Rubber seals

Rubber has very good sealing properties due to its pliable and elastic behaviour and is the best choice to make oil, water and gas tight seals in the most demanding environments in the chemical and other engineering industries. 

---

Consider the design of a glass window for a vacuum chamber (Fig. 18.6). It is a circular glass disc of radius R and thickness f, freely supported in a rubber seal around its periphery and subjected to a uniform pressure difference Ap = 0.1 MPa (1 atmosphere). The pressure bends the disc. We shall simply quote the result of the stress analysis of such a disc it is that the peak tensile stress is on the low-pressure face of... 

If the distribution network consists of pipes with screwed rubber sockets and only the service pipes are of steel, these can be protected with zinc or magnesium anodes. This requires an insulating service clip near the insulating connection. It is usually sufficient just to insulate the stirrup of the service clip since the rubber seal of the service pipe acts as an insulator. In the United Kingdom, the protection of numerous service pipes has been proved with magnesium anodes [31]. 

The pole has a eharaeteristie dimension of 8 mm from the rear of the bobbin to the reeess faee and has a toleranee assigned to it of 0.02 mm. From the pole reeess faee, the tube base toleranee is the last eomponent to make up the toleranee staek. The brass tube has been given a dimensional toleranee on its base of 0.2 0.025 mm. Note, the dimensional toleranee on the plunger is 28 0.05 mm, but the analysis will eoneentrate on the silieone rubber seal length of 6 mm beeause this is moulded onto the plunger and again is a mould related dimension. 

Caution ter/-Butyl hypochlorite is very reactive, e.g. it reacts violently with rubber seals particularly under the influence of light. 

Hydrate control is not included in this chapter, but is discussed in Chapter 13 because of the relative importance and difference in chemical mechanism. Many chemicals added to water will result in a depression of the freezing point. The practical application is restricted, however, because of some other unwanted effects, such as corrosion, destruction of rubber sealings in engine parts, or economic aspects. 

Richard Feynman loved to play the bongos. He also loved solving problems. He figured out the reason for the space shuttle Challenger s 1986 explosion by showing that cold weather caused the rubber seals of the booster rocket to fail. Feynman was one of the twentieth century s great theoretical physicists, a Nobel Prize winner who spent much of his career studying atoms. He knew as much about atoms as anyone in the world, and this is what he said about them in his book Six Easy Pieces ... 

The reaction block, which provides a fully enclosed reaction environment (Teflon, polypropylene, and silicone rubber seals) is a slightly modified version of a design first disclosed by Sphynx Pharmaceuticals [23]. Figure 9 shows the reaction block and the reagent vials (100, 30, and 10 mL sizes) in their fully assembled and disassembled states. Floles at the bottom of the wells of the 96-deepwell polypropylene plate (sealed in fully assembled reaction block) allow the reaction solutions to be removed from the wells (via a separate vacuum plenum) and the functionalized resin (retained by Teflon frits) to be washed with solvents. 

European machines in particular are operated with very low water levels in order to save energy and water. It is therefore important to ensure that the laundry load is soaked in water or suds as quickly as possible so that dry textiles do not rub unnecessarily against the drum or the rubber seal. This is achieved in European machines by constructional features that improve water absorption, shown in Fig. 3.3, such as lifter bars, circulation (jet) systems or direct injection. 

Burnay [14] has developed a predictive model, which is based on the use of the superposition technique to determine thermal and dose rate shift factors relative to a master curve of compression set of a rubber seal versus time. The relation between the shift factors and environmental parameters of temperature and dose rate are given by ... 

PMMA is prone to stress cracking and contact with plasticized PVC, rubber seals and silicone sealants must be avoided or carefully studied. 

Chicago, II., 13th-16th April 1999, Paper 69, pp.36 OPTIMIZATION OF THE PRODUCTION OF EPDM SPONGE RUBBER SEALS FOR THE AUTOMOTIVE INDUSTRY... 

HANDLING - Avoid all contact with liquid or its vapors. A good military gas mask and decontamination suit are required. If kept cold it is reasonably safe to transport but if warm the vapors can penetrate the rubber seals on the containers. This property makes it very difficult to store safely. 

GSE CurtainWall is installed in a trench that can also house a collection of leak detection systems. The vendor claims that GSE CurtainWall systems have been installed to depths exceeding 130 ft. A hydrophilic rubber seal is inserted into one or more of the interlocking chambers to prevent migration of contaminants at the panel connections. 

Shrinking of Rubber Seals/Fuel System Leaking... 

As rapidly as possible, after removal of the ethanol, the flask is fitted with a rubber-sealed stirrer, a dropping funnel, a distilling head containing a thermometer, and a condenser arranged for distillation into a flask protected by a calcium chloride tube. There are then added 300 ml. of dry diethyl carbonate, 80 ml. of dry toluene, and 58.5 g. (0.50 mole) of phenylacetonitrile (Note 2). The flask is heated, with good stirring, and the cake of sodium ethoxide soon dissolves. When distillation has started, dry toluene is added dropwise at about the same rate that the distillate is collected. Approximately 200-250 ml. of toluene should be added in a period of 2 hours (Note 3) while stirring and distillation are continued. 

C PLEXIGLASS CONTAINER D STAINLESS STEEL DISK S RUBBER SEAL B SELFLUBRICATED BEARING P PULLY... 

Place the ground up leaves in a polyethylene container with a well sealing polyethylene top. Polyethylene will not dissolve in isopropyl alcohol. Neither will glass but the rubber seals on glass jar lids may, so stick to polyethylene containers. 

Chemical compatibility is another important factor to reckon with in material selection as in the case of butterfly valves which are frequently used in industrial fluid flow systems where the valves are operated to load and unload different kinds of fluids for shipment or storage. These applications include tank trailers for transportation of fluids from one location to another as well as fluid flow pipelines. A typical butterfly valve usually incorporates a resilient rubber seal component which the valve pivots to seal off the flow lines and when opened allows the fluid to be conveyed to the flow line. The chemicals transported in tanks using butterfly valves are often caustic or acidic. These chemicals corrode the pivot area of the valve making its function ineffective. The rubber gasket material prevents leakage while the valve chamber is protected by a chemically resistant rubber material. 

If non-black fillers are used they produce excessive swelling and softening of the rubber sealing rings in the aqueous medium, where oxides become hydroxides and silicates are converted to water soluble bicarbonates by carbon dioxide and water. 

A careful study of the above tables and figure 12.1 will indicate why a rubber chemist spends a lot of time in designing compounds with various cross link densities for oil field service as well as for other critical applications. It can also be observed that tear strength, fatigue life and toughness, all important requirements for oil field, rubber seals pass through an optimum at low cross link density and fall off with increase in cross link, whereas the most important sealing properties such as hysteresis and compression set improve with increased cross link. 

---