{"id":152,"date":"2026-07-13T11:37:04","date_gmt":"2026-07-13T03:37:04","guid":{"rendered":"https:\/\/themebb.com\/en\/archives\/152"},"modified":"2026-07-13T11:37:04","modified_gmt":"2026-07-13T03:37:04","slug":"power-calculation-based-on-pressure-and-flow-compressor-shaft-power-calculation-principle-and-api-619-reference-method","status":"publish","type":"post","link":"https:\/\/themebb.com\/en\/archives\/152","title":{"rendered":"Power Calculation Based on Pressure and Flow: Compressor Shaft Power Calculation Principle and API 619 Reference Method"},"content":{"rendered":"<p>In compressor engineering selection and energy efficiency evaluation, accurate estimation of shaft power is the key link. Power is not a direct measurement, but indirectly derived through medium pressure, volume flow, variable efficiency and gas thermodynamic parameters.<\/p>\n<h2>Basic rating formula<\/h2>\n<p>for ideal adiabatic (isentropic) process, compressor shaft power (kW) can be approximately expressed:<\/p>\n<ul>\n<li><strong>P = (Q \u00d7 \u0394h<sub>isen<\/sub>)\/N<sub>isen<\/sub><\/strong>(Based on isentropic enthalpy rise)<\/li>\n<li>or use common engineering simplification:<strong>P \u2248 (Q \u00d7 P<sub>d<\/sub>\u00d7 k) \/ [(k\u22121) \u00d7 \u03b7<sub>poly<\/sub>] \u00d7 ln(P<sub>d<\/sub>\/P<sub>s<\/sub>)<\/strong><\/li>\n<\/ul>\n<p>where:<strong>Q<\/strong>volume flow under import conditions (m\u00b3\/s),<strong>P<sub>s<\/sub>, P<sub>d<\/sub><\/strong>for suction\/exhaust absolute pressure (Pa),<strong>k<\/strong>ratio of specific heat,<strong>N<sub>poly<\/sub><\/strong>for variable efficiency (usually 0.7-0.85, depending on the model and speed).<\/p>\n<h2>API 619 guiding significance<\/h2>\n<p>API RP 619 Rotary positive displacement compressor for petroleum, chemical and gas industries clearly requires that the manufacturer shall provide the shaft power under rated working conditions according to the measured performance curve or verified changeable model, and indicate the test conditions (such as suction temperature, relative humidity and gas composition). This standard does not provide a single conversion formula, but emphasizes that gas compressibility, leakage loss and mechanical efficiency correction must be considered.<\/p>\n<h2>Practical points of air compressor parameters<\/h2>\n<ul>\n<li>nominal traffic (such as 6 m\u00b3\/min &#8220;) usually refers to the free air flow (FAD), which needs to be converted to the compressor inlet state;<\/li>\n<li>the pressure unit must be unified as absolute pressure (for example, 0. 7 MPa (g) \u2248 0.8 MPa (a));<\/li>\n<li>the actual power is usually 10-higher than the theoretical value- 25%, should be included in the coupling loss, gearbox loss and motor efficiency.<\/li>\n<\/ul>\n<p>Schematic of compressor power calculation relationship<\/p>\n<p>Q, P\u209b<br \/>\nP<sub>d<\/sub><\/p>\n<p>\u2192 non-linear increase of power with pressure ratio and flow rate<\/p>\n<p><strong>Note:<\/strong>this calculation is only applicable to preliminary estimation. Engineering Design and contract acceptance must be based on GB\/T 3853, ISO measured performance test results specified in 1217 or API 619. It is forbidden to use the fan formula sleeve for positive displacement compressor.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>This paper analyzes how pressure and flow participate in the calculation of compressor shaft power, introduces the engineering formula based on changeable process, clarifies the requirements of API 619 for performance verification, and reminds the air compressor parameters (such as FAD and absolute pressure) the key role in conversion helps engineers avoid common estimation errors.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","zob_sync_key":"zsync_d6f22126b9936f70f335fb30","zob_sync_source_post_type":"post","zob_sync_lang":"en-US","zob_sync_source_url":"https:\/\/themebb.com\/blog\/archives\/219.html","zob_sync_key_version":"v1","zob_sync_source_blog_id":"1","zob_sync_source_post_id":"219"},"categories":[23],"tags":[],"class_list":["post-152","post","type-post","status-publish","format-standard","hentry","category-haha"],"_links":{"self":[{"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/posts\/152","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/comments?post=152"}],"version-history":[{"count":0,"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/posts\/152\/revisions"}],"wp:attachment":[{"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/media?parent=152"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/categories?post=152"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/themebb.com\/en\/wp-json\/wp\/v2\/tags?post=152"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}