How To Use Graphite Valve Packing

Anybody is familiar with stem packing. The near common blazon is braided pinch packing. Braided packing is used in a wide range of applications. Depending on the service, construction materials can be equally diverse as plants or beast derivatives, mineral fibers or synthetic plastics, and even metal. The procedure of cutting rings from rope packing, inserting them into a stuffing box, and torquing them to the right density is familiar, merely that is not ever the case.

Another manufacturing method that EGC has been using since 1978 is called die-molding. It is the process of wrapping a fabric around a mandrel, placing it in a die and preforming it to brand a seal. EGC has 10 presses some measuring as small equally a 2,000-pound pneumatic press up to a 400 tons hydraulic press. The smaller parts require lower loading merely faster actuation time. The larger hydraulic press is significantly slower but has a higher load capabilities. Using these and other manufacturing technologies, packing is institute to piece of work in applications as different equally aerospace, heavy trucking and ability generation. Information technology can be hard to believe but 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 applied science dating back over 5000 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 wearable, sail cloth and rope, encompass it 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 exist tightened to compress the packing textile, was created to ameliorate sealing and longevity. Hence, the birth of the term'southward compression packing, stuffing box and gland.

EGC Thermabraid Pinch packing

Over fourth dimension, many improvements in packing structure and materials were made. Packing today can be made of Flax, Kevlar, PTFE, Graphite or metal. Information technology typically has a square cross section and is sold in precut rings or in large coils, every bit shown in figure 1.

Synthetic aramid fibers are abrasion resistant and tin handle higher temperatures and shaft speeds. PTFE has fantabulous lubricity and chemic resistance. EGC graphite coupled with mica or an aramid fiber can stave off the heat generated by a rotating shaft and provide long life in some challenging applications.

EGC Thermafoil Die-formed packing

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Figure 2. Die Formed ring

Die-formed compression packings are first-class on sealing performance and reliability and offer a broad range of long-term, depression-emission and low maintenance products. See Effigy 2. Not only are EGC die formed rings easier and quicker to install but the pre-compression increases the density of each band and reduces the gland loads necessary to seat and shrink multiple rings in the stuffing box. The result is lower friction on the shaft or the spindle, with improved sealing operation and a longer life. When EGC designs a die-formed band, it checks the mating components around the ring. When the clearances are tight, graphite maybe all you demand. When the clearances are too high, EGC adds materials similar anti-extrusion, mesh ends and braided packing on the meridian and bottom that is Inconel reinforced.

EGC looks next at density. The standard is 85 lbs./cubic pes where you take no controlled compression. Where at that place is controlled compression, we bring the installed density to a level where that makes a skilful, solid seal. EGC is an adept at weight and tolerance control, a superior system for tool designs and the agreement the growth of graphite. So, what happens when you enter a high-temperature awarding? EGC uses Thermafoil X due to the corporeality of extreme graphite oxidation that standard grades have.

Gene in STAMPS

Equally mentioned in an article previously published by the Fluid Sealing Association (http://www.fluidsealing.com/sealingsense/Sep18.pdf) , there are several key factors to consider when choosing the right packing. They include:

Size or stuffing box bore;
Temperature within the stuffing box;
Application: whether information technology's a pump, valve, mixer, refiner, process, characteristics such as pH level, and chemic compatibility
Thousandotion: rotary, helical or reciprocal;
Pressure inside the stuffing box and;
Surface Speed expressed in feet per minute or meters per second.

Keeping this in mind, here are some applications to consider when you're going way beyond the typical stuffing box!

Graphite and Wire mesh for frazzle systems – EGC die molded configurations of flexible graphite, mica or vermiculite densifies well when loaded in these flange couplings to seal truck & auto emissions prior to being cleaned by the afterwards-treatment and catalytic scrubbing systems. Due to the loftier vibration nature of these applications, wire mesh is used in combination with the sealing textile to provide a skeleton giving the sealing cloth a structural component to add immovability.

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Figure 3. Dice Formed Wire Mesh Reinforced

VSG and VSG Pro

There is no one else in the world that tin can engineer, industry and send a pressure seal in every bit trivial as a single mean solar day. EGC tin can meet the demands of the power plant rebuilders getting the facility back on line, right abroad. It's made of high-density graphite which means that it'southward resilient and seals every time and rebounds afterwards every cycle. It's compressible and conformable and works in out-of-round, oversize, steam cut and pitted valves. And it will never fuse to valve components. In studies for valve maintenance, y'all can salvage about 75% installing graphite over metal. Information technology is the fastest pressure seal on the planet.

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Metallic Caps for force per unit area seals – In the typical stem packing in a valve stuffing box, the high centric to radial load transition of a die molded configuration from the gland load creates the seal effectually the stalk. Bonnet pressure seals were originally designed to be made of solid metal and relied on procedure force per unit area to effectuate a seal. The all metal seal utilized the angle of the bonnet to amplify the unit load on the toe creating a single point metal to metal seal. More recently, EGC engineers establish a manner to use the high axial to radial load transfer of die molded flexible graphite to create a full crenel seal. However, they had to find a style to keep the graphite from extruding nether high unit loads. The most common way was to place a thin cap on the top and bottom of the seal. As opposed to a total metal ring sealing only at the toe, and having a potential to damage the valve, the packing-way die molded graphitic seal fully compresses and densifies to fill and seal throughout the entire bonnet cavity. Come across Figure 4.

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Figure 4. Metal Caps for pressure seals

Near of these pressure level bonnet valve configurations are found in power generation facilities, and in today'due south surroundings these plants are on-demand requiring their units to cycle in pressure and temperature oft. The unique adequacy of the die molded flexible graphite to remain resilient at ambience and high temperatures serves this application well, without causing undue habiliment to the valve itself. These valves can be expected to be in service for over 50 years.

Valve Remainder Seal – Balance seals are very similar in nature to stem packing in a ascension stem valve. Encounter the illustration in Figure 5 . They provide both an within and outside diameter seal for a linear motion device and use axial load to shrink the seal. It is typical to see a wire reinforced ring on the meridian and lesser to provide anti extrusion and wiping just like a valve packing stuffing box. However, an EGC Remainder Seal is designed into a closed cavity configuration which does not allow for adjustments to exist made while in service. In some cases, the blueprint requires that the packing leaks to some extent.

Friction is the biggest trouble in high-temperature control valves. Typically, the balance seal ring is unloaded while information technology moves up and down. When information technology hits bottom it needs to seal. Most recent designs have a fixed seal even while the plug if moving upwardly and downward within the cage. Merely EGC'southward design is dissimilar. When the valve opens, friction is reduced. The stem will brainstorm to rising and unload the seal band while taking the pressure level off the side walls.

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Figure 5. Integrated Stalk Wiping System

Dry Bulk handling systems – Dry Bulk pipage systems use EGC braided configurations of flexible graphite or glass fibers equally well as some polymers to create a seal betwixt the pipe connections. Unlike a loftier-pressure liquid or gas pipe systems that utilise flanges for apartment gaskets to connect the joints, these systems utilize the centric to radial load transfer that is inherent to braided packing in gild to seal the joint as well equally create a solid connection.

Die Cut and Coined Parts – These highly engineered parts from EGC are typically more expensive than a standard die formed or braided packing, just they have pregnant advantages. EGC was the first to create the design and information technology can save the actuator. This type of inside and outside diameter sealing device is pre-compressed to a loftier density, (Effigy six.) It does not exert the same axial to radial load transfer experienced with other designs. The low axial to radial load transfer reduces the amount of friction acquired by the packing set equally well equally the corporeality of compression required to create a seal. In other words, you lot get less stem expanse friction compared to a standard blueprint. These types of sealing devices are typically used in pocket-size instrumentation devices.

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Figure half-dozen. Dice Cut and Coined Graphite Band

Clamped Joints – EGC Strap and V-Band style clamped joints can likewise many times benefit from the use of die molded packing fashion seals. The seal used in these configurations as well typically provides construction for the articulation as well. Information technology keeps the pipe from separating or rotating during high vibration operation and thermal cycling. These packings, in some cases, can exist fabricated in a composite structure of both molded sealing material mated with metal components. The metal components can then serve equally a portion of the clamped joint to achieve weight, toll savings, and ease of associates.

Exhaust Manifold packing – Some sealed joints move with much smaller travel than typical valve stem packing, just with much college frequency, vibration and temperature. EGC exhaust manifold skid joints sometimes use molded packing made from high temperature materials like flexible graphite and ceramics to keep soot, fuel and exhaust from escaping. This is a very challenging configuration for packing since sideslip joints have a great bargain of clearance to allow for thermal expansion, and experience extreme temperatures budgeted 1900F while operating in a very loftier vibration environment.

Aerospace packing – Outer space that is . . . Many don't know that high temperature molded packing materials such as flexible graphite too constitute an excellent sealing cloth in cryogenic weather condition. For example, EGC seals for the interconnects of fuel lines for the engines used to propel rocket launch vehicles are sometimes fabricated using die molded flexible graphite. These packing mode components are required to survive at a chilly -423 F and seal products like liquid hydrogen or oxygen. These are indeed unique applications.

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Corporate Profile

EGC is a recognized world leader in the engineering and manufacturing of graphite composites for high-temperature applications in sealing or thermal systems direction. The EGC website can be accessed at https://egcgraphite.com/.