Tag Archives: pressure seals

The New Hygienic Forseal and Hygienic Pressure Seal From Freudenberg

Strict hygiene regulations in the food industry present major challenges for sealing technology. Freudenberg Sealing Technologies is enhancing its proven portfolio of hygienic sealing solutions with two products that are also designed for high-pressure applications. This was made possible thanks to special design solutions and the premium elastomer and PTFE materials developed in-house.

Food processing demands strict hygiene and cleanliness standards. It’s also important to ensure that no substances can migrate from the materials coming in contact with food, which could lead to contamination of the product. With its hygienic product line, Freudenberg Sealing Technologies has developed sealing solutions that fulfill food industry standards and are also resistant to CIP/SIP media. The Hygienic Forseal and Hygienic Pressure Seal are the newest members of this innovative product family.

Lena Eberspach, Rainer Kreiselmaier and Sina Etter (f.l.t.r.) from Freudenberg Sealing Technologies discuss the new products of the company’s hygienic sealing solutions portfolio. Copyright: Freudenberg Sealing Technologies

One of the basic requirements for sealing solutions in accordance with the hygienic design standards is a dead-space-free construction. It prevents the collection and settling of product residues and micro-organisms in undercuts, for example. The selection of applied materials and their resistance to hot water, steam, acids, alkalis and high pressures are also relevant. Observing the deformation at the relevant temperature plays a particularly important role in detecting distortions and the associated formation of dead spaces at an early stage in the product development. Continue reading The New Hygienic Forseal and Hygienic Pressure Seal From Freudenberg

Compression Packing: A Look Beyond the Standard Stuffing Box

Compression Packing

How this application fits as a versatile solution.

Stem packing is a familiar product. The most common type is braided compression packing. Braided packing is used in a wide range of applications. Depending on the service, construction materials can be as diverse as plants or animal derivatives, mineral fibers or synthetic plastics and even metal. The process of cutting rings from rope packing, inserting them into a stuffing box and torquing them to the right density is common, but it is not always the best choice.

Another widely used manufacturing method is die-molding. It is the process of wrapping a material around a mandrel, placing it in a die and preforming it to make a seal. Using these and other manufacturing technologies, packing is found to work in applications as different as aerospace, heavy trucking and power generation. A review of some unusual applications demonstrates the versatility of compression packing as a sealing solution.

The Origin of Packing

Compression packing is an ancient technology dating back more than 5,000 years. Boats and ships used a rudder as a steering mechanism. The rudder shaft penetrates the hull of the vessel below the water line, so water can leak into the bilge. Ancient sailors, using the top technology of the day, would take pieces of clothing, sail cloth and rope, cover it with animal fat or wax and stuff it into the gap around the shaft. Eventually, a box was secured around the shaft and a gland, which could be tightened to compress the packing material, was created to improve sealing and longevity. The terms compression packing, stuffing box and gland come from these early sailors.

Compression Packing

Over time, many improvements in packing construction and materials were made. Packing today can be made of flax, Kevlar, polytetrafluoroethylene (PTFE), graphite or metal. It typically has a square cross-section and is sold in precut rings or in large coils, as shown in Image 1. Synthetic aramid fibers are abrasionresistant and can handle higher temperatures and shaft speeds. PTFE has excellent lubricity and chemical resistance. Graphite coupled with mica or an aramid fiber can stave off the heat generated by a rotating shaft and provide long life in challenging applications.

Die-Formed Packing

Die-formed compression packings are excellent in terms of sealing Picture of a die formed ringperformance and reliability and offer a wide range of long-term, low-emission and low maintenance products. See Image 2.

Not only are die formed rings easier and quicker to install, but the  pre-compression increases the density of each ring and reduces the gland loads necessary to seat and compress multiple rings in the stuffing box. The result is lower friction on the shaft or the spindle, with improved sealing performance and a longer life.

Factor in STAMPS

As mentioned in an article previously published by the Fluid Sealing Association, (Sealing Sense, Pumps & Systems, March 2005), there are several key factors to consider when choosing the right packing. They include:

  • size or stuffing box bore
  • temperature inside the stuffing box application: whether it’s a pump, valve, mixer, refiner, process, characteristics such as pH level and chemical compatibility
  • motion: rotary, helical or reciprocal
  • pressure inside the stuffing box
  • surface speed expressed in feet per minute or meters per second

Keeping this in mind, here are some applications to consider when you are going way beyond the typical stuffing box: Continue reading Compression Packing: A Look Beyond the Standard Stuffing Box