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Pump Suction Header Flow Improvement Device

IP.com Disclosure Number: IPCOM000250465D
Publication Date: 2017-Jul-21

Publishing Venue

The IP.com Prior Art Database

Abstract

A device to improve the flow characteristics of oil well fracturing pump suction headers at low flow rates to reduce pump sand- outs. Reducing sand-outs reduces downtime on jobs. In addition possible equipment damage is eliminated. The device is designed to be easily removed for higher flow rate pumping applications.

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Pump Suction Header Flow Improvement Device

Abstract A device to improve the flow characteristics of oil well fracturing pump suction headers at low flow rates to reduce pump sand- outs. Reducing sand-outs reduces downtime on jobs. In addition possible equipment damage is eliminated. The device is designed to be easily removed for higher flow rate pumping applications. Description A multi-cylinder positive displacement pump typically used in oil well fracturing service produces flow by using plungers to push fluid through the fluid end block. The individual cylinder flows are additive. Since the plunger motion is sinusoidal, the resulting total flow stream is sinusoidal (Figure 1). The flow pattern inside the suction header is complex due to the start/stop action at the suction inlet valves. This causes dead spots (i.e. zero velocity) in the header, and coupled with low-flow conditions, can allow proppant to settle out to the bottom of the header under the far cylinders. Pumps used in stimulation services provide a wide range of flow rates and pressures. The inlet (suction) piping is sized to handle the highest flow rates achievable in order to reduce the occurrence of cavitation, erosion, etc. When pumps are operated at the low end of their speed range, the flow velocity in the suction header can drop down to a point that allows proppant to settle-out from the pumping slurry. The minimum settling velocity for 20/40 sand in plain water is about 15 ft/sec. In gelled fluids the settling velocity is about 5 ft/sec. As the layer of proppant builds up, two conditions can occur;

1) A “slug” of proppant can be picked up during a rate change. If the slug is large enough, the pump plunger can make contact with a nearly-solid wall of proppant, causing a sand-out. If there is insufficient clearance in the plunger head space, physical damage can occur to the pump power end or even push a fluid end off of the pump. 2) Reduced flow causes proppant to stack up around the suction valve, and flow to the cylinder can be choked off, starving the pump for fluid. This will cause the pump to start missing, or running roughly.

Figure 1. Quintuplex flow pattern (Firing order: 1-5-2-3-4)

For example a typical oil well fracturing pump can produce a maximum flow rate of 20 bpm, but in operation they normally run 8 bpm. Many field locations report these pumps sand-out, and they routinely rake out the suction header to reduce the occurrences of sand-outs (Figures 2 and 3).

Figure 2. Plugged suction header

Figure 3. Raking out a suction header Large (2000 HP) pumps are especially susceptible to proppant settling in their headers because the horizontal run is extended in order to place the suction hose connections at the rear bumper for convenient hook up (Figure 4). The length of the run allows fluid to slow down below the proppant settling velocity before it reaches the outlets to the fluid end suction valves.

Figure 4. Typical large fracturing pump/suction header unit i...