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Water Jet Peened Fluid End for Reciprocating High Pressure Well Service Pump

IP.com Disclosure Number: IPCOM000242287D
Publication Date: 2015-Jul-01
Document File: 7 page(s) / 207K

Publishing Venue

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Abstract

Purpose of this publication is to discuss an alternative method to increase the cyclic fatigue life of well service fluid ends. Well servicing fluid ends are parts of reciprocating high pressure fracturing pumps. Well servicing pumps are used in generate high pressures for hydraulic fracturing. Cyclic fatigue is a serious cause of concern for reciprocating high pressure fracturing pumps in well service. In cyclic fatigue, a crack initiates and growth in presence of tensile stresses. The tensile stresses can be due to the manufacturing process or cyclic high pressure loading. A method/process that can reduce magnitude of tensile stress at critical locations can mitigate crack propagation and delay fatigue failure. This publication proposes to use high pressure water jet peening (WJP) to remove tensile stress due to machining and impart compressive stress layer on the interior surfaces of the well servicing fluid end. These compressive stresses will reduce the intensity of tensile stresses from cyclic loading and improve fatigue life of the fluid end.

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FILE NUMBER:  ENG4-57676

Title:    Water Jet Peened Fluid End for Reciprocating High Pressure Well Service Pump

Abstract:         Purpose of this publication is to discuss an alternative method to increase the cyclic fatigue life of well service fluid ends. Well servicing fluid ends are parts of reciprocating high pressure fracturing pumps. Well servicing pumps are used in generate high pressures for hydraulic fracturing. Cyclic fatigue is a serious cause of concern for reciprocating high pressure fracturing pumps in well service. In cyclic fatigue, a crack initiates and growth in presence of tensile stresses. The tensile stresses can be due to the manufacturing process or cyclic high pressure loading. A method/process that can reduce magnitude of tensile stress at critical locations can mitigate crack propagation and delay fatigue failure. This publication proposes to use high pressure water jet peening (WJP) to remove tensile stress due to machining and impart compressive stress layer on the interior surfaces of the well servicing fluid end. These compressive stresses will reduce the intensity of tensile stresses from cyclic loading and improve fatigue life of the fluid end.

Description:    

Well service industry uses reciprocating positive displacement pumps. These pumps are used to pump high pressure abrasive fluids during well service. Pump parts that are subjected to high pressure and abrasive fluids experience high wear and tear. These fluids can have high concentration of abrasive

solids (sand). The entire truck/pump unit is a complex system and is not explained in this publication as it is out of the scope. The main focus of this publication is fluid end of the pump. A not to scale schematic of a fluid end is shown in the figure below.

Figure 1: Fluid end cross section (not to scale)

The fluid in the figure has two intersecting bores: vertical bore and horizontal bore. The bottom end of the vertical bore is suction side and top end of the vertical bore is discharge side. Both suction and discharge sides have pressure operated valves. These valves open and close based on the pressure difference on the two sides of the valve. The left and right side of the horizontal bore are plunger side and suction cap side respectively. The area between the valves, suction cap and plunger is called cross bore (or pressure chamber) and is subjected to cyclic high pressure and abrasive fluids. The plunger is connected to the power end and creates pressure in the cross bore.

The pressure in the cross bore is lower than suction pressure as the plunger is moving backward (out of cross bore). This pressure difference opens the suction valve and cross bore is filled with fluid. The plunger starts to move back forward after reaching bottom dead center. The pressure in the cross bore starts to increase. The suction valve closes when pressure in the cross bore is higher than suction pressure. Since the fluid in the cross is not compressible, th...