Rethinking Ram Packing For Presses that Refuse to Stay Young

For decades, the cylinders in heavy-duty presses have been sealed the same way: a molded stack of rubber and fabric, replaced on a schedule and rarely questioned. System Seals set out to understand why that standard kept failing on aging equipment, and engineered a sealing platform built from diagnosis instead of a catalog.

Uptime is the single number that matters most on a forging or extrusion floor. Every hour a press sits idle because
of a hydraulic seal failure is an hour of lost throughput, a maintenance crew pulled off schedule, and, in some operations, a work product that has to be scrapped because fluid reached it. The ram packing is a critical component, and its cost is small only relative to the press itself. The cost of it failing is not.

And yet the packing itself has barely changed. The vast majority of heavy-duty presses in operation today still seal their rams with molded NBR or NBR/fabric V- packing, a design that has been the industry default for the better part of six decades. It is inexpensive, widely stocked, and familiar to every maintenance team in
the business. In a new press, running under clean conditions, it works well.

The problem is that presses do not stay new. Bushings wear. Ram surfaces score and pit. Geometry drifts out of round. And standard packing, designed for factory-fresh tolerances, has no way to adapt. As a press ages, the gap between what the packing was built for and what it actually has to seal keeps widening, and the maintenance calendar fills in the difference.

Why standard V-Packing runs out of answers on aging presses

We reviewed failed packing sets from forging and extrusion presses across a range of ages and duty cycles, and the same three conditions kept surfacing as the real drivers of early failure, conditions that standard V-packing was never engineered to accommodate.

Bushing wear widens the extrusion gap. Main rams ride on bronze bushings that are rarely replaced. As they wear, the clearance between ram and packing gland grows, and standard NBR/fabric adapters lack the stiffness to bridge it. Under pressure, the packing extrudes into the gap instead of resisting it.

Ram geometry drifts out of round. Years of load cycling can wear a ram into a subtle hourglass profile. That uneven surface defeats a packing stack designed for a uniform running surface, opening leak paths that vary across the stroke.

Surface condition turns the ram into an abrasive. Scoring, pitting, and corrosion on the ram face grind against the packing intermediates on every cycle. NBR/fabric has limited abrasion resistance, and on a degraded ram, service life drops fast.

A fourth condition is more subtle: main rams typically run without working pressure during the positioning stroke.
Standard compression-fit packing needs a minimum system pressure to function as designed, so below that threshold, fluid bypasses the stack. It shows up as oil weeping down the ram, and it is routinely misdiagnosed as worn packing, when it is really a gap in the original design.

Elite V-Packing: Engineering the stack to the press, not the part number

Our answer was not a better version of the same molded part. It was a change in how the packing gets specified in the first place. Elite V-Packing is a modular sealing platform, configured for each press from a diagnostic read of its actual condition: bushing wear, ram geometry, surface finish, and how the current packing is failing, rather than pulled from a catalog by size alone.

Where used packing is available, we go further and examine the extracted set directly. Extrusion damage shows up as deformation at the heel of the female adapter. Abrasive wear from a scored ram leaves uniform material loss across the intermediate lips. Compression set without surface wear points to a low-pressure bypass condition rather than mechanical damage. That evidence, not a part diagram, is what drives the configuration, and it keeps informing it after every service interval.

Anatomy of the stack (Machined, not molded)

The platform is built from three functional positions, each with design options selected to the failure modes a given press presents. Because every component is machined rather than molded, tolerances hold tight across a production run, a distinction that turns out to matter well beyond sealing performance, as we cover below.

Elite V-Packing stack, top to bottom

At the center, H-Polyurethane intermediates carry the primary sealing load and hold up substantially better against a scored or pitted ram. For presses losing fluid during the low-pressure positioning stroke, one heavy-duty ring can be replaced with a series of thinner V- rings tuned to generate a more appropriate sealing force.

At the top, a proprietary W-profile male adapter replaces the flat design used in standard configurations. It behaves as an active lip rather than a passive cap, adding sealing force independent of system pressure and directly addressing the low- pressure leakage that standard packing was never built to solve.

A machined stack changes the maintenance math too

Two practical effects follow from machining instead of molding, and neither shows up in a sealing spec sheet.

Traditional NBR/fabric packing has to be installed under compression to activate, and as it takes a compression set in service, shims come out to restore sealing force. Over time, the compressed material bonds to the gland walls. Removal at replacement can take hours per cylinder. Elite V-Packing's sealing force is built into the cross-section geometry itself, so the stack works correctly as installed, with no compression required. In practice, that
has cut removal time to hours, not shifts.

Molded packing also carries wide dimensional tolerances: three nominally identical sets can measure differently. On a press running multiple cylinders in tandem, that variation means uneven seal force across cylinders, producing a stick- slip effect that adds mechanical stress and accelerates bushing wear. Because Elite V-
Packing is machined, stack height is consistent, set to set: what we call a calibrated stack height. Multi-cylinder presses see uniform seal force and lose the stick-slip condition entirely.

"Standard packing is designed for a press in like-new condition. Almost none of the presses we're called into are in like-new condition. That mismatch, not a material defect, is the real source of most premature failures we see."

Results across an aging fleet

Across an aging fleet moved from standard NBR/fabric packing to Elite V-Packing, annual seal replacement events fell from twelve to four, a threefold extension of the service interval, from monthly to quarterly. Estimated annual downtime exposure dropped from roughly $600,000 to $400,000. The gains vary by press: units with severe ram scoring or advanced bushing wear see smaller improvements than presses in better mechanical condition. But in nearly every case, the reduction in unplanned stoppages outweighs the higher unit cost of the packing itself many times over.

That last point is worth stating plainly, because it runs against how packing is usually bought. Elite V-Packing costs more per set than a standard NBR/fabric configuration, and it is not positioned as a lower-cost replacement. Where unplanned downtime is the dominant cost in a sealing failure, as it is on most forging and extrusion lines, the price of the packing itself is rarely the number that matters.

A sustainability case, alongside the economic one

Extending a service interval threefold has a footprint alongside a cost. Fewer replacement events mean fewer packing sets manufactured, shipped, and scrapped over the life of a press. Preventing fluid bypass also protects the work product itself: material that would otherwise be contaminated and scrapped stays in the
production stream. And because a calibrated stack removes the stick-slip loading that accelerates bushing wear, it slows the mechanical aging of the press itself, extending the working life of equipment that is often decades old already, rather than just the seal inside it.

That case for refurbishment over replacement is becoming a bigger part of how presses get maintained, not just how they get sealed.

A new standard, not a new part number

Traditional suppliers compete on price, availability, and delivery: reasonable ground when a press is running in good condition and a like-for-like replacement is all that's needed. The gap opens once a press ages past what a standard catalog configuration was designed to handle. The typical response has been to replace packing more often. We think that response is treating a design limitation as routine maintenance.

Elite V-Packing is not an incremental upgrade to molded NBR/fabric: a harder compound, a tighter tolerance, a slightly better profile. It is a different way of specifying a seal: starting from the measured condition of the press instead of its bore diameter, and continuing to refine that specification as extracted sets come back from the field. For an industry that has sealed its rams the same way for sixty years, that is the actual innovation, not a new material, but a new starting point.

If your fleet is approaching the point where standard V-packing can no longer keep pace with how the equipment has actually aged, our engineers can walk through what a diagnostics-driven configuration would look like for your presses. Talk to our engineers or see the full results from one aging fleet in our case study, Restoring Uptime in Aging Forging Press Cylinders.