Tag Archives: Compression Packing

Upgrade from Pump Packing to Mechanical Seals

Mechanical sealing conserves water, improves energy efficiency, and minimizes environmental impact

The environmental performance of products and processes in all industrial sectors increasingly is cause for critical inspection, with sustainability, conservation of natural resources, and reduced environmental contamination concerns influencing equipment design and selection.

Many industrial processes can be addressed to improve sustainability and minimize environmental impact, while at the same time maintaining or reducing operating costs. Implementing energy-efficient and environmentally friendly processes and technologies should be embraced as a priority at the component, process, and system levels.

One aspect of these processes is mission-critical rotating equipment, and specifically centrifugal pumps, which represent a significant proportion of the equipment found in industrial operations. One vital component of a centrifugal pump is the seal around the rotating shaft that passes through a stationary pressure casing or housing. The seal contains the liquid or gas from escaping to the environment.

Sealing systems help maintain acceptable pump efficiency, reliability, energy consumption, water usage, and emissions control. These factors can materially facilitate achieving total-life cycle cost-reduction and sustainability objectives. Sealing performance can be improved for centrifugal pump applications by upgrading from traditional compression packing to mechanical seal technology.

When sealing a centrifugal pump, the objective is to allow the rotating shaft to enter the wet area of the pump without large volumes of pressurized fluid escaping. The pump discharge pressure forces the fluid back behind the impeller, where it is induced to exit by way of the rotating drive shaft. To minimize leakage, a seal is needed between the shaft and pump housing to contain the pressure of the process being pumped and withstand friction caused by shaft rotation.

Compression packing is the traditional means to seal centrifugal pumps, going back more than 100 years. Also referred to as gland packing, it is a braided, rope-like, and lubricated material packed around the shaft in rings, physically stuffing the gap between the shaft and the pump housing, within a stuffing box.

Water leakage and consumption

Charred packingFor compression packing to work, some leakage must be maintained to lubricate and cool the packing material. Therefore, packing rings allow for an adjustable, close-clearance leak path parallel to the shaft axis. As the packing is used, however, some of the lubricant that is embedded into the packing is lost, reducing the packing ring’s volume. The pressure squeezing the rings together is also reduced, increasing leakage.

Periodic adjustment of the packing follower brings the pressure back into specification and controls the excess leakage. In today’s world, however, this maintenance is not always being done at required intervals or adjusted correctly. As the number of centrifugal pumps incorporating the use of compression packing decreases, training for and understanding of packing maintenance has waned.

Consequently, under-tightening and over-tightening of packing rings is a prevalent and growing misapplication of centrifugal pump maintenance, with critical consequences to both water consumption and energy draw.

Under-tightening results in too much leakage. Already, when properly adjusted, packing leakage can amount to gallons of liquid leaked per minute. This can be either aqueous solutions comprised of varied benign or caustic chemical compositions, or particles in suspension or slurry, depending on the process.

The heavier the suspension or slurry content in the pumped liquid, the more water is needed to get packing to work reliably. Typically, a clean external flush is piped into the stuffing box through a lantern ring, which keeps the packing lubricated and cool while flushing abrasives and chemicals.

Normally, some portion of the leakage is released continually into the atmosphere. Under-tightening of the packing rings and use of external flushes increase this atmospheric release proportionately, along with environmental impact potential. Continue reading Upgrade from Pump Packing to Mechanical Seals

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

How to Investigate Compression Packing Failure Modes

Over-tightening, excessive speed and improper installation can cause a system to falter.

In many respects, troubleshooting and failure analysis of compression packing materials is similar to the investigation of a crime scene. A good investigator knows how to gather clues from many different sources and put them together to understand what has happened. A good troubleshooter uses the same information gathering method, familiarizing themselves with the sealing materials, the process equipment and the systems where they are used.

Start by Interviewing Witnesses

The troubleshooter should seek information from the people who work with the equipment on a regular basis. Seal installers, maintenance personnel, operators, process engineers and others can all shed light on potential causes of failure. Some key questions should be:

  • How is failure defined? Some examples include excessive leakage, overheating, high rate of flush water consumption, excessive friction load and blowout.
  • Is this application the source of chronic seal failures, or was this an unexpected event?
  • Were there any changes to the seal material, the equipment or the overall process that preceded the failure?
  • Were there any system upsets or cleaning cycles that preceded the failure?
  • Can you describe the installation procedure?

Gather Information About the Victim

Knowing the limitations of the sealing product is a key step. The acronym “STAMPS” will help remember the key elements to ensure the right packing is selected for the application.

  • S: Size. Is the correct packing cross-section being used? Are the rings cut or formed to the correct length?
  • T: Temperature. Check the system temperature against the packing manufacturer’s established temperature ratings for the product.
  • A: Application. Some packings are made specifically for rotary equipment while others are intended for valves or static seals. Check to make sure the packing is suitable for the equipment where it is being used.
  • M: Media. This refers to the fluid being sealed. Check with the manufacturer or with compatibility charts to be sure the seal material is compatible with the media. If the media is slurry, abrasion-resistant materials may need to be specified. If the media is toxic, explosive or required to be contained within certain maximum allowable leakage requirements, then a packing must also be selected on the basis of its ability to seal at low leakage levels.
  • P: Pressure. Check the system pressure against the packing manufacturer’s established pressure ratings for the product.
  • S: Speed. Check the equipment speed against the packing manufacturer’s established surface speed ratings for the product. Surface speed is expressed in feet per minute or meters per second and not revolutions per minute.

Investigate the Crime Scene

When possible, observe the equipment while it is running. Can you see, hear, feel, smell or use a sensor to make observations? Smoke, vibration, grinding noises, the scent of burning fibers and system pressure fluctuations are only a few of the clues that can be noticed or measured while the equipment is up and running.

Examine the condition of the equipment. Most packings are robust seals that can handle less than perfect equipment condition, but there are limits to the amount of degradation they can withstand.

Valve stems and pump shafts or sleeves should be checked for scratches, corrosion pitting and general surface roughness. Rough surfaces can damage the sealing surface and result in excessive leakage and quick wear of the seal.

Extrusion of the seal material
Image 1. Extrusion of the seal material

Excessive clearances at the top or bottom of the stuffing box can lead to extrusion of the seal material and intrusion of large solid particle into the seal area (see image 1).

In severe cases, excessive clearance may result in a seal blowout.

Most packings are not meant to function as both a seal and a bearing. In rotating equipment, poor bearing condition may result in shaft runout that “wallows out” the inside diameter of the seal. Misalignment may result in shaft/stuffing box offset that causes one side of the packing set to be heavily compressed while the other side is compressed much more lightly. A similar side loading of a packing set can occur in large horizontally oriented valves where the packing is forced to bear the weight of the stem.

Check to make sure all the parts are in place. During the breakdown, repair and reassembly of equipment it is possible to misplace parts. Equipment might be put back into service without seat rings, bushings, lantern rings, O-rings and other parts that are essential to proper equipment operation.

Look at the seal and the equipment as a part of a big picture.

Consider how this piece of equipment is affected by other equipment and control devices in the system. For example, is there a downstream valve that creates pressure spikes in an upstream pump seal when the valve closes and the pump is still operating?

Continue reading How to Investigate Compression Packing Failure Modes

VIDEO: Garlock Compression Packing

Garlock compression packing is rigorously tested to ensure effective sealing in valves, pumps, agitators, and other rotary equipment. The development of the compression packing line reflects the evolution and innovation in the materials used in its production. Garlock develops and manufactures it’s own technical yarn braided into packing, along with high performance proprietary coatings, that are essential in this age of sealing performance requirements.

Garlock’s product line includes industry recognized Low Emission valve stem packing, leading-edge and award winning pump packing sets like dry-running DSA, and water saving HYDRA-JUST.


Gallagher Fluid Seals is an Authorized Garlock Master Distributor, stocking many styles and cross-sections of compression packing.  Remember, all packings are not created equal, so feel free to contact us if you need assistance determining which packing is best for your application.

The 5 Ps of Compression Packing Installation

compression packing installationPump and valve packing is a tried and true way to seal an application.  But there are SO MANY styles of packing, choosing the correct braid configuration, fiber type, cross-section, etc., for your specific application can be extremely difficult.

Gallagher is here to help you along in the process.  We represent numerous packing braiders, so we can find the best packing for you and your company, or even create a custom one.  But where does the packing selection process start?

Lee Gillette, our GORE field sales representative, set out to answer that question in an article in Pumps and Systems magazine.

Continue reading The 5 Ps of Compression Packing Installation