Abstract:
A method of increasing efficiency of a Y strainer and Y strainer modified in accordance with the method. The Y strainer is of the type that has a filter cartridge receiving inflow through one end and outflow through apertures in a peripheral sidewall. The method involves slowing a velocity of fluids entering the filter cartridge of the Y strainer by having the fluids pass from a first bore of a first diameter into a second bore of a second diameter which is at least 50% larger than the first diameter prior to entering the filter cartridge. The filter cartridge also has the second diameter. This modification has been found to dramatically improve the performance of the Y strainer.

Description:
FIELD 
     There is described a method of increasing the efficiency of a Y strainer and a Y strainer that has been modified in accordance with the teachings of the method. 
     BACKGROUND 
     Y strainers are used to capture particulate matter in piping systems. They are so named due to their Y shaped configuration. Y strainers have also been referred to as Y “filters”. Whether a label of a Y “strainer” or Y “filter” is given to the device depends upon aperture size. As a general rule, Y devices which only are capable of capturing contaminants larger than 200 microns are termed “strainers” and Y devices apertures which are capable of capturing contaminants smaller than 200 microns are terms “filters”. For the purpose of this paper, no such distinction will be made and the term of Y strainer will be used in its broader more inclusive sense to denote the configuration. 
     When a hydrocarbon producing well has a sand problem, there are known sand separators that can be placed on the well. These sand separators are expensive units costing over $100,000.00 and are, therefore, only placed on wells that clearly have a long term, as opposed to a temporary sand problem. 
     When formation conditions are appropriate, hydrocarbon producing wells are stimulated by fracturing the formation with sand, a technique known as “fracing”. For this fracing procedure, very fine abrasive sand is used. Problems are being experienced with some of this fine abrasive sand appearing, without warning, in well production. The problem is not apparent until it manifests itself and sand starts appearing in the equipment. When it occurs, it can be difficult to determine whether the formation is merely “burping” small amounts of sand periodically or whether there is a more serious sand problem requiring a sand separator. The problem cannot be ignored. Even when present in small quantities, sand can damage equipment. When present in larger quantities, abrasive sand can wear through pipes and cause serious problems resulting in leakage into the environment and the threatening the lives of oil field workers. 
     Attempts have been made to use Y strainers until the magnitude of any sand problem can be determined. These attempts have been unsuccessful. The Y strainers presently available are not able to deal with the fine abrasive sand. There will now be described a method that was used to make the Y strainer more efficient in dealing with fine sand and a form of Y strainer that was built in accordance with the teachings of the method. 
     SUMMARY 
     According to one aspect, there is provided a method of increasing efficiency of a Y strainer. The Y strainer is of the type that has a filter cartridge receiving inflow through one end and outflow through apertures in a peripheral sidewall. The method involves slowing a velocity of fluids entering the filter cartridge of the Y strainer by having the fluids pass from a first bore of a first diameter into a second bore of a second diameter which is at least 50% larger than the first diameter prior to entering the filter cartridge. The filter cartridge also has the second diameter. 
     It was determined that by having fluids pass into a larger bore, the velocity of the fluids was reduced and a Y strainer that had previously had been ineffective captured a majority (over 75%) of the sand. 
     It was subsequently determined that the velocity of fluids entering the filter cartridge of the Y strainer could be further slowed by positioning a physical barrier across an inlet pipe, such that the fluids strike the physical barrier prior to entering the filter cartridge. The physical barrier used was a deflector plate. The deflector plate was originally added to protect the filter element. However, it was determined that the addition of the deflector plate also served to increase efficiency by bringing the amount of sand captured to over 90%. 
     According to another aspect, there is provided a Y strainer assembly constructed in accordance with the teachings of the method. The Y strainer has an inlet pipe having a first portion of a first diameter and a second portion of a second diameter that is 50% larger than the first diameter. An outlet pipe of similar construction is provided having a first portion of the first diameter and a second portion of the second diameter. A cartridge receiving pipe of the second diameter is in fluid communication with the second portion of the inlet pipe and the second portion of the outlet pipe. Fluids pass from the inlet pipe into the cartridge receiving pipe and from the cartridge receiving pipe into the outlet pipe. The cartridge receiving pipe has a closure which can be opened to facilitate insertion of a filter cartridge. A filter cartridge is provided having an inlet at an inlet end for receiving an inflow of fluids from the inlet pipe and apertures in a peripheral sidewall through which an outflow of fluids pass into the outlet pipe. 
     As described in relation to the method, the operation of the Y strainer assembly can be enhanced through the use of a deflector. It is preferred that the filter cartridge support a deflector, such that fluids flowing along the inlet pipe strike the deflector and are deflected into the inlet end of the filter cartridge. 
     In order to further improve performance, the filter cartridge has been modified to include an inner sleeve with flow apertures and a flexible mesh filter which is retained between the inner sleeve and the peripheral sidewall. The inner sleeve both supports and protects the flexible mesh filter. The flexible mesh filter can readily be inspected for wear and replaced. 
     In order to further improve performance, the filter cartridge has been modified so that the inlet end of filter cartridge defines a wedge. The wedge at the inlet end is wedged into the inlet pipe to make a connection through which fluids flow from the inlet pipe into the inlet end of the filter cartridge. 
     In order to monitor sand accumulation, an upstream sensor is positioned in the inlet pipe upstream of the filter cartridge and a downstream sensor is positioned in the outlet pipe downstream of the filter cartridge. A differential in output between the upstream sensor and the downstream sensor providing an indication of sand accumulation within the filter cartridge. 
     In order to empty the filter cartridge, a blow down valve is positioned in the closure of the cartridge receiving pipe. This allows service personnel to rapidly purge sand accumulations from the filter cartridge. 
     It is also preferred that valves are positioned on the inlet pipe and the outlet pipe. These valves can be used for a variety of purposes. One purpose is to selectively isolate the Y strainer. Another purpose is injection of chemicals, such as methanol. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features will become more apparent from the following description in which reference is made to the appended drawings, the drawings are for the purpose of illustration only and are not intended to be in any way limiting, wherein: 
         FIG. 1  is a top plan view of a Y strainer assembly. 
         FIG. 2  is a front elevation view of the Y strainer assembly shown in  FIG. 1 . 
         FIG. 3  is an exploded view of the cartridge receiving pipe and filter cartridge. 
         FIG. 4  is an exploded view of a filter cartridge. 
         FIG. 5  is a top plan view of the cartridge receiving pipe and filter cartridge. 
         FIG. 6  is an exploded view of a variation of the cartridge receiving pipe and filter cartridge. 
         FIG. 7  is a top plan view of a variation of a Y strainer assembly. 
         FIG. 8  is a front elevation view of the variation of the Y strainer assembly shown in  FIG. 7 . 
         FIG. 9  is an exploded view of a filter cartridge used in the Y strainer assembly shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
     A Y strainer assembly generally identified by reference numeral  10 , will be described with reference to  FIG. 1 through 5 . A variation of the Y strainer assembly generally identified by reference numeral  100 , will be described with reference to  FIG. 6  through  FIG. 9 . 
     Structure and Relationship of Parts: 
     Referring to  FIG. 1 , a Y strainer assembly  10  has an inlet pipe  12  with a first portion  14  of a first diameter and a second portion  16  of a second diameter that is 50% larger than the first diameter. An outlet pipe  18  has a first portion  20  of the first diameter and a second portion  22  of the second diameter. Referring to  FIG. 2  and  FIG. 5 , a cartridge receiving pipe  26  of the second diameter is in fluid communication with the second portion  16  of the inlet pipe  12  and the second portion  22  of the outlet pipe  18 . When filter cartridge  30  is in position, fluids are unable to pass directly from inlet pipe  12  to outlet pipe  18  without first passing through filter cartridge  30 . With filter cartridge  30  in position, fluids pass from the inlet pipe  12  into the cartridge receiving pipe  26  and from the cartridge receiving pipe  26  into the outlet pipe  18 . The cartridge receiving pipe  26  has a closure  28  which can be opened to facilitate insertion of filter cartridge  30 . Referring to  FIG. 3 , filter cartridge  30  has an inlet  32  at an inlet end  34  for receiving an inflow of fluids from the inlet pipe  12  and apertures  36  in a peripheral sidewall  44  through which an outflow of fluids pass into the outlet pipe  18 . An end plate  33  with a centrally positioned blow down opening  31  is positioned at the opposite end  35  from inlet end  34  of filter cartridge  30 . Blow down valve  52  is passed through blow down opening  31  when closure  28  is in the closed position. 
     In the embodiment shown, filter cartridge  30  supports a deflector  38 . Fluids flowing along the inlet pipe  12 , strike the deflector  38  and are deflected into the filter cartridge  30 . Referring to  FIG. 4 , filter cartridge  30  has an inner sleeve  40  with flow apertures  42  and a flexible mesh filter  43  which is retained between the inner sleeve  40  and the peripheral sidewall  44 . Referring to  FIG. 3 , inlet end  34  of filter cartridge  30  defines a wedge  45  which is wedged into the inlet pipe  12  to make a connection through which fluids flow from the inlet pipe  12  into the inlet end  34  of the filter cartridge  30 . 
     Referring to  FIG. 1  and  FIG. 2 , an upstream sensor  46  is positioned in the inlet pipe  12  upstream of the filter cartridge  30  and a downstream sensor  48  is positioned in the outlet pipe  18  downstream of the filter cartridge  30 . A differential sensor  50  compares the outflow between the upstream sensor  46  and the downstream sensor  48  which provides an indication of sand accumulation within the filter cartridge  30 . The above described sensors can be isolated from fluid flow, for servicing by closing valves  49 . Referring to  FIG. 1 , a blow down valve  52  is positioned in the closure  28  of the cartridge receiving pipe  26 ; to permit a conduit  53  to be attached through which sand accumulations on the filter cartridge  30  may be purged. Referring to  FIG. 1  and  FIG. 2 , valves  54  are positioned on the inlet pipe  12  and the outlet pipe  18  to permit the injection of fluids either upstream or downstream of filter cartridge  30  of Y strainer assembly  10 . Valves  55  are positioned at either end of Y strainer assembly  10  and provide means of isolating Y strainer assembly  10  during servicing and maintenance. 
     Operation: 
     Referring to  FIG. 3 , closure  28  is opened and a cartridge  30  is inserted into cartridge receiving pipe  26  such that inlet end  34  of filter cartridge  30  receives an inflow of fluids from the inlet pipe  12  and an outflow of fluids into the outlet pipe  18  must pass through filter cartridge  30 . Referring to  FIG. 1 , fluid flows through inlet pipe  12  through first portion  14  into second portion  16 . Due to the difference in diameter between first portion  14  and second portion  16 , the velocity of fluid is slowed. Fluid strikes deflector  38 , which deflects the fluid into cartridge  30  and further slows the velocity of the fluid. Referring to  FIG. 1  and  FIG. 2 , upstream sensor  46  senses the pressure of fluid flowing through inlet  12  and downstream sensor  48  senses the pressure of fluid flowing through outlet  18 . Differential  50  provides an indication of sand accumulation within the filter cartridge  30  by comparing the outflow between the upstream sensor  46  and the downstream sensor  48 . Valves  55  may be used to selectively isolate the Y strainer. Valves  54  may be used inject chemicals into Y strainer assembly  10 , either upstream or downstream of filter cartridge  30 . Valves  57  may be used to selectively isolate the upstream sensor  46  and the downstream sensor  48  from the Y strainer assembly  10  to allow for maintenance or replacement of sensors  46  and  48 . Referring to  FIG. 1 , periodically conduit  53  may be attached to blow down valve  52  and sand that has accumulated within the filter cartridge  30  may be purged using either system pressure or a circulation of fluids through valves  54 . 
     The velocity of fluids entering the filter cartridge  30  is slowed as fluids pass from first portion  14  of inlet pipe  12  to second portion  16  which has a larger diameter prior to entering the filter cartridge  30 . The velocity is further slowed by deflector  38  which is positioned across inlet pipe  12  at the inlet into filter cartridge  30 . The slowing of the velocity of the fluids passing through Y strainer assembly  10  has a dramatic effect on the ability of the Y strainer assembly to remove the sand. The use of the deflector  38  also helps to protect the filter elements in filter cartridge  30 . 
     When building test units going from a 4 inch diameter to a 6 inch diameter worked well. However, when a unit was built going from a 4 inch diameter to an 8 inch diameter it worked even better. 
     Advantages: 
     The Y strainer described above provides a number of advantages:
         There are devices that will work either when there is sand in gas or when there is sand in oil, but not both. The Y strainer described above can work with either gas or oil.   There are devices that are adversely affected by the presence of hydrates and condensates. The Y strainer described is not particularly sensitive to the presence of hydrates and condensates.   There are devices that can only operate efficiently within specified flow rate parameters and pressure level parameters. The Y strainer described above can work over a wide variety of flow rates and pressure levels.   Competitive sand removal devices are very expensive in comparison to the Y strainer described above.   The foot print of the Y strainer is relatively small and installation relatively simple, when compared to other sand removal technologies.   The Y strainer can be rapidly blown down in situ, to remove accumulated sand and place the Y strainer back into service.   The Y strainer can have sensors attached to determine the amount of sand accumulated. This can be as simple as an upstream and downstream pressure gauge that can be viewed by personnel on site or can be sensors that tie into a SCADA system for remote monitoring.   There are other devices with respect to which replacing worn parts can be relatively expensive. The primary consumable with the Y strainer described above is the flexible mesh. The flexible mesh costs approximately $10.00 and can be changed out in 15 to 20 minutes.   The “wedge” seating of the canister ensures correct placement.   The flexible mesh is protected by both the deflector plate and the interior sleeve.
 
Variations:
       

     A variation of a Y strainer assembly, generally referenced as numeral  100  will now be described with reference to  FIG. 6  and  FIG. 7 . 
     Referring to  FIG. 7 , Y strainer assembly  100  has an inlet pipe  102  with a first portion  104  of a first diameter and a second portion  106  of a second diameter that is 50% larger than the first diameter. An outlet pipe  108  has a first portion  120  of the first diameter and a second portion  122  of the second diameter. A cartridge receiving pipe  126  of the second diameter is in fluid communication with the second portion  106  of the inlet pipe  102  and the second portion  122  of the outlet pipe  108 . When filter cartridge  130  is in position, fluids are unable to pass directly from inlet pipe  102  to outlet pipe  108  without first passing through filter cartridge  130 . With filter cartridge  130  in position, fluids pass from the inlet pipe  102  into the cartridge receiving pipe  126  and from the cartridge receiving pipe  126  into the outlet pipe  108 . The cartridge receiving pipe  126  has a closure  128  which can be opened to facilitate insertion of filter cartridge  130 . 
     Referring to  FIG. 6 , filter cartridge  130  has an inlet  132  at an inlet end  134  for receiving an inflow of fluids from the inlet pipe  102  and apertures  136  in a peripheral sidewall  144  through which an outflow of fluids pass into the outlet pipe  108 . Referring to  FIG. 9 , filter cartridge  130  has an inner sleeve  140  with flow apertures  142  and a flexible mesh filter  143  which is retained between the inner sleeve  140  and the peripheral sidewall  144 . Referring to  FIG. 6 , an end plate  133  is positioned at the opposite end  135  from inlet end  134  of filter cartridge  130 . End plate  133  has a blow down opening  131  in an off center position along a lower side  137  when filter  130  is in position at an angle. This off center position allows for removal of virtually all of the sand on blow down. It was discovered during field tests that with a centrally positioned blow down opening a residue of sand would remain trapped along the edges of filter cartridge  130 . A blow down opening  131  in an off center position removes a greater amount of sand along the edges of filter cartridge  130  as sand from above falls to the lower side of filter cartridge  130  and a blow down through opening  131  directs the blow down to the lower side of filter cartridge  130 . In the embodiment shown, filter cartridge  130  supports a deflector  138 . Fluids flowing along the inlet pipe  102 , strike the deflector  138  and are deflected into the filter cartridge  130 . 
     Referring to  FIG. 7  and  FIG. 8 , an upstream sensor  146  is positioned in the inlet pipe  102  upstream of the filter cartridge  130  and a downstream sensor  148  is positioned in the outlet pipe  108  downstream of the filter cartridge  130 . A differential sensor  150  compares the outflow between the upstream sensor  146  and the downstream sensor  148  which provides an indication of sand accumulation within the filter cartridge  130 . Valves  157  may be used to selectively isolate the upstream sensor  146  and the downstream sensor  148  from the Y strainer assembly  100  to allow for maintenance or replacement of sensors  146  and  148 . Referring to  FIG. 8 , the above described sensors can be isolated from fluid flow, for servicing by closing valves  149 . Referring to  FIG. 7 , valves  154  are positioned on the inlet pipe  102  and the outlet pipe  108  to permit the injection of fluids either upstream or downstream of filter cartridge  130  of Y strainer assembly  100 . Valves  155  are positioned at either end of Y strainer assembly  100  and provide means of isolating Y strainer assembly  100  during servicing and maintenance. A series of valves  158  and  160  are positioned beyond closure  128  and in communication with a drain  162  and blow down opening  131  that enables a blow down procedure to be performed by opening and closing valves  158  and  160  to utilize system pressure. Beneficial results have been seen when valve  158  is a ball valve and valve  160  is a choke valve, however it will be understood that different types of valves may be used. This allows everything to remain online during the blow down to optimize production capacity of assembly  100 . 
     In this patent document, the word “comprising” is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article “a” does not exclude the possibility that more than one of the element is present, unless the context clearly requires that there be one and only one of the elements. 
     The following claims are to be understood to include what is specifically illustrated and described above, what is conceptually equivalent, and what can be obviously substituted. Those skilled in the art will appreciate that various adaptations and modifications of the described embodiments can be configured without departing from the scope of the claims. The illustrated embodiments have been set forth only as examples and should not be taken as limiting the invention. It is to be understood that, within the scope of the following claims, the invention may be practiced other than as specifically illustrated and described.