Abstract:
Disclosed is an in-flow pulsation dampening system for high-pressure (e.g., 10K psi and higher) fluid lines. At high fluid flow pressures, the dampening system is a dual stage dampening system, responsive to low (e.g., when first charging the fluid line) and to very high-pressure pulsations. An external containment shell handles the full fluid flow pressures. One or more internal shells contain and handle the internal gas dampening system. The in-flow relationship of the gas dampening component assures that pressure differences between the internal gas handling system and the high-pressure fluid flow is always relatively small. This enables the gas handling components to be constructed of less robust material than the external shell (even though the gas system&#39;s internal pressure can equal that of the fluid flow), and be less susceptible to pressure failure.

Description:
CONTINUITY DATA 
       [0001]    The present application claims the benefit of prior filed U.S. Provisional Patent Applications: Ser. No. 62/447,792 filed 18 Jan. 2017, Ser. No. 62/298,459 filed 23 Feb. 2016, and Ser. No. 62/286,367 filed 23 Jan. 2016; to which prior applications the present application is a regular US national application, and which prior applications are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is in the field of pipes and tubular conduits, including internal structures and end structures of the tubular member, and having fluid pressure compensators, e.g., accumulators or cushioning devices (Class 138). Specifically, the present invention relate to devices with pressure compensators attachable to a pipeline for dampening pulsations in pressure caused by a quick-shutoff of flow or by the non-uniform action of a pump system to maintain a more nearly constant pressure of the fluid (subclass 26). More specifically, the present invention relates to such devices having variable chambers (subclass 30), in which the chamber is of variable capacity by reason of a slideable piston or plunger (subclass 31). 
       BACKGROUND OF THE INVENTION 
       [0003]    An example use case for the present invention is in the field of high-pressure hydraulic fracturing (aka: “fracing”), as used in the oil production industry. Fracing includes the use of high-pressure, positive displacement, pulsing pumps to deliver suspended sand fracing fluids to subsurface areas containing oil deposits. The fracing process cracks the formation where oil resides and places sand in the fractures for improved oil flow and volume to the wellbore. 
         [0004]    Although utilizing the fracing process increases the cost of production for a well using it, the process can substantially increase the efficiency of the well&#39;s production. In times of high oil prices, the increase of production efficiency exceeds the cost of the fracing process. Demand for fracing, along with horizontal drilling spurred a boom in US oil and natural gas production. However, in times of low oil prices, the increase in production efficiency does not offset the cost of the fracing process for the well, and low producing wells are shut-in, rather than initiating a fracing operation. Even the largest hydraulic fracturing operations in the US have been forced to dramatically cut costs in response to reduced demand for services. With oil companies cutting and expecting to continue to cut more than 100 billion dollars in spending globally, fracing expenditures are expected to concomitantly fall as much as 35%. It has been reported that about half of the hydraulic fracturing companies operating in the US would be closed or sold by year-end 2015, because of falling oil prices and reduced oil company expenditure. 
         [0005]    With a continuing poor outlook for a significant increase in oil prices in near and mid-term future, solutions for reducing production expenses, including fracing costs, are expected to be a continued critical focus. One critically high cost common in the fracing industry is related to equipment failures, caused by the high-pressure, pulsating flow into the fracing piping. The high-pressure, pulsating flow results from the massive positive displacement pumps used to pump the fracing fluids into the fracing piping. The pressure pulses slam the couplings, joints and fittings of the piping with thousands of pounds of force three hundred (300) times per minute causing failure of these fittings. Replacement of high-pressure fracing equipment is very expensive. Failed fracing fixtures and pipe also results in costly downtime required to resource and replace failed components before the production process can continue. Pumps, piping, fittings, and valves are all adversely affected by the very high-pressure pulses from the massive positive displacement fracing pump systems. The industry has long been in search of meaningful solutions to the fracing iron failure problem. It would be seriously beneficial to the oil production industry, and hydraulic fracturing services specifically, if a means for reducing fracing costs could finally be provided with a solution. 
         [0006]    However, there are serious barriers to safe and successful implementation pulsation dampening on high-pressure pulsatile flow lines. One major barrier is to the use of “gas-cushioning” in pulsation dampeners. This is because in high-pressure applications (e.g., pressures on the order of 20,000 psig), the very highly compressed gas can present a very real explosion threat and potential injury to nearby persons and equipment. Another barrier that has long prevented the application of “gas-cushioning” in pulsation dampeners is the limitations of gas-seals in the dampener apparatus to withstand and be proof against the high Δ p  (pressure differentials) typical of high-pressure pulsatile flow systems. Also, in “gas-cushioning” type pulsation dampeners with moving interfaces (e.g., a sliding piston) the pressure differentials across barriers (e.g., walls) separating liquid and gaseous spaces can be distorted or caused to balloon under the pressure differences. This is a serious problem for maintaining liquid/gas seal integrity at a dampener&#39;s moving/sliding interfaces. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Reference Numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                  D 
                 Depth of the interior wall 
               
               
                   
                  L 
                 Length of Dampener housing 
               
               
                   
                  10 
                 HP flow pulsation dampener 
               
               
                   
                  12 
                 Dampener housing 
               
               
                   
                  14 
                 Dampener housing end 
               
               
                   
                  14a 
                 Dampener housing 1st end 
               
               
                   
                  14b 
                 Dampener housing 2nd end 
               
               
                   
                  15 
                 Dampener housing axis 
               
               
                   
                  16 
                 High-pressure fluid flow line 
               
               
                   
                  17 
                 Fluid I/O port 
               
               
                   
                  17a 
                 Fluid inlet port 
               
               
                   
                  17b 
                 Fluid outlet port 
               
               
                   
                  20 
                 Housing-to-flow line adapter 
               
               
                   
                  22 
                 Fluid flow thru-path 
               
               
                   
                  24 
                 Non-flow fluid chamber 
               
               
                   
                  26 
                 Liquid communication means 
               
               
                   
                  28 
                 Dampener housing fluid space 
               
               
                   
                  30 
                 Union 
               
               
                   
                  33 
                 Union flange member 
               
               
                   
                  34  
                 Union flange member 
               
               
                   
                 (a&amp;b) 
                   
               
               
                   
                  36 
                 Flange fasteners 
               
               
                   
                  50 
                 Damper canister 
               
               
                   
                  52 
                 Canister housing 
               
               
                   
                  53 
                 Canister housing axis 
               
               
                   
                  54 
                 Canister interior space 
               
               
                   
                  55 
                 Canister flange 
               
               
                   
                  56 
                 Canister opening 
               
               
                   
                  57 
                 Canister rim 
               
               
                   
                  58 
                 Canister interior wall 
               
               
                   
                  59 
                 Canister interior bulkhead 
               
               
                   
                  60 
                 Piston stop ring 
               
               
                   
                  61 
                 Fastener aperture 
               
               
                   
                  62 
                 Stop ring fasteners 
               
               
                   
                  64 
                 Through-flow spacer ring 
               
               
                   
                  66 
                 Radius stand-off 
               
               
                   
                  68 
                 Ring fluid port 
               
               
                   
                  69 
                 Canister piston stop shoulder 
               
               
                   
                  70 
                 Damper piston assembly 
               
               
                   
                  72 
                 Damper piston 
               
               
                   
                  74 
                 Damper piston head 
               
               
                   
                  75a 
                 Piston gas pressure surface 
               
               
                   
                  75b 
                 Piston fluid pressure surface 
               
               
                   
                  76 
                 Damper piston skirt 
               
               
                   
                  79 
                 Piston ring channel 
               
               
                   
                  82 
                 Wiper ring 
               
               
                   
                  90 
                 Gas port fitting 
               
               
                   
                  92 
                 Gas port 
               
               
                   
                  94 
                 Gas valve 
               
               
                   
                  96 
                 Gas port cover 
               
               
                   
                 102 
                 Canister gas port 
               
               
                   
                   
               
             
          
         
       
     
       SUMMARY OF THE INVENTION 
       [0007]    Pulsations from high-pressure, massive positive displacement can only effectively be controlled through the use of gas to provide dampening or “cushioning”. The use of high-pressure gas presents safety and design challenges. Gases under extreme high-pressure are, by their nature, explosive. Control of gases at pressures in excess of three thousand (3,000) psig requires extremely heavy wall containers and massive flanges, when contained using conventional material. This invention manages both the safety and the heavy wall concerns to present a safe and manageable solution to the requirement for pulsation reduction in high-pressure systems. 
         [0008]    Prior art pulsation dampeners typically have a gas bladder design. These prior art dampeners are generally low volume gas due to their limited pressure of 3,000 psig or below. Higher pressures require higher volumes of compressed gas due to the significantly reduced space as the gas is compressed for pulsation control service. Obviously, as the pressure increases with the resultant increase in high-pressure gas volume, safety concerns dominate. This concern eliminates the use of single volume bladders. Until this invention, high-pressure dampeners were not available, as companies would not allow such equipment in vibration service. Additionally, the size and weight of these high volume dampeners has limited their use. 
         [0009]    As stated, the typical single gas volume (bladder) has been the basis for pulsation control for prior art at much lower pressures. This invention embodies a new approach to the large gas volume by segmenting the large gas volume into discrete, single volumes of gas enclosed in cylinders. These cylinders are equipped with pistons and the pistons move vertically to compress the gas above and within the cylinder. The gas-containing, piston-driven cylinders are then placed internally along the pulsation dampener housing. The pulsation dampener housing is designed to withstand full hydraulic pressure of the process. The cylinders are designed, however, for only a minimum of 4,000 psig. 
         [0010]    The pulsation dampener housing is designed with eccentric reducers gradually increasing housing diameter from the flow piping to a large diameter pulsation dampener housing where the gas cylinders reside. The pulsation dampener housing is flanged for easy removal, inspection and replacement of the pressure cylinders from the pulsation dampener housing. The gas cylinders are placed in the pulsation dampener housing in such a manner that the process fluid passes directly below every canister as the flow enters, flows through and then exits the dampener. 
         [0011]    At the initiation of the process, the spaces around the sealed gas canisters become fluid-packed. After the dampener becomes fluid-packed, flow continues below the gas cylinders as designed. At that point, pressure pulses from the massive positive displacement pumps are transferred to all portions of the pulsation dampener housing and all external surfaces of the gas cylinders. Since the gas cylinders are preloaded with gas to 4,000 psig, as the external pressure increases on the gas cylinders, the differential pressure across the gas cylinder housing decreases, further reducing any threats of cylinder damage and gas release. As the pressure equalizes at 4000 psig and then continues to increase, the gas cylinder piston lifts due to the pressure differential across the piston. However, the pressure differential across the cylinder housing is now zero with full containment of the gas within the cylinder. The pulsation dampener housing is exposed only to the hydraulic pressure, while the gas is secondarily contained in stress-free gas cylinders. Further increases in pressure result in increased hydraulic pressure to the pulsation dampener housing only. These further pressure increases in the system and on the gas cylinders only serve to lift the gas cylinder pistons to maintain an internal pressure equal to the external pressure to the cylinders. 
         [0012]    As the high-pressure positive displacement pumps reach the required system pressure, high-pressure, equipment-damaging pulses initiate. As each pressure pulse from the reciprocating pistons of the positive displacement pumps enter the pulsation dampener, the increase in dampener housing pressure form the pulse causes the gas cylinder pistons to react and rise, dampening the pulse and reducing it to manageable magnitudes in the dampener. The magnitude of the pulse is dampened and the fluid flow through the dampener continues under the pistons as designed. The pulses are effectively dampened by the action of the piston movement to absorb the pulse in the gas volumes of the gas cylinders. During operation, the maximum pressure across the gas cylinders is around 250 psig, while the cylinders remove up to 3,000 psig pressure magnitude of the pulses during operation. The very low pressure of 250 psig offers little threat to the structural integrity of the cylinders designed to withstand 4,000 psig. During the high-pressure pumping process, the dampener housing is only exposed to a much safer lower hydraulic pressure. 
         [0013]    After the high-pressure process completes, the hydraulic pressure is relieved from the dampener housing. At that point, the gas cylinder pistons return to their original position at the start of the high-pressure process. Before, during and after, the gas cylinders are housed in a two (2) inch thick housing further adding protection from exposure to high-pressure gas release. 
         [0014]    Suspended solids are difficult to manage due to plugging and fouling. This invention handles suspended solids by incorporating a design that promotes high velocity under the gas cylinders such that suspended solids simply pass through the dampener with little effect on the dampener operation. Special wiper seals protect the piston seals during operation. The small amounts of solids infiltrating the dampener housing during the process initiation and the filling of the dampener with fluid simply settle to the lower flow stream. Since the upper portion sees little or no flow, solids are not carried to the upper section of the dampener. The flow-through design provides excellent solids management during the dampening process. 
         [0015]    The design includes high yield strength, hardened stainless steel using patented welding processes to reduce the required wall thickness for the pulsation dampener housing. Coupled with the flow-through design, the hardened stainless steel provides both excellent erosion (suspended solids) and corrosion resistance for improved and extended equipment life for the dampener and gas cylinders. 
         [0016]    The gas cylinders are filled through a single aperture in the piston, which also houses a one-way check valve allowing the gas to flow into the gas cylinder but restricting flow from the gas cylinder. The check valve is not a perfect seal, such that a gas inlet seal system is employed to assure no decrease in pressure prior to deployment. The check valve leakage also provides a method for depressurizing the cylinder. Depressurizing the gas cylinder is accomplished by removing the gas inlet seal, and allowing the to leak down through the check valve. 
         [0017]    This invention is designed to safely utilize high-pressure gas to provide a “cushion” to the very high-pressure pulsation generated by high-pressure, pulse-generating pressure source such as positive displacement pumps. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1A  is a side elevation schematic view of a preferred embodiment of the present high-pressure flow pulsation dampener. 
           [0019]      FIG. 1B  is a schematic perspective view of a series of high-pressure flow pulsation dampeners of the present invention. 
           [0020]      FIG. 2A  is a side elevation cross-sectional schematic view of the high-pressure flow pulsation dampener of  FIG. 1A . 
           [0021]      FIG. 2B  is a bottom plan partial cut-away view of the high-pressure flow pulsation dampener of  FIG. 1A . 
           [0022]      FIG. 2C  is an end-on cross-sectional schematic view of the high-pressure flow pulsation dampener of  FIG. 1A . 
           [0023]      FIGS. 3A and 3B  are: (A) a side elevation schematic view and (B) a bottom plan view of a damper canister of the present high-pressure flow pulsation dampener. 
           [0024]      FIG. 4  is an exploded perspective view of components of a damper canister of the present high-pressure flow pulsation dampener. 
           [0025]      FIG. 5  is a side elevation cross-sectional schematic view of the piston assembly of the present high-pressure flow pulsation dampener. 
           [0026]      FIGS. 6A &amp; 6B  are: (A) a partial phantom perspective view of a damper canister, and (B) a cross-sectional view of a damper canister showing an alternative disposition of the gas port fitting. 
           [0027]      FIG. 7A  &amp;  FIG. 7B  are: (A) a side elevation view, and a perspective view of an alternative embodiment of the present high-pressure flow pulsation dampener apparatus. 
           [0028]      FIG. 8  is an exploded perspective view of the HP flow pulsation dampener apparatus of  FIG. 7  showing a tandem damper canister in exploded view. 
           [0029]      FIGS. 9A-9D  are views of the canister housing of the tandem damper canister for practice in the present apparatus. 
           [0030]      FIGS. 10A-10D  are various views of a damper piston for use in the present apparatus. 
           [0031]      FIGS. 11A-11D  are various view of a stop ring for practice in the present apparatus. 
           [0032]      FIGS. 12A-12D  are various view of a through-flow spacer ring for practice in the present apparatus. 
           [0033]      FIGS. 13A-13D  are various view of a canister housing for practice with tandem damper canisters in the present apparatus. 
           [0034]      FIGS. 14A-14D  are various view of an inlet port type union flange for practice in the present apparatus. 
           [0035]      FIG. 15  is a cross-sectional view through a side elevation of a tandem damper canister HP flow pulsation dampener apparatus of  FIG. 7 . 
           [0036]      FIGS. 16A &amp; 16B  are partial cross-sectional (A) end view and (B) side elevation view of single canister dampener housings disposed in a series in a HP fluid flow line to accomplish the present HP flow pulsation dampener apparatus. 
       
    
    
     DESCRIPTION OF THE INVENTION 
       [0037]    Referring now to the drawings, the details of preferred embodiments of the present invention are graphically and schematically illustrated. Like elements in the drawings are represented by like numbers, and any similar elements are represented by like numbers with a different lower case letter suffix. 
         [0038]    The present pulsation dampener apparatus  10  is disclosed for use in a Hydraulic Fracturing (“frac” or “fracing”) process. In use in a fracing process, the pulsation dampener apparatus  10  is installed inline with the flow of the fracing fluid, and acts to dampen pressure pulses in the high-pressure fluid flow in the fracing fluid line  16 . However, it is to be noted that although the embodiments set forth herein use the fracing process as an example of a pumping system utilizing high-pressure, pulsatile fluid flow, the present apparatus can be practiced with substantially any such high-pressure, pulsatile fluid flow system to dampen high-pressure pulsations . . . especially in such system utilizing fluid suspensions and having abrasive properties. It is important to note that the exemplified fracing fluids process operates at flow rates and line pressures using highly abrasive liquid suspensions that can be corrosive as well. Line pressures on the order of 12,000 psi and flow rates of over 30 mph are not unusual, all of which is intended in the present invention. In major part, the pulsation dampener apparatus  10  includes: a dampener housing  12 ; housing-to-flow line adapters  20 ; a series of damper canisters  50  internally disposed inside the dampener housing  12 ; and union interfaces  30  for joining a dampener housing end  14  to a housing-to-flow line adapter  20  or to the dampener housing end  14  of another dampener housing  12 . 
         [0039]    In the embodiments illustrated in  FIG. 1A  and  FIG. 2 , the dampener housing  12  of the pulsation dampener apparatus  10  is an elongated pipe having two ends  14 , with first-end  14   a  shown as being directly connected (by welding) to a housing-to-flow line adapter  20 , and a second-end  14   b  shown as being directly connected (by welding) to a union interface  30 . In the preferred embodiment illustrated, the high-pressure components, such as the dampener housing  12 , are anticipated as being made of martensitic steel (e.g., SS-420). However, high-pressure metal/steel component fabrications currently available in the field may also be used for practicing the present invention 
         [0040]      FIGS. 2A-2C  show internal structure of a dampener housing  12 , which includes a fluid flow thru-path  22  and a non-flow fluid chamber(s)  24 , both of which are disposed along the length L of the dampener housing  12 . Inside the pulsation dampener apparatus  10 , and specifically inside the dampener housing  12 , the fluid flow thru-path  22  and the non-flow fluid chamber(s)  24  are in liquid communication with each other. The liquid communication means  26  is adapted and disposed so that the flow rate of the fracing fluid in the fracing fluid line  16  is not substantially impacted. This is accomplished by having as close to the minimal actual fluid transfer as possible between the fluid flow thru-path  22  and the non-flow fluid chamber(s)  24 . The minimal actual fluid transfer is that amount necessary to enable any gas trapped in the dampener housing  12  to be dissolved and eventually carried away. This setup also is adapted to allow the fluid pressure of the fluid flow thru-path  22  to be fully communicated the fluid in the non-flow fluid chamber(s)  24 . This is an important feature of the present invention, as it directly impacts a safety benefit of the present invention, as will be explained below. The liquid communication means  26  in the embodiments illustrated is simply a plurality of through-holes in the structure or wall separating portions of the fluid flow thru-path  22  and the non-flow fluid chamber(s)  24 . 
         [0041]    A housing-to-flow line adapter  20  is used to adaptively connect one or both ends  14  of the dampener housing  12  to a high-pressure fluid flow line  16  at the inlet port (pump side)  17   a  of the high-pressure fluid flow line  16  or the outlet port (down-hole side)  17   b.  As with the dampener housing  12 , the housing-to-flow line adapter  20  is also designed to so that the flow rate of the fluid in the high-pressure fluid line  16  is not substantially impacted. 
         [0042]    The series of damper canisters  50  internally disposed inside the dampener housing  12  are the heart of the present high-pressure pulsation dampener apparatus  10 . The series of damper canisters  50  is internally disposed in the non-flow fluid chamber  24  of the dampener housing  12 . Each damper canister  50  has its upper portion immersed in the fluid (and fluid pressure) of the non-flow fluid chamber  24 . However, the bottom of each canister  50  is disposed so that it is exposed to the pressure and fluid flow of the thru-path  22 . 
         [0043]    Because the canister bottoms are in pressure communication with the fluid flow thru-path  22 , each damper canister  50  is disposed to dampen a portion of a pressure change of the fluid in the fluid flow thru-path  22 . Additionally, because the canisters are initially gas pressurized from about 2,500 to 5,000 psi, the series of canisters  50  in the housing  12  distribute the risk of a catastrophic failure of the pressure dampening system over the total number of pressure vessels (damper canister). This greatly reduces or eliminates the risk of a catastrophic failure event from the failure of a single pressure vessel. 
         [0044]    Union interfaces  30  are designed and used to accomplish unions in the present invention in a number of situations. For example, union interfaces  30  can be used to join an end  14  of a dampener housing  12  to a housing-to-flow line adapter  20  (see  FIGS. 1A  and  FIG. 2 ), or to an end  14  of another dampener housing  12  (see  FIG. 1B ). A union interface  30  has a flange member  33  connectable to another flange member  33  (e.g., on the housing-to-flow line adapter  20 ), using flange fasteners  36 . 
         [0045]    The damper canisters  50  are intended for use in the present pulsation dampener apparatus  10  as a plurality of damper canisters  50  in series. See  FIG. 2 . It is the series of damper canisters  50  that cumulatively accomplish the dampening of the fluid pressure pulses in a high-pressure fluid flow line  16 . That is to say that the amplitude of fluid pressure pulses at the fluid outlet port  17   b  is lower than at the fluid inlet port  17   a.  In the embodiments illustrated, the damper canisters  50  in the depicted series are all substantially identical in structure, operational specifications and function. However, they do not have to be, and there are situations in which the series may not consist of a homogeneous set of damper canisters  50 . For example, an initial gas charge in some canisters may be lower than for other canisters in the series set, to accomplish a more gradual onset of damping action upon startup and initial fluid charging of the damper apparatus  10 . An assembled damper canister  50  is disposed to withstand an operating environment having varying gas and fluid pressures up to 12,500 psi. The major components of the damper canisters  50  are all similar Each damper canister  50  ( FIGS. 3A &amp; 3B ) has a canister housing  52 , a damper piston assembly  70 , a piston stop ring  60 , and a gas port fitting  90 , as illustrated in  FIGS. 4 &amp; 5  and  FIGS. 6A &amp; 6B . 
         [0046]    The canister housing  52  is in the form of a high-pressure gas cylinder, open at one end. The canister housing  52  has a housing interior space  54  and a cross-sectional housing opening  56  at the one open end. The interior wall  58  of the canister housing  52  is adapted to closely receive a piston assembly  70 . The piston assembly is slideable along the interior wall  56  from the rim  57  at the housing opening  56  to a depth D of the interior wall  56 . Though closely received in the cross-section of the housing opening  56  of the canister housing  52 , the damper piston assembly  70  is freely slideable along the depth D of the interior wall  56  in response to a difference in pressure across the piston assembly  70 . 
         [0047]    A stop ring  60  is fixable to the housing rim  57  at the housing opening  56  of the canister housing  52 . The stop ring  60  is fixed to the housing rim  57  with stop ring fastening means  62 ; which are threaded fasteners in the illustrated embodiment. The piston stop ring  60  is adapted to retain the damper piston assembly  70  slideably within the canister housing  52 . The further adaptation of the piston stop ring  60  is not obvious and is important because of the high-pressure and fluid suspension environment in which it operates. To use fracing fluid as a fluid suspension example, fracing fluid is not only abrasive (because it contains sand suspended in the fluid), the solids that form the suspension can and do settle-out on horizontal surfaces, accumulate like plaques, and can hinder/restrict travel of the piston. Therefore, the structural cross-section of the top ring  60  and the features of its interface with the housing rim  57  and piston skirt  76  are adapted to avoid accumulating sand/suspension plaques. The canister housing  52 , damper piston assembly  70  and stop ring  60  in combination are adapted to contain a gas in the housing interior space  54  at continuously varying pressures of up to 12,500 psi, to accomplish the present damper canister  50 . 
         [0048]    The piston assembly  70  comprises a damper piston  72  having a damper piston head  74  portion and a damper piston skirt  76  portion. The piston head  74  portion has a gas pressure surface  75   a  and a fluid pressure surface  75   b.  The piston skirt  76  portion has at least one piston ring channel  79 , within each of which a piston ring  82  is received. A first piston ring  82  is a gas/fluid sealing ring. A sealing type piston ring  82  is biased by the ring channel  79  to form a slideable gas/fluid pressure seal between the piston skirt  76  and the interior wall  56  of the canister housing  52 . Other rings may also be provided for sealing and/or particle wiping. The for example, in another embodiment (not shown) the piston skirt  76  has two ring channels  79  for mounting a gas/fluid sealing ring, and also a wiper ring between the gas/fluid sealing ring and the frac fluid. The wiper ring is adapted to prevent sand or suspension material from impacting the gas/fluid sealing ring. The piston assembly  70  is slideable within the canister housing  52  in response to a sufficient pressure difference between the gas pressure within the housing interior space  54  of the damper canister  50  and the fluid pressure of the fluid flow thru-path  22  outside of the damper canister  50 . 
         [0049]    Additionally, the damper piston head  74  portion of the damper piston  72  has a gas port fitting  90 . The gas port fitting  90  is adapted to provide a sealable through-port between the gas pressure surface  75   a  and the fluid pressure surface  75   b  of the piston head  74 . The gas port fitting enables the housing interior space  54  to receive and contain a gas charge to bias the housing interior space  54  at an initial gas pressure. The gas port fitting  90  component of the damper piston  72  has a gas through-port  92  between the gas pressure surface  75   a  and the fluid pressure surface  75   b  of the piston head  74 . A normally closed gas check valve  94  provides a means to charge the housing interior space  54  with a gas, such as nitrogen, and prevents the gas from escaping. A gas port cover  96  protects the gas valve  94  from the fluid at the fluid pressure surface  75   b  of the piston head  74 , and further seals the gas port fitting to prevent gas from leaking out of the canister housing  52 . Although illustrated as a component of the damper piston  72  in  FIGS. 4 &amp; 5 , the gas port fitting  90  may be disposed elsewhere on a damper canister  50  as selectable by on of skill in the art, see  FIGS. 6A &amp; 6B . 
         [0050]    In an alternative embodiment for dampening pressure pulsations in a high-pressure fluid flow line/conduit, the pulsation dampener apparatus  10   a  of the present invention can be configured as illustrated in  FIGS. 7A &amp; 7B . In this embodiment, the dampener housing  12   a  is also a substantially cylindrical tube having a dampener interior fluid space  28  along an axis  15  of length L of the dampener housing  12   a.  The dampener housing  12   a  has a first end  14   a  open and a second end  14   c  closed. The first end  14   a  is shown in fluid communication with the high-pressure fluid flow line  16  via flange members  33  &amp;  34   a  of a pipe union  30 . See  FIGS. 14A-14D  for an example of a flow-through union flange member  34   a.  The second end  14   c  is closed with a flange member  33  and a flange plate  34   b.  However, if desired the second end  14   c  of the pulsation dampener apparatus  10   a  may be connected to the fluid flow line  16  or in series to another pulsation dampener apparatus  10   a  by replacing the flange plate  34   b  with an appropriate flange member (e.g.,  34   a ). Also see  FIG. 8  and  FIGS. 13A-13C . 
         [0051]    As exemplified in  FIGS. 9A-9D , a dampener housing  12   a  contains at least one “tandem” damper gas canister  50   a.  The “tandem” feature of the damper gas canister  50   a  derives from the gas canister  50   a  housing two separate damper piston assemblies  70   a.  The gas canister  50   a  has a canister axis  53 , and one or more tandem damper gas canisters  50   a  are received within the dampener housing  12   a  with its canister axis  53  parallel to the housing axis  15 . The damper gas canisters  50   a  are in pressure communication with the interior fluid space  28  of the dampener housing  12   a.  The canister housing  52   a  of a tandem damper gas canister  50   a  is in the form of a high-pressure gas cylinder having a housing interior space  54  and a cross-sectional housing opening  56  at each end, and an interior wall  58 . The interior wall  58  is adapted to slideably receive a damper piston assembly  70   a  along a depth D of the interior wall  58 . 
         [0052]    A damper piston assembly  70   a  is closely received within the cross-sectional opening  56  of each end of the canister housing  52   a.  In the embodiments illustrated, the damper piston assemblies  70   a  are freely slideable along the depth D of the interior wall  58  of the canister housing  52   a.  As exemplified in  FIGS. 10A-10D , the damper piston  72  of the piston assembly  70   a  has a piston head  74  portion and a piston skirt  76  portion. The piston head  74  portion of the damper piston  72  has a gas pressure surface  75   a  and a fluid pressure surface  75   b.  The piston skirt  76  portion has at least one piston ring channel  79 . Piston ring channels each will contain a wiper ring  82 . Wiper rings  82  are biased by the ring channel  79  to form a slideable gas/fluid pressure seal between the piston skirt  76  and the interior wall  58  of the canister housing  52   a.  The piston assembly  70   a  is slideable in one direction or another within the canister housing  52   a  in response to a sufficient pressure difference between the gas pressure within the canister interior space  54  and the fluid pressure of the fluid contained within the dampener housing interior fluid space  28  of said pulsation dampener apparatus  10   a.  That is, when there is a Δ Press  across the gas pressure surface  75   a  and the fluid pressure surface  75   b  of the piston head  74 . The structure of the piston head  74  provides a pressure differential energized seal system substantially similar to that described for the piston head  74  of  FIG. 5 . Wherein, the deformation of the piston head  74  from the pressure differential across the piston head surfaces  75   a  &amp;  75   b  causes the dome of the piston head  74  to flatten, thus further biasing the seal portion of the piston assembly radially and toward the canister wall  58 , effecting an improved seal. 
         [0053]    As illustrated in the figures, this embodiment of the damper piston head  74  portion of the damper piston  72  has a gas port fitting  90 . Although illustrated as a component of the damper piston  72  in  FIGS. 4 &amp; 5 , the gas port fitting  90  may be disposed elsewhere on a damper canister  50  as selectable by on of skill in the art, see  FIGS. 6A &amp; 6B . The gas port fitting  90  is adapted to provide a sealable through-port between the gas pressure surface  75   a  and the fluid pressure surface  75   b  of the piston head  74 . The gas port fitting  90  is provided to enable the canister interior space  54  to receive and contain a gas charge to bias the canister interior space  54  at an initial gas pressure, e.g., at 4,000 psi. In the embodiment exemplified in  FIGS. 10A-10D , the gas port fitting  90  is substantially the same as that depicted in  FIG. 5 . 
         [0054]    As shown in  FIGS. 11A-11D , a stop ring  60  is fixable to the housing rim  57  at each housing opening  56 , using such means as exemplified in  FIG. 4 , or by other means as selected by the skilled artisan and adapted to retain the damper piston assembly  70   a  slideably within the canister housing  50 . The canister housing  52   a,  damper piston assembly  70   a  and stop ring  60  in combination are adapted to contain a gas in the housing interior space  54  at continuously varying pressures up to 12,000 psi to provide the present damper canister  50   a.    
         [0055]    As illustrated in  FIG. 15 , the present pressure pulsation dampener apparatus  10   a  is adapted to receive a plurality of tandem damper gas canisters  50   a  in series within the dampener housing  12   a.  In this embodiment, all of the tandem canister axes  53  are parallel (and coaxial) to the dampener housing axis  15 . A through-flow spacer ring  64  (see  FIGS. 12A-12D ) is disposed between adjacent tandem damper gas canisters  50   a . The through-flow spacer rings  64  enable fluid (from the high-pressure fluid flow line  16 ) to be communicated throughout the housing fluid space  28  of the dampener housing  12   a,  and thence to the piston fluid pressure surfaces  75   b  of the piston heads  74  between adjacent tandem damper gas canisters  50   a.    
         [0056]    In another alternative embodiment exemplified in  FIGS. 16A &amp; 16B , the present pressure pulsation dampener apparatus  10   a  may be configured as a single canister dampener housings  50   c  disposed in a series in a high-pressure fluid flow line  16  to accomplish the present invention. 
         [0057]    Attached as an Appendix is an engineering &amp; design report exemplifying materials and design considerations for various embodiments of the present invention. The report is included herein by reference. 
         [0058]    While the above description contains many specifics, these should not be construed as limitations on the scope of the invention, but rather as exemplifications of one or another preferred embodiment thereof Many other variations are possible, which would be obvious to one skilled in the art. Accordingly, the scope of the invention should be determined by the scope of the appended claims and their equivalents, and not just by the embodiments.