Valve rubbers

The discharge strainer often becomes clogged with pieces of piston and valve rubber. This may increase the pump pressure that is not shown by the pressure gauge beyond the strainer. The strainer should be inspected and cleaned frequently to prevent a pressure buildup. 

In figure 4 is shown how a separatory funnel and a pressure equalized addition funnel are made. The funnel part is just a PP funnel from the grocery store and what it is attached to is a stainless steel ball valve. See how the addition funnel is made by using a rubber stopper and an extra extension of tubing to the top of the funnel Well, that s how one can make a sealed addition funnel out of the ordinary glass separatory funnel that one gets with a distillation kit or from wherever. 

Figure 2.14 Close-up of annular regions below rubber O-rings on a cast iron valve block. Note how damage varies from hole to hole, probably due to variation in the crevice geometry.

Let s consider an industrial boiler. You may need at least three of these previous mentioned o-rings just to prevent leaks and drips in a simple hydronie or steam boiler. Raw water comes into the boiler room with pipes, gauges, valves and instrumentation. All these fittings would probably use Nitrile rubber o-ring seals to give long-term leak free service. 

The twisting rubber hoses or o ringed elbows which connect the rotating pan necks with pipe and the wear plate to the face of the stationary valve The condition of the high impact nozzles mounted on the cloth wash manifold and, for wet cake discharge, the sluicing manifold The support rollers which take the vertical load of the entire machine and the horizontal thrust rolls that maintain the rotating frame concentric The toothed rim and sprocket which drives the pan filter... 

Process systems handling polymers and resins (e.g., butyl rubber or ethylene-propylene diene monomer rubbers) are often subject to plugging at dead-end locations such as PR valve inlets. In extreme cases, complete blockage of inlet piping and valve nozzle can result. This problem can be eliminated by the application of a flush-seated PR valve, in which dead-end areas are eliminated by placing the valve disc flush with the vessel wall, in the flow pattern of the contents. 

Hydrogen fluoride reacts witlr metal carbonates, oxides, and hydroxides. Accumulation of these fluoride compounds can render valves and other close-fitting moving parts inoperable in a process system, causing possible equipment or process failures. Hydrogen fluoride also attacks glass, silicate ceramics, leather, natural rubber, and wood, but does not promote their combustion. 

Figure 7-3A. Safety relief valve with rubber or plastic seats. By permission, Anderson, Greenwood and Co.

Figure 4-389 gives a series of schematics that show how the spacer and cement slurry displace drilling mud in the well. Two wiper plugs are usually used to separate the spacer and the cement slurry from the drilling mud in the well. The cementing head has two retainer valves that hold the two flexible rubber wiper plugs with two separate plug-release pins (see Figure 4-389a). When the spacer and the cement slurry are to be pumped to the inside of the casing...

These have been developed for special uses. For example, since petroleum-based materials harm natural rubber, a grease based on castor oil and lead stearate is available for use on the steel parts of rubber bushes, engine mountings, hydraulic equipment components, etc. (but not on copper or cadmium alloys). Some soft-film solvent-deposited materials have water-displacing properties and are designed for use on surfaces which cannot be dried properly, e.g. water-spaces of internal combustion engines and the cylinders or valve chests of steam engines. 

It is quite necessary that the welding of the tank is perfect and free from pin holes. Leaks frequently appear where the tubes are welded in the top of the tank. These may be eliminated by brazing the joints. A less satisfactory way is to use a cement of litharge and glycerol. This cement may also be used with success on leaky valves. Occasionally leaks occur in the rubber tubing or its connections with the bottle or tank, but these are unusual. 

To use such pipettes, a suitable pipette filler is first attached to the upper or suction tube. These devices are obtainable in various forms, a simple version consisting of a rubber or plastic bulb fitted with glass ball valves which can be operated between finger and thumb these control the entry and expulsion of air from the bulb and thus the flow of liquid into and out of the pipette. Suction by mouth must never be used to fill a pipette with liquid chemicals or with a solution containing chemicals. 

In certain processes (such as rubber tire manufacture and plastic injection molding operations), it is common for a valve sequencing system to first provide hot steam followed by cold cooling water and thus for cross-contamination to occur. The result may be the stripping of passivated cooling system surfaces by steam and for the condensate to be infiltrated by cooling water. 

---