Tag Archives: rotary seals

Designing the Perfect Rotary Shaft Seal

When it comes to maintaining a high-functioning rotary shaft, you need to select the appropriate lip seal.

The shaft seal protects the rotary shaft from contaminants such as dust and dirt, and it keeps water out and lubricant in.

A rotary seal, also known as a radial shaft seal, typically sits between a rotary shaft and a fixed housing — such as a cylinder wall — to stop fluid leaking along the shaft. The rotary seal’s outside surface is fixed to the housing, while the seal’s inner lip presses against the rotating shaft.

Common applications for shaft seals include motors, gear boxes, pumps and axles. They’re also increasingly used for food and chemical processing, as well in pressurized gas applications.

Three of the most important considerations when the choosing the best lip seal for a rotary shaft are:

  1. The material the seal is made of,
  2. the hardness of the shaft’s surface, and
  3. the roughness of the shaft’s surface.

Here’s your quick go-to guide on how to achieve optimum performance and longevity for your seals and shafts, ultimately minimizing the risk of seal failure. Presented by our partners at Eclipse Engineering: Continue reading Designing the Perfect Rotary Shaft Seal

Preventing Seal Failure

Seals are small components that have a big function. At their most essential purpose, they keep fluid in and debris out. Failure to do this can lead to costly machine destruction, and even endanger the lives of people working around these machines. Preventing seal failure is very important on many different levels.

What Seals Are Up Against

Many factors can cause a seal failure. Being aware of these factors will help you in preventing an avoidable failure. Seals are under constant pressure because of the liquid or gas being contained. Typically, the seals in pipes or machinery have some type of matter within transferred at high velocities. This is a huge part of what they were designed to do, but too much or too little pressure could wear down the seals.

In addition, extreme temperatures can cause the seal to become brittle. A mixture of extreme temperatures and pressure is a recipe for cracking and leaking. Also, debris can contaminate the integrity of the seal. Even in clean environments, the small shavings from pistons or hydraulics can get into the seal. Chemical compounds can cause a much faster seal breakdown, so be aware of what type of matter stays concealed. Finally, time will cause the seal to break down. There is no way to avoid this one, so ensuring you mitigate the other factors can help the longevity of a seals life.

Different Types of Seals

Each seal has a specific purpose and function. Putting the right seal in the right environment will help you have a more successful operation.

  • Types of O-Ring ApplicationsO-rings are the most popular type of seal. They are meant for static conditions and can conceal liquid and gas.
  • Rod seals should work with hydraulic cylinders. They typically work best with concealing fluid and can withstand movement.
  • Piston seals should also be used with hydraulics, but specifically pistons instead of cylinders.
  • Wear rings find usage in sewage pumps mostly. They are used to decrease the leakage around an impeller, which is the rotor that increases the flow of liquid.

Preventing Seal Failure: How To

These are the main points of failure for seals and the best ways to avoid them:

  • Install the seal properly. Even with improper installation, a seal can work initially, but it will fail much quicker. Seals need to have the exact size for a precise fit. Or they will fail. Make sure to get the correct seal for the area in which you plan to install it.
  • Cleanliness is paramount. Although it is important to keep debris away from the seals, that is not where cleanliness needs to begin. You also need to make sure that the area is clean of debris during installation.
  • Find the proper rating for the environment. Seals have different ratings for temperature and pressure. Make sure the seal can handle these two factors for longevity.
  • The finish of the seal and the shaft need to match. You can’t have a smooth shaft with a seal that has edges or burrs. Anything that can be caught or cause friction will create debris. This mismatch can also throw the seal out of alignment.
  • Ensure all other parts of the machinery are functioning correctly. An anomaly somewhere else can cause undue stress to the seals.
  • Periodically check the fluid conditions. The purpose of a seal is to prevent leaks, but too much or too little fluid can cause damage. Verifying the fluid conditions stay consistent will keep the seal in good shape.
  • Replace seals promptly. This one comes more with experience. Always replace seals before they get too worn to stay effective.

The original article was written by staff at Real Seal and can be found on their website here.

For more information about seal problems you are having and how Gallagher Fluid Seals can help, contact our engineering department.

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

[VIDEO] NEW! Rubber Energized Seals Webinar

Rubber Energized SealsGallagher recently recorded the Rubber Energized Seals webinar, discussing rubber energized rod or piston seals, and the advantages and disadvantages to using some of the most common seal profiles.  This webinar is presented in conjunction with one of our trusted partners, Eclipse Engineering, Inc.

Continue reading [VIDEO] NEW! Rubber Energized Seals Webinar