Vesconite Sliding Wear Plates Operate Beyond 1300 Hours

Test-work on Vesconite polymer sliding wear plates have shown promising results on a crawler drill that is employed at a zinc project in the Northern Cape, South Africa.

The wear plates were installed on the rotary head slide of a drill that carries out exploration drilling at the mine from which the goal is to exploit one of the largest zinc orebodies in the world.

The rotary head moves the drill into the ground for deeper and shallower drilling. It also allows the drill to be changed.

Since the rotary head moves approximately 120 times a day, wear on the slides has been considerable, and the original-equipment-manufacturer’s (OEM’s) nylon wear pads were only lasting 500 hours.

As a result, the OEM crawler drill supplier involved in the zinc project sought a solution to extend the life of its wear pads and investigated other wear-resistant materials that could cope with highly-abrasive materials such as chrome and silica that come in contact with the pads.

Vesconite Bearings technical representative Phillip de Villiers recommended the use of Vesconite in the application to improve the total wear life of the slides.

The OEM equipment supplier reports that the Vesconite polymer wear plates have lasted more than twice as long as the OEM nylon wear pads – more than 1300 hours of operation to date. They will continue to be used and the wear life will be closely monitored in comparison with the nylon OEM parts.

The wear life will be tested and proved on the 10 wear plate picture of wear padsassemblies, which is comprised of 20 separate wear plates on the crawler drill.

On a separate application on the crawler drill, Vesconite wear plates have also been employed on the boom slide. This is the rear part of the crawler drill. It is moved and adjusted to the drilling height, and provides stability to the drill. This boom moves roughly six times a day, so the wear is not nearly as considerable as the rotary head slide.

However, with the previously-installed OEM nylon slides lasting 1000 hours on this application, there was still a need to improve the lifespan of these slides.

The OEM equipment supplier hopes that the Vesconite will last much longer than the 1000 hours of the OEM material.

With low wear on the 6 Vesconite assemblies, comprising of 12 wear plate halves, early indications are that the Vesconite will also perform well in this application.

The equipment supplier imports crawler drills from Korea for resale, and also supplies parts for these and other drills that are used in mining-exploration drilling and borehole water drilling.

Gallagher is a distributor of Vesconite products for all industries.  If you have questions about using Vesconite in any application, contact our engineering department.

Water Regulations and NSF 61 Compliant Elastomers

Replacing Aging Water Infrastructure With NSF Compliant Materials

There are over 155,000 public water systems in the United States and more than 286 million Americans who rely on community water systems daily.  Since most of the infrastructure was built between the early 1900’s and 1960 using outdated technology/products and capabilities, nearly everything is approaching the natural end of it’s lifespan.

Some estimates put the repairs and replacement of thePicture of NSF Compliant Gaskets infrastructure between $250B and $500B over the next 20-30 years. Several applications will need to be updated or fully replaced for the safety of consumers and quality of delivery, including:

  • Joining and sealing materials
  • Mechanical devices
  • Pipes or related products
  • Process media
  • Plumbing devices
  • Non-metallic potable water materials
  • Hydrants
  • and Public drinking water distribution (tanks and reservoirs, maters, individual components)

Joining and Sealing Materials

When these systems were being constructed and assembled decades ago, there were limited regulations and requirements that needed to be met. Gaskets, at least the traditional ones, were often made in two different ways: (1) Red Rubber (ASTM D1330 Grade 1 &2) with compressed non-asbestos or (2) cloth-inserted rubber with compressed asbestos.

However, today’s acceptable gasket requirements for the potable water industry differ greatly from those in the past. Gaskets have strict guidelines to abide by and must be:

  • Chemically resistant
  • NSF compliant
  • Food grade compliant
  • Electrically isolating

Because of the need for health and safety, the National Sanitation Foundation (NSF) was created in order to establish minimum requirements for the control of potential adverse human health effects from products that contact drinking water. In addition to gaskets, the NSF covers a variety of products and parts relevant to the water industry, including: pipes, hoses, fittings, cements, coatings, gaskets, adhesives, lubricants, media, water meters, valves, filters, faucets, fountains, and more.

So you might ask – why does the NSF require different materials and regulations for gaskets compared to years ago?

First things first – leaks are a major issue with the aging infrastructure. Improperly placed gaskets & seals or faulty products can cause leaks. This in turn could pose health risks to people drinking potable water or using products processed with potable water.

Additionally, the treatment process and chemicals utilized are Picture of NSF 61 Compliant Sealsdifferent from previous “standard” products. For example, research and testing over many years has concluded that traditional gaskets, which were used many years ago, could pose a safety threat to those drinking water processed with specific materials. This led to updated regulations for NSF 61’s drinking water system components.

Lastly, engineered sealing solutions are more important than ever. There’s a wide variety of custom engineered water systems throughout the U.S. – climate, geographic terrain, and the needs of the community are all reasons for why water infrastructure is so unique. Because of this, custom gaskets, seals, and other products are needed to supplement those systems.

Luckily there are many companies dedicated to providing the highest quality NSF 61 products. These trusted brands have proven materials to count-on when replacing or repairing water infrastructure:

Garlock’s NSF 61 Family of products

Parker’s NSF compliant products

Freudenberg’s new generation of NSF products

For more information on how Gallagher Fluid Seals’s engineers can help you with a custom solution, call us at 800.822.4063

Case Study: Self-Lubricated Polyisoprene for Medical Septum Applications

Case Study: Self-Lubricated Polyisoprene for Medical Septum Applications

The project

Develop a system that reduces the needle drag and piercing resistance of the septum and injection site materials to increase product performance.

The solution

Chemists developed a family of self-lubricated polyisoprene materials that have been manufactured with a proprietary lubricant system and show a minimal reduction of physical and mechanical properties.

By Saman Nanayakkara and Shu Peng

Due to its availability as an ISO 10993 medical grade compound, polyisoprene rubber, which has a unique set of combined mechanical and chemical properties, has been widely used in medical device applications. The material is ideal for septums and injection sites for medical fluid transfer applications. Medical grade polyisoprene compounds have high tear strength and high elastic resilience. These characteristics can provide the desired resealability properties of the septum or injection site after piercing one or more times with a needle.

Medical device manufacturers have long sought a reduction in needle drag or piercing resistance of septum and injection site materials to increase product performance. Post molding surface treatment to modify coefficient of friction is the conventional approach taken to reduce tackiness for improved part handling. This process, however, is a surface treatment for reducing surface friction and does not effectively reduce needle drag, which is caused largely by friction within the septum and injection site materials. Furthermore, this secondary surface treatment adds additional cost to the component.

Table of mechanical property comparisons

Continue reading Case Study: Self-Lubricated Polyisoprene for Medical Septum Applications

The Basics of Microwave Absorber Materials

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.

You’ve probably heard a bit about microwave absorbers and how they are used to reduce or absorb the energy that is present in a microwave. But what are they exactly? And how do they work? Go ahead, read on.

What are microwave absorbers?Picture of Microwave Absorber

Simply put, microwave absorbers are special materials, often elastomer or rubber based, which are designed to offer a user-friendly approach to the reduction of unwanted electromagnetic radiation from electronic equipment. They also work well to minimize cavity to cavity cross-coupling, and microwave cavity resonances. When comprised of a silicone elastomer matrix with ferrous filler material, microwave absorbers provide RF absorption performance over a broadband frequency range from 500 MHz to 18 GHz.

Continue reading The Basics of Microwave Absorber Materials

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

A Guide to Elastomer Technology in Mechanical Seals

Elastomer Technology in Mechanical Seals

Evaluate properties of rubber during installation and seal life.

Elastomers (or rubbers) are a ubiquitous family of materials whose use stretches across nearly the entire range of mechanical seal designs.  From plant-sourced natural rubber, so named by John Priestly in 1770 for its utility in rubbing away pencil graphite, to petroleum-sourced synthetic rubber first developed around the turn of the 20th century, the “elastomer” and their properties are familiar but should not be overlooked—especially when dealing with mechanical seals.

How Elastomers Work in Mechanical Seals

Rubber seals come in a variety of profiles—O-rings, cup gaskets, bellows diaphragms, sealing/wiper lips and many others. They are classified as either static or dynamic and create positive pressure
against surfaces to eliminate or control the leakage of liquids and/or gases while preventing the entrance of external contaminants such as dust and dirt. Static sealing occurs between adjacent surfaces with no relative motion, such as between the pump casing and cover. Due to frictional wear and heat generation, dynamic sealing is less straightforward, occurring between adjacent surfaces that are continuously or intermittently moving relative to another, such as between the pump casing and shaft.

In mechanical face seals, elastomers tend to take second chair because the primary seal—the dynamic seal between the housing and rotating shaft—is achieved by sliding contact between the pair of stiffer, lapped-flat sealing faces, one stationary in the housing and one rotating with the shaft. In many designs, rubber provides the secondary seal between each seal face and adjacent surface. One seal face is fixed and sealed statically using an O-ring or cup gasket. The other is spring-loaded and requires a semi-dynamic seal to accommodate some axial play, such as a dynamic O-ring in pusher-type mechanical face seals or elastomeric bellows in nonpusher ones. These semi-dynamic applications (involving flexing and sliding of the elastomer) can be critical for maintaining proper contact between the faces through face wear, shaft movement, etc.

Although the seal face pair tends to be the most critical design feature, mechanical face seals are  often used in the most demanding applications.

Rubber technology features prominently in radial lip seals, where typical applications have lower pressurevelocity (PV) values relative to those involving mechanical face seals. Still, the flexible elastomer lip must handle considerable relative motion in the form of shaft/bore rotation, reciprocation or a combination of both. In addition to standard designs and sizes, numerous customizations and proprietary approaches exist. The simplest designs rely on a single rubber lip’s inherent resiliency, although common enhancements include multiple sealing lips, a circumferential garter spring installed in a groove over the sealing lip to maintain contact with the shaft, and an auxiliary wiper lip or “excluder” to prevent abrasive dust or debris from compromising the primary sealing surface. For improving service life and performance in rotary applications, unidirectional or bidirectional hydrodynamic pumping aids can be added in the form of custom-shaped extrusions on the backside of the sealing lip to return leaked fluid to the sealing interface, increase lip lubrication and lower operating temperatures.

Diagram of secondary, dynamic elastomeric seals in mechanical face seals.

Benefits of Rubber

The definition of an elastomer provides initial insight into where rubber gets its resilient sealing quality: “a macromolecular material which, in the vulcanized state and at room temperature, can be stretched repeatedly to at least twice its original length and which, upon release of the stress, will immediately return to approximately its original length.”

When the rubber is squeezed by the adjacent surfaces of the clearance gap to be sealed, it has the characteristic
properties of malleably deforming and taking the shape of each  surface in response to the stress and applying a force back against the surfaces in its attempt to return to its original dimensions. Elastomers consist of large molecules called polymers (from the Greek “poly” meaning “many” and “meros” meaning “parts”), which are long chains of the same or different repeating units, called monomers, usually linked together by carbon-carbon bonds (the
most notable exception being silicone elastomers, which are linked by silicon-oxygen bonds). Soft and hard plastics are also composed of polymers. However, the regularity of the monomers in their polymer chains allows neighboring segments to align and form crystals, making the macromolecular plastic material rigid and inelastic.

One can prevent this crystallization by breaking up the regularity of the polymer chain, resulting usually in a viscous “gum” that is readily shaped into molds. At the molecular level, the polymer chains are similar to spaghetti-like strands flowing past each other.

During the process of vulcanization, Representatin of three polymer chains after formation of crosslinking via vulcanizationor curing, the viscous liquid is heated with sulfur or peroxides and other vulcanizing agents, and crosslinks form between polymer chains, tying them together with chemical bonds, converting the gum into an elastic, thermoset solid rubber that retains its shape after moderate deformation.

In addition to the selection and preparation of base polymer(s) and cure system ingredients, formulating the final rubber product, also known as compounding, involves five other broad categories of ingredients, which have percentage compositions expressed in parts per hundred rubber (phr). Fillers include various powders that thicken the polymer mixture, improve strength and resistance to abrasives, and reduce final cost. Plasticizers are oils and other liquid hydrocarbons that lower viscosity to ease processing, soften the final compound and in some cases improve low temperature performance. Process aids are specialized chemicals added in low concentrations to improve mixing, flow properties and final appearance.

Antidegradants protect the rubber from environmental attack. Finally, various miscellaneous ingredients may be added for special purposes, including foaming agents, dyes, fungicides, flame
retardants, abrasives, lubricants and electrically conductive particles. A simplified description of processing these ingredients includes mixing via tangential or intermeshing mixers, forming into desired shapes and vulcanizing into the final product.

Continue reading A Guide to Elastomer Technology in Mechanical Seals

A User’s Guide to Expansion Joint Control Units

Expansion Joint Control Units

Elongation settings are a vital factor to assembly effectiveness.

Diagram of Control Unit and Control Rod Components

It is no secret that one of the greatest demands for an expansion joint is the expectation to serve a long, leak-free life with little-to-no maintenance. Once installed, these flexible rubber connectors should require little attention. The preservation of this investment (and one’s sanity) can be maximized with an in-depth overview of how control units can prevent a new expansion joint from being overstressed.

The purpose of a control unit is to act as a safety device against excessive movement resulting from pressure thrust. A typical control unit assembly is comprised of threaded rods, steel gusset plates, nuts and washers (see Images 1 and 2).Diagram of Effects of Pressure Thrust

The usage of control units with an expansion joint is always beneficial; pressure spikes during a system upset can cause uncontrolled surges through the expansion joint. This is a prime example of how valuable it is to have control units installed to protect these rubber assets from damage.

Methods to the Madness

A common misconception about control units  is that they are designed to support the weight of pipe members or act as a substitute for adequate mounting. They are not. The sole purpose of a control unit is to allow the expansion joint to move freely within a specific range of movement while preventing the joint from being overstretched from pressure thrust forces.

The control units in no way impede the joint from performing its other duties beyond movement  (vibration absorption, cycling or compensation for misalignment). The few extra steps needed to install the control units with the expansion joint could pay notable dividends in the long run.

Pressure thrust plays a huge role in how an expansion joint functions. While under pressure, the forces acting on the inside walls of the expansion joint actually cause the joint to swell and elongate. In the real world, an expansion joint is held comfortably between two pipe flanges, which in most cases are restrained by a pump lagged to the floor or mounted to a structural beam. Although it may not be apparent to the naked eye, once the expansion joint sees pressure, it produces a thrust force that acts axially on both pipe flanges.

Theoretically, what would be the result if the expansion joint was unrestrained on each end while pressurized?

Without fixed ends, the pressure thrust would force the joint to elongate without bounds.

Most useful in high pressure applications, the control rods will  engage with the gusset plates once a pre-specified amount of growth for the expansion joint has been reached, restricting the joint from stretching any further. At this point, the control rods are absorbing any additional thrust  acting on the pipe flange, thus limiting the amount of stress that is exerted onto adjoining equipment.

The design theory for sizing control unit hardware is based on the pressure thrust. Nominal inside diameter (ID) and arch geometry of the expansion joint are key drivers for calculating the thrust force that will be applied to the pipe at maximum line pressure. Per

Arch Diameter Diagram

industry standards set by the Fluid Sealing Association (FSA), both control rods and gusset plates are designed to withstand no more than 65 percent of the yield strength of the material.

Magnitude of the pressure thrust can be calculated by knowing the internal pressure and the effective area of the expansion joint. Effective area is found using the arch diameter of the expansion joint, which takes into account the size of the arch.

For example, we can calculate the resulting pressure thrust for a 10-inch ID expansion joint using an arch height of 1.5 inches that is rated for a maximum pressure of 250 pounds per square inch (psi).

The equation for pressure thrust “T” is:

Equation for pressure thrust

These design limitations based around yield stress are the reasons why some control units made from lower yield strength stainless steel contain thicker components or more rods per set than the standard carbon steel control units.

Installation & Inspection

For a control unit assembly to be effective, rod positioning and elongation settings are critical during installation. Each control rod should be evenly spaced around the flange to best distribute the load. Elongation settings (see Image 5) are often overlooked, yet are a vital factor to ensure the control units fulfill their intended use.

Every expansion joint comes with movement ratings based on arch size, configuration and number. These movement design ratings of the expansion joint are critical pieces of information that are absolutely required during the installation of control units. The general rule of thumb is the gap between the gusset plate and the nut should be adjusted to match the joint’s elongation rating.

Having this information at hand during installation is great, but what about the existing control units currently in operation? Visual inspections of these components are a basic task that goes a long way toward extending the life of the joint.

Here are the top 4 anomalies to look for when performing a field inspection: Continue reading A User’s Guide to Expansion Joint Control Units

Gallagher Case Study: Design and Fabrication of Custom Molded Gasket

Gallagher Fluid Seals helps meters & instruments manufacturer through the design and fabrication of a custom-molded gasket with an engineered profile.


The Problempicture of micro corrector

Our client’s micro corrector was experiencing water intrusion past the gasket, caused by improper seal material and configuration.

The Approach

Gallagher Applications Engineer Benjamin Mell worked closely with our client to identify & address the issue and suggested sending a sample of the instrument to GFS headquarters. Our engineering team received the hardware and investigated the root cause of the seal failure.

GFS engineers observed that our client’s closed-cell foam gasket had taken a severe compression set. This was limiting the life & effectiveness of the foam seal, which in turn allowed water to penetrate the instrument and damage the electronics.

The Solution

picture of the red seal inside the micro corrector
Figure 1.

Based on our experience and industry insights, GFS was contracted to design & fabricate a custom-molded gasket with an engineered profile to properly mate with the hardware and perform to customer expectations/ requirements. (see Figure 1. red seal)

Results / Next Steps

The Gallagher-engineered gasket solution was a success; it eliminated water intrusion and damage to the electronics, reduced warranty claims, and provided a more reliable product.

With the success of this project, GFS is partnering with our client for additional custom solutions. Next, we plan to help design and fabricate a window seal on the micro corrector to further decrease the possibility of water intrusion.

For more background about this case study, click here.

The Rise of Metal Detectable O-Rings

Food Safety Modernization Act (FSMA)

Every year, nearly 1 in 6 people in the U.S. get sick (~48 million people), 100,000+ are hospitalized, and 3,000 die from foodborne illnesses or diseases, according to data from the CDC. Though this is largely a preventable problem, it still poses a significant public health burden.

The FDA Food Safety Modernization Act (FSMA), enacted by Congress in 2011, is “transforming the nation’s food safety system by shifting the focus from responding to foodborne illness to preventing it.”

Although one might think the relevancy of the FSMA isPastries on a Conveyor Belt more geared towards the food or beverage product itself, this act is actually vital to the processing operations in food, beverage, and pharmaceutical industry.

Over time, exposure to continuous vibration, volatile temperatures, and corrosive chemicals can cause O-rings in processing operations to become worn and eventually fail. When this occurs, particles of rubber from seals and gaskets can shear-off and migrate through sanitary systems, piping mechanisms, or by other means, eventually entering the product stream.

In some cases when a problem is discovered, equipment must be shut down and visual inspections conducted to find the source of contamination. This leads to downtime, lost production, and lost revenue. If the contaminant ends up in the supply chain, even more risk is assumed due to recalls or litigation.

Enter the metal detectable O-ring.

Continue reading The Rise of Metal Detectable O-Rings

Engineered Materials and Sealing Solutions for Flow Batteries

Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Blog.

Sealing can often be a frustrating challenge when dealing  with flow batteries. Determining what materials are compatible with certain chemistries or developing a profile that provides optimal sealing under available compression can be a time-consuming task for those outside the sealing industry. A trial and error approach can have a significant overall cost impact through multiple prototype iterations, prolonged testing, and ultimately, delaying product commercialization.

Specialized support

Parker’s design and material engineers can provide support to your team in the critical, early stages of product development. With hundreds of engineered elastomeric materials to choose from, our team can identify and recommend a compound that works with your specific electrolytes or other fluids. With the exceptionally long lifetime requirements of flow batteries, our homogeneous rubber provides the elasticity needed to handle the many charge-discharge cycles the battery will see in its life.

Continue reading Engineered Materials and Sealing Solutions for Flow Batteries