Basics of Gas
Compressor Stations
Inside a Natural Gas Compressor Station
Natural gas is pressurized as it travels through the interstate
pipeline system. To ensure that the gas continues
to flow optimally, it must be periodically compressed and pushed through pipelines.
Over distance, friction and geographic elevation
differences slow the gas and reduce the pressure, so compressor stations are placed
typically 40 to 70 miles apart along the pipeline to give the gas a “boost.” These stations operate day and night, year-round
to push re-pressurized gas through the pipelines.
Safety Systems
Compressor stations integrate a variety of safety systems and practices
to protect the public and station employees and property. For example, every station has an emergency shutdown
system that stops the compressor units and isolates and vents the compressor station
gas piping.
Regulations require that compressor stations periodically test or
perform maintenance on the emergency shutdown system to ensure reliability. During the shutdown, natural gas in the pipeline
is routed around the station.
(For more information, see Compressor Stations and Emergency Shutdowns
document)
Personnel
All compressor stations are monitored – and some are even controlled
remotely – by highly trained personnel at a centralized gas control center. Experienced personnel operate and maintain the
station equipment and pipelines.
Key Components
A typical compressor station consists of yard piping and compressor
unit(s), a gas or electric power source, safety systems and personnel, all working
together for the safe and efficient transmission of natural gas.
Station Yard Piping
Station yard piping moves natural gas between the pipeline and compressor
station.
Filter Separators / Scrubbers
Filter separators or scrubbers remove any solids or liquids from
the natural gas that enters the compressor station.
Compressor Units
The compressor station runs compressor units sufficient to re-pressurize
the volume of gas flowing through the pipeline.
Gas Cooling System
When natural gas is compressed, its pressure and temperature increase.
The gas may be cooled before its return to
the pipeline to protect the pipeline’s inner coating and increase its transmission
efficiency.
Lube Oil System
Compressor units have lube oil systems to lubricate, cool and protect
the moving parts.
Mufflers (Exhaust Silencers)
Mufflers decrease the volume level of compressor units to meet federal
standards.
Fuel Gas System
At most stations, compressor units are fueled by natural gas from
the pipeline, though some are driven by large electric motors.
Backup Generators
Backup generators stand ready in case of an electrical outage.
Frequently Asked Questions
Q. How are compressor station sites determined?
A. The Federal
Energy Regulatory Commission (FERC) and U.S. Department of Transportation
(USDOT) have established, respectively, rigorous siting and safety requirements
for interstate pipeline compressor stations. The Environmental Protection
Agency (EPA), through the state environmental agencies, strictly regulates
compressor station emissions. Location criteria for compressor stations are
determined by a number of factors that include: 1.) stakeholder considerations;
2.) engineering design with favorable pipeline hydraulic performance; 3.)
geographic suitability; 4.) environmental resource impacts; and, 5.)
constructible terrain. As part of its environmental review, FERC makes the final
decision as to the compressor station location generally considering these
factors.
Q. How are interstate pipeline compressor stations monitored?
A. To ensure safe
operations, well trained gas controllers work around the clock in a high-tech
control center to monitor and control the gas as it travels through all
sections of our pipeline network. Compressor stations are maintained by highly
skilled and experienced pipeline personnel along our pipeline systems. Our
employees operate over 100 compressor station sites around the clock – with
nearly two million horsepower in the United States and over 65 years of
success.
Q. How loud are interstate pipeline compressor stations?
A. FERC regulates
interstate pipeline compressor stations and require that the station’s noise
levels do not exceed an average day-night sound level (Ldn) of 55 decibels
(dBA) at the nearest noise sensitive area (NSA), e.g., residences, schools,
hospitals, churches, playgrounds and camping facilities, when operating at full
load. Noise surveys are conducted before and after construction to verify these
federal noise levels are not exceeded. As a point of reference, the average
home dishwasher is 50 dBA.
Q. What are the public safety measures in place at compressor
stations?
A. Compressor
stations are highly regulated facilities that must meet rigorous siting, safety
and environmental standards established respectively by FERC, USDOT and the
EPA. Texas Eastern’s compressor stations integrate a variety of safety systems
and practices designed to protect the public, our employees and the
environment. The proposed Ohio Pipeline Energy Network project’s 30 inch
diameter high-strength steel pipeline will at a minimum meet the USDOT’s Code
of Federal Regulations and is planned to be certificated by FERC for an
operating pressure up to 1200 pounds per square inch.
Compressor
stations are designed with continuous monitoring devices along with emergency
shutdown systems capable of isolating the station and safely venting the gas
very quickly in the unlikely event of an emergency. Since natural gas is
lighter than air, natural gas rises and dissipates quickly into the atmosphere.
These systems are designed and routinely tested to be reliable, which is why it
is extremely rare to have compressor station incidents.
Compressors
stations are also designed with emergency manual shutdown buttons strategically
placed throughout the facility which can be activated by station operators.
Every one of our compressor stations is operated and maintained by highly
skilled, experienced personnel trained to safely maintain the station and its
pipelines.
Q. Do you coordinate with local first responders?
A. Texas Eastern
is committed to providing pertinent information about our facilities and
working with nearby emergency responders. USDOT also requires interstate
pipeline operators to develop a public liaison program for each municipality we
go through. An emergency response plan specific to each compressor station is
developed and local first responder organizations are trained in how to
coordinate a response with Texas Eastern in the unlikely event of an emergency
at the compressor station. Evacuation of areas surrounding the compressor
station property is not typically necessary in the unlikely event of an emergency.
However, if evacuation is warranted, the evacuation zone would be dependent on
the nature, extent and location of the incident.
Q. What will the emissions be from the compressor station?
A. The turbines
that drive the gas compressors will have low emission technology and are fueled
by clean burning natural gas. Federal regulations require the turbines to be
designed to achieve a nitrogen oxide (NOx) emission rate of 25 ppmvd (parts per
million by volume, dry basis) during normal operations. The Ohio Environmental
Protection Agency (OHEPA) requirements are the same as the federal
requirements. The turbines will be designed to achieve a NOx emission rate of
15 ppmvd during normal operations. This is lower than what is required by
federal and state regulation.
In addition,
while this is not required by any federal regulations or OHEPA, we will be
equipping the turbines with oxidation catalysts, which are designed to
significantly reduce carbon monoxide, volatile organic compounds, and Hazardous
Air Pollutants emissions.
Q. Are pipeline liquids generated at the compressor station and
how is this material managed?
A. Stations are
equipped with filter separators and/or scrubbers that remove any natural gas
liquids or solid particles that may have entered the pipeline from various
interconnects and/or receipt points along the pipeline prior to the gas
entering the gas compressors. Any pipeline liquids collected in these systems
are managed in accordance with all regulations and transported to federal and
state approved sites.
Q. What will be seen/heard when an emergency shutdown occurs?
A. In the
unlikely event of an emergency shutdown, you would hear a very loud noise often
compared to the sound of a jet engine or a freight train, depending on how
close you were to the station The sound will last anywhere from one to four
minutes. This sound is the result of the release of pressure from the
compressor station piping. You would likely see a vapor cloud discharging into
the air.
