The bolt as a screw is one of the six simple machines. A simple machine magnifies or changes the direction of an input force. By means of mechanical advantage, a bolt can dramatically increase its input force. Take for example an 8-bolt flange with 3/4-inch diameter bolts. By manual effort alone, a person can easily develop a total bolt load of over 110 tons. This article explains the mechanics by which the mechanical advantage is possible and then draws attention to how friction can deteriorate the end effect of a bolt’s mechanical advantage.
The means by which a bolt can greatly magnify input load is by leverage. One source of this leverage is afforded by the geometry of the bolt. The other is the leverage from a tightening tool—in this example, a torque wrench. To illustrate the mechanics of a screw thread, consider a 3/4-inch diameter, Unified Course (UNC), A193 B7 bolt with a yield
The hole is either aligned with flow and open, or perpendicular to flow and closed. The straightforward, quarter-turn action is fast and simple to operate, and the position of the handle provides a clear indicator of whether the valve is open or closed.
Most ball valves are typically used as a shut-off valve. Many households likely use ball valves at some point in the water supply plumbing.
Not relegated to common plumbing, many industries use ball valves for critical control applications including aerospace and cryogenics. Their reliable operation and high-pressure handling ability make them an attractive solution for many specialty operations.
The seals inside the ball valve play an important role in their performance and reliability. There are two main seals in a common ball valve, which are referred to as seats.
The seats are typically machined or molded to match the diameter of the ball and are mechanically compressed against the ball face. Seat material varies by application needs, but virgin PTFE is frequently used for this application.
The customer wanted a very specialized ball seat: utilizing a spring energizer in the seat. While easy to suggest, this would create a significant challenge in how the seal is manufactured.
The customer was looking for a sealing solution for a ball valve in their industrial gas processing plant. The ball valve would serve as a critical shut-off point in the system. The valve would be actuated by an electric motor, and could therefore be operated remotely.
The customer was looking for an improvement in the overall wear life of the ball seats, while still providing consistent and predictable actuation torque. Being motor activated, the torque required to move the ball open or closed was limited—so the friction generated by the ball seats would need to be carefully controlled.
Operating Conditions:
The drive for operational efficiency, optimization of assets, and adherence to the International Standards Organization (ISO) 14001 Standard for environmental management systems and ISO-50001 standard for energy management systems must always be balanced against the bottom line.
However, it is fair to say in some cases this can lead to short-sightedness when it comes to selecting sealing solutions, with lower cost at point-of-purchase taking precedence over total cost of ownership.
Mechanical seals have been on the market for around 80 years, and while pump design has remained largely unaltered, sealing technology has evolved over time. This has resulted in advances in reliability, operational efficiency, and environmental sustainability.
Traditional sealing options like gland packed seals and lip seals are traditional for a reason. These products are comparatively inexpensive when taking the purchase price into account, and work well in many applications. This article will take a look at the differences between mechanical seals, gland packed seals and lip seals.
Leakage, product loss and bearing contamination that leads to premature failure are three common issues with traditional seals.
There is no reason why bearings should not last for their full predicted lifespan, which is typically calculated at roughly 15,250 operational hours. Leakage caused by inefficient sealing is the simple reason why they do not last. With research showing that water contamination of just 0.002 percent—a single drop—in a bearings chamber can reduce bearing life by almost half, it is easy to see why bearing failure is one of the most frequent causes of pump malfunction. The cost of regularly replacing damaged seals and bearings accumulates over time and can escalate if the pump shaft suffers wear damage and must be repaired or replaced.
Another key cost, which is often overlooked, is the number of hours demanded to maintain, repair and replace these components.
Article re-posted with permission from Parker Hannifin Sealing & Shielding Team.
Original content can be found on Parker’s Website and was written by Nathaniel Reis, applications engineer, Parker O-Ring & Engineered Seals Division.
When it comes to semiconductor fabrication processes, reducing the cost of ownership is a multi-faceted goal approached from a variety of angles. Tool engineers and equipment technicians take pride in their ability to identify factors that limit tool uptime. One constant headache they face is the mechanical failure
When it comes to food, Freudenberg wants to be sure that its sealing materials are free of harmful substances.
In the food processing industry, in order to guarantee food safety, both the food and the hardware that come into contact with it must meet particularly stringent criteria. These guidelines also apply to sealing materials.
In China, specific standards were created in 2016 with the two standards GB 4806 and GB 9685, which deviate from the existing relevant American and European regulations for food-grade materials. To meet the stringent Chinese regulations, FST has now successfully tested two proven VMQ materials: 70 VMQ 117055 and 60 VMQ 117117 for their conformity with Chinese guidelines.
The Chinese standard GB 9685
The search for the ideal Polytetrafluoroethylene (PTFE) gasket has been elusive. Competing applications and workplace variables have led to the creation of myriad solutions, yet none that has proven fully adaptable and appropriate for universal adoption.
Garlock Sealing Technologies considered this to be a critical yet entirely solvable shortcoming. And it is against this backdrop that in 2016, they set out to compile a comprehensive list of attributes for the ideal PTFE gasket — a wish list, as it were — in order to build a better gasket.
Working with a third-party survey development company, Garlock developed an exhaustive questionnaire that probed every aspect and functionality of PTFE gaskets, testing and adjusting the questions until they had a workable, finalized version.
Using this final questionnaire, Garlock conducted extensive interviews at 15 major chemical processor companies, speaking with 20 engineers responsible for process operations, projects, maintenance and reliability. The goal was simple: to discover the ideal characteristics and their relative importance that engineers sought in a PTFE gasket.
After several months of data collection, Garlock analyzed the feedback and noted the most popular responses:
From those answers, Garlock drew the following conclusions, representing the most desirable and essential PTFE gasket characteristics:
Garlock used this feedback in developing a next generation PTFE gasket — GYLON EPIX. Featuring a hexagonal surface profile, GYLON EPIX offers superior compressibility and sealing for use in chemical processing environments. Its enhanced surface profile performs as well or better than existing 1/16″ or 1/8″ gaskets, allowing end-users and distributors to consolidate inventory, lower the risk of using incorrect gasket thicknesses and reduce stocking costs.
GYLON EPIX checks off the most desirable gasket attributes:
GYLON EPIX with its raised, hexagonal profile allows it to perform the job of both traditional 1/16” and 1/8” gaskets. It accomplishes this by combining the bolt retention of the former with the forgiveness for bad flange conditions of the latter, a truly innovative feature for PTFE sheet gasketing.
Rubber Compound Data sheets usually display a number of physical properties as recorded from standard test methods. Among the most common are three measured on the Tensometer:
The Tensometer stretches a specimen, or dumbbell, cut from a sheet of rubber, until it breaks. During the test, the force required and length of the gauged section are measured continuously. These measurements are used to calculate the various results, which considers the actual dimensions of the test specimen.
While Tensile Strength and Ultimate
Chemical plants are one of the biggest industrial users of corrugated metal hose assemblies. Processes performed in the plants involve some of the most demanding environments:
Metal hose can handle all of these factors and has some other inherent benefits over other hose types when it comes to the kind of applications seen in chemical plants. Let’s dig into some of the main areas of consideration and concern when dealing with chemical hoses.
Mishandling of hoses is one of the main contributors to premature failure. Because chemical plants have so many different inputs and outputs, hoses are often used to facilitate the transfer of chemicals from trucks, trains, or barges to the plant and even within the plant from one unit to another. Chemical blending manifolds are a great example of this, where a single hose assembly may be used for various connections at different times depending on what operations the plant is performing.
The need to easily connect and disconnect these hoses quickly and often makes cam and groove couplings a popular choice for chemical plants. When moving hoses from one outlet to another, it’s tempting for users to abuse the “arms” on the fitting and over-bend the hose or torque it into position. Always try and keep the hose as straight as possible, and avoid twisting it. Additionally, hoses are made to flex, but extremely tight bends (especially near the end fitting) can damage the hose and cause it to fail prematurely. Operators should keep this in mind to prevent deformation of the hose when making connections (guidance on using bend radius information can be found here).
There are several intrinsic features of metal hose assemblies that make them well-suited for chemical plant service. Chiefly among them is that they are not susceptible to permeation. This is a huge benefit for both operator safety, and plant safety. The metal core is puncture-resistant, and in the event of a leak, the hose will typically develop a small crack or pin-hole and does not burst apart!
Metal hoses also have a more compact end fitting configuration. Because end fittings are welded onto the end of the hose instead of a barbed or crimped mechanical attachment they don’t take up as much of the hose’s flexible length. This results in more working live length compared to non-metallic assemblies, which further facilitates handling and easier installation by the operators. It also means that metal hose is easily customized without the need for adapters. Stainless steel fabrication techniques provide the ability to use a wide array of fitting configurations, and can be tailored to prevent media entrapment, resist end-pull, or to accommodate high system pressures.
Finally, one of the handling benefits of metal hose is its light weight. Calling metal hose lightweight might sound contradictory, but pound for pound, metal hoses generally offer higher working pressures than rubber or composite chemical transfer hoses. This gives metal hose a wide range of potential applications, and also translates into easier handling and installation by operators.