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  1. Why Should You Choose Flex-Tex Expanded PTFE Instead of PTFE?

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    Expanded polytetrafluoroethylene (ePTFE) is a type of PTFE that offers flexibility, permeability, chemical resistance, and linear strength. It has widespread applications, in everything from the medical, pharmaceutical, and dental industries to aerospace and telecommunications. While it shares some properties with conventional PTFE, its unique structure makes ePTFE a preferred material for various applications. In this blog, we will explore ePTFE, its primary properties, and the applications that depend on the material.

    Flexibility

    Common for tubing, cords, and sealing tapes, Flex-Tex — another name for ePTFE — offers greater flexibility compared to conventional PTFE. The synthetic fluoropolymer material has a soft, spongy feel reminiscent of a marshmallow. Its pliability is a product of its microporous structure, which consists of a high strength fibril matrix.

    The ePTFE production process creates this heavily connected fibril matrix as manufacturers expand the material in controlled environments. Manufacturers can adjust the material’s flexibility to meet the needs of a specific client or application by varying the production process. Gaskets, seals, and related applications that benefit from increased flexibility utilize conformable ePTFE.

    Permeability

    ePTFE is also an excellent material for applications requiring high permeability. Its microporous nature makes it permeable to air, which PTFE is not, as well as other gases and water vapor. Despite this, ePTFE still maintains its resistance to particulates and liquids. Flex-Tex’s permeability makes it ideal for applications in the following:

    • Ventilation
    • Filtration
    • Making waterproof and breathable fabrics

    Like with ePTFE’s flexibility, the production process allows manufacturers to create Flex-Tex with the desired permeability for a specific application.

    Chemical Resistance and High Linear Strength

    As a fully fluorinated polymer like standard PTFE, Flex-Tex provides excellent resistance to various chemicals. It’s also chemically inert and non-reactive when applications expose it to most other chemicals and solvents. The material can maintain its integrity in the presence of concentrated nitric or sulfuric acids, as well as other corrosive substances.

    As a fully fluorinated polymer like standard PTFE, Flex-Tex provides excellent resistance to various chemicals. It’s also chemically inert and non-reactive when applications expose it to most other chemicals and solvents. The material can maintain its integrity in the presence of concentrated nitric or sulfuric acids, as well as other corrosive substances.

    ePTFE Services From Master Packing and Rubber Company

    Flex-Tex or ePTFE is expanded under controlled conditions to deliver unique material properties that conventional PTFE cannot. That said, it’s the requirements of your individual application that determine whether standard PTFE or ePTFE would be your best option. When selecting a material for your project, speak with an engineer or materials specialist first to help you determine the ideal choice.

    At Master Packing and Rubber Company (MPRC), we’ve been delivering innovative, USA-made sealing solutions for clients since 1982. Among our product line of custom cut gaskets and seals, mechanical packing solutions, chemicals, and materials, we offer versatile, high-performance Flex-Tex expanded PTFE as a reliable joint sealant, ribbon, pipe tape, and valve stem packing option. With an adhesive backing, Flex-Tex can help you handle your maintenance and emergency needs in industrial equipment.

    This FDA-compliant material of 100% pure PTFE is compatible with nearly any surface material, producing an exceptionally tight seal with simple application. As a form-in-place gasket, it’s rated for temperatures ranging between -350°F and 550°F as well as a pH of 0 to 14, and resists cold flow and creep. This long-lasting sealing solution also provides an unlimited shelf life, not experiencing deterioration over time.

    At MPRC, we strive to provide real solutions to diverse problems and environments. Contact us to find out if Flex-Tex is the ideal choice for your application, or request a quote today to get started.

  2. What Are O-Rings? All You Need to Know

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    What is an O-ring, and what purposes do various O-rings serve? While an O-ring’s basic function is relatively simple, there are several important considerations to make when choosing the right one for your application to ensure your O-ring can withstand high pressures, temperatures, and other operating conditions. Read on to learn more about O-rings, what various industries use them, and how to select the right O-ring for your needs.

    What Are O-Rings?

    O-rings, also known as rubber rings or toric joints, are ring-shaped seals possessing a circular cross-section to resemble their namesake letter O. They’re primarily made of a rubber elastomeric material and provide an affordable and reliable means of sealing hydraulic, pneumatic, and related machinery components. It should also be understood that in addition to elastomeric materials such as the standards as Nitrile, Neoprene, EPDM, Silicone, and others, that O-rings are also made from metals, thermoplastics, fluoroelastomers (FKMs) like Viton™, all application-specific materials for optimal performance. Popular for their easy manufacturability and fit, they secure to mating surfaces and prevent pressurized liquids or gases from escaping hoses, piping, and other such system passageways.

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    What Are O-Rings Used For

    What Are O-Rings Used For?

    O-rings have applications across diverse industries to fulfill varied sealing needs.

    Transportation

    O-rings are essential to the transportation sector, supporting modes of transport ranging from cars and trucks to railroads, marine boats, and aircraft. The best elastomer for a given transportation application depends on its intended exposure to vibration, temperature extremes, chemicals, and harsh environmental conditions. These O-rings will also have to comply with emission and biofuel regulations, which is why manufacturers continue to innovate to create custom O-rings that meet Tier 1 and OEM standards.

    Oil, Gas, & Industrial

    Oil and gas refineries use countless valves, fittings, pumps, storage tanks, and other components that require durable seals. O-rings for industrial use must stand up to high pressures and temperatures, as well as corrosive chemicals. Such applications benefit from O-rings composed of peroxide and triazine-cured perfluoroelastomers and other such specialized compounds.

    Electronics

    O-ring uses in the electronics industry include protecting sensitive electronic components from contaminants like dust. To fulfill this sector’s need for particulate-free O-rings for applications like semiconductor processing, manufacturers can produce them in clean environments from an array of material options.

    Healthcare

    The medical sector depends on O-rings for connectors, filtration systems, pumps, and syringes. To ensure product safety for patients and healthcare workers, manufacturers of O-rings for medical equipment must construct them from specialized, medical-grade materials and in sterile clean room conditions.

    Food & Beverage

    Equipment for food and beverage processing and dispensing, as well as water filtration applications, all require effective, FDA-compliant sealing solutions. Specialized O-rings constructed in accordance with food safety and sanitation standards are available to meet NSF-61 and 3A sanitary requirements.

    Considerations for Choosing an O-Ring

    While there are numerous types of O-rings available, the right option is the one that precisely matches the intended application. When comparing different O-ring materials, you can make the proper selection by evaluating multiple factors.

    Material

    Choosing the right material is critical to ensuring an O-ring can handle your application’s:

    • Pressure limits
    • Ambient and operating temperatures
    • Exposure to chemicals, acids and bases, and other sources of corrosion
    • Likelihood of experiencing vibration
    • Industry standards (e.g., sanitation, food safety, etc.)

    Pressure Rating

    O-rings provide leak protection within pressurized systems, and each comes with its own pressure rating. It’s important to have a thorough understanding of the maximum pressure utilized in your system and select an O-ring with a PSI rating that exceeds that maximum by a safe margin.

    Sizing

    In designing for O-ring use, whether standard AS 568A sizes will be used or a custom size, it is critical that not only compatibility to the media being sealed is considered along with temperature and pressure, but also stretch and squeeze of the O-ring for the application, whether it is to be used as a static seal or to be used as a dynamic seal, in which case friction must also be considered.

    Durometer Hardness

    O-rings must also be the right hardness for their intended application so as not to experience deformation. Manufacturers can verify an elastomer material’s hardness using a Shore durometer. Typical O-rings usually have durometer ratings that normally fall between 40 and 90, meaning that their material is on the softer or harder side, respectively.

    O-Ring Solutions From MPRC

    Choosing the right seal for your application depends entirely on the use conditions involved. At Master Packing and Rubber Company (MPRC), we specialize in rubber elastomer and related seal technologies to withstand varied environmental exposures and operating conditions. Our cut gaskets and seals support peak performance in your systems, designed for optimal leak protection. O-rings from MPRC are available in a range of material and design options so that we can provide the product versatility that clients in diverse industries require to find ideal sealing solutions. While we produce a variety of customer specific designs, we also provide standard AS 568A sizes and stock in several elastomeric materials.

    Contact us to learn more about the various O-rings we offer, or request a quote today.

  3. Exhaust Gasket Material: Types and Applications

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    Exhaust Gasket Material: Types and Applications

    Exhaust systems are exposed to extreme levels of heat, which means their gaskets must have the properties to withstand this and other harsh conditions. Learn about the characteristics to look for in exhaust gasket materials so that you can select the right types of gaskets for your exhaust system.

    Ideal Characteristics of Exhaust Gasket Materials

    The following are some of the specific characteristics to look for in exhaust gasket material types.

    Heat-Tolerant Filler Material

    The facing/filler material of the exhaust gasket must be able to handle exposure to high temperatures without any compromise in its structural integrity. Otherwise, the seal can experience premature wear and failure.

    Metal Reinforcement

    Gaskets with metal reinforcements will benefit from increased durability, strength, and holding power throughout their service life.

    Low Creep Relaxation

    Graphite filler materials give the gasket low creep relaxation. Low creep relaxation means that the gasket material won’t experience much loss in thickness over time or under exposure to extreme heat. As a result, the gasket will maintain reliable flange loading that keeps the seal intact.

    Abrasion Resistance

    If your exhaust system contains joints with high thermal motion—including joints made of two or more dissimilar metals with varying contraction and expansion rates under heat—you may benefit from a clad-style exhaust gasket material to resist abrasion.

    Exhaust Gasket Material Types

    Based on the characteristics required of your gasket material, you may select one of the following gasket material types:

    • Composite graphite — Some gaskets may use composite graphite for its superior performance and lighter weight. Many of our composite graphite exhaust gaskets have a Kammprofile design, especially for use in the marine and rail sectors.
    • Multi-layer steel — These gasket materials comprise multiple sheets of either carbon or spring steel with the sealing material between them. Our rail and marine multi-layer exhaust gaskets are double-jacketed.
    • Multi-layer steel with MOS coating — This multi-layer steel material has a dry film lubricant coating made of molybdenum disulfide (MOS) to help reduce wear.
    • Ceramic coating — A gasket with a ceramic coating will withstand road grime, water stains, and other types of substances.
    • Sandwich type — These gaskets include two thin layers of aluminum, copper, steel, or another type of metal with a center layer of graphite.

    Exhaust Gasket Material Applications

    Our exhaust flange gasket materials are compatible with a wide range of exhaust systems from major manufacturers:

    • Caterpillar: C7, C9, C10, C12, C13, C15, C27, C32, and G3500 engines
    • Cummins: QSK60, IX, ISB, K38, ISX12, and QSB3.3 engines
    • Detroit Diesel: S60 and DD15 engines
    • Mack: E7 engines
    • MTU: Series 4000, Series 396, and Series 2000 engines
    • Navistar: DT466 engines
    • Volvo: D12 engines
    • EMD: 567, 645, and 710 engines
    • Wabtec: GE 7FDL engines

    Find the Best Exhaust Gasket Materials at MPRC

    It’s important to find the right exhaust gasket material for your application based on the types of conditions your exhaust system experiences. At Master Packing and Rubber Company, we provide our customers with innovatively designed and manufactured gasket exhaust materials that meet the requirements of various engines.

    For more information about our products and capabilities, request a quote today.

  4. Cut Gaskets vs. Molded Gaskets: What Is the Difference?

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    Cut Gaskets vs. Molded Gaskets: What Is the Difference?

    Gaskets fill the gap between the surfaces of two parts, joining them and creating an effective seal that prevents leakage. Manufacturers have multiple methods for producing various types of high-quality gaskets, depending upon the material selection, available equipment, and application requirements.
    Two common options are cut gaskets, which manufacturers cut from sheets of raw material, and molded gaskets, which are the product of one of several molding processes. Learn more about the unique advantages and proper applications of each type to help you choose the right option to fulfill your gasket needs.

    Cut Gaskets Explained

    From a sheet of material, CNC machinery cuts large volumes of components at high speeds, producing identical gaskets. They sit between two surfaces and create a tight seal through compressive force, filling any space caused by unevenness, gaps, or imperfections on those surfaces to make up for any design flaws. With common mechanical and plumbing applications, they’re useful for:

    • Automobiles
    • Bearings
    • Controls
    • Plumbing systems
    • Pumps
    • Valves

    Advantages of Using Cut Gaskets

    Some of the key advantages of CNC-cut gaskets include:

    • Production speed. As you won’t need to first create a custom die to generate your gaskets with die-less gasket cutting, you can achieve quality gaskets in a matter of minutes or hours rather than the process taking days or even weeks.
    • Cost-effectiveness. CNC-cut gaskets don’t require expensive tooling or molds, just development costs for the computer-aided design (CAD) file to guide the cutting process. This process makes cut gaskets more affordable to produce than using alternate techniques.
    • Shape customization capabilities. When you need gaskets in specific sizes or unique profiles, CNC-cut gaskets offer versatility in their customization options.
    • Resistance abilities. Equipment systems commonly utilize hot fluids, meaning gaskets must withstand high temperatures and pressures. Cut gaskets come in an array of materials, allowing you to choose one with the right pressure and heat resistance for a long-lasting seal.

    Molded Gaskets Explained

    Molded gaskets offer more complex and versatile designs. First, manufacturers build a precision mold with a cavity in the shape of the desired gasket. Then they fill the cavity with a plastic, rubber, or other uncured elastomer substrate where, through heat and pressure, the material sets and cures, retaining the mold’s shape.
    Three common techniques for producing molded gaskets are:

    • Injection molding. The fastest of the molding processes, injection molding produces highly consistent gaskets that minimize or eliminate the need for secondary finishing or trim work due to their optimal surface finish without flashing.
    • Compression molding. Manufacturers turn to compression molding to generate large-sized molded gaskets. It’s a cost-effective method with low mold and per-part costs, and it produces little unreusable waste.
    • Transfer molding. This process is relatively fast and, compared to compression molding, transfer molding offers enhanced uniformity in gaskets. It’s well-suited to manufacturing molded rubber-to-metal components.

    Advantages of Using Molded Gaskets

    While there are tooling costs that accompany the molding process, molded gaskets offer a range of benefits, including:

    • Enhanced design options. Using custom molds, you can generate three-dimensional gaskets, integrate additional parts into your mold’s design, create parts with varying cross-sections, incorporate engraving, and more. 
    • Dimensional accuracy. Molded gaskets offer tighter tolerances than cut gaskets, particularly where thickness is concerned. They create a secure bond between surfaces while enabling joint flexibility.
    • Improved leakage protection. Molded gaskets don’t have splices, creating fewer opportunities for leakage.
    • Minimal waste. Molding generates little material waste, which equates to the added benefit of per-part cost reductions.

    Gaskets We Offer

    At MPRC, we offer a wide range of gaskets and manufacturing options to suit your needs, including:

    • Molded gaskets. Through injection, compression, or transfer molding, molded gaskets form through heat and pressure, offering design freedom, high performance, and close tolerances.
    • Lathe-cut gaskets. A CNC lathe turns a tube of material on a mandrel against a tool to cut material away and achieve completed, structurally stable gaskets in the desired shape.
    • Extruded gaskets. Elastomeric polymers like uncured rubber are forced through an extrusion die before being cut into the appropriate dimensions, taking the shape —  be it simple or complex — of the die.
    • Spliced gaskets. These gaskets start as extruded of material cut into specific lengths, after which the ends bond together through heat and/or adhesives for strong joints.
    • Metal gaskets. Formed or cut from large sheets of metal or alloys, these highly durable gaskets create a tight seal with good pressure and chemical resistance capabilities.
    • Die-cut gaskets. Using a premade die and any of several die-cutting processes, you can cut gaskets with tight tolerances out of a sheet of material.

    Find the Gaskets You Need With MPRC

    Master Packing and Rubber Company (MPRC) is a leading provider of seals, gaskets, and mechanical packing materials, with USA-made products for clients across the globe. Contact us today to learn more about what type of gasket is the right fit for your next project or to start your order.

  5. Mechanical Seals vs. Mechanical Packing — Which Sealing Method Works Best?

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    Seals are a simple method of preventing fluid from escaping a vessel. Equipment like centrifugal pumps rely on seals to contain large volumes of pressurized fluid. There are two types of seals: the traditional pump packing known as mechanical packing or gland packing and the more modern mechanical seal. Mechanical packings rely on a rope-like packing, cut into rings, that wraps around the shaft of a pump to fill the voids and throttle or control the fluid from leaking.

    mechanical seals vs. mechanical packing

    Mechanical seals are often preferred when leakage is unacceptable, such as applications involving hazardous materials. Their durable construction can withstand more wear and tear than mechanical packing without leaking. We will explain how pump sealing works and describe the differences between pump packing versus mechanical seals to help you determine the best solution for your application.

    Mechanical Pump Sealing Explained

    Mechanical seals consist of three sealing components: rotating, stationary, and secondary seals. The seals prevent leaks from the circumferential gap between the shaft and other pump components. The rotating and stationary seals are lapped flat to keep fluid and gas from escaping. The rotating primary sealing element, fastened to the shaft, seals against the primary stationary sealing element, normally fastened to the gland.

    Secondary seals are usually mounted between the stationary unit and the pump housing, and between the rotating unit and the pump shaft or sleeve. These are static seals, normally O-rings, PTFE wedges, or V-rings, and prevent leakage through these elements.

    The rotating and stationary primary seals are the most vital sealing points. The faces of the mechanical seals press together with the force of a spring. In some cases, mechanical seals can also come as hydraulically balanced, in which case the fluid takes over from spring pressure to keep faces together while the pump is running. To make the mating surface as flat as possible, surfaces are lapped flat and machinists use high-precision light-band optical flats to ensure accuracy.

    Mechanical Packing

    Choosing Between Mechanical Pump Packing vs. Mechanical Seals

    Pump packing and mechanical seals each provide benefits depending on the application. Mechanical seals offer the following advantages:

    • Reliability & Reduced Downtime: Long-term reliability and less downtime deliver a better return on investment.
    • Protect Fluid Products From Leakage: Eliminates leaking common in packing. Leakage from packing is common compared to mechanical seals and can waste significant product.
    • Low Maintenance: A lower risk of leakage reduces the need for time-consuming cleanup and adjustment compared to the glands in pump packing.
    • Less Frequent Access to Stuffing Box: It is unnecessary to access the stuffing box for adjustment or replacement of the packing gland.
    • Eliminates Sleeve Wear: Reliability of the seals eliminates frequent maintenance and removal of the sleeve that can result in costly sleeve replacement.

    Pump packing offers the following advantages:

    • Inexpensive: The initial cost of packing is lower than mechanical seals.
    • Quick Installation: There is no need to decouple the driveshaft when installing packing rings, as with mechanical seals.
    • Less Dependence on Equipment Condition: Mechanical seals often require excellent equipment conditions to be installed correctly.
    • Misalignment and Axial/Radial Movement: Packing can tolerate misalignment and axial or radial movements more readily than mechanical seals.
    • Flexible and Accommodating: Packing simplifies maintenance procedures and can reduce expensive parts inventory.

    Seals We Offer

    At MPRC Seals, we offer a range of sealing solutions. Our seals include:

    • Outside Seals: A seal mounted outside the seal chamber boundaries.
    • Bellows: A metal tube with an accordion function with little friction and no leaks.
    • Cartridge Seals: Combines seal components, gland, and shaft sleeve into a single cartridge. They facilitate normally easier installation with preset face loading and quicker removal from pump shafts.
    • Single: Two seal faces made from a hard and soft material for the rotating and stationary face.
    • Double Seals: Eliminates fluid and gas leakage to deliver the highest safety levels, normally set up with a flush.
    • Tandem Seals: Mounts an additional sealing chamber to the shaft seal to prevent evaporation and leakage.

    Rely on MPRC Seals

    At MPRC Seals, we have been delivering reliable seals since 1982. We find solutions to the most difficult sealing issues for customers in a range of industries. To learn more about our customer-focused sealing solutions, request a quote today.

     

  6. Hello From Robb

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    With our new website on it’s way up, we have decided to join the world of “blogging” and updating on “social media” to provide more information on our products, our beliefs and where we think we are heading.

    What initially started out as a one man rep agency on the “south-side” of Chicago calling on the refineries and steel mills, has developed in to a manufacturing business, now located in Cedar Rapids, Iowa. Starting out in 1982 and after some years of great struggle, we now sell worldwide into several markets, most notably the rail and marine engine rebuild and maintenance business. Today that represents about 60% of our business. The balance is in the maintenance business across a number of industries, predominately in the broader Midwest of the United States.

    With so many competitors in the fluid sealing market, we decided to create and develop our own brand name and products, and to look constantly for that next best material and / or process to always provide greater products and superior service for our customers.

    Today, we operate a number of computer controlled cutting tables so that we can, and do, deliver finished cut gaskets within less than 20 minutes to local customers, where down-time is critical and parts must be at their plant. We maintain a large diverse inventory of materials, from beater-add roll stock to high end PTFE and pure graphite sheet, all in a range of thicknesses.

    Years ago we started our own rubber molding department, and now with presses from 8” to 24” capacity, including vacuum injection equipment, we are molding parts that we had previously purchased from overseas sources. We are proud to be bringing jobs back to our great country, especially to be able to control our quality and output.

    We are also very proud of our entire team who consistently come through for our customers, to get orders entered, produced accurately through our quality program and shipped out the door for on time deliveries. And our MPRCseals.com Team is ready to perform for you. Give us a call and let us know how we might be able to work with you.

  7. Materials by the ASTM Specs

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    Materials and Understanding Choices through the ASTM Tests

    So many good competitors…so many good materials. It adds to the dilemma in picking who to work with and even more importantly, what to work with, when picking designs and materials for seals. I use the term “seals” broadly here to include all types of seals; die-formed packing rings, cut gaskets, o-rings, hydraulic packing, you name it…all are seals.

    I remember, when in the mid-70’s, two really exciting new materials hit the market. Expanded PTFE and exfoliated graphite. These products changed the fluid sealing industry in many ways, and yet, there are still a lot of people who resist them even today, more for lack of understand them and their potential to eliminate sealing problems.

    Some companies, including us, to some degree, promote gasket materials that have great “crush resistance” under heavy loads and higher temperatures. A valid point as we have seen applications where mechanical or virgin grade PTFE gaskets as an example, have extruded or cold-flowed under constant load and temperature over a period of time, leading to leaking and eventual re-torque until the gasket totally fails and needs to be replaced. A material with high “crush resistance”, creeps, or cold-flows only slightly, having high torque retention and requiring less maintenance time. But there are many other qualities in materials to consider. Crush resistance, while important for torque retention, is not the only property to consider.

    The new expanded PTFE materials are interesting because they resist creep / cold-flow much better and are also engineered with different types of fillers to take even greater loads, having higher torque retention and again, reducing maintenance time. Exfoliated graphite gaskets, when installed, will compress more, but when under operating load and temperature, resists creep / cold-flow extremely well and requires little maintenance time because of very high torque retention. But if you only looked at crush resistance as a qualifier, you would have to omit both of these materials.

    All of this becomes important when trying to decide on a material of choice for the application you may be working on. I don’t want to be pushing material at this point but rather some of the terms that we like to promote, to help the decision maker better understand what is important in making the choice. I believe you will find these helpful. They are not all of the tests, but these are key in trying to make a decision. Comments – questions??? Let me know.

    STANDARDIZATION OF PHYSICAL CHARACTERISTICS

    SEALABILITY

    Sealability is measured according to the ASTM F37 specifications. It is an indication of the materials sealing ability under a set of conditions; a seating stress of 2000 psi is imposed through the flanges on the material sealing iso-octane at an internal pressure of 14.7 psi. The test is done at ambient temperature and the number shown is the amount of leakage in milliliters per hour. A lower number would generally indicate a better material.

    COMPRESSIBILITY

    Compressibility is measured according to the ASTM F36A specification. A load of 5,000 psi is imposed on the material and the loss of thickness is measured and expressed as a percentage of the original height. The compressibility of a material indicates, to a degree, its ability to fill flange scratches, nicks or voids and to flow or move to assist in sealing misaligned or warped flanges. In general, the higher the number, the easier it is to seat the material.

    RECOVERY

    Recovery is also tested under the ASTM F36A specification. Recovery is the measured rebound or increase in thickness from the compressed measurement once the load is removed. It is written as a percentage of increase over the compressed measurement and indicates the ability of the material to resist temperature and pressure. The higher the number, the better the material is at holding torque.

    CREEP RELAXATION

    Creep relaxation, also referred to as Torque Retention, is measured according to the ASTM F38 specification and indicates the materials ability to hold stress or bolt load over a period of time. It is expressed as a percentage of the original load and shows the amount of lost stress from that load. A lower number indicates a more stable material retaining torque and resisting leakage.

    TENSILE STRENGTH

    Tensile strength is measured under ASTM F152 and is given in pounds per square inch. It is the total force required to pull the material apart and is not related to the sealing function of the material. It relates more to the manufacturing process.

  8. Maintenance Procedures For Better Sealing

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    Throughout the years, we run across a maintenance practice that does more harm than good. It is the practice of putting down a wet film of silicone RTV sealant, either on the gasket or on the flanges and then bolting up. There are basically two problems with this practice. First, by using any type of “lubricating material”, you remove the friction between the gasket and the flanges. That friction is needed to hold the gasket in place. With RTV silicone or oils, etc., the gasket will extrude, especially any gaskets made from sheet rubber products. Second, the RTV silicone contains a lot of volatiles which, when in its wet or gel state, off-gas into the gasket material and soften the elastomeric binder. The result is uncontrolled creep / cold flow which can result in failure of the gasket. We ran the tests shown so the results can be seen and compared.

    The gaskets on the LEFT, top (1/16” thick) and bottom (1/8” thick), were installed dry, tested to 572°F for 32 hours and removed. Almost no creep from original OD or ID. The gaskets on the RIGHT, top (1/16” thick) and bottom (1/8” thick) were installed with RTV Silicone Sealant and tested in the same manner. Both right hand column gaskets failed from excessive creep.

    For this test, we did not use any internal pressure so there was no blow-out force to further push out the gaskets on the right. The failures are the result of the gaskets elastomeric binders softened and a lack of friction between the gasket surfaces and the flange surfaces.

    It is important to remember that in order to achieve the best seal from a gasket material, friction between the gasket surfaces and the flange surfaces are critical. If you lubricate the surfaces with RTV Silicone Sealant, oil, or anti-seize compounds to name a few, you will experience premature gasket failure. For most flanges that have some type of “phonographic” finish, we recommend installing our gaskets dry. For smooth flanges we recommend either 3M Spray #77 or Permatex Aviation Grade Sealant. Both should be put on sparingly and allowed to “tack up”. The spray should be a quick pass over the gasket. The objective is to increase the friction between the surfaces of the gasket and the flanges, not to lubricate.

    It is also important to tighten gaskets properly. For instance, in a round gasket with just 4 bolts, you would start at the top, then proceed to the bottom, then the left, and then the right. Bring torque to 50% on the first pass. Repeat with torque to 75%. Repeat for a 3rd pass at 100%. You will experience some relaxation in the material after a 24 hour period and should do a re-torque at 100% and for that, you can start at the 12 o-clock position and just go around the clock. Do not over torque as you can crush and destroy the gasket and yield your fasteners. Over torquing a round gasket can also create “dishbowling” where the OD of the gasket becomes a fulcrum point and as the outer edges of the flanges come together, leak paths are created through the bolt holes.

    We hope you find this helpful in eliminating leaks and thank you for using our gaskets and seals.

    Master Packing & Rubber Company

    Web site: www.mprcseals.com

    Email to: sales@mprcseals.com