The liquids captured are referred to as natural gasoline or drip gas, which is often used as a blend in motor gasoline. Most compressor stations are fueled by a portion of the natural gas flowing through the station, although in some areas of the country, all or some of the units may be electrically powered primarily for environmental or security reasons. Gas-powered compressors may be driven by either conventional piston engines or natural gas turbine units.
There are site design and operational differences, as well as unique air and sound emissions, between these competing compressor engine technologies. There may be one or more individual compressor units at a station, which can be out in the open, or more often, housed in a building to facilitate maintenance and sound management.
Newer units are often housed one per building, but there may be multiple units in one large building. Compressor buildings generally incorporate insulated walls, shielded exhaust systems, and advanced fan technology to dampen sound.
Newly constructed compressor buildings may incorporate these features where local, state, or federal regulations require noise mitigation Figure 2. Figure 2. Inside compressor building. Courtesy of the Marcellus Education Team. Compressor station yards for gathering lines are often larger than transmission line compressors due to multiple pipelines coming into the complex, and in some cases, additional equipment needed to filter and remove liquids from the gas stream Figure 3.
Other components of a compressor complex include backup generators, gas metering equipment, gas filtration systems, and system monitoring and safety controls. There may also be odorization equipment to add mercaptan, which provides the distinctive sulfurous odor to natural gas. Figure 3. Compression station yard. Courtesy of Spectra Energy. Station Yard Piping 2. Compressor Units 4. Gas Cooling System 5. Lube Oil System 6. Mufflers Exhaust Silencers 7.
Fuel Gas System 8. Backup Generators. Compressor stations are either permitted and regulated at the federal or state level depending on the type of the pipeline the compressor services. It should be noted that it is the purpose, not the size of the pipe, that defines whether a pipeline is a gathering or interstate line.
Gathering lines are commonly smaller diameter pipelines generally in the range of 6 to 20 inches that move natural gas from the wellhead to a natural gas processing facility or an interconnection with a larger mainline pipeline. Gathering lines are regulated at the state level and compressor stations that are part of a gathering system are also regulated by the state. In Pennsylvania, the Department of Environmental Protection PA DEP is responsible for environmental permitting and regulation during gathering system compressor planning and construction.
PA PUC regulation includes material and design specifications, on-site inspections, and review of company maintenance and safety procedures.
Natural gas within a gathering system can arrive at a compressor station at a variety of pressures depending on the pressure of the wells feeding the system and the distance gas travels from the wellhead to the compressor. Regardless of the incoming pressure, the gas must be regulated or compressed to transmission pressures generally to 1, psi before it can enter an interstate transmission system. Because compression requirements can be significant within the gathering system, these compressor systems are generally large facilities consisting of 6 to 12 compressors in several buildings.
Many of these gathering system compressor stations are scaled up in size as more wells are drilled in an area, increasing the demand for compression. The permanent land requirements of a gathering system compressor are generally 5 to 15 acres, but they can exceed this, considering slope of land and other factors.
Transmission pipelines are generally wide-diameter inches , long-distance pipelines that transport natural gas from producing areas to market areas. These interstate pipelines carry natural gas across state boundaries--in some cases, clear across the country. The FERC review process includes an environmental review, evaluation of site alternatives, and interfacing with landowners and the public.
Once federally regulated interstate compressor stations become operational, station safety is regulated, monitored, and enforced by the U. Department of Transportation DOT. Interstate transmission lines are regulated at the federal level and compressor stations that are part of an interstate transmission system are also federally regulated.
Interstate compressor facilities must generally comply with local and state regulations; however, if there is a conflict, the more stringent regulations will prevail. Natural gas within an interstate pipeline is generally already pressurized at to 1, psi. To ensure that gas continues to flow optimally, it must be periodically compressed and pushed through the pipeline. Friction and elevation differences slow the gas and reduce the pressure, so compressor stations are placed typically 40 to 70 miles apart along the pipeline to provide a boost in pressure.
Because they are only providing a boost in pressure, interstate transmission system compressors are generally smaller facilities compared to gathering system compressors. A typical facility may consist of two compressor units one that is operational and one that serves as a backup unit within a single building.
The typical permanent land requirement of an interstate compressor is 4 to 5 acres. Compressor stations incorporate a variety of safety systems and practices to protect the public and station employees in the event of an emergency.
For example, every station has an emergency shutdown system ESD connected to a control system that can detect abnormal conditions such as an unanticipated pressure drop or natural gas leakage Figure 4. These emergency systems will automatically stop the compressor units and isolate and vent compressor station gas piping sometimes referred to as a blow down.
Regulations require that compressor stations periodically test and perform maintenance on the emergency shutdown system to ensure reliability. It is advisable for landowners, neighbors, and first responders to become familiar with safety systems, testing procedures, and emergency response protocols for compressor stations in their area.
Figure 4. Emergency shutdown valve on incoming pipeline. Natural gas is a colorless, odorless gas, so an odorant, typically mercaptan, is added to the gas stream as an additional safety mechanism. Odorization of natural gas in Interstate and gathering transmission systems is regulated under Title 49, part of the Federal Code of Regulations, which requires transmission lines in highly populated areas Class 3 and 4 locations to be odorized.
High-consequence areas are subject to added layers of regulation to ensure public safety. Class location is determined by the number of dwelling units within yards in a sliding mile of the pipeline. Classes 3 and 4 are those locations with 46 or more buildings or a building occupied by 20 or more persons at least 5 days a week for 10 weeks schools, community centers, etc. Transportation pipelines in Class 1 and 2 locations--rural areas with fewer than 46 buildings per sliding mile--are exempt from the odorization regulations.
On a practical basis, gas that is odorized for a Class 3 or 4 location "upstream" will retain some level of odorant in the gas stream as it travels through Class 1 and 2 areas.
Although some oil and gas leases and pipeline easement agreements may allow the construction of compressor stations on the leased acreage, most compressor station agreements are negotiated as a separate contract with the landowner. When dealing with mineral leases, rights-of-way, or other agreements, it is generally advisable to keep the agreement as narrow as possible and not allow the placement of surface structures--such as compressor stations--within the agreement.
By doing this, the landowner may be able to receive additional value from a compressor lease and can concentrate on negotiating terms that are unique to a compressor lease or sale or avoid it altogether.
For example, site location, sound mitigation, traffic, and lighting restrictions may be more important considerations in a compressor site than other agreements. If a compressor station is already included in a mineral lease or a pipeline agreement, the landowner may want to ask the operator for a surface use agreement to provide guidelines and restrictions for construction of a compressor station; however, this is usually easier to negotiate before you have signed a mineral lease.
Compressor operators may have a preference to own the property rather than lease the acreage where the compressor station is built. Landowners should consider the implications of selling versus leasing their property for a compressor station.
Selling the site may alleviate some concerns for landowners such as liability, property taxes, trespass, and site reclamation. Types of compressor units Properties of working medium. Gas compression Compression process Basics steps to compressor selection to include Data sheet of compressor equipment Design particulars of compressor equipment Designing a compressor Pipeline flanges and nominal value Oil lubrication system and lubricating oil Materials Process compression stages Choosing a one-stage or multiple-stage compressor Algorithm for choosing an air compressor based on capacity and pressure values.
Scheme of compressor selection Example of a piston compressor selection. Types of compressor units. The basics steps for selecting a compressor unit.
Properties of working medium. Gas compression. The simplest gas equation is the ideal gas equation. Compression process. Basics steps to compressor selection to include. Data sheet of compressor equipment. Most important data sheets of compressor equipment are emphasized below: Outlet pressure in atm and bars.
Most popular household compressors produce from 6 to 8 bars pressure; industrial compression units may produce 25 bars pressure. Pressure means that any given model of compressor may produce pressure internally and discharge the air mass into a sealed cavity. Pressure index is calculated by class and capacity of compression unit. The use of extra-high pressure compressors for household needs is not necessary.
A small unit with up to 10 bars operational pressure will be sufficient. Large industrial facilities may not always operate at such values; in this case more powerful compression machines or units shall be used. Operational pressure of compressor is an average between maximum producible pressure to stop the discharge process and minimum pressure in the system to start-up the compressor. Normally, the pressure differential is 2 bars between stop and start-up the compressor.
Given this index all compressors are divided into compression machines of low, medium and high pressure. Not all compressors have sufficient capacity to compress the air while producing high pressure; as a matter of fact only heavy-duty piston units may reach 30 atm pressure index. Least inlet gas flow shall be indicated in data sheet of compressor units. This is required to ensure the compressor capacity. Pressure may be absolute or surplus.
Relative note shall be made in the data sheet as well as units of indicated pressure. Inlet temperature. Volume flow rate, pressure requirements and required power may affect the inlet temperature. Thus, maximum inlet temperature shall be also specified. Discharge temperature. Discharge temperature T d depends on inlet temperature, compression index, gas specific heat and compression performance indicator.
This temperature is important for mechanical design of compressor, selection of compression stage, calculations of cooler and pipelines. Suction capacity or air discharge amount of induced or forced air at outlet. Regularly, first value is stated by manufacturers of compressor equipment in technical passports, because running compressors lose capacity at discharge due to air loss and suction capacity is always a bit higher.
Various compressor types vary in capacity to specify particular application of compressor equipment. Amount of inlet air consumed upon a particular given time prior to compression is also considered a unit capacity.
Otherwise this parameter is called the air flow rate. The reality is that there is a difference between two parameters. So one shall rely on outlet capacity. Motor may be diesel, turbine or electric. Motor power is one of the core parameters to ensure compressor to manage air discharge. The higher the capacity the more power is consumed. Failure to calculate the power correctly may result in power consumption without effect. Usually, heavy-duty motors are installed in high power units requiring this particular drive; Compressor weight and overall dimensions.
These values may vary from typical small size units easy to transport and operate in a garage to heavy-duty ones to require more space for installation. Big facilities do not pay serious attention to weight and dimensions, since the equipment is fixed and installed in a separate engine room. Dimensions and weight of compression unit always refer to its capabilities.
Alternatively, household compressor is quite compact, so most dimensions refer to receivers of 50, , liters and more. Optionally, compressors with rotating blades may be used to constantly discharge air without the need for receivers. Sure, with no receivers installed weight and dimensions of compressors are significantly less making the unit easily relocatable; Air receiver is also an important parameter to enable idle operations.
Air receivers are tanks designed for collecting compressed air. Receiver volume enables continuous off-line operations of pneumatics. It serves to energy saving. Another advantage is that compressor unit may discharge air with given pressure parameters. Corrosiveness of transferred gas. Composition of corrosive gas shall be identified for all operating conditions. It is important because of cracks coming from corrosion under pressure in high-strength material. Liquid in gas flow.
Liquid in gas shall be avoided. Otherwise, it may cause malfunction of compressor. Separator shall be installed to dewater working medium; electrical tracing and insulation of inlet port shall be made when outside temperature is below gas dew point or hydrocarbon components heavier than ethane are compressed. Design particulars of compressor equipment. Design particulars of compressor are as follows: Type of drive. ICE or electric motor; Stage numbers for air compression. This parameter is justified and important for selection of piston compressors to enable gas compression in several cylinders in stages; Cooling system oil, air and water.
Compressors to be fixed on special foundation or on trailer for ease of transportation; Part element arrangement. All constituents of compressor unit may be frame or receiver mounted; Receiver installation: vertical or horizontal.
Designing a compressor. Pipeline flanges and nominal value. Oil lubrication system and lubricating oil. Process compression stages. To reduce temperature at inlet compression stage to drop the flow required for reaching the set compression ratio. To ensure differential pressure limits of various compressor types, e. To reduce power consumption compressor drive due to interim coolers operation between stages and to maintain safe temperature limits.
Choosing a one-stage or multiple-stage compressor. The choice of proper number of compression stages is largely based on the compression ratio. Compressor design b h Semiprofessional compressors 1,7 0,55 Professional compressors 1,5 0,65 Heavy-duty compressors 1,3 0,75 Rotary compressors 1 1.
Algorithm for choosing an air compressor based on capacity and pressure values. Scheme of compressor selection. Example of a piston compressor selection. Air and gas blowers Axial vane compressors Booster compressor stations Compressors Diaphragm compressors Example problems for the calculation and selection of compressors Examples of Pipeline Calculation and Selection Problems with Solutions Main characteristics of a compressor. Throughput and power Pipeline Design and Selection.
Optimum Pipeline Diameter Positive displacement compressors Reciprocating compressors Rotor compressor Rotor compressor lines Screw compressors. Examples of centrifuge calculations Examples of Pipeline Calculation and Selection Problems with Solutions Example problems for the calculation and selection of compressors Filters calculation and selection Hydrocyclone Filter Calculation Parameters Main characteristics of a compressor.
The purpose of an air compressor is to produce clean, pure, compressed air that will ultimately power numerous functions. To ensure the quality of air that comes out at the end, the ambient air that goes into the compressor must be filtered of impurities before it leaves the machines. None of that could be possible without a clean air filter. If the air filter is dirty, impurities and particulates could corrupt the compressed air and degrade the quality of end-point applications.
Therefore, clean the air filter regularly. Change it out at regular intervals, which vary based on the environment. Oil can degrade the quality of compressed air if it passes through the system and gets carried to the end of an application. Some of the worst-affected processes would include pneumatic spray painters, air cleaners and anything else where oil could corrupt the surface in question. Therefore, it is crucial to ensure oil, when present in the system, is removed from the compressed air before the air leaves the machine.
Check oil filters weekly, regardless of whether the compressor is lubricated or non-lubricated. Moreover, replace the oil filter entirely at recommended intervals, which can range from 4, to 8, hours of use depending on your unit. If the oil filter gets heavily covered in oily residue before that time, replace it sooner.
Lubricant is one of the most vital elements in the function of an air compressor. On all the internal metal parts and joints, lubricant allows for smooth, non-corrosive movement. Without lubrication, tension occurs between the touching metal surfaces, which leads to the corrosion of parts and joints. Once corrosion takes hold, rust is liable to spread and eat through certain mechanical parts. However, even when lubricant is present, it can lose its viscosity and become corrosive if it gets too old.
Check the lubricant level daily to ensure the health of your air compressor. Every three to six months, wipe off old lubricant and reapply a fresh coat. Each time you replace the lubricant, be sure you also change out the separator element. For a motor to run, the bearings must have proper lubrication.
The tiny metal balls are constantly rolling against each other, as well as against the interior walls of the round encasement. Consequently, rust could form on the bearings without proper lubrication. If rust forms, the bearings will gradually slow and ultimately become stuck in place. When this happens, the motor fails.
To protect the health and performance of the air compressor motor, grease the bearings every 4, hours. Be sure to inspect the bearings at quarterly intervals between each greasing to ensure they remain sufficiently lubricated. For an air compressor to go about its internal motions, it is crucial for the belts to have proper tension. The rubber of each belt must also remain firm, yet flexible, to ensure balanced movement between the pulleys of connected parts.
Over time, however, the rubber on a belt will inevitably wear down and crack in certain places. Therefore, it is crucial to replace the belts before they lose their tension or, even worse, snap in the middle of an operation. Inspect each belt once per week to verify they are free of wear.
Adjust the tension if necessary and replace each belt once wear takes hold. An air compressor performs the magic feat of transforming ambient air into something that can power heavy-duty machinery and effectively serve as a replacement for electrical power. That said, the compressor itself can only do so much to turn mundane air into something powerful.
While internal components do their job to purify the air for end-point use, that job is harder for the machine to perform if the intake vents become lined with dirt and grime. To ensure the incoming air remains as clean as possible and to prevent dirt from getting sucked into the system, inspect the intake vents weekly and clean them when necessary.
In addition to the periodic cleaning, lubrication and replacement of parts, check various points along the air compressor and its attachments at regular intervals. Inspect the following on a weekly basis:. Inspect the air compressor for signs of oil or air leaks. Also check the pneumatic hoses for air leaks, as leakage severely reduces the efficiency of an air compressor. Furthermore, make sure the coolers are free of dirt. When you make an air compressor preventive maintenance checklist, you need to first take into account the type of compressor in question.
Most compressors need preventive maintenance on various system parts at intervals that range from daily to annually. Daily: Perform the following steps every day, or after every eight hours of use. When the weather is humid or the environment is dusty, perform the preceding steps twice weekly, or every 20 hours.
Monthly: Every month, or after every hours of use, inspect the belt tension inside the air compressor. Quarterly: Every three months, or after every hours of use, perform the following steps. Biannually: Every six months, or after every 1, hours of use, perform the following steps:. Biannually: Every six months, or after every 1, hours of use, perform these tasks.
Every Three Months: Every three months, or after hours of running use, do the following. Company staff at a given facility or plant can generally perform air compressor preventive maintenance in-house. Unless your company is staffed with highly skilled personnel to handle maintenance tasks with air compressors, it is best to contact a professional for the following:. When you hire a professional for these and other time-consuming and possibly dangerous tasks, it can help you save time and money and also ensure that the job is done properly.
Moreover, professional maintenance ensures utmost safety for the more difficult aspects of the job. To ensure maximum efficiency and an absolute minimum of downtime and repair costs with your air compressor, complete preventive maintenance checklist tasks according to a set schedule. Depending on the needs of a given component, perform maintenance daily, weekly, monthly, quarterly or annually.
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