Dump valve

Charge solids materials by means of a closed system (e.g., hopper and rotary airlock, screw feeder, double-dump valve system, etc.)... 

Operator exposure Charge liquids and solids materials by means of a to fumes or inerts. closed system (e.g., hard piping, hopper and rotary airlock, screw feeder, double-dump valve system, etc.) Provide local ventilation Use proper personnel protective equipment (PPE) ACGIH 1986 CCPS G-22 CCPS G-23 CCPS G-29... 

The gas, condensate, and free water are then discharged from the ncs scl through backpressure and liquid dump valves. The gas leaving the separator is saturated with water vapor at the temperature and pressure of the top of the low temperature separator. If this temperature is low enough, the gas may be sufficiently dehydrated to meet sales specifications. Dehydration is discussed in greater detail in Chapter 8. 

Note Liquid dump valves are normally fail closed to prevent giis blowby. That means that in ca.se of loss of instrument gas or air pressure, the spring will drive the valve to the closed position. However, the valve can mechanically fail because the level controller malfunctions or the seat cuts out due to solids erosion, which would cause it to fail in an open configuration. 

In general, the downhole positive displacement motor constructed on the Moineau principle is composed of four sections (1) the dump valve section, (2) the multistage motor section, (3) the connecting rod section and (4) the thrust and radial-bearing section. These sections are shown in Figure 4-202. Usually the positive displacement motor has multichambers, however, the number of chambers in a positive displacement motor is much less than the number of stages in a turbine motor. A typical positive displacement motor has from two to seven chambers. 

The dump valve is a very important feature of the positive displacement motor. The positive displacement motor does not permit fluid to flow through the motor unless the motor is rotating. Therefore, a dump valve at the top of the motor allows drilling fluid to be circulated to the annulus even if the motor is not rotating. Most dump valve designs allow the fluid to circulate to the annulus when the pressure is below a certain threshold, say below 50 psi or so. Only when the surface pump is operated does the valve close to force all fluid through the motor. 

Level, e.g. Overfilling Leakage from a dump valve Flooding of condensers (heat exchangers) ... 

Vertical separator. Fig. 2 is a schematic of a vertical separator. In this configuration inlet flow enters the vessel through the side. As in the horizontal separator, the inlet diverter does the initial gross separation. Liquid flows down to the liquid collection section of the vessel, then down to the liquid outlet. As liquid reaches equilibrium, gas bubbles flow counter to the direction of liquid flow and eventually migrate to the vapor space. The level controller and liquid dump valve operate in the same manner as in a horizontal separator. 

Fig. 3—Bucket and weir configuration for three-phase horizontal separator eliminates interface controller and uses conventional displacement fioal lo operate oil and water dump valves This design is useful if paraffin or large volumes o emulsions that would loul interlace controllers are expected.

Produced water flows from a nozzle in the vessel located upstream of the oil weir. An interface level controller senses height of rhe oil/water interface The controller actuates the water dump valve, allowing the correct amount of water to leave the vessel so that the oil/water interface is maintained at design height. 

An alternate configuration (Fig. 3), the "bucket and weir" design, eliminates the need for a liquid interface controller. Both oil and water flow over weirs where level control is accomplished by a simple displacer float. Oil overflows the oil weir into an oil bucket where its level is controlled by a level controller operating the oil dump valve. Water flows under the oil bucket and then over a water weir. The level downstream of this weir is controlled by a level controller operating the water dump valve. 

The second method shown uses a weir to control the gasoil interface level at a constant position. This results in better oil/water separation as ail the oil must rise to the height of the oil weir before exiting the vessel. Disadvantages arc that the oil box takes up vessel volume and costs money to fabricate. Sediment and solids can collect in the oil box and be difficult to drain, and a separate low-level shut-down may be required to guard against the oil dump valve failing open. 

Variations 1n liquid level resulting 1n liquid dump valve hunting1. 

An associated problem concerning a water-dump-valve vortex reaching up into the interface can also cause oily effluent water even if the Interface is clear. This can be eliminated by the installation of a vortex breaker installed over the interior of the outlet. 

Another method is to get a sample of oil from the top sight glass of the vessel and compare Its shakeout to a sample obtained from the dump valve. Should the oil from the sight glass be cleaner, it is quite possible that there is a hole In the heat exchanger. The same result would show up if there were a leak in the top plate of the treater which separates the gas sec-r,onv or a hole in the upper pan of the down line. 

Oil and emulsion rise user heater fire tubes to a coalescing section where sullicicnt retention tune is provided to allow small water particles in the oil continuous phase to coalesce and settle to the bottom Treated oil Hows out the oil outlet Gas. flashed from the heated oil. flows through an equalizing line to the gas spare above Oil level is maintained by pneumatic or lever-operated dump valves Oil-water inter-fare height is regulated hy an interface controller or by an adjustable external water leg... 

Horizontal treaters. Multiwell installations normally require horizontal treaters. Fig 2 shows a typical design. Flow enters the front section of the tteatei where gas is flushed. Liq uid falls to the vicinity of the oil-water interface where it is water washed and freewater separated Oil and emulsion rise past the lire tubes and are. skimmed into the oil surge i Irani -her. "Fhe oil-water interface in the inlet section is controlled by an interface level controller that operates a dump valve for the freewater... 

Oil and emulsion t low through a spreader into (lie back, or coalescing, section ot the vessel that is lluid packed. Tlic spreader distributes flow evenly throughout the length ol this section Treated oil is collected at the top by means of a collection device sized to maintain a uniform vertical oil flow Coalescing water droplets fall countercurrent to the rising oil continuous phase. The oil-water interface is maintained by a level controller and dump valve for this section of the vessel. 

A level control in the oil surge chamber operates a dump valve in die oil outlet line that regulates oil flow out of the vessel to maintain a fluid-packed condition... 

Cross-flow devices. Equipment manufacturers have modified the CPI configuration for horizontal water flow perpendicular to the axis of plate corrugations. This allows plates to Lie installed at a steeper angle to facilitate sediment removal and enables the plate pack to be more conveniently packaged in a pressure vessel. The latter advantage is critical if gas blowby through an upstream dump valve could cause relief problems in an atmospheric tank. 

Because of dispersion through the water dump valve, oil size distribution at the outlet of a free water knockout or heater treater is not a significant design parameter. From dispersion theory, it can be shown that after passing through the dump valve, a maximum droplet diametet on the order of 10 to V) microns will exist, no matter what the droplet vi/e distribution was upstream of this valve. 

If there, were sufficient time for coalescence to occur in piping downstream of die dump valve, then maximum droplet diameter would be defined by tlie dispersion equation prior to water entering the first vessel in the water treating svsiern. 

For relief-protection dump valves, relief valves, and finally rupture discs are used. The sizing of the relief devices is based on the rate of pressure-rise. The flow area should be large enough to stop the pressure rise as soon as the set pressure is reached. 

During one aerial application with XLR (experiment 4) the spray equipment malfunctioned. The applicator, in an attempt to correct the problem, accidently opened the dumping valve to the spray tank and the formulation splashed on him. The result was a total HDE of 367 mg/h, with almost half of it on the forearms. Since such an exposure would not be continuous, the calculation on an hourly basis is unrealistic. Therefore, the data were not used in determining the HDE to applicators. 

Heat tracing can also be used however, it is usually best used if the problem is localized, for example around a valve. Points notorious for freezing in the acid gas injection scheme are the dump valves from the interstage knockout drums. 

The drains after the dump valve should be heat traced. The water content is high, and with a high acid gas content, these lines freeze easily. As we have seen, hydrates readily form in acid gas mixtures. 

Check level controllers Check dump valves Excessive circulation... 

---