14. Scope Limits Format¶

Revision: 2.0

This document defines the format of scope limits files for use in Apex products (GageMap, GmScript, DS, DR, DV, and DX). All products do not necessarily use all components of a scope limits file.

Overview

Scope limits files typically contain the modal information of one or more parts within a structure. The information is defined as sensor (e.g., strain gage) properties. These properties can then be used to assist the test engineer and analyst in assessing the frequency response relative to a “limit”. The modal information consists of the following:

1. Mode name: Used to identify a specific frequency response with a non-numerical description, e.g., “1B”, “1F”, “2CWB”, etc.
2. Frequency: The modal frequency in Hertz. These are typically derived from a normal modes analysis. A frequency should be provided for each mode.
3. Ratio: The ratio of the sensor magnitude to some critical location. The critical location can be either the maximum vibratory location or the critical location. These locations may be different with the inclusion of static stress in the analysis. Ratios are typically less than 1.0 but may be greater than 1.0. A ratio should be provided for each mode.
4. Limit: The maximum vibratory response such that when achieved results in 100%. These are referred to as the “red line” limits. A limit should be provided for each mode.
5. Reduced Limit: The maximum vibratory response such that when achieved results in less than 100% of limit. These are referred to as the “yellow line” limits. A limit should be provided for each mode.

Scope limits files can be configured such that multiple sensors share the same modal information (mode names & frequencies) or for each sensor to have its own modal information. In the case of the former, where multiple sensors exist on the same part, the modal ratio information can be used to assist in assignment of the proper mode to the response.

Capability is also provided to permit the frequency, ratio and limit definitions to vary with some other measured parameter. Typically, this is the rotational velocity of the part, e.g., shaft speed.

Layout

The scope limits are defined in a Comma Separated Value (CSV) file. The file consists of a keyword followed by one or more values separated by a comma. Some keywords are optional and are identified below as such. Not all keywords are used by all products, those are also identified below. The order of the keywords as they appear in the file is important as the file is read sequentially from top to bottom. Some flexibility does exist and variations are shown in the examples.

Keyword: “Project” (Required) The project keyword contains meta-data information

Fields:

1. Project Name, string (optional)
2. Engine Model, string (optional)
3. Facility ID, string (optional)
4. Manufacturer, string (optional)
5. Number of Parts, integer (required)

Example:

project, Test Rig, SN0001, Spring Hill, Apex Turbine Engines, 2

Keyword: “Part” (Required) Modal information regarding a specific “part”. Multiple similar parts may form a component. Parts share the same modal information.

Fields:

1. Part Name, string (optional)
2. Component Name, string (optional)
3. Number of Modes, integer (required)
4. Number of Parameter entries, integer (optional)
5. Number of Sensors, integer (required)
6. Parameter Name, string (optional)

Example:

part, Blade 01, Fan R1, 10, 3, 2, N,

In the example above, “Blade 01” is a member of component “Fan R1” and contains 2 sensors (signals as defined below). There are 10 modes defined for “Blade 01”, 3 parameter entries and the reference parameter is “N”. The existence of multiple parameter entries means that at least some of the modal information (frequencies, limits and ratios) vary with the measured parameter “N”. “N” must be defined as a parameter in the DS setup or in the DX design. If the parameter “N” does not exist then the first (or lowest N) parameter information is used.

Keyword: “modenames” (Required) Must immediately follow the “part” keyword. A non-numerical description for each frequency bin.

Fields: comma-separated entries the number of which must match the part keyword, field #3

Example:

modenames,1B,1T,2B,2T,1CWB,

Keyword: “ftol” (Optional) Must follow the “modenames” keyword. “ftol” defines the single peak frequency tolerance (Hz) band for which each mode applies. “ftol” is not permitted to vary with the reference parameter. “ftol” is optional and if not present, results in adjacent mode bins. “ftol”, at most, can result in adjacent mode bins, i.e., ftol will be truncated such that overlapping mode bins are not permitted.

Fields: comma-separated entries the number of which must match the part keyword, field #3

Example:

ftol,50,100,25,200,

Keyword: “param(#)” (Optional) Must be subsequent to the “part” keyword. Defines the variation of the basis for varying frequencies, limits and ratios. The “param” entries are required if the part keyword field #4 is greater than 0. The “#” following “param” is simply an index that goes from 1 to the value in the part keyword field #4. While the parameter values are permitted to vary by mode it is discouraged such that a subsequent release of the scope limits format will remove this capability. The parameter entries must increase with the index value.

Fields: comma-separated entries the number of which must match the part keyword, field #3

Assume part keyword #4 is equal to 3, therefore, there must be 3 “param” fields indexed by 1, 2 and 3.

Example:

param1, 2000, 2000, 2000, 2000,

param2, 5000, 5000, 5000, 5000,

param3, 10000, 10000, 10000, 10000,

Keyword: “freq(#)” (Required) Must be subsequent to the “part” keyword. Mode frequency values in Hertz. Multiple “freq” entries are required if the part keyword field #4 is greater than 0. The “#” following “freq” is simply an index that goes from 1 to the value in the part keyword field #4. A “time domain” can be defined by specifying a frequency of 0 Hz. This must be the first mode defined.

Fields: comma-separated entries the number of which must match the part keyword, field #3

Example:

freq1, 100, 250, 400, 600, 1000,

Keyword: “signal” (Required) Must be subsequent to the “part” & “freq” keywords. Must exactly match a channel name in the dynamic data file. The number of signal entries must match the 5^th field in the part keyword prior to the next “part” keyword.

Fields: signal name (string)

Example:

signal,SG01,

Keyword: “scopelimit(#)” (Optional) Must be subsequent to the “signal” keyword. Mode limit values, e.g., “red line” limits. Multiple “scopelimit” entries are required if the part keyword field #4 is greater than 0. The “#” following “scopelimit” is simply an index that goes from 1 to the value in the part keyword field #4. The values should be consistent with the units (PSI, KSE, MPa, g’s, etc.) and scaling (Peak-to-Peak, RMS, single Peak) used for decoding the dynamic signal data.

Fields: comma-separated entries the number of which must match the part keyword, field #3

Example:

scopelimit1, 200, 100, 80, 60, 35,

Keyword: “reducedlimit (#)” (Optional) Must be subsequent to the “signal” keyword. Mode limit values, e.g., “yellow line” limits. Multiple “reducedlimit” entries are required if the part keyword field #4 is greater than 0. The “#” following “reducedlimit” is simply an index that goes from 1 to the value in the part keyword field #4. The values should be consistent with the units (PSI, KSE, MPa, g’s, etc.) and scaling (Peak-to-Peak, RMS, single Peak) used for decoding the dynamic signal data. “Yellow” limits are generally lower than “red” limits but this is not enforced. “reducedlimit” is not required and not utilized in DX.

Fields: comma-separated entries the number of which must match the part keyword, field #3

Example:

reducedlimit1, 120, 60, 50, 30, 25,

Keyword: “strainratio (#)” (Optional) Must be subsequent to the “signal” keyword. Mode ratio values. Multiple “strainratio” entries are required if the part keyword field #4 is greater than 0. The “#” following “strainratio” is simply an index that goes from 1 to the value in the part keyword field #4. The values are typically less than 1 and can be either positive or negative. “strainratio” is not required and not utilized in DS & DR.

Fields: comma-separated entries the number of which must match the part keyword, field #3

Example:

strainratio1, -0.85, 0.32, -0.90, 0.01, 0.65,

project,,,,,1

part,Part 1,,1,,4,

modenames,all_modes,

freq1,2500,

signal,SG01,

signal,SG02,

signal,SG03,

signal,SG04,

strainratio1,1.0,

scopelimit1,60,

reducedlimit1,40,

project,,,,,1

part,Part 1,,1,,4,

modenames,all_modes,

freq1,2500,

signal,SG01,

scopelimit1,40,

strainratio1,1.0,

signal,SG02,

scopelimit1,60,

strainratio1,1.0,

signal,SG03,

scopelimit1,30,

strainratio1,1.0,

signal,SG04,

scopelimit1,100,

strainratio1,1.0,

project,,,,,1,

part,Part 1,,2,,4,

modenames,Time,Freq,

freq1,0,2500,

signal,SG01,

signal,SG02,

signal,SG03,

signal,SG04,

scopelimit1,80,60,

strainratio1,1.0,1.0,

project,,,,,1,

part,Part 1,,4,,4,

modenames,1F,1T,2F,Unk,

freq1,500,1000,2000,3000,

signal,SG01,

scopelimit1,30,40,50,60,

signal,SG02,

scopelimit1,55,44,53,68,

signal,SG03,

scopelimit1,89,100,64,77,

signal,SG04,

scopelimit1,41,93,47,35,

project,,,,,1,

part,Part 1,,4,,4,

modenames,1F,1T,2F,Unk,

ftol,50,100,200,0

freq1,500,1000,2000,3000,

signal,SG01,

scopelimit1,30,40,50,60,

signal,SG02,

scopelimit1,55,44,53,68,

signal,SG03,

scopelimit1,89,100,64,77,

signal,SG04,

scopelimit1,41,93,47,35,

project,,,,,1,

part,Part 1,,5,4,1,N,0,

modenames,Time,1F,1T,2F,Unk,

param1, 600, 600, 600, 600, 600,

freq1 , 0, 300, 800, 1500, 2000,

param2, 1200, 1200, 1200, 1200, 1200,

freq2 , 0, 400, 900, 1700, 2200,

param3, 6000, 6000, 6000, 6000, 6000,

freq3 , 0, 500, 950, 1900, 2400,

param4, 9000, 9000, 9000, 9000, 9000,

freq4 , 0, 600, 1100, 2000, 2500,

signal,SG01,

scopelimit1,90,60,40,50,60,

scopelimit2,80,55,35,45,60,

scopelimit3,70,50,30,40,60,

scopelimit4,60,45,25,35,60,

project,,,,,1,

part,Part 1,,5,4,1,N,0,

modenames,Time,1F,1T,2F,Unk,

param1, 600, 600, 600, 600, 600,

param2, 1200, 1200, 1200, 1200, 1200,

param3, 6000, 6000, 6000, 6000, 6000,

param4, 9000, 9000, 9000, 9000, 9000,

freq1 , 0, 300, 800, 1500, 2000,

freq2 , 0, 400, 900, 1700, 2200,

freq3 , 0, 500, 950, 1900, 2400,

freq4 , 0, 600, 1100, 2000, 2500,

signal,SG01,

scopelimit1,90,60,40,50,60,

scopelimit2,80,55,35,45,60,

scopelimit3,70,50,30,40,60,

scopelimit4,60,45,25,35,60,