Gasket materials in underground mines are those that minimize dangerous site ignitability hazards. The products described below only serve to prove one hard fact: There can be no gambling, no wagering with what are essentially high-risk work conditions here, not when lives and limbs are at stake. Fire Resistant and Anti-Static FRAS products, therefore, exist to prevent flame propagation events, to basically fireproof mines and to minimize the electrical build-ups down there that could cause an explosion.

Reviewing FRAS Issues in Underground Mines

Let’s use a coal mine to highlight the hazards found down here, although any mining installation could trigger a fire threat. If anthracite and bitumen are exposed in a mine chamber, it’ll likely produce a fine black mist. Of some concern, this is a solid fuel. It’s not as combustible as some gaseous fuels, but it will ignite if the conditions are right. Besides, coal mines can also release pockets of methane. In fact, any mining facility can unlock a chamber full of methane. Bad enough, this “Firedamp,” this potentially explosive mixture is floating around, but it’s also contained, trapped in an underground mine’s many subterranean chambers, where workers are going about their business. By adding static to the already highly volatile mix, the whole installation begins to resemble a closed-in tinder box.

Anti-Static and Anti-Flame Propagation Solutions

FRAS products are essentially made from large rubber sheets, although they’re also sometimes die-cut into smaller, thinner strips as well. The rubber acts as a sheath for exposed metal surfaces, pipes, equipment frames, and all manner of underground mine apparatus. The goal is to insulate and isolate conductive parts, to prevent static build-up and to fireproof flammable materials. If a situation occurs where a spark could be generated, fire-retarding FRAS rubber minimizes the accumulation of static electricity. Moving onto FRAS-rated gear, composite pulley linings and conveyor skirts can be used to illustrate another example of a FRAS safe equipment build. This time, instead of layers of rubber sheeting blanketing a pipe or vent duct, special rubber composites are fabricated as integral equipment components.

There are also FRAS rated screening decks and belt scrapers. Steel-reinforced crushers and vibratory pans use FRAS materials as well. Of some benefit here, the anti-static materials also function fairly well as impact dampening surfaces, so they protect underlying steel surfaces from high-velocity aggregate loads. Up higher, above the equipment lines, anti-static and flame resistant plastic meshes function as mine ceiling guards. They line ceilings and walls. Indeed, high-functioning FRAS mechanisms line every conceivable underground mine assembly, including the ventilation ducts that work tirelessly to extract that ignitable coal dust.

Vent Bands

In an underground mine, a vent tube is beneficial in dealing with the high concentration of gas emitted from the drilling site and borehole. Vent band, also known as vent tube rubber is used for wrapping around the ventilation tube, to seal the joint thus maintaining air pressure. Further, the vent band can be used to repair damage to the vent tube.

Given that the operation of underground coal mines poses a high number of risks of fire and explosion, materials used as vent band are required to be certified fire retardant and anti-static (FRAS). That means, they need to be able to control ignitability and flame propagation. Further, they also require the capability to reduce static electricity, which could lead to possible sparking.

To comply with the requirement, some manufacturers produce polyurethane systems with the ability to self-extinguish in the case of fire and also provides excellent antistatic protection. These materials have been documented to possess a highly durable, longer lasting, wear and abrasion resistance characteristic; and most importantly, they comply with all relevant Australian FRAS standards.

The hardness of elastomeric gasket materials is estimated with a durometer. Knowing how this gadget is utilised aides in deciphering determinations and choosing gasket material. The following is an outline of durometer measurement of gasket material hardness.

The Basics of Durometer Construction

Durometers come in two structures, simple and advanced. Simple durometers resemble the conventional stopwatch with a solitary hand that clears around the dial. This dial is mounted on a level foot, from which juts a pin. The pin is spring-stacked, so when the foot is squeezed against the gasket material the pin climbs into the body of the durometer. The harder the material, the more the pin moves into the body. Or on the other hand to put it another way, softer materials let the pin press in more profound. The dial is set apart from zero to 100. These numbers have no units except for are identified with the spring load and the size and state of the top of the pin, all the more appropriately called the ‘indenter.’

Durometer Measurement of Shore Hardness

Spring quality and indenter calculation are indicated in ASTM standard D2240. This fixes each part of elastic hardness testing, including the size of the ‘presser foot’, test arrangement, the term for which the indenter is squeezed into the material, and count and introduction of results.

Elastic and elastic like materials can shift hugely in hardness, so ASTM D2240 characterizes various scales. Each scale has its own indenter structure and spring load. Gasket materials are normally estimated on the Shore A scale. The ‘A’ indenter is a pin of 1.27mm (0.050″) measurement, tightened at 35 degrees to complete as a shortened cone with a level territory of 0.79mm (0.031″) width. At a perusing of 100 (no space,) the spring power will be 8.05 Newtons.

Durometer Measurement in Deciding the Hardness Number

As indicated by ASTM D2240, the test example ought to be at any rate 6.0mm (0.24″) thick. Hardness is determined as the mean or middle of five measurements taken in any event 12.0mm (0.48″) from any edge.

A Comparative Measure in Durometer Measurement

Being dimensionless, the Shore A number reveals to you about the properties of an individual material. Its genuine worth is as a government sanctioned test strategy, permitting correlation of elective materials for elastomeric gaskets.

Consult VSRP for more information on durometer measurement of gasket material hardness. We ensure consistent and reliable quality of rubber products so your business can rely on the products you source. If you find it important to have products produced to your specifications, it’s reassuring to know that VSRP control tooling and retain ownership. Our manufacturing partners are always able to meet your exact needs.

The question of how hard a gasket should be comes up quite often. For an answer we need to look at what the gasket actually does. Aside from that, it is important to be familiar on how they vary depending on the gasket material used. Below is an overview about gasket material hardness.

What is the Function of a Gasket Material

The job of every gasket is to fill an uneven gap between two surfaces, forming a barrier that stops fluid moving to where it shouldn’t be. Larger gaps and more uneven surfaces need a softer gasket. For example, a gasket between two parallel machined pipe flanges can be hard, resisting loads as the joint faces are tightened together. In contrast, the gasket sealing an electrical enclosure needs to be softer and compress more because the enclosure door will tend to bend as it’s latched.

So a general rule is that a gasket should be as soft as possible in order to fill the gap between two surfaces. At the same time it must be strong enough to resist the lateral forces acting on it. For elastomeric gasket materials two parameters define hardness: Shore hardness and compression force deflection (CFD.) Here’s what these two terms mean.

Shore Hardness – Hardness in this context is a measure of how well a material resists a permanent indentation. The hardness of rubber and elastomeric materials is measured on a durometer and reported as a “Shore A” number. Very soft materials like a rubber band will be around 20, a pencil eraser is between 30 to 40, and car tires measure 60 to 70 Shore A.

Compression Force Deflection – CFD measures firmness and is defined in ASTM standard D1056 as the force needed to reduce the material in thickness by 25%. According to this standard materials are given a grade correlating to their firmness. Grade 0 material needs less than 2 psi to reduce its thickness by 25%, so is very soft. At the other end of the spectrum a grade 5 material needs at least 17 psi to achieve the same compression. A gasket material that compresses easily accommodates variation in the gap between two surfaces without needing more closing force than can be applied by the clamps or latches.

Know more about gasket material hardness from VSRP. We are an Australian based company with a subsidiary manufacturing facility in Vietnam and close and long-term manufacturing partners. We specialise in customised tooling design and manufacture according to our customers’ specifications. Our staff have extensive experience in the rubber industry, providing you with high quality, professionally produced products. No job is too small or too big.

Source

Hennig Gasket and Seals. (n.d.). Understanding Gasket Material Hardness. Retrieved 10 19, 2020, from Hennig Gasket and Seals: https://www.henniggasket.com/gasket-answers/rubber-gaskets/understanding-gasket-material-hardness/

There are a few rubber gasket compounds for use in raised temperature applications. There are, of course, numerous things to assess before choosing the best possible material. Other than the temperature, the liquid (or media), framework weight, and presentation conditions should be thought of. Those variables will influence the last decision, however this concise outline will highlight temperature limits.

Read on below to compare the best rubber compound for high temperature gasket applications.

Silicone

For applications where the rubber material won’t be presented to acids, soluble bases, superheated steam (over 250ºF), sweet-smelling hydrocarbons, and certain powers, Silicone is a decent decision for the gasket you will utilizing. Silicone has an unrivalled temperature go, for the most part staying adaptable from – 75ºF to + 450ºF, and is the compound of decision for hot, dry air gasket applications.

Viton

Viton®, while not an awesome compound for low temperatures, is a magnificent decision in high temperature gasket applications up to around 400ºF. Viton® has better obstruction than a wide assortment of synthetic compounds, including numerous acids, powers, fragrant hydrocarbons, chlorinated hydrocarbons, and non-combustible water driven liquids. The entirety of the Viton® gaskets we gracefully are produced using certifiable DuPont material; not a nonexclusive FKM.

EPDM

EPDM is the best rubber gasket material for steam and boiling water applications to 350ºF, with some EPDM materials equipped for taking care of temperatures in steam to 400ºF. EPDM isn’t viable with oil based liquids, yet can deal with numerous Glycol based liquids to 300ºF.

Perfluoroelastomers

Perfluoroelastomers handle a more extensive scope of synthetics than Viton®, however most usually are accessible just as O-rings. Perfluoroelastomers (the most usually known is Kalrez®) by and large are heat impervious to 600ºF, yet because of their extraordinary cost, and restricted shape and size accessibility, ought to be viewed as just when the application can’t be fixed with another material. At the point when temperatures surpass the cut-off points noted above, it is likely a material other than rubber will be required.

Rubber gaskets fall flat for an assortment of reasons. MTAP, an abbreviation that assists engineers with planning better gaskets, clarifies four common causes of gasket tear. On the off chance that you need better rubber seals, plan them with media (M), temperature (T), application (An), and pressure (P) as a top priority. Else, you have hazard fixing tears that can have costly, awkward, perilous, or even disastrous outcomes.

Media

The M in MTAP stands for media, which incorporates substances, for example, powers, synthetics, and cleaners that come into contact with rubber gaskets. This contact might be an inconsistent and coincidental, or nonstop and long haul. With regards to the M in MTAP, make sure to consider both the sort of media and the idea of the contact. Over-building a gasket includes pointless costs, however, gasket tear can be exorbitant.

Think about this portable hardware model. Gaskets made of an inappropriate rubber were introduced on the fuel entryways of an armada of vehicles. Since the rubber couldn’t avoid oil-based commodities, the seals crumbled rapidly and made little bits of rubber enter the fuel lines. The vehicles were taken out from administration and motor upkeep was required. It was a costly exercise about compound choice.

Temperature

The T in MTAP stands for temperature, which covers the whole scope of temperatures to which a rubber gasket is uncovered. This incorporates the ordinary scope of working temperatures just as boundaries. Regardless of whether a seal doesn’t fizzle, execution turns out to be less unsurprising when rubber arrives at the restrictions of its administration temperature run. Rubber softens at high temperatures, however cold can make it hard and weak. The O-rings split and allowed a fumes release that caused a tank brimming with fluid oxygen and hydrogen to crack not long after takeoff.

Application

The An in MTAP stands for application, a term that envelops something beyond gasket establishment and use. To evade seal tear, consider a typical day for your rubber part – just as what befalls it throughout weeks, months, and even years. For instance, consider the instance of a rubber gasket that is utilized with underground versatile hardware.

An organization had introduced a nitrile rubber part on a drill that is utilized with wells. Nitrile offers incredible oil opposition, yet coincidental contact with oil-based commodities wasn’t the most concerning issue. Although the hardware was utilized underground, it was put away over-the-ground and outside. Since nitrile is assaulted by bright (UV) light, the sun’s beams demolished the rubber gaskets.

Weight

The P in MTAP stands for pressure, which likewise incorporates vacuum levels. With high-pressure seals like the ones utilized in water-powered frameworks, gasket tear can make the close sever or even fly. Littler, less perceptible holes may likewise happen. Vacuum pressures are impressively lower than barometrical weight, however, that doesn’t mean vacuum seals aren’t defenceless to tear.

Consider the case of a thermoplastic part that was utilized onboard planes. This part required a rubber gasket, yet the gasket was too soft to even consider creating a satisfactory vacuum. Thusly, spilling happened. Inflatable seals that are loaded up with air additionally need to keep up sufficient strain to guarantee to fix activity during assembling tasks.

Different Reasons That Rubber Gaskets Fail

MTAP depicts four reasons why rubber gaskets come up short and give simple to-recall rules to all the more likely seal plan. However, media (M), temperature (T), application (An), and pressure (P) aren’t the main reasons that a gasket undertaking can fall flat. Over engineering a gasket is likewise a tear of sorts since paying a lot for a material that you don’t generally require is a type of assembling waste.