Pressure balancing holes

Referring to Fig. 37.1, note that the seal flush liquid enters the pump case between the rotating face (for internal assembly seals) and the back of the pump s impeller. The idea is for the relatively small flow of the seal flush liquid to flow back into the suction of the pump, and thus be returned to the process steam. (Incidentally, for external assembly seals, the fixed face is closer to the impeller. See reference 2 for details on internal vs. external assembly seals.) 

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Pressure Balancing Holes— Allows seal flush liquid that escapes past the throat bushing to flow back into the suction of the pump. 

These are called pressure balancing holes. They prevent the accumulation of pressure behind the mechanical seal. This could cause the seal pressure to exceed the pump section pressure, which would overpressure the seal faces. 

One of my clients that pumps hydrocarbons contaminated with solids has observed that these pressure balancing holes often plug. 

This pump is used extensively in the petroleum industry. This design is similar and yet different from ANSI pumps. It s designed for non-eorrosive liquids in applications with high temperature and pressure, It incorporates closed impellers with balance holes (Figure 6-9). 

Reducing the pressure acting on the fluid behind the impeller can be accomplished by two different methods, or a combination of both, on an open-impeller unit. One method is where small pumping vanes are cast on the backside of the impeller. The other method is for balance holes to be drilled through the impeller to the suction eye. 

T stands for the time needed for the manometric hole room to achieve the pressure balance right after the hole is sealed ... 

The primary difference in the design of a slurry impeller is the use of radial balancing ribs on the top impeller shroud in place of the top wear ring on a conventional pump. In a conventional pump (I ig. 8-3) there are small holes which vent the area within the top wear ring to the pump suction pressure. This is done to balance some of the hy draulic thrust and therefore reduce the load on the thrust bearing. In certain cases these balancing holes have become plugged with slurry [IG], which upsets the... 

An important safety feature on every modern rig is the blowout preventer (BOP). As discussed earlier on, one of the purposes of the drilling mud is to provide a hydrostatic head of fluid to counterbalance the pore pressure of fluids in permeable formations. However, for a variety of reasons (see section 3.6 Drilling Problems ) the well may kick , i.e. formation fluids may enter the wellbore, upsetting the balance of the system, pushing mud out of the hole, and exposing the upper part of the hole and equipment to the higher pressures of the deep subsurface. If left uncontrolled, this can lead to a blowout, a situation where formation fluids flow to the surface in an uncontrolled manner. 

Reservoir pressure is measured in selected wells using either permanent or nonpermanent bottom hole pressure gauges or wireline tools in new wells (RFT, MDT, see Section 5.3.5) to determine the profile of the pressure depletion in the reservoir. The pressures indicate the continuity of the reservoir, and the connectivity of sand layers and are used in material balance calculations and in the reservoir simulation model to confirm the volume of the fluids in the reservoir and the natural influx of water from the aquifer. The following example shows an RFT pressure plot from a development well in a field which has been producing for some time. 

The flow can be radial, that is, in or out through a hole in the center of one of the plates [75] the relationship between E and f (Eq. V-46) is independent of geometry. As an example, a streaming potential of 8 mV was measured for 2-cm-radius mica disks (one with a 3-mm exit hole) under an applied pressure of 20 cm H2 on QT M KCl at 21°C [75]. The i potentials of mica measured from the streaming potential correspond well to those obtained from force balance measurements (see Section V-6 and Chapter VI) for some univalent electrolytes however, important discrepancies arise for some monovalent and all multivalent ions. The streaming potential results generally support a single-site dissociation model for mica with Oo, Uff, and at defined by the surface site equilibrium [76]. 

For small-scale laboratory work, the exhaust surface is often made as a separate section added to the side of a table or put into a large hole in a table. These tables usually have a sheet metal surface that is resistant to the chemicals used and is easily cleaned. Many circular holes are cut into the metal surface to allow for airflow. This perforation makes the pressure difference over the table quite high and at the same time gives an even distribution of the airflow over the entire surface. These types of exhaust surfaces could be formed to suit different working conditions, e.g., the surface could be made to fit into a sink or to be placed below and around a balance. Using side walls that are not too high, on three or four sides, transforms the table to a partial enclosure, which increases... 

The pressure drop remains essentially constant as long as the liquid flow on tray remains steady during the period point A to point B on the diagram (the open balance point) [201]. At point B all valves are completely open off their seats, but are on the verge of closing and may be oscillating from open to closed. At point B the vapor velocity through the holes, opened balance point is ... 

They must perform their required functions in a superior manner e.g., completion fluids must balance the formation pressure and, thus, avoid the possible loss of the well due to blow-out. Drilling fluids should minimize the cost of making hole. 

The EPA Method 2 probe uses a standard S-type Pitot tube to determine the velocity pressure by measuring gas flow as a unidirectional vector. This method is typically 10-20% higher than the calculated flue gas rate from the FCC heat balance. The newly develop EPA Method 2F probe is a five-holed prism tip with a thermocouple. A centrally located tap measures the stagnation pressure, while two lateral taps measure the static pressure. The yaw angle is determined by rotating the probe until the difference between the two lateral holes is zero. This method closely matches the... 

The interaction between the two gas-liquid interfaces across a foam film can directly be measured by a thin-film balance (TFB) [571-573], A single thin foam film is formed in a hole drilled through a porous glass plate (Fig. 12.19). The plate, and therefore the liquid in the foam, is connected to a reservoir with a constant reference pressure Pr by a capillary tube. The film holder is placed into a closed cell. A constant pressure Pg is applied to the gas in the... 

Kitamori s group has proposed selective chemical surface modification utilizing capillarity (called the capillarity restricted modification or CARM method) (Hibara et al., 2005). In the CARM method, a microchannel structure combining shallow and deep microchannels and the principle of capillarity are utilized. The procedures are shown in Figure 19. A portion of an ODS/toluene solution (lwt%) is dropped onto the inlet hole of the shallow channel, and the solution is spontaneously drawn into this channel by capillary action. The solution is stopped at the boundary between the shallow and deep channels by the balance between the solid-liquid and gas-liquid interfacial energies. Therefore, the solution does not enter the deep channel. It remains at the boundary for several minutes and is then pushed from the deep channel side by air pressure. 

Between the closed and open balance points, the dry pressure drop is constant (Fig. 6.216), and equals the pressure drop at either the closed or open balance points. Therefore, Eq. (6.44a) can be used, with uh in Eq. (6.42) set equal to the velocity at the closed balance point, u-uk cBp- Alternatively, Eq, (6.446) can be used with uh in Eq. (6.42) set equal to the velocity at the open balance point, uvh Qbp-Note that between the open and closed balance points the hole velocity at the relevant balance point, and not the actual gas velocity of gas through the holes, is used as uh in Eq. (6.42). 

In order to determine whether the valves are fully open, fully closed or in between, and in order to apply the pressure drop equation between the open and closed balance points, the vapor hole velocities aft each balance point must be evaluated. The balance-point hole velocities are evaluated from a balance between the vapor force pushing the valve open and the gravity force tending to close it. This force balance gives (71,80)... 

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