Pump | Blended stock | 40–55 °C | 2–5 bar | Slurry cartridge, external springs (catalogue ref. HS860) | SiC vs SiC / EPDM | API Plan 32 |
| Fan Pump (headbox feed) | Dilute stock (0.5–1.5 %) in white water | 40–55 °C | 2–5 bar | Slurry cartridge, external springs (catalogue ref. HS860) | SiC vs SiC / EPDM | API Plan 32 (fresh water flush) |
| White Water / Save-all Pump | White water with fines and fillers | 40–55 °C | 2–4 bar | Slurry cartridge, external springs (catalogue ref. HS860) | SiC vs SiC / EPDM | API Plan 32 or Plan 62 quench |
| Broke Pump | Broke pulp | 40–55 °C | 2–4 bar | Slurry cartridge, external springs (catalogue ref. HS860) | SiC vs SiC / EPDM | API Plan 32 |
| Coating Colour Pump | Calcium carbonate / kaolin coating colour, abrasive, dries in air | 30–50 °C | 2–6 bar | Double cartridge, back-to-back (pressurised) | SiC vs SiC / EPDM | API Plan 53A (water barrier ≥ 1.4 bar above seal chamber) |
| Dryer Condensate Return Pump | Steam condensate from dryer cans | 90–150 °C | Low NPSH margin — confirm seal-chamber pressure per pump | Balanced multi-spring cartridge | SiC vs carbon / EPDM (peroxide-cured) | API Plan 23 (or Plan 11 below the seal temperature limit) |
| Liquid Ring Vacuum Pump (wire and felt suction) | Seal water with fibre and fillers | Ambient–50 °C | Suction under vacuum | Single-spring cartridge | SiC vs SiC / EPDM | Flushed from clean seal water |
Reviewed by Gipfel Engineering’s technical team.
Technical Information Disclaimer
The information on this page, including process descriptions, flow diagrams, operating ranges, seal arrangements, materials and piping plans, is general technical guidance for information only. Values shown are typical industry ranges, not guaranteed ratings or specifications of any Gipfel Engineering product. Each application differs. Seal selection, material compatibility, installation and operation must be verified by qualified personnel against the specific equipment data sheet, process conditions, applicable codes and the pump manufacturer’s instructions. A binding recommendation is given only in a written quotation or technical offer from Gipfel Engineering.
References to standards (such as API 682, ISO 21049, ISO 3069, FDA 21 CFR 177.2600 and NACE MR0175 / ISO 15156) describe common industry practice. They do not mean that any product is certified, qualified or approved to that standard unless this is confirmed in writing for a specific order. Third-party company and product names, including “equivalent to” references, are used for identification only and remain the trademarks of their owners. No affiliation, endorsement or OEM approval is implied.
Compliance with safety, hazardous-area, environmental and statutory requirements at the user’s site remains the responsibility of the plant owner or operator. To the extent permitted by law, Gipfel Engineering accepts no liability for loss or damage arising from reliance on this general information without a confirmed written recommendation. Content may change without notice.