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Sinopec Engineering Construction Company Design Standard SEPD 0113-20021 General Provisions 1.1 Purpose 1.2 Scope 1.3 Referenced Standards 2 Piping Design 2.1 General Requirements 2.2 Suction Piping 2.3 Exhaust Piping 2.4 Lubricating Oil and Sealing Oil Piping 3 Support and Hanger Installation 3.1 Supports and Hangers for Suction and Exhaust Piping 3.2 Supports for Branch Piping 1 General Provisions 1.1 Purpose This standard is formulated to unify the piping design for centrifugal compressors in petrochemical plants. 1.2 Scope 1.2.1 This standard specifies the general requirements for the piping of centrifugal compressors in petrochemical plants, including the design of suction pipes, exhaust pipes, lubricating oil and seal oil pipelines, as well as the requirements for the installation of supports and hangers. 1.2.2 This standard applies to the piping design of centrifugal compressors in petrochemical plants. 1.3 Referenced Standards When using this standard, the latest versions of the following standards shall be employed. GB 50160 \"Code for Fire Protection Design of Petrochemical Enterprises\" SH 3012 \"General Rules for the Design of Pipeline Layout in Petrochemical Plants\" SEPD 0112 \"Specifications for the Pipeline Design of Reciprocating Compressors\" 2 Pipeline Design 2.1 General Requirements 2.1.1 The pipeline design for centrifugal compressors shall comply with the requirements regarding pipeline layout for compressors as specified in GB 50160 and SH 3012. 2.1.2 The piping design shall comply with the design requirements for piping layouts specified in the process piping and instrumentation diagram (hereinafter referred to as PID) and the manufacturer’s drawings. 2.1.3 The layout of the pipes, as well as the installation of supports, hangers, and compensators, should all be designed to reduce the forces and moments acting on the nozzles of the mechanical equipment. 2.1.4 The layout of the compressor’s intake and exhaust ducts shall be determined through stress analysis, so that the forces and moments acting on the compressor’s intake and exhaust nozzles are below their allowable values, and the resultant forces and moments resulting from their combination are also below their allowable values. 2.1.5 The layout of pipes and valves should not hinder equipment maintenance and should facilitate operation. 2.1.6 Under the conditions of satisfying pipeline thermal compensation and mechanical allowable stress, the piping should adopt the shortest possible route and the minimum number of fittings. 2.1.7 Pipeline layout examples that have been successfully implemented should be adopted or referenced. 2.1.8 Centrifugal compressor housings come in two basic types: vertically split and horizontally split. a) In the case of vertically split compressors, there should be no pipes or other obstacles in front of them ； b) Horizontal split-type compressor, with no pipes or other obstacles above it. If piping must be installed, flange connections should be used to facilitate disassembly. 2.1.9 When both the suction and discharge nozzles of the compressor point upward, removable sections should be installed on the inlet and outlet pipes to facilitate compressor maintenance. 2.1.10 When both the suction and exhaust nozzles of the compressor point downward, the suction and exhaust pipes should be arranged side by side on the ground to facilitate support; the height from the bottom of the pipes to the ground should not be less than 600 mm. 2.1.11 The layout of the compressor’s suction and discharge pipes should preferably accommodate the direction of thermal displacement of the compressor nozzles. Make the pipeline displacement between the nozzle and the fixed support consistent with the thermal displacements in the three directions of the nozzle itself. This can offset part of the force exerted by the pipe on the nozzle. 2.1.12 The layout of the compressor’s suction and discharge pipelines should make use of the natural compensation provided by the pipes to meet the requirements regarding flexibility of the pipes and the stresses on the nozzles. If the natural compensation is not sufficient to meet these stress requirements, wave-shaped expansion joints can be installed on the pipes, provided that the operating pressure permits it. 2.1.12.1 Expansion joints should be installed near the compressor nozzles. 2.1.12.2 Expansion joints with attachments have relatively large lateral dimensions; when installing them, consideration should be given to the required installation space and deformation space to avoid collisions. 2.1.12.3 Due to the pulsating flow within the exhaust pipes, pressure fluctuations occur, resulting in large pressure variations; therefore, wave-shaped expansion joints are not suitable for use. 2.1.13 For air compressors installed within the plant, the suction and exhaust pipelines should be designed to reduce noise in accordance with relevant regulations; the following measures can be adopted: a) Install silencers ； b) Wrap the outer wall of the pipe with sound-absorbing material. 2.1.14 When the center height of the handwheel or actuator of the overhead suction and exhaust pipeline valves above the ground is greater than 2 m, an operation and maintenance platform shall be provided. 2.2 Intake ducts 2.2.1 The layout of the intake ducts should facilitate uniform fluid distribution at the inlet; the following measures can be taken. 2.2.1.1 A straight section must be provided between the elbow of the suction pipeline and the flange of the compressor nozzle, and its length shall meet the requirements specified by the manufacturer; generally, the length of this straight section is 3 to 5 times the diameter of the compressor nozzle. 2.2.1.2 The bend radius of the intake duct should be no less than 1.5 times the diameter of the duct. 2.2.2 In PID, when the diameter of the suction pipe differs from that of the suction nozzle on the compressor, and a transition fitting is used for connection, the reduction angle must meet the requirements specified by the manufacturer; generally, this angle is between 6° and 7°. As shown in Figure 2.2.2, the piping layout at the inlet should be confirmed by the manufacturer. 2.2.3 Filters should be installed on the intake pipelines as required by the PID; the pipeline filters must provide space for removing the filter screens ； The temporary filter should be equipped with a short pipe for a removable filter. 2.2.4 When two or more compressors are operated in parallel, the suction pipeline for each compressor should lead from the top of the main pipe. 2.2.5 The suction pipeline of the air compressor should be installed in a location with fresh air; the suction inlet should be at least 2 meters above the ground, and the total length of the suction pipeline should not exceed 25 m. 2.3 Exhaust Piping 2.3.1 Subject to the allowable stress requirements for the compressor nozzles, the exhaust piping should be arranged close to the intake piping, which facilitates the installation of an operation platform. 2.3.2 The check valve on the exhaust pipeline should be installed near the compressor outlet nozzle in order to reduce the severity of surge in mechanical equipment. 2.3.3 When two or more compressors operate in parallel, in order to reduce losses in efficiency due to parallel operation and to avoid airflow conflicts at the junction of the exhaust pipes caused by differences in flow rate and pressure among the individual compressors, each compressor’s exhaust pipe should be connected to the main pipe in the same direction as the airflow, as shown in Figures 2.3.3-1 and 2.3.3-2. In the figure: d —— diameter of the branch pipe ； L — Length of the branch pipe extending into the main pipe. 1—Branch pipe ； 2—Branch pipe ； 3—Piping diagram 2.3.3-2 Schematic illustration of the inclined tube connection for the compressor exhaust pipelines 2.4 Lubricating oil and seal oil pipelines The piping design specifications for lubricating oil and seal oil pipelines shall be in accordance with SEPD 0112. 3 Installation of supports and hangers 3.1 Supports and hangers for intake and exhaust pipes 3.1.1 The proper installation of supports and hangers has a direct impact on the stress experienced by the compressor nozzles; therefore, their location should be carefully considered during pipeline layout. 3.1.1.1 When arranging the pipes, it should be taken into account to create displacement \"dead points\" on the pipes, so that fixing brackets or limit brackets can be installed at these points to prevent the forces acting on the system pipes from affecting the equipment. 3.1.1.2 When arranging the pipes, it is also necessary to consider providing several support points on the pipes that are sufficient to balance the weight; in particular, there must be locations near the device’s outlet where spring supports or spring hangers can be installed. 3.1.2 The type of support and hanger should be determined based on piping stress analysis. 3.1.3 The layout of the supports and hangers for the inlet and outlet pipes of the compressor shall meet the following requirements: a) They shall be installed near the inlet and outlet of the compressor ； b) The first support near the compressor nozzle should be a spring support ； c) Suspension brackets should be used in the middle of the piping system to reduce friction ； d) To reduce the force acting in a certain direction, limit brackets should be used. 3.1.4 Pipe supports shall not be installed on the compressor casing or on the base that supports the compressor. 3.2 Branch pipe supports Branch pipes connected to the intake and exhaust ducts with a DN of 40 or less should be supported using footplate supports, as shown in Figure 3.2.