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Rotating Equipment

Steam Turbine — Mechanical Drive

Mechanical-drive steam turbine — small (NEMA SM-23 / API 611) or special-purpose (API 612).

Category
Rotating Equipment
Subcategory
Driver
Applicable standards
5
Issuing bodies
3

Description

Mechanical-drive steam turbine — small (NEMA SM-23 / API 611) or special-purpose (API 612).

Applicable Standards (5)

API — 3 standards

API 611 General-Purpose Steam Turbines for Petroleum, Chemical and Gas Industry Services
Edition: 6th Edition (2020) Region: USA, Global
Steam turbines used as drivers for general-purpose service (typically <1000 hp).
Key requirements (8)
  • General-purpose steam turbines (mechanical drive) — alternative to NEMA SM-23.
  • Power range: typically up to 1500 kW.
  • Mechanical run test: 4 hours at maximum continuous speed.
  • Hydrotest: 1.5× MAWP for casing.
  • Maximum allowable speed: 105% MCS for trip.
  • Vibration: per API 670 — bearing housing < 7.6 mm/s typical.
  • Single-stage or multistage; condensing or back-pressure.
  • Lighter governor / lube oil requirements vs API 612.
API 612 Petroleum, Petrochemical and Natural Gas Industries — Steam Turbines — Special-Purpose Applications
Edition: 8th Edition (2020) Region: USA, Global
Special-purpose steam turbine drivers for critical, large, or high-energy applications. Identical to ISO 10437.
Key requirements (8)
  • Special-purpose steam turbines for petroleum, petrochemical, gas industries.
  • Heavy-duty for critical service > 1500 kW typical.
  • Mechanical run test: 4 hours at MCS, plus overspeed test.
  • Hydrotest: 1.5× MAWP all pressure parts.
  • Trip speed: 110% rated; warning at 103% typical.
  • API 670 instrumentation mandatory: shaft vibration, axial position, bearing temperatures.
  • API 614 lube oil system; API 671 high-speed couplings.
  • Casing materials: typically forged CS, alloy steel, or chrome-moly for high temp.
API 670 Machinery Protection Systems
Edition: 5th Edition (2014, R2021) Region: USA, Global
Vibration, axial-position, bearing temperature monitoring for rotating machinery.
Key requirements (7)
  • Machinery protection systems for rotating equipment.
  • Standard sensors: 8 mm proximity probes (eddy current), velocity sensors, accelerometers, KPH probes for speed.
  • Signal: 200 mV/mil sensitivity for proximity probes (5 V across 25 mil gap).
  • Standard alert/shutdown: 25 µm Alert / 50 µm Trip on shaft displacement (typical, tunable).
  • Bearing temperature RTD: 100 Ω Pt; 110 °C Alert / 120 °C Trip typical.
  • Casing vibration (accelerometer / velocity): 7.6 mm/s RMS typical alert for centrifugal machines.
  • API 670 monitoring system has 2-out-of-3 voting for trips, with bypass keys for maintenance.

ASME — 1 standard

ASME PTC 6 Steam Turbines — Performance Test Code
Edition: 2004 (R2014) Region: USA, Global
Performance acceptance testing of steam turbines.

ISO — 1 standard

ISO 10437 Petroleum, petrochemical and natural gas industries — Steam turbines — Special-purpose applications
Edition: 2003 Region: Global
International equivalent of API 612.