GB/T 11348.4-2015Mechanical vibration -- Evaluation of machine vibration by measurements on rotating shafts -- Part 4: Gas turbine sets with fluid-film bearings (English PDF)

Foreword

GB/T 11348 Mechanical vibration of non-reciprocating machines -

Measurements on rotating shafts and evaluation criteria consists of the

following five parts:

- Part 1: General guidelines;

- Part 2: Large land-based steam turbine generator sets;

- Part 3: Coupled industrial machines;

- Part 4: Gas turbine sets with fluid-film bearings;

- Part 5: Machine sets in hydraulic power generating and pumping plants.

This Part is the 4th part of GB/T 11348.

This Part was drafted in accordance with the rules given in GB/T 1.1-2009.

This Part replaces GB/T 11348.4-1999 Mechanical vibration of non-

reciprocating machines - Measurements on rotating shafts and evaluation

criteria - Part 4: Gas turbine sets.

Compared with GB/T 11348.4-1999, the main modifications are as follows:

- modified standard's name from "Mechanical vibration of non-reciprocating

machines - Measurements on rotating shafts and evaluation criteria - Part

4: Gas turbine sets" to "Mechanical vibration of non-reciprocating

machines - Measurements on rotating shafts and evaluation criteria";

- added the acceptance criterion agreed by the supplier and the user before

gas turbine installation;

- added the evaluation on vibration of gas turbine under transient operating

conditions;

- modified the translation of "vibration amplitude" in Edition 1999 to

"vibration value";

- modified examples of using boundary values for different regions in the

clause of evaluation regional boundaries (see 4.2.2.4);

- modified "when new machine does not establish valid baseline data, the

ALARM limit recommended under its stable operating working rotation

speed" to "may be less than the zone B/C boundary" (see 4.2.3.2);

- added a second ALARM of setting of TRIPS (see 4.2.3.3);

Mechanical vibration - Evaluation of machine vibration

by measurements on rotating shafts -

Part 4: Gas turbine sets with fluid-film bearings

1 Scope

This Part of GB/T 11348 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 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 3000 r/min and 30000

r/min. This includes gas turbines coupled to other rotating machinery either

directly or through a gearbox. In some cases, this Part 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, but that of the steam turbine and generator is according to GB/T 11348.1 or

ISO 7919-3.

This Part is not applicable to the following:

a) aero-derivative gas turbines (including gas turbines with dynamic

properties similar to those of aeroderivatives);

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.

revolution rotational frequency component. Consequently, it can be difficult to

identify the effects of the crack propagation by looking at the change in the

broad-band vibration only. Therefore, although monitoring the change in broad-

band vibration gives some indication of potential problems, it can be necessary

in certain applications to use measurement and analysis equipment which is

capable of determining the trends of the vibration vector changes which occur

for individual frequency components. This equipment can be more

sophisticated than that used for normal supervisory monitoring and its use and

application requires specialist knowledge. The specification of detailed criteria

for measurements of this type is beyond the scope of this Part (see 4.5).