From primary production to direct use, gas mixtures go through several technological stages. To optimize transportation and intermediate storage between these processes, the raw materials are subjected to compressor compression. Technically similar tasks are realized by gas pumping units (GPU) at different nodes of the trunk networks.
Device and equipment design
The unit is a multi-component functional component of gas pipelines. Its main parts include compressors, fans and blowers. The installation is driven by an engine represented by an electric motor or a gas-air turbine. By the way, the range of capacities of a gas turbine gas pumping unit on average varies from 4 to 25 MW. The equipment has a special shelter in a modular design, which protects the working filling from external influences. The frame is made of high-strength sheet steel with technological outputs. As additional functional blocks, buffer storages, fuel-exhaust channels, exhaust systems, heating and air-conditioning modules can be used. The security system without fail includes fire protection equipment, automatic equipment for emergency shutdown and sensors for monitoring individual network parameters like pressure and temperature.
Principle of operation
The unit connected to the line after starting the drive unit starts the rotation of the compressor. The rotor impeller is designed in such a way that the pressure during its rotation increases and air is sucked into the compressor. If necessary, pressure correction, as well as air conditioning and air purification are carried out by connected fans. Gas pumping units compress the transported mixture during the adiabatic process, that is, without a sharp increase in temperature (about 200 ° C). Further, the gas-air mixture is delivered to the distributor unit, to the main line for further delivery through the nozzles with filters or to the buffer storage zone.
Piston compressor units
The traditional design of the GPU, in which two- or four-stroke engines are used, are directly coupled to the compressor unit. According to the level of supported pressure, the piston units are divided in this way:
- Low pressure systems (up to 2 MPa). They are used at the head compressor nodes in the transport network, the source of gas in which are depleted deposits.
- Medium pressure systems (average 3-5 MPa). Involved mainly in the infrastructure of intermediate stations in order to normalize the throughput of gas pipeline lines.
- High pressure systems (10-15 MPa). Used for pumping raw materials into underground gas storages at large compressor stations.
The advantages of reciprocating gas pumping units with a gas turbine drive include a high degree of technical reliability, maintainability and the possibility of application in wide ranges in terms of pressure indicators.
Centrifugal units
This equipment is characterized by a higher capacity of about 20-30 million m3 / day. and the ability to compress gas-air mixtures in 1.5-1.7 times. Centrifugal blowers do not have mechanical rubbing elements, which extends their service life, eliminating the need for regular use of lubricating fluids. This design feature determines the uniformity of gas flows at high speed without ripple. If we talk about the weaknesses of centrifugal gas pumping units, then a high degree of compression is achieved only through the serial connection of several stations in one complex. Therefore, with high performance, fuel consumption increases.
GPA control system
Modern gas pumping complexes are provided with automation to control work processes and the state of functional modules. In particular, the following tasks are implemented:
- Adjustment of the supercharger in revolutions when the fuel mixture is fed into the engine.
- Adjustment with control of the minimum surplus reserves.
- Alarm monitoring.
- Regulation of the mechanical organs of the compressor.
- Registration, processing and display of information on the supervisor display.
In addition, the operation of gas pumping units provides for monitoring the serviceability and proper setting of actuators, sensors and communication lines. For this, input and output channels are used. In equipment of previous generations, analog devices like thermocouples and discrete regulators can still be used.
GPU Maintenance
At gas pumping stations, a maintenance schedule is in force with a set of works aimed at maintaining the mechanics and software in working condition. During the audit of the unit, structural integrity, the correct functioning of the executive bodies are checked, indirect operating parameters are evaluated, system diagnostics are carried out, etc. Based on the audit results, a decision is made on the possible repair of the gas pumping unit with the inspection of operational parts and assemblies. During overhauls, worn-out elements can be replaced, structural parts, oil piping segments restored, etc. Small repair operations are usually associated with restoring the tightness of containers, eliminating leaks, and updating consumables.
GPA reviews
The combination of pipeline networks and compressor installations is still considered the optimal solution for optimizing transportation processes in relation to oil and gas raw materials. According to the employees of enterprises in this field, GPU equipment allows increasing the energy efficiency of trunk lines without compromising reliability and safety indicators for fuel delivery. At the same time, the list of functions of gas pumping units is regularly expanding due to the same automation, which saves on the organization of auxiliary control points for the operation of transport infrastructure. As for the negative reviews, they are associated with the high cost of modern gas compressor units and the technological complexity that requires appropriate qualifications from the maintenance staff.
Conclusion
In recent years, the oil and gas industry is experiencing a phase of abandonment of technical equipment that was put into operation in the 20th century. The technical infrastructure is approaching its service life, requiring updating. Among the first places in this list are compressor stations. Oil and gas enterprises are increasingly introducing new generation gas pumping units into the work process, using the principles of computer simulation. Combined with the latest supervisory control tools, this provides extensive gas transportation management capabilities. The real effect of modernization today is confirmed by actual data on the operational characteristics of compressor equipment and trunk networks.