Gas explosions: understanding the complex system behind natural gas delivery

In New England we were very worry about gas explosions that happened last week, and it is quite natural to become curious about WHY it happened. To better understand some possible source for the problem, we have to understand how the gas system works.

A house on fire
Photo Credit: theatlantic.com

The gas flowing from higher to lower pressure is the fundamental principle of the natural gas delivery systems. From the well, the natural gas goes into “gathering” lines, which are like branches on a tree, getting larger as they get closer to the central collection point. A gathering system may need one or more field compressors to move the gas to the pipeline or the processing plant.

From the gathering system, the natural gas moves into the transmission system, which is generally composed of about 272,000 miles of high-strength steel piper. These large transmission lines for natural gas can be compared to the interstate highway system for cars. They move large amounts of natural gas thousands of miles from the producing regions to local distribution companies (LDCs). The pressure of gas in each section of line typically ranges from 200 pounds to 1,500 pounds per square inch (psi), depending on the type of area in which the pipeline is operating. As a safety measure, pipelines are designed and constructed to handle much more pressure than is ever actually reached in the system. For example, pipelines in more populated areas operate at less than one-half of their design pressure level. Many major interstate pipelines are “looped” — there are two or more lines running parallel to each other in the same right of way. This is important to provides maximum capacity during periods of peak demand.

Another important part of the system are the compressor stations located approximately every 50 to 60 miles along each pipeline to boost the pressure that is lost through the friction of the natural gas moving through the steel pipe. The majority of the compressor stations are completely automated, so the equipment can be started or stopped from a pipeline’s central control room. The control room can also remotely operate shut-off valves along the transmission system. The operators of the system keep detailed operating data on each compressor station, and continuously adjust the mix of engines that are running to maximize efficiency and safety. Natural gas moves through the transmission system at up to 30 miles per hour, so it takes several days for gas from Texas to arrive at a utility receipt point in the Northeast. Along the way, there are many interconnections with other pipelines and other utility systems.

When the natural gas in a transmission pipeline reaches a local gas utility, it normally passes through a gate station. Utilities frequently have gate stations receiving gas at many different locations and from several different pipelines. Gate stations serve three purposes. First, they reduce the pressure in the line from transmission levels (200 to 1,500 pounds) to distribution levels, which range from ¼ pound to 200 pounds. Then an odorant, the distinctive sour scent associated with natural gas, is added, so that consumers can smell even small quantities of gas. Finally, the gate station measures the flow rate of the gas to determine the amount being received by the utility.

From the gate station, natural gas moves into distribution lines or “mains” that range from 2 inches to more than 24 inches in diameter. Within each distribution system, there are sections that operate at different pressures, with regulators controlling the pressure. Some regulators are remotely controlled by the utility to change pressures in parts of the system to optimize efficiency. Generally speaking, the closer natural gas gets to a customer, the smaller the pipe diameter is and the lower the pressure is. Distribution lines typically operate at less than one-fifth of their design pressure. Sophisticated computer programs are used to evaluate the delivery capacity of the network and to ensure that all customers receive adequate supplies of gas at or above the minimum pressure level required by their gas appliances. Distribution mains are interconnected in multiple grid patterns with strategically located shut-off valves. These valves minimize the need for customer disruption to service during maintenance operations and emergencies.

Natural gas runs from the main into a home or business in what’s called a service line. Typically, the natural gas utility is responsible for maintaining and operating gas pipeline and facilities up to the residential gas meter. All equipment and gas supply lines downstream of the residential meter are the responsibility of the customer. When the gas reaches a customer’s meter, it passes through another pressure regulator to reduce its pressure to under ¼ pound, if necessary. Some services lines carry gas that is already at very low pressure. This is the normal pressure for natural gas within a household piping system, and is less than the pressure created by a child blowing bubbles through a straw in a glass of milk. When a gas furnace or stove is turned on, the gas pressure is slightly higher than the air pressure, so the gas flows out of the burner and ignites in its familiar clean blue flame.

As you can see, the system is complex, and depends a lot of computers and physical connections, working at different pressure. We don’t know what causes the problem here in Massachusetts, but probably it was related with a high pressure entering a connection system within some pipe that was not prepare to absorb the pressure safely.

(Source: American Gas Association website)

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Hard water: how to solve it

In a recent post we discussed the problems that you may have with your water when you have a well. Hard water is a common condition here in New England, and to solve this problems you have to install a softener system.

Salt Water Softener Wise Home Building
Water Softener System (with the salt tank in the left side)

Waster treatment systems also have a lot of other functions. There are multiple systems by which water treatment systems companies can remove contaminants and the hardness from water:

  • Point of entry systems: they are able to treat all of the water entering a home and are installed after a water meter or storage tank – you can install after your pump filter, for example, inside a mechanical room (if you have available space).
  • Point of use systems: used where people directly access the water, like a kitchen sink or a shower head.

Specialized companies perform several different types of water treatment, such as treating hardness with water softeners and removing pollutants. They can also be treated by ionic exchange and granular active carbon.

Hard water treatment

Water softening by definition is the process to remove calcium and magnesium from the water through a process called ion exchange using a polymer resin bed which gives off a sodium particle in exchange for hardness minerals. You need salt on the system to do it, and that’s the most common process used (at the least expensive)

Salt based water softeners use an electronic metered valve mounted atop a fiberglass resin tank that meter water by the gallon and then run a cleaning cycle when the ion resin bed reaches a saturation point. During the cleaning cycle, the electronic valve cycles a series of back flushes to purge the hardness particulates that have been captured from the system and flush them down a drain line. The sodium is also replenished in the resin bed during the cycle and all is ready to go again.

Some systems are salt-free, and doesn’t remove the naturally occurring healthy minerals such as calcium and magnesium from your water. Also they don’t put excess salt waste or chemicals into your waste water or the environment. Some of theses systems are available at the internet. Salt free water softeners are actually not softeners, they are water conditioners. We don’t have experience with the use of these systems, but it seems reasonable to think about that.

Hard water: myths and truths

If you have a water well in your house probably you are familiar with this term. But if you are starting to look for a way to have a well in your house and are confuse about that, you can find some information here.

Water well wise home building

As water moves through soil (after some rain, for example) it dissolves very small amounts of minerals and holds them in solution. Water described as hard has a high amount of dissolved minerals, specifically calcium and magnesium. Hard water is not a health risk, but a nuisance because of mineral buildup on fixtures and poor soap and/or detergent performance. Hard water is very common to be found in New England region because of the characteristics of the soil.

Hard water can satin my clothes during washing: TRUE 

Hard water interferes with almost every cleaning task from laundering and dish washing to bathing and personal grooming, and even more problems can happen:

  • Clothes laundered in hard water may look dingy and feel harsh and scratchy.
  • Dishes and glasses may be spotted when dry.
  • Hard water may cause a film on glass shower doors, shower walls, bathtubs, sinks and faucets
  • Hair washed in hard water may feel sticky and look dull.
  • Pipes can become clogged with scale that reduces water flow and ultimately requires pipe replacement

Hard water can damage my appliances: TRUE

Hard water also contributes to inefficient and costly operation of water-using appliances. Heated hard water forms a scale of calcium and magnesium minerals that can contribute to the inefficient operation or failure of water-using appliances. The water filters in some refrigerators can quickly be clogged.

Hard water is dangerous for health: MYTH

Hard water is not a health hazard. In fact, the National Research Council from the National Academy of Sciences states that hard drinking water generally contributes a small amount toward total calcium and magnesium human dietary needs. They further state that in some instances, where dissolved calcium and magnesium are very high, water could be a major contributor of calcium and magnesium to the diet.  The problem with hard water can be the arsenic content, and because of that is recommended for every well installation that you perform a test in qualified lab facilities.

Hard water can easily be managed by installing a softener system: TRUE

The water softener is just a special type of “filter” that removes the calcium and magnesium in hard water by using plastic beads and cleans itself periodically by a process called regeneration.

Water softeners have three main components: a mineral tank, a brine tank, and a control valve. We will talk about them in other posts. The cost to install a system can vary from several hundred dollars up to several thousands, depending on what you would like to do with your water within your house. You can also add filters and more complex process (like the reverse osmosis) to have almost a completely sterile water.