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Large Vertical Motor Load Testing Minimizes Downtime And Expense For The Oil Field

Load Testing is critical to ensure reliability of motors in the field and in mission-critical situations.

This article originally appeared in the March 2014 print edition of IMPO. 
Bradleys, Inc. has recently expanded its world class Hi-Power Electric Motor Load Testing System to include Large Vertical Motor Load Testing. Bradleys is located just sixty miles from the Eagle Ford Shale play in Gregory, TX, and is an internationally recognized leader in the electric motor repair and load testing industry. 
Why Load Test
Load Testing is critical to ensure reliability of motors in the field and in mission-critical situations. Load testing a motor has the following benefits:
  1. A critical motor recently repaired can be tested to validate the success of a major repair without the expense of installation and start-up delays. If a motor has performance issues it may be easier to load test the motor on a different installation to determine if the problem is motor related or site related. 
  2. If a critical motor is destined for a warehouse for many years and high reliability is important, testing has value.
  3. In today’s world, many used motors are repurposed for different applications. Some of this repurposing requires HP and speed changes. Load testing the motor can validate the redesign. 
  4. Some organizations have had serious and expensive startup issues with problematic systems. Load testing a motor and drive system can help minimize the startup problems. Systems can be overloaded to verify trip circuits. VFD systems can have power studies performed to verify compliance with strict power quality requirements, and 24 to 48 hour burn-in test can be performed to help eliminated infant mortality failures.  
How Vertical Load Testing Works
To serve the increasing Vertical Motor Load Testing needs of customers, Bradleys built two different load test stands. “For a motor weighing up to 50,000 pounds, Hi-Power Stand 1 accommodates 0-1200 rpm up to 2500 horsepower, and 21,000 ft/lbs of torque; Stand 2 is designed for motors weighing up to 15,000 lbs, and accommodates 0-3600 rpm up to 2000 HP, and 5,000 ft/lbs of torque,” says Jim Williams, President. These stands are designed with vibration monitoring in mind. All of the typical performance parameters are monitored and recorded during the load test. All power (KW, KVA, Volts, Amps, Power factor, Efficiency, etc.); temperatures (six stator, two bearing, two ambient, cooling water, etc); speed; torque; vibration; and other required data points are recorded real time. Data collection of 100 samples per second recording of speed, current, voltage, and torque helps create high resolution speed versus current and torque curves. 
“The required minimum thrust bearing load poses challenges for vertical motors for only a few hours of the load testing process. Many times the internal clearance of a motor can be adjusted to solve the problem. In other cases, the preload load springs are removed and the internal motor end float is reduced to zero or a light preload is created to facilitate the four hour load test,” says Williams.
Engineered external thrust load can also be added to the system during the load test. Opposing thrust bearings are loaded hydraulically to simulate the external thrust loads. In-house engineering, fabrication, SolidWorks software draftsmen, and CNC machine shop capabilities enhance Bradleys’ ability to design and manufacture a myriad of special features for load testing.
“The flexibility of our Hi-Power Load Testing System enables Bradleys’ to meet its’ customers unique motor and system testing requirements,” said Williams. Variable voltage supplies of 480V@2500 amps up to 13.2KV@250 amps are available for a variety of test setups. Water cooled motors are supported with a 150 GPM supply providing up to 200 KW of heat dissipation. Additionally, Bradleys can provide full voltage locked rotor testing up to 1500 HP. IEEE 112 Procedures are followed, and synchronous motor testing is performed using the IEEE 115 Procedure.
Bradleys encourages all customers to be present and witness their load test. The company’s customer observation room allows a customer to witness the load test from a safe and quiet distance, where all real time data is displayed live on dedicated monitors. A web address can be provided for live data and video camera feeds over the internet if your schedule does not allow you to witness the Load Test on-site.    
If your application requires testing with a VFD, this service is also available.    Additional services are also available such as Dual frequency testing of vertical motors up to 7000 HP. ANSI sound testing can be performed.
 The demand for Bradleys’ Hi-Power Load Testing has already spread like wildfire in the Eagle Ford Shale. “We are dedicated to ensuring our customers have the services available to increase their motors’ reliability. We recognize lost productivity in operations is lost revenue. The Bradleys’ team is dedicated to adding new capabilities such as Vertical Motor Load Testing, to prevent and minimize downtime for our customers,” says Williams.
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