CENTRIFUGAL COMPRESSORS FOR HYDROCARBON SERVICE

Compressor packages shall be designed and constructed to operate for a minimum of 3 years uninterrupted site duty, and shall be designed for a 20 year service life. No proto-type equipment or equipment with less than five (5) years of proven experience shall be used. The design life shall be achievable with a minimum on site maintenance and a maximum availability.

Spare parts and Tool shall include Start-up and commissioning spares, two years spare. Tools and fixtures required to disassemble, assemble or maintain the unit, shall be included in the bid and furnished as part of the initial supply of the compressor (such as torque wrenches, hydraulic devices, etc, and normal wrenches).

The scope of instrumentation to be clarified with Company based on proposed schematic diagrams, prior to order.

As a rule of The Centrifugal Compressor package for hydrocarbon service shall be designed to API 617.

In case of conflict among this specification, data sheets, referred codes & standards and statutory requirements & regulations, the Contractor shall bring the conflict into the notice of Company in writing for resolution before proceeding with the work.

The compressor shall comply with compressor data sheet and this specification. All components shall be suitable for the operating conditions stated on the compressor data sheet.

Material shall be new, free from defects.

All equipment supplied shall be finished machined.  On site only pure assembly work is acceptable.  Piping not completely prefabricated is to be marked on the Piping arrangement drawing(s).  All spare components are to be machined at manufacturer’s shop with suitable tolerances in order to allow replacement without any re-machining.

The compressor and its auxiliaries shall be suitable for outdoor installation (without roof) unless otherwise stated in the data sheet. All equipment supplied must be suitable for start-up and for operation at minimum ambient site temperature as indicated in the specification’s data sheets.

Driver shall be Gas turbine, the specification please see Gas Turbine below.

At normal speed and normal suction condition, the volume capacity at the surge point shall not exceed 70% of the normal operating point. The rise in pressure ratio from the normal operating point to the surge point at normal speed shall not be less than 5%. The head developed at 115% of the normal operating flow at normal speed shall be not less than 85% of the head developed at normal operating point.

Noise emission data shall be provided as well as data of other emissions exhausted to the atmosphere (gas leakages, oil vapour, etc) with the proposal. Please see bellow for specification of noise.

Facility for optical alignment shall be provide and the manufacturer’s supervisor shall be present during initial alignment check at site.

Process gas compressors will be run-in on air in the field. Run-in on air means mechanical test run in the field where compressor is priming and discharging to atmosphere. Compressor manufacturer to propose procedure for run-in on air (flows, discharge pressures and temperature, speed, horsepower requirement, necessity of bleed connections, safety screens, etc) and to provide performance curves and temperature limitations, etc, for this operation. If specified in the specification’s data sheet, process gas compressors will be operated for several weeks on air for pre-start-up equipment drying.

All casing drains shall have isolation valves.  All casing drains down stream of isolation valve shall be connected to common drain header terminated with a flange connection at the edge of skid/base plate.

Compressor shall be designed to withstand the external loading defined bellow:

•             Vertical component. Combined forces and moments due to all piping connections or to any one piping connection resulting in a vertical reaction (either upward or downward) at any support point of at least one-half the dead weight reaction of the compressor at the support point.

•             Horizontal transverse component. Combined forces and moments due to all piping connections or to any one piping connection resulting in a horizontal transverse reaction at any support point of at least one-third the total dead weight reaction of the compressor at the support point.

•             Axial component. Combined axial forces of all piping connections or to any one piping connection resulting in an axial force on the compressor casing of at least one-sixth the compressor weight.

Shaft shall be made of one-piece, heat treated steel that is suitably machined. Shafts shall be made of forged steel.

Impellers shall be assembled on the shaft with fit and a key. Other methods shall not be acceptable without Company approval. Impellers shall be designed to limit the maximum stress at maximum continuous speed to a value not exceeding 70% of the material yield strength. Proven impellers shall be provide.

Balance line sizing shall consider also noise generation due to high gas velocities in the balance line. During mechanical run test in manufacturer’s shop balance line (s) must be installed.

If the compressor is driven by turbine particular attention concerning bearing design must be given to turbine turning gear speed, which may be very low.  Compressor manufacturer to coordinate with turbine manufacturer.

Nonpressurised bearing housings shall be provided with a 25 mm vent connection equipped with the standard breather cap or closed with a steel plug, if no venting is necessary.

Torsional Analysis, A composite torsional vibration analysis shall be performed for all compressor units.  For compressor units driven by electric motor or turbine through a gear box, both the compressor and driver manufacturer shall perform an independent torsional analysis. The input and results of this analysis shall be prepared for submission to Company.

Vibration and Balancing, the final balancing of the rotating element shall be carried out with the coupling half installed. Along with the compressor a fully integrated vibration monitoring system complete with the cabinet (series and protection as defined by Purchaser suitable for service) shall be provided. Vibration probes and system shall be inaccordance with API 670.

Drivers shall be sized and rated to develop at least 110% of the horsepower or as specified in data sheet (whichever is higher) at the maximum compressor operating conditions, including either gear or hydraulic coupling losses, or both. Steam turbine drivers for compressors shall be in accordance with API 611 or API 612 as called for in the individual turbine specifications.  Auxiliary drive turbine shall be capable of continuously developing 110 % of the horsepower required at the relief valve pressure of the driven equipment, at the corresponding speed under minimum steam inlet and maximum back pressure.

The coupling (whether hydraulically or mechanically fitted) shall be designed for easy removal. Devices shall be provided by the manufacturer for the mounting and removal of this coupling.