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Steel forging is a fascinating process to watch, and involves the transmission of enough energy to change the shape of a solid steel.  One often forgotten aspect of forging involves the seals used in tandem with the forging hammers.

In this blog post, our focus will be seals for steel forging hammers.

Steel ForgingSource

Seals for Forging Rams

Steel forges require very heavy duty hydraulic seals for use with the positioning cylinders and manipulating rams.  The rams use a multi-lip seal formation referred to a V-packing for the main ram seal.  In V-packing, rubber seals are stacked in sets and the seals themselves are usually a cotton fabric proofed with rubber.  These are non-standard hydraulic seals, and pose their own interesting set of challenges.

Key Issues for Forging Ram Seals

The key issues for ram seals include:

  • lip compliance
  • abrasion resistance
  • reliability

Once the first two issues are addressed by a seal design, the third issue usually falls into place; in other words, improving lip compliance and abrasion resistance drastically increases reliability.

Improving lip compliance and abrasion resistance drastically increases reliability

Lip compliance and seal abrasion resistance are a serious problem when replacing seals on the older forging machines.  Through the years, the rams become narrowed and develop an hour-glass shape. This shape means the rubber seals alone simply cannot be as effective, resulting in oil leakage and possible extrusion.  In addition, scoring on the ram itself can abrade and destroy the rubber seals very quickly.  Improved abrasion resistance makes all the difference in extending the life of these seals.

Forging Ram Seal Solutions

More modern seal designs making use of additives to enhance the properties of the rubber.  One example would be implementing at least one polyurethane seal and a polyamide female header (taking the place of a traditional rubber header) with the classic style rubber and fabric seal that has been used on forging rams for many, many years.   The polyurethane provides excellent abrasion resistance, and the polyamide header aids in preventing extrusion and maintains better contact with the surface of the ram.  

The gland ring may also be replaced with a polymer such as wear resistant nylon.  This provides better abrasion resistance than the rubber-cloth materials and does an excellent job of cover those extrusion gaps caused by narrowing of the ram and resisting abrasion.  Note that sometimes an energizing male adapter may be included, also.


There is no doubt that developing seals for hammers in the steel forging industry is quite the challenge, but the use of modern materials with traditional main ram seal design provides a solution that works for both old and new machines.  The classic V-packing formation combined with a wear-resistant nylon gland ring and  the addition of at least one polyurethane ring is just one example of improvements that can drastically increase the life of the main ram seal.


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