BS ISO 7919-4:2009+A1:2017

Mechanical vibration. Evaluation of machine vibration by measurements on rotating shafts. Gas turbine sets with fluid-film bearings | Status: Superseded, Withdrawn

1 Scope This part of ISO 7919 establishes provisions for evaluating the severity of in-situ, broad-band shaft vibration measured radial (i.e. transverse) to the shaft axis at, or close to, the main bearings. These are in terms of:

• — vibration under normal steady-state operating conditions;
• — vibration during other (non-steady-state) conditions when transient changes are taking place, including run up or run down, initial loading and load changes;
• — changes in vibration which can occur during normal steady-state operation.

This part of ISO 7919 is applicable to heavy-duty gas turbine sets used in electrical and mechanical drive applications, with fluid-film bearings, outputs greater than 3 MW and an operating speed range under load between 3 000 r/min and 30 000 r/min. This includes gas turbines coupled to other rotating machinery either directly or through a gearbox. In some cases, this part of ISO 7919 is not applicable to the evaluation of the vibration of the coupled equipment (see the list of exclusions in this clause).

EXAMPLE

For single-shaft combined-cycle power units in which a gas turbine is coupled to a steam turbine and/or generator, the evaluation of the gas turbine vibration is according to this part of ISO 7919, but that of the steam turbine and generator is according to text deletedISO 7919‑3. This part of ISO 7919 is not applicable to the following:

1. a) aero-derivative gas turbines (including gas turbines with dynamic properties similar to those of aero-derivatives);

   NOTE ISO 3977‑3 defines aero-derivatives as aircraft propulsion gas generators adapted to drive mechanical, electrical or marine propulsion equipment. Large differences exist between heavy-duty and aero-derivative gas turbines, for example in casing flexibility, bearing design, rotor-to-stator mass ratio and mounting structure. Different criteria therefore apply for these two turbine types.

2. b) gas turbines with outputs greater than 40 MW and with rated speeds of 1 500 r/min, 1 800 r/min, 3 000 r/min or 3 600 r/min (see ISO 20816‑2);
3. c) gas turbines with outputs less than or equal to 3 MW (see ISO 7919‑3);
4. d) gas turbine driven rotodynamic pumps (see ISO 7919‑3 and ISO 10816‑7);
5. e) coupled steam turbines and/or generators with outputs less than or equal to 40 MW (see ISO 7919‑3);
6. f) coupled steam turbines and/or generators with outputs greater than 40 MW and speeds of 1 500 r/min, 1 800 r/min, 3 000 r/min or 3 600 r/min (see ISO 20816‑2);
7. g) coupled steam turbines and/or generators with outputs greater than 40 MW and speeds other than 1 500 r/min, 1 800 r/min, 3 000 r/min or 3 600 r/min (although generators seldom fall into this category) (see ISO 7919‑3);
8. h) synchronizing clutches which couple the gas turbine to a steam turbine or generator (see ISO 20816‑2);
9. i) coupled rotary compressors (see ISO 7919‑3);
10. j) gearbox vibration (see this clause);
11. k) rolling element bearing vibration of any driven equipment.

This part of ISO 7919 is applicable to other driven equipment not included in this list of exclusions. This part of ISO 7919 is applicable to machines which can be coupled to a gearbox, but does not address the evaluation of the vibration condition of those gears. Specialist techniques are required for evaluating the vibration condition of gears which are outside the scope of this part of ISO 7919. The numerical values specified are not intended to serve as the only basis for judging the severity of vibration. For gas turbine sets, it is also common to judge the vibration based on measurements taken on non-rotating parts. For such vibration measurement requirements, see ISO 20816-1 and ISO 10816‑4.