Fluid, rupture

Agglomerates in a sheared fluid rupture when the hydrodynamic stress exceeds a critical value in dimensionless form the criterion for rupture is Fa > Facrjt. Rupture occurs within a short time of application of the critical stress, and thus can be distinguished from erosion, which occurs over much longer time scales. 

Although liquid temperatures are uniform throughout the Venturi in noncavitating flow, the effective tensions obtained at incipient cavitation (Fig. 7) indicate that the fluid is locally superheated and thus not in a state of thermodynamic equilibrium. When the fluid ruptures or cavitates, a phase change occurs because the voids rapidly fill with vapor. Vapor generation requires heat of vaporization, which must be drawn from the surrounding liquid. This should result in a cooling of the vapor-liquid interface and a reduction in temperature around and within the cavity. If conditions within the cavity are in thermodynamic equilibrium, then a definite pressure drop should accompany the drop in temperature. 

Successive reflections of the pressure wave between the pipe inlet and the closed valve result in alternating pressure increases and decreases, which are gradually attenuated by fluid friction and imperfect elasticity of the pipe. Periods of reduced pressure occur while the reflected pressure wave is travehng from inlet to valve. Degassing of the liquid may occur, as may vaporization if the pressure drops below the vapor pressure of the liquid. Gas and vapor bubbles decrease the wave velocity. Vaporization may lead to what is often called liquid column separation subsequent collapse of the vapor pocket can result in pipe rupture. 

Two-Fluid (Pneumatic) Atomizers This general category includes such diverse apphcations as venturi atomizers and reac tor-effluent quench systems in addition to two-fluid spray nozzles. Depending on the manner in which the two fluids meet, several of the breakup mechanisms may be apphcable, but the final one is high-level turbulent rupture. 

Rupture Disks A rupture disk is a device designed to function by the bursting of a pressure-retaining disk (Fig. 26-15). This assembly consists of a thin, circular membrane usually made of metal, plastic, or graphite that is firmly clamped in a disk holder. When the process reaches the bursting pressure of the disk, the disk ruptures and releases the pressure. Rupture disks can be installed alone or in combination with other types of devices. Once blown, rupture disks do not reseat thus, the entire contents of the upstream process equipment will be vented. Rupture disks are commonly used in series (upstream) with a relief valve to prevent corrosive fluids from contacting the metal parts of the valve. In addition, this combination is a reclosing system. 

Sealless pumps rely on the process fluid to lubricate the bearings. If the wear rate of the bearings in the fluid being handled is not known, the bearings can wear unexpec tedly, causing rupture of the can. 

U-Tube U-Bundle Only one tube sheet required. Tubes bent in U-shape. Bundle is removable. High temperature differentials which might require provision for expansion in fixed tube units. Clean service or easily cleaned conditions on both tube side and shell side. Horizontal or vertical. Bends must be carefully made or mechanical damage and danger of rupture can result. Tube side velocities can cause erosion of inside of bends. Fluid should be free of suspended particles. 1.08... 

Resistance to common aircraft fluids such as water, salt water, hydraulic fluid and jet fuel is determined by additional shear testing after exposure to these fluids. Since adhesives are typically only exposed at bond edges, are protected by secondary primers and enamels and are not expected to be exposed to these fluids (save for water) for extended periods, exposure time prior to testing is relatively short. Lastly, the adhesive is tested for propensity to creep rupture under load in standard and aggressive environments. This testing indicates whether the polymer is crosslinked sufficiently to resist long-term creep under low load. 

Stage 1 may last less than one second to several seconds. It is characterized by a very fast transient and a pressure spike immediately after the tube rupture. After the low-pressure side fills with high-pressure fluid, the transition to stage 2... 

A vapor poeket on the exchanger s low-pressure side can create a cushion that may greatly diminish the pressure transient s intensity. A transient analysis may not be required if sufficient low-pressure side vapor exists (although tube rupture should still be considered as a viable relief scenario). However, if the low-pressure fluid is liquid from a separator that has a small amount of vapor from flashing across a level control valve, the vapor pocket may collapse after the pressure has exceeded the fluid s bubble point. The bubble point will be at the separator pressure. Transient analysis will prediet a gradually inereasing pressure until the pressure reaches the bubble point. Then, the pressure will increase rapidly. For this ease, a transient analysis should be considered. 

Other factors which promote brittleness are geometrical discontinuities (stress concentrations) and aggressive environments which are likely to cause ESC (see Section 1.4.2). The absorption of fluids into plastics (e.g. water into nylon) can also affect their creep rupture characteristics, so advice should be sought where it is envisaged that this may occur. 

Tube Rupture. It is common for a heat exhanger to have a high-pressure fluid in the tubes and a lower-pressure rated shell. If there is a break in one of the tubes, the higher pressure fluid will leak to the shell, resulting in overpressure. It is conservative to assume a tube is completely split with choked flow from both sides of the break. 

Rupture discs are also used below relief valves to protect them from corrosion due to ves.sel fluids. The rupture disc bursts first and the relief valve immediately opens. The relief valve reseals, limiting flow when the pressure declines. When this configuration is used, it is necessary to monitor the pressure in the space between the rupture disk and the relief valve, either with a pressure indicator or a high pressure switch. Othei-wise, if a pinhole leak develops in the rupture disk, the pressure would equalize on both sides, and the rupture disk would not rupture at its set pressure because it works on differential pressure. 

Adsorbers, distillation colunuis, and packed lowers are more complicated vessels and as a result, the potential exists for more serious hazards. These vessels are subject to tlie same potential haz. uds discussed previously in relation to leaks, corrosion, and stress. However, llicse separation columns contain a wide variety of internals or separation devices. Adsorbers or strippers usually contain packing, packing supports, liquid distributors, hold-down plates, and weirs. Depending on tlie physical and chemical properties of the fluids being passed tlirough tlie tower, potential liazards may result if incompatible materials are used for llie internals. Reactivity with llie metals used may cause undesirable reactions, which may lead to elevated temperatures and pressures and, ullinialely, to vessel rupture. Distillation columns may contain internals such as sieve trays, bubble caps, and valve plates, wliicli are also in conlacl with tlie... 

Protection against osmotic or mechanical rupture. The walls of neighboring cells interact in cementing the cells together to form the plant. Channels for fluid circulation and for cell-cell communication pass through the walls. 

Lysozyme is an enzyme that hydrolyzes polysaccharide chains. It ruptures certain bacterial cells by cleaving the polysaccharide chains that make up their cell wall. Lysozyme is found in many body fluids, but the most thoroughly studied form is from hen egg whites. The Russian scientist P. Laschtchenko first described the bacteriolytic properties of hen egg white lysozyme in 1909. In 1922, Alexander Fleming, the London bacteriologist who later discovered penicillin, gave the name lysozyme to the agent in mucus and tears that destroyed certain bacteria, because it was an enzyme that caused bacterial lysis. 

Figure 7-11. Safety valve and rupture disk installation using pressure rupturing disk on inlet to safety relief valve, and low pressure disk on valve discharge to protect against back flow/con-osion of fluid on valve discharge side, possibly discharge manifold. By permission, Fike Metal Products Div., Fike Corporation, Inc.

The contents of the vessel are clean fluids, free from gumming or clogging matter, so that accumulation in the space between the valve inlet and the rupture disk (or in any other outlet drat may be provided) will not clog the outlet. 

Initially fermentation broth has to be characterised on the viscosity of the fluid. If the presence of the biomass or cells causes trouble, they have to be removed. Tire product is stored inside the cells, the cells must be ruptured and the product must be freed. Intracellular protein can easily be precipitated, settled or filtered. In fact the product in diluted broth may not be economical enough for efficient recovery. Enrichment of the product from the bioreactor effluents for increasing product concentration may reduce the cost of product recovery. There are several economical methods for pure product recovery, such as crystallisation of the product from the concentrated broth or liquid phase. Even small amounts of cellular proteins can be lyophilised or dried from crude solution of biological products such as hormone or enzymes.2,3... 

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