Valved-tipped

These effects are important when considering the design of tritium systems. Damage to components, such as gaskets, valve tips, and 0-rings, must be carefully considered. Component failure during service can cause a major release of tritium. Because elastomer seals often become embrittled, maintenance on nearby sections of piping may cause seals to develop leaks as the result of mechanical movement in the seal area. 

Fujii et al. [9] studied how the needle-valve tip geometry affects the spray characteristics of a PFI. An increase in the angle of the needle-valve taper leads to a decrease in the droplet size. In addition, the standard deviation of the size... 

Catheters for chemotherapy are available with two basic tip configurations end-hole or valved-tipped. End-hole catheters can be trimmed at the tip to fit the patienfs anatomy. Valved-tipped catheters have specially designed slits that allow solutions to be infused, but will not allow blood to reflux into the catheter lumen when not in use (Delmore et al. 1989). These catheters cannot be trimmed at the tip, but have... 

Tunneled chest wall external catheters are the prototypical chemotherapy external device. They are available with single, dual or triple lumen, end-hole or valved-tipped, and made from silicone or polyurethane material. Each device has a tissue ingrowth cuff attached to the portion of the catheter shaft that is situated within the subcutaneous tunnel (Jaques et al. 1989). This subcutaneous tunnel provides the necessary long-term stability and protection from infection. The cuff incites an ingrowth of fibrous tissue within 4-6 weeks, creating a long-term device that can be used for months to years (Fig. 6.2). 

Fig. 6.2. Tunneled chest wall catheters. Outer, single lumen silicone catheter with end hole middle, dual lumen silicone catheter with end holes inner, dual lumen catheter with valved-tip. Arrows mark location of cuff that is placed within the subcutaneous tunnel for stabilization. (Published with permission of Lippincott, Williams and Wilkins)...

Horizontal Rotating Pan Filters. These filters (Fig. 10) represent a further development of the tipping pan filter for continuous operation. They consist of a circular pan rotating around the central filter valve. The pan is divided into wedge-shaped sections covered with the filter medium. Vacuum is appHed from below. Each section is provided with a drainage pipe which connects to a rotary filter valve of the same type as in dmm filters. 

Parts made from fluoroelastomers ate used ia appHcations that justify their high cost, usually where the maintenance and replacement costs are high enough to offset the initial cost of the part. These include automotive appHcations such as valve stem seals, fuel injector components, radiator, crankcase and transmission seals, and carburetor needle tips. Numerous seals and gaskets in the marine, oilfield, and chemical processing industries employ fluoroelastomers. In addition, many hoses in the automotive and chemical industry are made entirely of fluoroelastomer compounds or have a veneer of the fluoroelastomer as a barrier exposed to the harsh environment. Seals and gaskets in military appHcations and the binder for flares and missile appHcations ate made with fluoroelastomers. 

Chlorimet 2 has 63 percent Ni and 32 percent Mo and is somewhat similar to Hastelloy B-2. It is available only in cast form, mainly as valves and pumps. This is a tough alloy, very resistant to mechanical and thermal snock. It can be machined with carbide-tipped tools and welded with metal-arc techniques. 

Figure 7.19 Pits on a carbon steel check valve. Note how pits intersect to form areas of jagged metal loss. A steel prohe tip is in the photo. (Magnification 7.5x.)...

Mak has developed an improved method of relief valve manifold design. The APT has adopted this method, which starts at the flare tip (atmospheric pressure) and calculates backwards to the relief valves, thus avoiding the trial and error of other methods. This is especially helpful when a large number of relief valves may discharge simultaneously to the same manifold. 

Starting at the flare tip calculate logical segments using Figure 1 until all relief valve outlet pressures are found. 

The basic difference between this type of valve and the normal external loop sample valve is the incorporation of an extra port at the front of the valve. This port allows the injection of a sample by a syringe directly into the front of the sample loop. Position (A) shows the load position. Injection in the front port causes the sample to flow into the sample loop. The tip of the needle passes through the rotor seal and, on... 

Another version of the dewatering screw that has been used successfully in a number of installations (Figure 40) consists of an inclined screw with a box-like back end and an internal overflow weir. The drive is usually a variable-speed motor reducer. Rotary air lock fitted with a variable-speed drive is typically used as shown in Figure 37 in connection with the plain receiving tank and an inclined screw conveyor. Materials of construction can be chrome-plated cast iron or nickel-hard casing. The rotary valve is made of hard faced tips or stainless steel replaceable blades. 

Flare stack sizing and pressure drop is included with considerations of pressure drop through the safety valve headers, blowdown drums, flare headers, seal drum, etc. Elevated flare tips incorporating various steam injection nozzle configurations are normally sized for a velocity of 120 m/s at maximum flow, as limited by excessive noise and the ability of manufacturers to design tips which will insure flame stability. This velocity is based on the inclusion of steam flow if injected internally, but the steam is not included if added through jets external to the main tip. 

The flow of a compressible fluid through an orifice is limited by critical flow. Critical flow is also referred to as choked flow, sonic flow, or Mach 1. It can occur at a restriction in a line such as a relief valve orifice or a choke, where piping goes from a small branch into a larger header, where pipe size increases, or at the vent tip. The maximum flow occurs at... 

When the relieving scenarios are defined, assume line sizes, and calculate pressure drop from the vent tip back to each relief valve to assure that the back-pressure is less than or equal to allowable for each scenario. The velocities in the relief piping should be limited to 500 ft/sec, on the high pressure system and 200 ft/sec on the low pressure system. Avoid sonic flow in the relief header because small calculation errors can lead to large pressure drop errors. Velocity at the vent or flare outlet should be between 500 ft/sec and MACH 1 to ensure good dispersion. Sonic velocity is acceptable at the vent tip and may be chosen to impose back-pressure on (he vent scrubber. 

Principles and Characteristics Continuous-flow (or dynamic) FAB/FTB [102] and frit FAB/F1B [103] offer a means of introducing samples in solution into a continuous flow of solvent which terminates at the modified FAB/FIB probe tip, and they extend the applicability of FAB. Samples are injected through a conventional HPLC injection valve, or solutions are simply drawn in by the high vacuum in the ionisation source of the mass spectrometer. These very similar techniques are particularly amenable to coupling with HPLC columns, and ionisation of the sample is unchanged with respect to conventional FAB and FIB/LSIMS. 

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