Abstract:
The useful life of an abrasive material transport hose ( 10 ) can be maximized if the hose is repositioned at the first signs of internal wear. This is accomplished by disposing at least two wear sensing elements ( 17, 21 ), each at a specified distance from the inwardmost surface of the inner tube ( 12 ), and each monitoring a condition indicative of wear of the hose ( 10 ) at its specified distance from the inwardmost surface of the inner tube. When the innermost wear sensing element ( 17 ) implies wear, the hose can be repositioned to extend the useful life until the outermost wear sensing element ( 21 ) indicates wear requiring replacement of the hose.

Description:
FIELD OF THE INVENTION 
     The invention relates to a hose for transporting abrasive material and in particular to a hose for transporting abrasive material having sensors for detecting wear of the hose. 
     BACKGROUND OF THE INVENTION 
     A hose for transporting abrasive material, either fluidized or dry bulk, is usually constructed with an inner lining or tube made of abrasion resistant material, a carcass composed of layers of reinforcement plies to resist pressure within the tube and a rubber cover, typically of an elastomeric materials, to protect the carcass. The hose may include, a reinforcing steel wire helix embedded between the layers and a built-in coupling at each end. 
     Since the hose is used for transporting abrasive material, the inner lining and reinforcing layers of the hose can be worn through by the flow of the material during usage. Since the wear is within an internal section of the hose, it is not possible to visually inspect the degree of wear. The hose, if operated until total failure, can create unforeseeable and unwanted problems including leakage, rupture or explosion. 
     U.S. Pat. No. 4,446,892 (&#39;892) by Maxwell discloses a fluid transport hose having two or more plies comprising a sensing element located between the plies, the sensing element being adapted to respond to the failure of an inner ply of the hose by presenting an open circuit. The purpose of the sensing element in the hose is to detect imminent breakdown of a hose section and to permit the user to replace the hose prior to external leakage. The &#39;892 patent also discloses a secondary sensing element disposed between the outermost plies of the hose to detect the occurrence of physical damage to the outer plies of the hose. 
     U.S. Pat. No. 5,634,497 (&#39;497) by Neto discloses a hose for suction and discharge of abrasive material with a sensor circuit which indicates the total or partial wear of the inner lining of the hose, thus permitting hose replacement prior to its rupture or blow up. The &#39;497 patent discloses a sensing element comprised of a bi-polar (two-pole) socket fixed to one of the external layers of the hose and connected, preferably, to the terminal ends of wires which extend spirally along the entire length of the hose. In order to determine the wear of the hose, it is necessary to verify, by means of the bi-polar socket, the continuity of the sensing element. In the case where the sensing element is interrupted, this means that the wire wound within the hose has been broken, implying that the hose shows signs of internal wear and should be replaced. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved hose using a sensing system to detect the internal wear of a hose, as defined in one or more of the appended claims and, as such, having the capability of being constructed to accomplish one or more of the subsidiary objects. 
     It is another object of the present invention to provide a hose capable of transporting abrasive material, either dry bulk or fluid. 
     It is a further object of the present invention to detect wear of the hose without interrupting the transport of the abrasive material. 
     It is yet another object of the present invention to detect wear of the hose to avoid an operating accident such as leakage, rupture, and explosion. 
     It is still another object of the present invention to provide multiple levels of hose wear detection in order to permit hose reposition prior to replacement in order to maximize the hose&#39;s useful life. 
     It is an object of the present invention to provide a hose with a wear-sensing element, which can be disposed within the tube or between the reinforcement plies of the hose using either wire or chemically sensitive tape. 
     In accordance with the invention, a hose for transporting abrasive material comprises first and second wear-sensing elements, one disposed at a first distance from the innermost surface of the inner lining (tube) and a second disposed at a second distance from the innermost surface of the inner lining (tube), the second distance being greater than the first distance. By monitoring the first and second wear-sensing elements with wear sensing devices, it is possible to detect wear of the inner lining and further wear as it propagates to one of the many layers disposed over (radially outward) the inner lining. 
     The first wear-sensing element is disposed adjacent to or within the inner lining (tube) or one of the reinforcement plies, running substantially the entire length of the hose. The first wear-sensing element, made up of a first set of two sensor wires, extends spirally over the length of the hose. One end of the first set of two sensor wires making up the first wear-sensing element are joined together. The other end of the first set of two wires making up the first wear-sensing element are connected to a first two-pole socket. 
     The second wear-sensing element comprises a second set of two sensor wires, each of the two sensor wires having one end extending to or even beyond one end of the hose and an opposite end extending to or even beyond the other end of the hose and joined (spliced) together. At the one end of the hose, the second set of sensor wires are connect to a second two-pole socket. 
     The means or structural components to detect wear is provided by connecting to the first and second two-pole sockets, through which the first and second wear-sensing elements can be monitored. Sensing wear at the first, innermost wear-sensing element permits the user to reposition the hose so as to continue operation until wear is sensed at the outermost second wear-sensing element, at which point the hose needs to be replaced prior to its failure during use. Repositioning the hose after sensing wear in the innermost layers of the hose extends the useful life of the hose. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The structure, operation, and advantages of the present preferred embodiment of the invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying drawings, wherein: 
     FIG. 1 is a perspective view, partial cutaway, of a section of an embodiment of a hose of this invention incorporating sensor wire applied over the length of the hose; 
     FIG. 2 is a perspective view of the hose of FIG. 1, showing a later stage of construction, incorporating two-pole sockets connected to sensor wire and assembled on the hose; 
     FIG. 3 is a perspective view of the hose of FIG. 2 showing a completed hose of this invention, incorporating two wear sensor circuits and a wear-sensing device attached to each circuit; 
     FIG. 4 is a detailed view of a wear-sensing device of FIG. 3, including local annunciation and optional remote station connection; 
     FIG. 5 is a simplified schematic block diagram of a hose wear-sensing device of FIG. 4; and 
     FIG. 6 is a perspective partial cut-away view of a section of another embodiment of a hose of this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A hose for transporting abrasive material wears due to the effects of contact with the material being transported. Wear initiates on the inner lining and then propagates to subsequent reinforcement layers until total failure of the hose occurs, resulting in leakage, rupture, or explosion. 
     From the prior art, it is known that wire may be disposed in a hose in order to detect the wear of inner layers to permit replacement prior to total failure of the hose. Wire used for this purpose is called “sensor wire”. A “wear sensing element” comprises a layer of sensor wire in a hose. A layer of hose surrounded by a wear-sensing element is called a “sensed layer”. A device used to monitor a wear sensing element is called a “wear sensing device”. A “wear sensing system” comprises a wear sensing device attached to a wear sensing element. 
     A sensed layer, either an inner lining (also called a tube herein) or a reinforcement ply covering the tube, wears due to the effects of the abrasive material being transported. Once the sensed layer has worn through, the abrasive material can make contact with and cause wear of the sensor wire in the wear sensing element. A wear sensing system determines whether the wear sensing element is worn by testing for continuity. The presence of continuity of the wear sensing element implies that the sensed layer is not worn. Conversely, the absence of continuity of the wear sensing element implies wear of the sensed layer. 
     A hose of the present invention includes at least two distinct wear sensing elements. The use of multiple wear sensing elements permits the detection of wear at different depths of the hose. As is commonly understood in the industry, the wear of a hose in abrasive material applications typically occurs at specific points within the hose, typically where the hose has a bend in it. The wear sensing element for the innermost sensed layer provides the first indication of hose wear. Wear detected at the innermost sensed layer permits the user to know when a hose should be repositioned (typically rotated) to transfer the material abrading to other locations of the hose inner layers, thereby extending the useful life of the hose. This process can be repeated until wear is detected in the outermost wear sensing element, implying wear in the outermost sensed layer, indicating the need for hose replacement. 
     The aforementioned U.S. Pat. No. 5,634,497 to Neto discloses a hose with two layers of sensor wire arranged so as to form only one wear sensing element. In contrast thereto, the hose of the present invention has at least two wear sensing elements and corresponding at least two wear sensing systems arranged such that, in the case of two wear sensing elements, the inner wear sensing element detects the initiation of wear in the inner lining and the outer wear sensing element detects propagation of wear to a subsequent, outwardly disposed reinforcement layer. 
     U.S. Pat. No. 4,446,892 to Maxwell discloses a hose with two wear sensing elements, the sensing elements arranged such that the inner sensing element detects wear in the inner lining, and the outer sensing element detects damage to the hose exterior. In contrast thereto, the at least two sensing elements of the present invention are arranged such that the progress of a wear problem can be “tracked” as it propagates from the inner lining to subsequent reinforcement layers. 
     FIG. 1 shows a preferred embodiment of the hose  10  for transporting abrasive material of the present invention in a partially completed stage of construction. The hose  10  has two ends  10   a  and  10   b , and comprises an inner, preferably wear-resistant elastomeric lining (tube or tubes)  12  having an innermost surface  11 . A first set of sensor wires  14  and  16  are spirally wound on the inner lining  12  and extend to or even beyond both ends of the hose  10 . The first ends  14   a  and  16   a  of the sensor wires  14  and  16 , respectively, extend to or even beyond the end  10   a  of the hose  10  and are connected to a two-pole socket  42 . The opposite second ends  14   b  and  16   b  of the sensor wires  14  and  16 , respectively, extend to or even beyond the opposite end  10   b  of the hose  10  and are connected (spliced) to one another. 
     In this manner, the two sensor wires  14  and  16  effectively form a single wear sensing element  17  extending along the entire length of the hose  10  over a “sensed layer”  13 . The single wear sensing element  17  has two ends  14   a  and  16   a  which typically extend to one end  10   a  of the hose  10 . As described hereinbelow, the ‘free ends’  14   a  and  16   a  of wires  14  and  16 , respectively, are connected to a conventional two-pole socket  42 , and a wear sensing device  60  is attached to the wear sensing element  17  via the socket, to form a “wear sensing system”  19 . According to the invention, additional wear sensing elements  21  may be formed in the hose  10  to monitor progress of abrasion as it propagates from the sensed layer  13  of the hose towards an outer sensed layer  23  of the hose. 
     The second sensed layer  23  of tube or reinforcement ply is applied over the wear sensor wires  14  and  16 . In a manner similar to that described hereinabove with respect to the wear sensing element  17 , a pair of sensor wires  20  and  22  are spirally wound around the layer  18  of reinforcement ply and typically extend to or even beyond both ends  10   a  and  10   b  of the hose  10 . The free ends  20   a  and  22   a  of the sensor wires  20  and  22  can extend to or beyond the end  10   a  of the hose  10  and are connected to a conventional two-pole socket  44 . The ends  20   b  and  22   b  of the sensor wires  20  and  22  extend to or beyond the opposite end  10   b  of the hose  10  and are connected (spliced) to one another to complete a second wear sensing element  21 . The wear sensing element  21  is used to detect wear in the “sensed layer”  23 . 
     In this manner, two wear sensing elements  17 , 21  are provided in the hose  10 . The first wear sensing element  17  comprises the sensor wires  14  and  16  and is disposed at a first distance from the most inner surface  11  of the inner lining  12 . The second wear sensing element  21  comprises the sensor wires  20  and  22  disposed at a second distance which is greater than the first distance from the most inner surface  11  of the inner lining  12 . 
     Additional layers of reinforcement ply, as represented by ply layers  24 ,  26 ,  28 ,  30  ( 24 - 30 ), are disposed over the sensed layers  12  and  23 . In addition, reinforcing steel wire helix wires (not shown) can be embedded between the ply layers as is conventionally known in the hose construction art. In the manner described hereinabove, additional wear sensing elements can be incorporated into the hose construction, over any one of these additional ply layers, at increasing distances from the inner surface  11  of inner lining  12 , to provide additional levels of wear detection, as may be desired. 
     FIG. 2 shows a further stage of construction of the hose  10  of the present invention. On the outmost shown layer  40  of reinforcement ply, first and second two-pole sockets  42 , 44  are affixed by any conventional means, and are connected to free ends  14   a ,  16   a  and  20   a ,  22   a , respectively, of the sensor wires  14 , 16  and  20 , 22  of sensing elements  17 , 21 , respectively. At the opposite end of the hose  10 , free ends  14   b ,  16   b ,  20   b ,  22   b  of the sensor wires  14 ,  16  and  20 ,  22  are spliced together as shown in FIG.  1 . While the wires  14 , 16  and  20 , 22  are shown spliced together, it is within the terms of the present invention to join them in any conventional manner including forming them of a single length of sensor wire. As shown in FIG. 2, sensor wires  14 , 16  and the first two-pole socket  42  represent the first wear sensing element  17  and sensor wires  20 , 22  and second two-pole socket  44  represent the second wear sensing element  21 . 
     FIG. 3 shows a completed construction of a typical hose  10  of the present invention. The hose  10  receives an outermost cover layer  50  to protect the plies  24 - 30  forming the hose carcass, thus enclosing the two-pole sockets  42 , 44  (shown in FIG. 2) and exposing terminal ends  52 , 54 , respectively. While the sockets  42 , 44  are shown as being mounted within the hose  10 , it is also within the terms of the invention to mount the sockets on the exterior of the hose, i.e. upon the cover layer  50 , so that they can be easily replaced with other sockets depending on the particular installation. A user inserts plugs  56 , 58  of wear sensing devices  60 , 62  (described hereinafter with regard to FIG. 4) into terminal ends  52 , 54 , respectively, of two-pole sockets  42 , 44  to detect the degree of internal wear of hose  10 . 
     Hose  10  is generally constructed in accordance with techniques already known for manufacturing of hoses used for transporting abrasive materials. For example, hose  10  may be constructed with various inner diameters of interior surface  11  as well as different final lengths. However, the hose usually has an inner diameter in the range of from 2.5 to 120 cm (1 to 48 inches). 
     Another embodiment of the present invention may be considered (not shown) where sensor wire  14 , 16  is replaced with a chemical sensitive tape for application where material being transported is of a nature such that its presence may be sensed by means other than continuity. That is, the chemical sensitive tape can function as the sensor wires by indicating that the sensed layer about which the chemical sensitive tape is wrapped is worn by the absence of electrical continuity through the tape caused by chemical erosion or wear of the tape. 
     FIG. 4 shows a typical wear sensing device  60  (substantially identical with wear sensing device  62 ) comprising an ON/OFF switch  72 , a power source (not shown), an LED  74 , a buzzer  76 , a Push-to-Test button  78 , a buzzer select/deselect switch  80 , an optional remote output  82 , and an industrial strength RCA phono jack  56  (comparable to plug  58  of wear sensing devices  62 ) for connecting to the first and second two-pole sockets  42 , 44  of sensing elements  17 , 21 . Internally (not shown), the wear sensing device  60  contains a wear monitor circuit (described hereinbelow with respect to FIG. 5) to monitor a wear sensing element  17 , 21  and control an alarm circuit. 
     Functionally, a wear sensing device  60 , 62  monitors a sensing element  17 , 21  by constantly checking continuity (resistance) of the circuit. A functioning circuit will measure a resistance, such as for example, less than 10,000 ohms that indicates that continuity of the sensing element is intact, implying that the sensed layer is functioning as required. Measuring a higher resistance, such as for example, greater than 100,000 ohms, indicates that continuity of the sensing element  17 , 21  has been broken, implying that the sensed layer has malfunctioned. In the latter instance, the functioning circuit activates an alarm  75 . Alarm  75  consists of a flashing LED  74 , an audible buzzer  76 , and an optional signal from output  82  for a remote Programmable Logic Controller (PLC). Any or all of these alarms may be deployed, depending on the usage. 
     FIG. 5 shows a simplified block diagram of a hose wear monitor circuit  80  of a wear sensing device  60 , 62 . The circuit  80  includes an Input Interference and Overvoltage Protection circuit  90 , which connects by output  91  to a wear sensing system  19 , 23  and protects the corresponding wear sensing device  60 , 62  from external noise and voltage spikes. The wear monitor circuit  80  also includes a Resistance Monitoring circuit  92 , which measures the resistance of a wear sensing elements  17 , 21  to determine if continuity is present. A Multivibrator and Oscillator circuit  94  flashes an LED  96  if an alarm condition is present. Using a Buzzer Select/Deselect switch  98  the operator enables an audible alarm  100 . A separate transistor output  102  can also be included as part of the wear sensing device  60 . A device such as a Programmable Logic Controller (PLC) (not shown) monitors the transistor output  102  to annunciate alarms in a centralized control room or other remote location. A Push-to-Test switch  104  verifies proper operation of the wear sensing device  60 . An ON/OFF switch  106  controls power flow to the wear sensing device  60  from conventional means such as a 6V battery circuit  108 . 
     ALTERNATE EMBODIMENT 
     FIG. 6 shows a hose  110  constructed in accordance with a second embodiment of the present invention. Over a mandrel (not shown), an inner lining or tube  112  is applied, upon which a sensor wire  114  is spirally wound thereabout. Subsequently, an additional layer of insulating liner or tube  116  is applied, upon which a sensor wire  118  is spirally wound. The free ends  114   a ,  118   a  of sensor wires  114 , 118 , respectively, are extended to or even beyond one end of the hose  110  and connect to a first two-pole socket (not shown but comparable to two-pole socket  42 ) as described hereinbefore. The other free ends  114   b ,  118   b  of sensor wires  114 , 118 , respectively, are joined or spliced together to complete a first wear sensing element  119  (sensor wires  114 , 118  and two-pole socket  42 ) to detect wear in sensed layer  113 . Subsequently, a layer  120  of tube or reinforcement ply is disposed over insulating tube or fabric layer  116 . Layer  120  in turn has a single turn of sensor wire  122  spirally wound thereabout. A layer  124  of insulating tube or fabric is next applied, upon which a single turn of sensor wire  126  is spirally wound thereabout. Next, a reinforcement ply  128  is disposed over the layer  124  and sensor wire  126 . The free ends  122   a ,  126   a  of sensor wires  122 , 126 , respectively, extend to or even beyond one end of the hose  110  to connect to a second two-pole socket (not shown) in the manner described hereinbefore regarding the embodiment shown in FIGS. 1 and 2. The other free ends  122   b ,  126   b  of sensor wires  122 , 126  are joined or spliced together to complete a first sensing element  119 . It is within the terms of the invention to provide wires  122 , 126  from a single strand of sensor wire that is simply applied on the inner layer  120  and then applied on the outer layer  124 . The first sensing element  119  detects wear in sensed layer  113 . Subsequent layers of sensor wires, carcass fabrics, tubes and reinforcement plies can be applied using this method depending on the number of wear sensing elements and reinforcement plies required for the usage. 
     Completion of the construction of the embodiment presented in FIG. 6 is similar with the construction method described regarding the first embodiment illustrated in FIGS. 2 and 3. The second embodiment can be connected to wear sensing devices such as devices  60 , 62  as described hereinbefore. 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.