Patent Publication Number: US-6669455-B2

Title: Fluid-pumping system employing air-driven pump and employing at least one pulsation dampener

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of U.S. Provisional Patent Application Serial No. 60/353,709, which was filed on Jan. 31, 2002, and the disclosure of which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     This invention pertains to a fluid-pumping system employing an air-driven pump, which may be a double-diaphragm pump, and employing at least one pulsation dampener to dampen pressure pulsations at an outlet of the air-driven pump. 
     BACKGROUND OF THE INVENTION 
     In fluid-pumping systems, pressure pulsations are known to occur in fluids being pumped. It is known to employ pulsation dampeners to dampen such fluctuations. Such pulsations are known to occur even if air-driven pumps are employed, whether single-diaphragm pumps, double-diaphragm pumps, or piston pumps. 
     One example of a pulsation dampener is disclosed in U.S. Pat. No. 4,979,441. The pulsation dampener disclosed therein employs an inner, perforated tube, an outer, rigid tube, and an intermediate, elastomeric sleeve. Gas pressure in a space between the outer, rigid tube and the intermediate, elastomeric sleeve dampens pressure pulsations in a fluid being pumped through the inner, perforated tube. With the pulsation dampener disclosed therein, it is difficult to compensate for minute losses of gas pressure in the space between the outer, rigid tube and the intermediate, elastomeric sleeve. 
     SUMMARY OF THE INVENTION 
     This invention provides a fluid-pumping system comprising a pump having an inlet and an outlet and a pulsation dampener arranged to dampen pressure pulsations at the outlet. The pump is arranged to be driven by air delivered to the pump at a regulated pressure. The pulsation dampener is arranged to be charged by air delivered at a regulated pressure via a pressure-reducing regulator, which is arranged to regulate the air pressure in the charging line by reference to the average pressure of the air driving the pump. 
     Preferably, the pressure-reducing regulator is arranged to regulate the air pressure in the charging line to a selected differential above or below the average pressure of the air driving the pump. In a preferred embodiment, wherein an averaging tank is connected to a driving line, via an orifice, the pressure-reducing regulator is arranged to regulate the air pressure in the charging line by reference to the air pressure in the averaging tank. The fluid-pumping system may comprise two pulsation dampeners, i.e., one arranged to dampen pressure drops at the outlet and another arranged to dampen pressure surges at the outlet. 
     Preferably, each pulsation dampener comprises an air-side chamber, which is adapted to be charged through the charging line, a fluid-side chamber, which is adapted to communicate with the outlet conduit so that the fluid pumped through the outlet conduit can enter the fluid-side chamber, and an elastomeric diaphragm, which is mounted so as to separate the outer and fluid-side chambers. Preferably, each pulsation dampener comprises two apertured walls, between which the diaphragm is mounted. One said wall is mounted so as to limit displacement of the diaphragm in a direction to decrease the volume of the air-side chamber and, thereby, to increase the volume of the fluid-side chamber. The other wall is mounted so as to limit displacement of the diaphragm in a direction to increase the volume of the air-side chamber and, thereby, to decrease the volume of the fluid-side chamber. Preferably, outside said one wall, the air-side chamber has a volume at least three times larger than the volume between the apertured walls. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partly schematic layout of a fluid-pumping system employing an air-driven pump, employing a pulsation dampener, and embodying this invention. 
     FIG. 2, on a larger scale, is a partly cross-sectioned, partly broken-away view of the pulsation dampener and of adjacent portions of an outlet conduit, in the system of FIG.  1 . 
     FIG. 3, on an intermediate scale, is a layout of two pulsation dampeners and adjacent portions of an outlet line, in a modified system embodying this invention. 
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT 
     As illustrated in FIG. 1, a fluid-pumping system  10  comprises an air-driven pump  20 , which may be a double-diaphragm pump, which is arranged to draw a fluid through an inlet conduit  22 , into an inlet  24  of the pump  20 , and which is arranged to pump the fluid from an outlet  26  of the pump  20 , through an outlet conduit  28 . The pump  20  is driven by air delivered to the pump  20  through a driving line  32 , via a pressure-reducing regulator  30 , which receives air at a higher pressure from a source (not shown) and which reduces the air pressure to a regulated pressure suitable for driving the pump  20 . 
     Moreover, the system  10  comprises a pulsation dampener  40 , which is arranged to dampen pulsations in the pressure of the fluid being pumped through the outlet conduit  28 . The pulsation dampener  40  is charged by air delivered to the pulsation dampener  40 , through a charging line  42 , via a pressure-reducing regulator  50 , which receives air at a higher pressure from the same source and which reduces the air pressure in the charging line  42  to a regulated pressure by reference to the average pressure of the air driving the pump  20 . 
     As illustrated in FIG. 1, an averaging tank  60  is connected to the driving line  32 , via an orifice  62 , and the pressure-reducing regulator  50  is arranged to regulate the air pressure in the charging line  42  by reference to the air pressure in the averaging tank  60 . Alternatively, the average pressure of the air driving the pump  20  may be electronically measured via a pressure transmitter (not shown) which is connected to the driving line  32  and which is arranged to average multiple pressure readings and to control the pressure-reducing regulator  50  accordingly. 
     As illustrated in FIG. 2, the pulsation dampener  40  comprises an air-side chamber  72 , which has a variable volume and which is charged through the charging line  42 , a fluid-side chamber  74 , which has a variable volume and which communicates with the outlet  26  of the pump  20 , via the outlet conduit  28 , so that the fluid pumped through the outlet  26  of the pump  20  can enter the fluid-side chamber  74 , and an elastomeric diaphragm  80 , which is mounted so as to separate the air-side chamber  72  and the fluid-side chamber  74 . The pulsation dampener  40  comprises two apertured walls, between which the diaphragm  80  is mounted. One said wall  82  is mounted so as to limit displacement of the diaphragm  80  in a direction to decrease the volume of the air-side chamber  72  and, thereby, to increase the volume of the fluid-side chamber  74 . The other wall  84  is mounted so as to limit displacement of the diaphragm  80  in a direction to increase the volume of the air-side chamber  74  and, thereby, to decrease the volume of the fluid-side chamber  74 . Moreover, outside the apertured wall  82 , the air-side chamber  72  has a volume at least three times larger than the volume between the apertured walls  82 ,  84 . 
     If the pressure of the fluid entering the fluid-side chamber  74  from the outlet conduit  28  surges above the pressure of the air in the air-side chamber  72 , the diaphragm  80  is displaced so as to decrease the volume of the air-side chamber  72  and so as to increase the volume of the fluid-side chamber  74 , whereby to dampen the pressure surge in the fluid being pumped through the outlet conduit  28 . If the pressure of the fluid entering the fluid-side chamber  74  from the outlet conduit  28  drops below the pressure of the air in the air-side chamber  72 , the diaphragm  80  is displaced so as to increase the volume of the air-side chamber  72  and so as to decrease the volume of the fluid-side chamber  74 , whereby to dampen the pressure drop in the fluid being pumped through the outlet conduit  28 . Depending upon whether the air pressure in the air-side chamber  72  is regulated to a normal pressure above, below, or approximately at the normal pressure of the fluid in the fluid-side chamber  74 , via the pressure-reducing regulator  50 , the pulsation dampener  40  can be thus controlled so as to dampen pressure surges in the fluid being pumped through the outlet conduit  28 , so as to dampen pressure drops therein, or so as to dampen pressure surges therein and pressure drops therein. 
     Because of the low mass of the diaphragm  80  and the large volume of air in the air-side chamber  72 , the pulsation dampener  40  responds quickly to pressure fluctuations in the fluid being pumped through the outlet conduit  28 . Moreover, even if minute losses of air in the air-side chamber  72  occur, the pressure-reducing regulator  50  compensates for those losses so as to maintain the air pressure in the air-side chamber  72 . 
     If the fluid being pumped by the system  10  is a liquid or employs a liquid carrier, the pulsation dampener  40  may be advantageously provided with a liquid sensor  90 , which is mounted in the air-side chamber  72 , which is arranged to detect any liquid that may have entered the air-side chamber  72 , and which is arranged, if the sensor  90  detects any liquid, to activate an alarm signal, shut down the system  10 , or both. 
     As illustrated in FIG. 3, two pulsation dampeners  40 A,  40 B, are employed in a modified system  10 A, each being similar to the pulsation dampener  40 , each being controlled similarly, and each communicating similarly with the outlet  26  of the pump  20 , via the outlet conduit  28 . The pulsation dampener regulator  40 A can be thus controlled so as to dampen pressure surges in the fluid being pumped through the outlet conduit  28 . The pulsation dampener  40 B can be thus controlled so as to dampen pressure drops in the fluid being pumped through the outlet conduit  28 .