Advanced condition monitoring methods have been used to operate rotating machines reliably and efficiently. Practical notes on availability improvement plans, condition monitoring techniques, predictive maintenance methods, trouble-shooting techniques and smart operation are discussed in the article.
The state-of-the-art compressor for offshore and subsea compression is hermetically sealed direct driven centrifugal unit using magnetic bearing without seal or oil auxiliary systems. This is a simple and small footprint machine with maintenance intervals more than five years.
Compressors, drivers and gear units are usually designed and fabricated by different manufacturers. Generally they are selected from pre-designed and pre-engineered models. Their dimensions are fixed and proper supports are required to keep them in same train centre-line.
Centrifugal compressor purchasers and end-users realize the value and payback of accurate and proper shop performance test and shop mechanical run test. Shop test is a necessary step for centrifugal compressor future reliability and trouble free operation. ASME-PTC-10 type 1 performance test should be done wherever possible. Otherwise arrangement and details of ASME-PTC-10 type 2 performance test, as close to specified operating condition as possible, should be fixed before machine order. Three case studies are discussed.
Liquefaction of natural gas to LNG in floating module is the only available option for remote offshore gas reservoirs. Aero-derivative gas turbine driven centrifugal compressors -- because of compact, light-weight, simple and reliable design -- are the best and optimum selection for offshore LNG units. Presented concepts and details in this article allow substantial reduction in total cost of ownership, better production flexibility and reliability of offshore refrigeration centrifugal compressor trains.
An externally heated Brayton cycle turbine might be used to generate power from heat recovered from the exhaust of a conventional internally fired Brayton gas turbine. However the Brayton turbine is very sensitive to ambient conditions and to the turbine inlet temperature, which in this application is dependent on the exhaust temperature of the primary turbine. These factors limit its use as a backing device, and this article received little support.
The operating range of centrifugal or axial compressors is limited by an instability range commonly called 'Surge' which occurs during low flow or high head conditions and can result in extensive damage. In compressor surge, the energy of flow reversal is accompanied by a loud explosive noise and excessive vibration. Resulting flow reversal and pressure pulsation from surge can cause extensive damage to the compressor system through induced forces such as thrust reversal, radial and axial excitation of the rotor, etc.
Common dry gas seal failures are discussed below along with their causes and remedies. This is from a case study by Rajmal Majhi and Riccardo Schiappacasse of GE Oil & Gas Global Services Engineering presented at the first Middle East Turbomachinery Symposium (Feb. 14-16) in Qatar.
Recuperators have been used by a number of manufacturers to increase their gas turbine's efficiency. The recuperator is a heat exchanger that utilizes the gas turbine's hot exhaust air to pre-heat the combustion air. If done properly, theoretical efficiency improvements up to 20% are possible over a wide operating range. This advanced cycle is often applied to small to mid-size electrical power generation gas turbines (30 kW to 6 MW) so that they can compete with reciprocating engines on efficiency.