Michel Sanchez
June 5, 2026

How to Replace Plunger Packings on a Gaulin Homogeniser

Why Plunger Packings Matter

Plunger packings are the primary sealing elements in the high-pressure compression section of every homogeniser. They prevent product from leaking past the plungers during the compression stroke, ensuring that full operating pressure is maintained. Worn packings are one of the most common causes of pressure loss, product contamination, and unplanned downtime.

This guide covers the step-by-step procedure for replacing plunger packings on Gaulin homogenisers, including the MC, K, and M series. The general principles apply to APV, Rannie, and other high-pressure homogenisers as well, though specific components may differ.

When to Replace Plunger Packings

Replace your plunger packings when you observe any of the following: visible product leakage around the plunger area, a gradual decline in homogenising pressure, increased motor current draw (the machine is working harder to maintain pressure), or when the packings have reached the manufacturer’s recommended service interval — typically every 500 to 1,500 operating hours depending on product and pressure.

Do not wait for complete packing failure. A slow leak that is ignored will damage the plunger surface, turning a simple packing replacement into a costly plunger replacement.

Tools and Materials Required

Before starting, gather the following: a complete packing set for your specific machine model and plunger diameter (never reuse old packings), the correct spanners and socket set for your machine, a packing extraction tool or hook, clean food-grade lubricant for packing installation, clean cloths, a torque wrench (if specified in your manual), and appropriate personal protective equipment including safety glasses and gloves.

BOS supplies complete packing kits for Gaulin, APV, Rannie, and SPX homogenisers. Each kit contains all packings, O-rings, and backup rings needed for one plunger. Order one kit per plunger.

Safety First

Before beginning any work on the compression end:

1. Shut down the machine completely — switch off the main motor and wait for all moving parts to stop.

2. Lock out and tag out — isolate the electrical supply at the main breaker and apply a lockout device. Follow your facility’s LOTO procedures.

3. Depressurise the system — open the pressure relief valve or drain valve to release all residual pressure. Verify on the pressure gauge that the system reads zero.

4. Drain the product — flush the compression cylinders with water or CIP solution and drain completely.

Never work on a pressurised system. High-pressure product release can cause severe injury.

Step-by-Step Packing Replacement

Step 1: Remove the Packing Gland

Loosen and remove the packing gland nuts evenly. Remove the gland follower (the metal disc that presses against the packings). On Gaulin MC series machines, this requires a ring spanner — do not use adjustable wrenches as they can damage the gland nuts.

Step 2: Remove the Old Packings

Use a packing extraction tool or hook to carefully remove all old packing rings, spacer rings, and backup rings from the packing chamber. Remove them in sequence and note the order — the new packings must be installed in exactly the same arrangement. Clean the packing chamber thoroughly, removing any product residue, old lubricant, or debris.

Step 3: Inspect the Plunger

While the packings are removed, carefully inspect the plunger surface. Run your fingernail across it — if you can feel any grooves, scoring, or roughness, the plunger should be replaced or re-polished before installing new packings. Installing new packings on a damaged plunger will cause premature packing failure. BOS stocks replacement plungers for all major homogeniser brands.

Step 4: Inspect the Packing Chamber

Check the packing chamber bore for scoring, corrosion, or damage. The chamber walls must be smooth and free of defects. Also check the chamber shoulder (the bottom of the bore) for wear.

Step 5: Install New Packings

Lubricate each new packing ring with clean food-grade lubricant before installation. Install the packings in the exact sequence specified by the manufacturer — this is critical, as the arrangement of pressure rings, spacer rings, and backup rings determines the sealing performance.

Press each ring firmly into the chamber, ensuring it seats squarely without twisting. For lip-type packings, ensure the lip faces the pressure side (towards the cylinder). Stagger the joints of split-ring packings so they do not align.

Step 6: Reassemble the Gland

Replace the gland follower and tighten the gland nuts evenly and gradually. Do not over-tighten — the packings need to be compressed enough to seal, but excessive compression causes friction heat, accelerated wear, and increased power consumption. Tighten to the torque specified in your manual, or if no torque is given, tighten until snug and then back off a quarter turn.

Step 7: Run-In Procedure

After reassembly, run the machine at low pressure (approximately 50 bar) for 10 to 15 minutes. This allows the packings to bed in and conform to the plunger surface. Check for leaks during this period. Minor weeping is normal during run-in and should stop within the first 15 minutes.

Gradually increase pressure to the operating setpoint. Monitor for leaks and abnormal temperature at the packing gland. If the gland becomes hot to the touch, reduce pressure and slightly loosen the gland nuts.

Common Mistakes to Avoid

Replacing only some packings: Always replace the complete set. Mixing old and new packings causes uneven sealing and accelerated failure.

Wrong packing orientation: Lip packings installed backwards will not seal. Always verify the lip direction faces the high-pressure side.

Skipping plunger inspection: New packings on a scored plunger will fail within hours. Always inspect — and replace if necessary — the plunger during packing changes.

Over-tightening the gland: This is the most common cause of premature packing failure. Tighter is not better — correct torque is essential.

Recommended Service Intervals

For standard dairy and food applications at moderate pressures (150-250 bar), plan for packing replacement every 1,000 to 1,500 operating hours. For high-pressure applications (above 400 bar) or abrasive products, reduce the interval to 500 to 800 hours. Keep a log of packing changes to establish the optimal interval for your specific conditions.

Need Parts or Assistance?

BOS Homogenisers stocks packing kits for all major homogeniser brands and models, with many available for same-day dispatch. For on-site service in the Netherlands, Belgium, and Germany, or for remote technical support worldwide, contact our service team.

BOS Homogenisers B.V. — +31 35 621 3190 — sales@boshomogenisers.com