September 2017, Vol. 244, No. 9


New Tools Can Cut Station Drying Times in Half

Sugar Land, TX-based Pipeline Drying International, LLC, said it has developed new proprietary tools and techniques that, when used in combination with its patented Mobil Drying Units (MDU), can dry compressor stations, meter stations and some vessels faster than anyone else in the industry.

The company is offering new proprietary tools that can remove standing water from most station piping.

In general, pipeline drying, as well as the drying of compressor stations, meter stations and most vessels, is all done in the same manner.

One of the fastest and most cost-effective methods is to run high volumes of super-dry air or nitrogen through the piping after thoroughly dewatering. The higher and dryer the volume of air or nitrogen runs through the pipe, the faster the evaporation rate. However, small pools of standing water in and around tees, valves or other pipeline features can slow drying no matter what method is used.

A few miles of pipeline can usually be dried faster than a few hundred feet of compressor or meter-station piping because by running pigs in a pipeline, the water surface can be spread. Pigs can seldom run in station piping due to the configuration. It can take weeks or months to dry a few hundred feet of compressor station piping.

Eliminating standing water via a thorough dewatering is critical to rapid drying. An illustration of why dewatering is important is visible in a parking lot after a brief rain shower. If you look closely, you will see small puddles still standing long after the rest of the parking lot is dry. A thin layer of water over a large area will evaporate quickly because the dry air molecules can pick up more water molecules over a larger area. Small puddles or pools of water have a small surface area and take far longer to evaporate.

The problem with dewatering in stations has become an even larger issue due to the Federal Energy Regulatory Commission (FERC) and general environmental awareness. It had been common practice to pressure up piping in a station with air, quickly open a valve and simply blow all standing water out of low-point drains into the ditch and into the atmosphere. More often today, water is pumped into tanks. Dewatering with pumps leaves far more standing water in the piping.

Why can’t all of the water be pumped out of station piping? After dewatering with a pump, there is almost always water left standing in and around sagging pipe, tees, valves, bends, reducers or other pipeline features. The low-point drains don’t always end up at the actual lowest point in a run of pipe. Sometimes there aren’t enough low-point drains. No matter what the reason, significant volumes of water standing in station piping after dewatering is becoming more common.

So, what can be done to overcome standing water, even debris such as mud or sand? In some station projects, crews enter large-diameter pipe with brooms, mops, rags, pumps and wet/dry shop vacuums. Once the standing water is removed or spread over the pipe surface, the drying time can be reduced dramatically. But why put personnel in a confined space if you don’t have to?

A tool called the Puddle Buster basically removes standing water and some debris and will reduce substantially drying time.

First, it can pull standing water from a pipe (Figure 1). In most station piping, it can remove all standing water. Second, while using the tool some of the standing water can be atomized. With the volume of air that the Mobil Drying Unit produces, much of this atomized water can be blown out of the pipe in the mist produced. Third, some of the mist is spread over the pipe’s inside surface. Once again, spreading the water surface area greatly improves the evaporation rate.

Screen Shot 2017-09-19 at 11.44.20 AM

Several tools and techniques are also available that include “dead leg pumping” and “membrane blasting” to aid in maximum water removal. No matter how it is accomplished, as soon as all standing water has been removed or spread through a pipeline, drying to dew points of -40°F or greater can be reached within a relatively short time period.

Each MDU is self-contained in a 20-foot container and provides the equivalent super dry air volume as four 1,600 CFM air compressors with desiccant dryers, all through two 6-inch air outlets. All 6-inch hoses and connections are provided with each MDU and the equipment is ready for drying about two hours after arrival on site.

Related Articles


{{ error }}
{{ comment.comment.Name }} • {{ comment.timeAgo }}
{{ comment.comment.Text }}