{"openapi":"3.1.0","info":{"title":"Valve Flow Coefficient API","version":"1.0.0","description":"Control-valve flow-coefficient (Cv / Kv) maths as an API, computed locally and deterministically. The liquid endpoint sizes a control valve for liquid service using Q = Kv·√(ΔP/SG): give any two of the flow rate (m³/h), the pressure drop across the valve (bar) and the flow coefficient Kv, and it returns the third — the required Kv to size a valve, the flow a valve passes, or the pressure drop it develops — together with the equivalent Cv. The convert endpoint converts between the three flow coefficients in use around the world: the metric Kv, the US Cv = 1.156·Kv, and the SI Av = 2.4e-5·Cv. The opening endpoint computes how far a valve must open to pass an operating Kv against its rated Kvs, for both a linear trim (opening = Kv/Kvs) and an equal-percentage trim (opening = 1 + ln(Kv/Kvs)/ln(R) for a rangeability R), so you can keep the valve in its controllable 20–80 % travel band. Everything is computed locally and deterministically, so it is instant and private. Ideal for process, instrumentation and HVAC engineering tools, control-valve selection and commissioning, hydronic-balancing and plant-design apps, and engineering education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is control-valve sizing; for pump power and head use a pump API and for orifice-plate metering use an orifice API.","contact":{"name":"PremiumApi","url":"https://www.oanor.com/by/premiumapi"}},"servers":[{"url":"https://api.oanor.com/valveflow-api","description":"oanor gateway"}],"tags":[{"name":"Valve"},{"name":"Meta"}],"components":{"securitySchemes":{"oanorKey":{"type":"apiKey","in":"header","name":"x-oanor-key","description":"Get your key at https://www.oanor.com/developer/keys"}}},"security":[{"oanorKey":[]}],"paths":{"/v1/convert":{"get":{"operationId":"get_v1_convert","tags":["Valve"],"summary":"Cv / Kv / Av conversion","description":"","parameters":[{"name":"kv","in":"query","required":false,"description":"Metric flow coefficient Kv","schema":{"type":"string"},"example":"10"},{"name":"cv","in":"query","required":false,"description":"Or US flow coefficient Cv","schema":{"type":"string"}}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"cv":11.56,"kv":10,"note":"Cv = 1.156·Kv (Cv in US gpm/√psi, Kv in m³/h/√bar). 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Required flow coefficient for the duty; pick a valve whose Kvs exceeds this.","inputs":{"flow":10,"pressure_drop":2,"specific_gravity":1}},"meta":{"timestamp":"2026-06-04T18:38:25.892Z","request_id":"1cfef2f8-0cb9-4ef3-8403-91bd67482c36"},"status":"ok","message":"Liquid valve sizing","success":true}}}},"401":{"description":"Missing or invalid x-oanor-key header"},"402":{"description":"Active subscription required"},"429":{"description":"Rate-limit or monthly quota reached"},"502":{"description":"Upstream did not respond"}}}},"/v1/opening":{"get":{"operationId":"get_v1_opening","tags":["Valve"],"summary":"Required valve opening","description":"","parameters":[{"name":"rated_kv","in":"query","required":true,"description":"Rated Kvs (fully open)","schema":{"type":"string"},"example":"20"},{"name":"operating_kv","in":"query","required":true,"description":"Operating Kv at duty","schema":{"type":"string"},"example":"7.07"},{"name":"rangeability","in":"query","required":false,"description":"Equal-% rangeability R (default 50)","schema":{"type":"string"},"example":"50"}],"security":[{"oanorKey":[]}],"responses":{"200":{"description":"OK","content":{"application/json":{"example":{"data":{"note":"Linear opening = Kv/Kvs. Equal-percentage opening = 1 + ln(Kv/Kvs)/ln(R). 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