Cleaning Natural Gas with a 'Hole' Lot of Pressure
When we turn on a light, turn up the heat, or fill our car's gas tank, how often do we think about how the energy got there? One everyday source of energy is natural gas, used in everything from cooking, heating, cooling, to ?energy generation, transportation and more. But the natural gas that is extracted out of underground wells is quite different than what we use in our homes and businesses.
Gas as it comes out of the ground is dirty. It contains a variety of undesirable liquids and solids that must be removed before it is pumped to processing and distribution stations. Unclean gas can quickly ruin millions of dollars in equipment. The old method for cleaning gas used large paper filters in special pressure vessels. These filters had to be changed regularly, sometimes as often as every 8 hours, depending on how dirty the gas was. This can be a very time-consuming and environmentally costly process. (Right, completed pressure vessel system.)
One company located outside of Houston TX has changed the way natural gas gets cleaned. Mueller Environmental Designs manufactures a patented helical separator system that eliminates virtually all of the solids, water, oil, black powder, and a variety of contaminants from the natural gas. Their separator delivers clean natural gas for processing and distribution. But Mueller had a problem with the separator's construction that was only solved when they turned to Hougen Manufacturing.
A Complex Construction Problem
The pressure vessels Mueller Environmental manufactures measure anywhere from 4 to 8 ft in diameter and are made from ? in. to 3-1/2 in. thick 5617 rolled steel plate. Diameter and material thickness depends upon the pressure the vessel must withstand; sometimes pressures can reach as high as 3,000 psi. Inside the vessels is a proprietary gas-cleaning separator and an area to hold the accumulated solids and liquids that are removed. This material is drained automatically as the holding area fills up.
To measure the amount of waste material inside the tank, two liquid level indicators must be installed. A low level indicator is placed roughly 1 to 2 in. off the bottom of the tank and a high level indicator is ?located in the middle of the tank.
Holes must be drilled into the vessels for the level indicators. Drilling a hole in the center of a large pressure vessel presents its own set of challenges, but nothing like the challenges of drilling the radically angled hole at the bottom of the vessel. These holes range from 1 to 2 in. in diameter.
For years the method used to drill the lower level holes was an old mag drill with a drill chuck and twist drills. Starting with a 3/8 in. twist drill, a pilot hole was drilled. Then a 5/8 in. twist drill was used to enlarge the hole. Next, the hole was enlarged to ? in. This process continued until the proper hole diameter was achieved. Depending on the hole angle and location, sometimes arc gouging and grinding were needed to finish the hole. The entire process took 8 to 12 hr per hole -- a very time-consuming operation -- and each vessel requires two holes.
"Time is Money"
After Mueller Environmental opened their new manufacturing facility a couple of years ago, plant manager Mark Allen said, "One of my jobs when I took over was to reduce the time we spent on some of our operations. As we all know, time is money." One operation that was taking an extreme amount of time was the lower level holes being drilled on the pressure vessels. He knew there had to be a better method.
Following some research, Allen contacted Hougen Manufacturing and had their local sales rep, Terry Fuller, take a look at the application to see if Hougen could help.
"When Mark drew the hole on the end of the rolled steel to show the angle of cut, I took a step back," said Fuller. "A severely interrupted hole like this on the side of a curved vessel was not something of an everyday application."
After taking notes on what needed to be done, Fuller returned with a standard Hougen HMD915 magnetic drill and a couple of Rotabroach? cutters. On a thinner-walled vessel, Allen had his guys weld a platform that was perpendicular to the angle that needed to be drilled. The platform would serve two purposes, first for the mag drill to magnetize to and second, the plate would act as a guide bushing for the cutter to drill through and into the edge of the vessel. The test was successful. It drilled through the wall of the vessel and on the proper angle without a problem. But looking ahead at future projects, the depth of cut on the larger vessels was going to be up to 8 in. deep. Standard Rotabroach cutters are available up to a 6 in. depth of cut.
Collaborating on a Solution
The test information was taken back to Hougen, where their engineers decided to take a stock HMD915 mag drill and increase the stroke from a standard 3 in. to 6 in. to accommodate a larger Rotabroach Cutter. With this extra stroke, on the vessels requiring a 1 in. hole, Mueller Environmental could use a 6 in. depth Rotabroach to drill straight through. On the 2 in. diameter holes and through the 3 in. thick side-walled vessels, a step-up method of drilling could be utilized. This means drilling down with one depth of cut tool, then using a longer depth of cut tool to continue drilling the rest of the hole. For deep holes this lessens the horsepower needed and helps in chip extraction when the cutter is deep in the hole. Hougen suggested using the Industrial Series of Rotabroach Cutters, which offer a thicker cutter wall for increased durability, patented tooth geometry for the long deep cuts, and extended resharpenability. Special custom-made 2 in. diameter by 8 in. depth Rotabroach Cutters were made to drill through the longest areas with the most extreme angles. (Left, completed hole on the curved edge of the pressure vessel.)
?When it came time for the next pressure vessel, Allen and his team at Mueller Environmental put their new method to the test. Using the modified HMD915 magnetic drill and Hougen's Industrial Series of Rotabroach Cutters, they went to work. The first holes needed were 1 in. diameter through 2 in. thick side wall. The guide platform was welded on and everything was aligned. The HMD915 drilled down through the plate, into and through the side wall of the vessel in 20 minutes, saving Mueller 8 hours of time per hole. (Right, HougenHMD915 magnetic drill and Rotabroach? ?Industrial Cutters used for both the 1 and 2 in. dia holes.) ?
The next vessel required 2 in. diameter holes drilled through a 3 in. side.wall with a total drilling depth of 8 in. Once the guide plate was set up, they drilled through the guide plate and down 3 in. Next, a 6 in. cutter was inserted in the hole and drilling continued down until the cutter bottomed out. Finally, the custom made 8 in. Rotabroach cutter was inserted into the hole to complete the job. Total drilling time took only 45 minutes, saving Mueller 12 hr per hole.
Allen and his team at Mueller Environment were ecstatic with the time savings they have achieved.
?"It's not only the time savings we are experiencing but also the quality of the hole," Allen says. "The hole is round and true with a great finish. We get more accurate readings from our level indicators now, it's much easier to stay within tolerances, and the tool will pay for itself."
With the success of their patented system to clean the natural gas, and the time-saving efforts of Allen and his team, Mueller Environmental looks at increasing production by the end of the year.
"Hougen's been a big problem solver for us. We've been able to find a better way and in doing that, it saved us money," says Allen. "We hope that once we expand our manufacturing facility we will be able to bring in more Hougen drills for use not only on the pressure vessels but other parts we fabricate as well. Having American-made products is important in our business."
