Abstract: The improved system allows an operator overseeing a well stimulation hydraulic fracturing operation to bring frac pumps online and offline as necessary. A control panel allows the operator to remain at a safe distance from high-pressure equipment, including the frac pumps and respective remotely actuated isolation valves, yet allows monitoring and operation of same. The operating condition of the frac pumps and the isolation valves is monitored by an automated processing device, which prevents operation of same during certain pump and valve conditions. A wireless operator interface is also provided.

Abstract: A densimeter contains an inlet pipe section, a second pipe section joined to the downstream end of the inlet pipe section, and an outlet pipe section joined to the downstream end of the second pipe section. The inlet and outlet pipe sections are constrained by a support structure, while flexible couplings allow the second section of pipe to undergo a limited amount of radial motion relative to the adjacent pipe sections. The weight of the second pipe section is supported by a weight measuring unit, which continuously measures the weight of the second pipe section as fluid flows through the densimeter. One preferred embodiment of the invention uses the densimeter to measure the density of a proppant in a blender system for preparing fluid mixtures for fracturing and propping oil bearing geological formations.

Abstract: A wheel of a golf cart includes a connecting member, a rotary main body, and an axle for the rotary main body; the connecting member can be detached from a support part of a main frame of the golf cart for reducing dimension of the cart in packaging and transportation; the connecting member has an engaging element pivoted thereto and biased to an engaging position by means of a torsion spring; the axle can be easily separated from the rotary main body for maintenance and replacement; the axle has an annular engaging recess thereon, and can be inserted in the connecting member to engage the engaging element for connecting the rotary main body to the connecting member; thus, the rotary main body can be easily separated from the main frame of the golf cart together with the axle after the engaging element is pivoted such as to disengage the axle.

Abstract: A foldable golf cart includes two main rods, and a handle connected to the main rods by means of a joining member, which includes left and right parts respectively coupled to the main rods, an intermediate part positioned between the left and the right parts and coupled to the handle, a knob arranged next to the right part, and a pivotal bolt inserted through the above parts and the knob; the left and the right parts have radial teeth opposing radial teeth of the intermediate part; the knob and the right part have protrusions, and slopes between the protrusions on opposing sides such that space can be provided between the parts, and the radial teeth disengage for allowing angular displacement of the left and the right parts relative to the intermediate part when the knob is turned such that the protrusions contact lower ends of the slopes of the right part.