Brezplačno inženirsko orodje
Kompenzacija toplotne rasti za poravnavo gredi
Izračunajte navpično rast središčne črte zaradi toplotnega raztezanja za pogonske in gnane stroje. Določite ciljni predodmik hladne poravnave za dosego poravnave pri obratovalni temperaturi.
Rezultati
Formula za toplotno rast
Ko se stroj segreje, se njegov okvir navpično razteza in dvigne os gredi:
- H — višina od stopala do središčne črte (mm)
- α — koeficient toplotnega raztezanja (×10⁻⁶ /°C)
- Top — delovna temperatura (°C)
- Tamb — temperatura okolice (°C)
Vrednosti CTE materiala
| Material | α (×10⁻⁶ /°C) |
|---|---|
| Ogljikovo jeklo | 12.0 |
| Lito železo | 10.5 |
| Nerjaveče jeklo (304/316) | 16.0 |
| Aluminij | 23.0 |
Tipične delovne temperature
| Vrsta stroja | Tipična temperatura ohišja (°C) |
|---|---|
| Elektromotor | 60–90 |
| Centrifugalna črpalka (hladna voda) | 40–70 |
| Parna turbina | 80–200 |
| Menjalnik | 50–80 |
| Kompresor | 60–120 |
Praktični primer
Dano: Temperatura okolice = 20 °C
Motor: H = 200 mm, jeklo (α = 12×10⁻⁶), Top = 80 °C
Črpalka: H = 250 mm, jeklo (α = 12×10⁻⁶), Top = 60 °C
ΔHmotor = 200 × 12 × 10⁻⁶ × (80 − 20) = 0,144 mm
ΔHčrpalka = 250 × 12 × 10⁻⁶ × (60 − 20) = 0,120 mm
Razlika = 0,144 − 0,120 = 0,024 mm
Motor zraste bolj → motor nastavite 0,024 mm NIZKO med hladnim poravnavanjem.
💡 Nasvet: Stroj, ki bolj raste, naj bo pri hladni poravnavi nastavljen na NIZKO. Ko se oba segrejeta, ju diferencialna rast poravna.
⚠️ Opomba: Ta izračun predpostavlja enakomerno toplotno raztezanje okvirja stroja. V praksi lahko toplotni gradienti, napetosti cevi in vplivi temeljev povzročijo dodatne premike. Kadar je mogoče, vedno preverite s preverjanjem poravnave v vročem stanju.
Thermal growth is the vertical expansion of a machine's shaft centerline height as the machine heats up from ambient to operating temperature. All materials expand when heated, and for rotating machinery this means the shaft centerline rises.
The growth is calculated as: ΔH = H × α × (Top − Tamb), where H is the foot-to-centerline height, α is the coefficient of thermal expansion, and the temperatures are in °C.
Machines are aligned when cold (not running) but operate when hot. If the driver and driven machines grow by different amounts vertically, perfect cold alignment will result in misalignment at operating temperature.
By intentionally offsetting the cold alignment by the expected differential growth, the machines come into proper alignment when they reach operating temperature. The machine that grows more is set low during cold alignment.
Operating temperatures can be measured on running equipment using:
- Infrared thermometer — quick non-contact measurement at machine feet or bearing housings
- Contact thermocouple probes — more accurate surface temperature
- RTDs/thermocouples — permanently installed sensors
Measure at the machine feet or base, not at the top of the casing, as this best represents the temperature affecting vertical growth. Allow the machine to reach thermal steady state (typically 2–4 hours).
Typical casing/foot temperatures for common machines:
- Electric motors: 60–90°C (depending on frame size and load)
- Centrifugal pumps: 40–70°C (cold water), up to 200°C+ (hot process)
- Steam turbines: 80–200°C
- Gearboxes: 50–80°C
- Compressors: 60–120°C
These are approximate values. Always measure on the actual equipment when possible.
A hot alignment check is performed immediately after shutting down equipment that has been running at normal operating temperature. The alignment is measured before significant cooling occurs (typically within 15–30 minutes of shutdown).
This check verifies whether:
- The calculated thermal growth predictions were accurate
- The cold pre-offset was correct
- Other factors (piping strain, foundation movement) are affecting alignment
A hot check is the gold standard for validating alignment and should be performed whenever practical, especially on critical machinery.
Postopki, opisani na tej strani, so bili razviti in terensko preizkušeni s strani ekipe Vibromera z uporabo naprave Balanset-1A, prenosnega dvokanalnega uravnoteževalnika in analizatorja vibracij za uravnoteženje rotorjev na mestu uporabe.
Profesionalni instrumenti za lasersko poravnavo in analizo vibracij. Dosezite natančno poravnavo s kompenzacijo toplotne rasti na kraju samem. Uporabljajo se v več kot 50 državah.
Nikolai Shelkovenko
Nikolai Shelkovenko je inženir vibracijske analize ter ustanovitelj in izvršni direktor podjetja Vibromera. Že več kot 15 let uravnotežuje vrtečo se opremo na terenu, in ne na preizkuševališču: mulčerje, industrijske ventilatorje, drobilnike, centrifuge, gredi in vretena. Prav iz tega dela so nastali instrumenti Balanset — zasnovani so bili kot orodje, ki ga strokovnjak lahko prinese do stroja in ga uporabi sam, na mestu samem, ne pa kot laboratorijska oprema. Vibromera je bila ustanovljena leta 2017, od leta 2023 pa ima sedež v Portu na Portugalskem. Tu potekajo razvoj, sestavljanje in podpora za linijo Balanset. Vodilni instrument je Balanset-1A, prenosni analizator za enoravninsko in dvoravninsko uravnoteženje ter za vibracijsko diagnostiko. Nikolai osebno sodeluje pri podpori strankam, pri reševanju zahtevnih primerov uravnoteženja in pri razvoju programske opreme. S strankami dela po vsem svetu, v katerem koli jeziku.
