Personal Safety and Human Factors Risk Assessment during Maintenance of Fracturing Pumps at Well Service Operations

Abstract

Abstract High pressure pumps used in oil well stimulation are usually powered by diesel engines using multispeed transmissions. Many high pressure well service pumps are reciprocating single-acting positive displacement pumps, mounted on a specially designed trailer chassis frame at a certain height to perform well servicing operations. These pumps require frequent maintenance at fluid ends (discharge area). These maintenance operations require the technician to place his or her hands inside the fluid end to replace valves and related components. This is potentially problematic when the pumping equipment is remotely controlled and the person starting the engine might not have a clear view of the pump. During maintenance of the fluid end, it is necessary to rotate the input shaft of the pump to retract the plungers out of the way to access the valves. The equipment technician often must stand at an elevated height to perform these maintenance tasks, and must manage and hold various tools and equipment to perform this job. This can involve significant risk in terms of human factors, operational safety, and control of falling objects. This paper addresses how a retrofitted safety work platform was incorporated into fracturing pump trailers to more safely perform effective maintenance. The real field operation conditions, field engineer's input, and district requirements, such as railings, ladder position, and gratings are considered. In addition, different variables, such as road travel positioning, duration of work, frequency, task difficulty, work envelope, and ground level access requirements were evaluated during design and installation of the work platform on the unit at the field operation. An ergonomically designed work platform adds benefit by providing worker stability, minimizing postural fatigue, and anthropometry, thereby reducing risk of personal injury incidents while performing maintenance of equipment at an elevated height. This outlined approach to increased safety will be useful to engineers, operators, and safety professionals to help reduce risk and improve worker performance. Introduction Hydraulic fracturing is a well stimulation technique that was first tested in the oil and gas industry in 1947, and the process was accepted commercially by 1950 (King 2012). To perform hydraulic fracturing operations, a fluid must be pumped into the well's production casing (or a treating string) at a high pressure. It is necessary that production casing has been installed and cemented, and that it is capable of withstanding the pressure for which it will be subjected during hydraulic fracturing operations. The hydraulic fracturing process requires an array of specialized equipment and materials. These materials and equipment are necessary to perform typical hydraulic fracturing operations in vertical and horizontal wells. The equipment required to perform a hydraulic fracturing treatment includes fluid storage tanks, proppant transport equipment, blending equipment, pumping equipment, and all ancillary equipment, such as hoses, piping, valves, and manifolds. Before beginning the hydraulic fracture treatment, all equipment should be tested to help ensure it is in good operating condition. All high-pressure lines leading from the pump trucks to the wellhead should be pressure tested to the maximum treating pressure. Any leaks must be eliminated before initiation of the hydraulic fracture treatment (American Petroleum Institute 2009). Hydraulic pumping trailers located or installed at rig sites are primarily diesel powered high pressure pumping units designed for oil well stimulation. Typically, a pumping trailer unit consists of diesel engines, transmissions, and triplex or quintuplex pumps equipped with advanced digital controls for transmissions and engines. The fracturing trailer unit needs frequent maintenance of various systems such as fluid end lubrications, recirculating air/oil systems and grease systems. Fig. 1 shows a typical example of a modern diesel powered fracturing pump trailer.