Work Order Coding


Related article – “Database management principles

One advantage of a maintenance computer over a paper-based work management system is its ability to filter and sort work orders in many different ways. If the necessary data is correctly entered, it should be simple to extract a list of priority work, or work that can be done when a part of the plant is shut down, or the work that is required to address safety issues, etc, or any combination of these.

However, many computer system implementation projects do not fully consider the way in which each field in the database should be populated to ensure consistent and relevant reporting. Often the “out of the box” system will have work order fields named “Type” or “Class” which invite the entry of mixed data, resulting in low value (sometimes useless) reporting.

An example is the following actual example of a list of 15 “Work Order Type” codes, a mandatory field from which only one option could be selected.


Capital Warranty Process mod.
Corrective Modification Preventive
Contractor Machine/tooling Spares
Emergency Maint. project Safety
Environment Production support Standing WO


Consider selecting the correct code from this list for a work order for the emergency capital replacement, by a contractor, of an unsafe machine tool. Would the correct selection be “Capital”, “Contractor”, “Emergency”, “Machine/Tooling” or “Safety”? Each of these options is valid.

It is obvious that such a list would lead to very inconsistent selections and would make any resulting reporting of little value. For example, many “safety” jobs would be missed because they had been given one of the other codes that applied to the work.

Field “Characteristics” and “mutually exclusive” value lists.

Consider the simple example of the characteristics of a set of wooden blocks of different shapes and colours. An unstructured list of block “types” may include “blue”, “square”, “round”, “red” and “triangular”. Obviously, for a red, square block either “red” or “square” could be selected. It is this mixture of characteristics that creates the problem in the work order “type” list example above.

Good database principles dictate that each field should apply to one characteristic only. In the wooden block example, there should be one field for the characteristic “Shape” and another field for the characteristic “Colour”, and these fields should be named “Shape” and “Colour”, not “Type” or “Class”. The “Colour” field would contain the options “Red”, “Blue”, etc and the “Shape” field would contain the options “Round”, “Square”, “Triangular”, etc.

The correct assignment of fields to each work order characteristic, and the correct selection of options or “values” for each of these fields enables consistent and high-value reporting.

Well-structured value lists will also satisfy the principle of “mutually exclusive” value selections, which is:

From any work order field value list, a knowledgeable person will always be able select one, and only one value that applies to any particular work order.

The list of work order options in the example on the previous page would have to be separated into different fields for the characteristics “Urgency”, “Source of funds”, “Equipment type”, “Reason”, etc to satisfy this principle, as illustrated below.


Value Characteristic (Field name)   Value Characteristic (Field name)
Capital Source of funds Maint. project Resource
Corrective Action to take Production support Resource
Contractor Resource Process mod

Action to take OR

Reason for work*

Emergency Urgency Preventive Reason for work
Environment Reason for work Spares

Source of funds OR

Action to take*

Warranty Source of funds Safety Reason for work
Modification Action to take Standing WO

Source of funds OR

Equip type*

Machine/tooling Equipment type
* These, and perhaps other fields, require very careful definition because the intent may cover a range of possible characteristics.


For accurate reporting, the meaning of each “value” for each field must be carefully defined. For example, in a work order field for the “Action to be taken” characteristic, if the list includes both “Service” and “Lubrication”, the value “service” must be defined to exclude lubrication service.

In many cases the “process effects” should also be defined. “Process effects” are the way in which the system will manipulate the information to provide the required output. For example, for the “Urgency” field, if “Emergency” is the selected value, the process effect may be that the system will assign a work order number immediately, will allow the purchase of materials for this work order without approval and will include the work on an “Emergency work order” report to responsible managers.

The work order fields and value lists on the following pages are just one possible structure for work order coding, and must always be adapted to suit the plant or operation to which they are applied. Many maintenance systems lack the functionality to achieve the “one field per characteristic” and “mutual exclusivity” goals and some compromises may have to be made, however, if the tables are carefully designed good reporting will still be possible.


Work Order Characteristics and Value Lists


WO – Urgency

Work order characteristic described by this field: The values assigned define the priority or urgency of the work, normally based on the probability of a breakdown (or accident or environmental incident, etc) in a defined time period and its consequences.
Abbrev Value Definition Process effect
E Emergency Work which must be started immediately (any time of the day or night), usually because of a breakdown. The approval process is by-passed. A filtered report of all “emergency” work orders should be sent daily to maintenance supervisors, superintendents and the maintenance manager.
U Urgent Work which need not start immediately, but which is identified after the schedule cut-off time and is important enough to break in to the current schedule. Any non-shutdown work which is required within one week is usually in this category
Urgent work plus emergency work is sometimes called “break-in” work.
“Urgent” work should be challenged. The number of “urgent” jobs and the hours worked against them are important KPI’s and should be reported weekly and reviewed at the weekly scheduling meeting, with action plans generated to reduce urgent work.
# Priority rating The priority number is could be calculated using a tool such as a priority matrix. More practically, it will be based on the time frame in which the work should be executed, usually a subjective assessment by knowledgeable and responsible people. Priority ratings should be in a field by which the backlog can be easily sorted (see “Setting Priorities“).
Comments: Do not use the “emergency” or “urgent” codes unless there is a business process, with clear responsibilities, to follow-up and take action to reduce emergencies and urgent work orders. Do not use the “emergency” code if better control information can be obtained from the production loss tracking system.


WO – Timing

Work order characteristic described by this field: The values are assigned to different limitations which are placed on the timing of the execution of the work.
Abbrev Value Definition Process effect
R “Run” or “Non Shutdown” Any work which can be performed with the plant operating. It includes work on individual items of equipment which can be shut down for maintenance without affecting plant operation  









Used for filtering and sorting work order lists and reports


A “Area shutdown” Work which requires one area of the plant to be shut down for maintenance access
M “Major shutdown” or “Shutdown” Work which requires two or more parallel processing operations to be shut down for maintenance access OR requires one process line to be shut down for an extended time, such as an annual outage. It excludes a total plant outage (see “T” below).
P “Shut preparation” Work required to prepare for any shutdown
T “Total outage” Work which requires the entire plant shut down for maintenance access
U “Must run” Work which can only be done while the equipment is running, e.g. vibration analysis
D Deadline Has a completion date which must be met to comply with regulatory requirements or because of a scheduled event for which it is necessary. NOTE – there are few such maintenance jobs. An “event” does not include a scheduled shutdown, for which the values A, M or T should be used.
Comments: – The restrictions on scheduling work have nothing to do with its priority or importance.

– There may be other possible options. For example, where parts of an operation are not required to produce certain products, or where maintenance opportunities are created by product changes, there may be a “value” to describe this scheduling restriction.

Another possible value may be “must be at full load”, e.g. for infrared inspection of electrical systems


WO – Reason

Work order characteristic described by this field: The values assigned describe the reason for the work to be done
Abbrev Value Definition Process effect
CA Capacity Work which will increase the operating rate of any process equipment  










Used for filtering and sorting work order lists and reports

CO Community relations Any work which has the purpose of improving community relations (e.g. landscaping, noise reduction, etc)
CR Customer or investor relations Work required to build favorable relationships with customers or investors
EN Environment Work required to remain in compliance with environmental regulations
ER Employee relations Work intended to improve working conditions
LE Legal requirement Work that is required to remain in compliance with all regulations, except environmental
OP Operations Work that is required to maintain the plant in good operating condition. Most maintenance will be covered by this value
QU Quality Work required to improve or maintain product quality
RI Reliability Work intended to improve plant reliability
SA Safety Work intended to maintain or improve employee safety
Comments: 1. More than one reason code may apply, e.g. some work to comply with environmental regulations may also improve safety. Clear directions on the selection of just one value should be documented (e.g. “select the value that describes the primary purpose of the work”).
2. Each value must be clearly defined to avoid confusion, e.g. a “safety” work order may be defined as “Work which is intended to reduce accidents where no practical alternative exists or the work which results from a formal accident investigation”
3. Use this field with caution. It is not uncommon for plants to record several values for work “reason” and to never use this information to create value.



WO – Action

Work order characteristic described by this field: The values assigned define the type of action that a craftsperson will take when executing the work described on the work order.
Abbrev Value Definition Process effect
IN Inspection All work required to assess the condition of the equipment. Includes vibration analysis, non-destructive testing, look-listen-touch-smell inspections, etc  








Used for filtering and sorting work order lists and reports

SE Service All preventive maintenance work that will extend the life of the equipment, such as lubrication, cleaning, adjusting, balancing, aligning, calibrating, winterizing, cycling or other care of standby or stored equipment, etc. This also includes “documented service” (e.g. hours-based servicing of mobile equipment) which may include a combination of inspection, lubrication, topping-up, cleaning and other activities.
RE Repair All work that is required to correct a found defect or failure
RB Rebuild Work required to return a complete item of equipment or a repairable component to “as-new” condition
IM Improvement Physical changes to equipment to improve operating capacity or performance, reliability, safety or environmental performance
NM Non-maintenance Meetings, administrative and other activities which do not involve the performance of maintenance work
Comments: 1. This is a short list. IF IT IS OF VALUE these lists can be expanded, with each item in italics in the above definitions as a separate value. Each value must be clearly defined, as in the examples below. Note that exceptions must be described.

2. Note that “documented service” may duplicate some of the other listed activities. If that is the case, the definition of the other activities should specifically exclude all activities covered under documented servicing.
3. The amount of “improvement” work is important to some operations. Some work orders may cover a combination of “improvement” and “repair”, e.g. replacing part of a corroded and leaking galvanized iron pipe with a stainless steel pipe. If of value, a separate field to record the “% improvement” may be of use or the procedure could be to select “repair” or “improvement” based on which component of the work has the higher cost. Improvements to process and other equipment may also be subject to control through a “management of change” procedure, which is outside the scope of this article.


Example of items in an expanded value list
VA Vibration analysis All work required to gather and analyze vibration levels of rotating equipment
TH Thermography Infra-red inspection of equipment
NT Non-destructive testing (NDT) All work to assess the condition of equipment using non-destructive testing machines or techniques such as ultrasonics, dye-penetrants and eddy-current testing, but excluding vibration analysis and thermography
IN Inspections All work required to assess the condition of equipment, except vibration analysis, thermography and NDT



WO – Funding

Work order characteristic described by this field: The values assigned identify the general account category to which the cost of the work will be charged
Abbrev Value Definition Process effect
R Routine expense Used for general maintenance work. Usually set as a default in the work order system
M Major maintenance This may be required if the plant has special budget provisions or uses a more sophisticated project management process for maintenance work over a certain dollar value. Requires the ability to over-ride the work order account code, often using a project number
C Capital For capital projects and capital purchases Requires the ability to over-ride the work order account code, often using a project number
W Warranty All work covered by a warranty The maintenance computer system should have the functionality to track warranties and to “flag” equipment with current warranties whenever a new work order against that equipment is opened
I Inventory Work which is charged to the Storeroom inventory account The maintenance computer system must have the functionality to comply with the plant’s accounting procedures
D Disposal The cost of expensing items removed from Storeroom inventory for disposal or sale This should be separate from the Maintenance budget, in order to encourage Maintenance to properly dispose of surplus and obsolete stock



WO – How Initiated (“ID by”)

Work order characteristic described by this field: The values assigned record the person, skill or position that identified the need for the work and initiated the request for work
Abbrev Value Definition Process effect
B Business Initiated by management as a business improvement opportunity  










Used for filtering and sorting work order lists and reports

E Engineering Initiated in a capital plan or other improvement program
H Hours Generated by the computer because of the operating hours since the last inspection (e.g. for mobile equipment)
I Investigation Initiated at a formal investigation (accident investigation, root cause problem analysis investigation, etc)
L Lubrication inspection Initiated by lubrication mechanics
M Maintenance inspection Initiated as the result of a formal, scheduled maintenance inspection excluding vibration and NDT
N NDT Initiated as the result of any non-destructive test, excluding vibration analysis
O Operations inspection Initiated as the result of a formal, scheduled operator inspection
S Shift log book Initiated by shift mechanics and recorded in a shift log book (or a computer log)
T Time Generated by the computer because of the elapsed time since the last inspection was completed or initiated (Includes most PM inspections)
U Unscheduled observation Breakdown, or initiated by anyone, by any means not included elsewhere in this list of options.
V Vibration analysis Initiated by the vibration technicians
W Work order Initiated as the result of other maintenance work
A Other Use for non-maintenance work
Comment: This field may be important during the implementation of a reliability or vibration analysis program to assess the value of the spending on components of the inspection process. Because the same failure may be identified by different inspectors, reports using this data should include, and be sorted by, the work request date so that the first “inspector” to detect the failure is identified.


WO – Status

Work order characteristic described by this field: The values are assigned to each work order as it progress through the planning, scheduling and execution process
Abbrev Value Definition Process effect
WR Work requested Not yet reviewed by operating and maintenance supervision The work order number should be assigned automatically when the request is entered in the maintenance computer system (NB – Some systems use a different number for work requests and work orders. In others, the work request is simply an un-approved work order.)
WA Waiting approval The work  request has  been reviewed by operating and maintenance supervision, has been given a preliminary scope and estimate by the planner and has been sent for approval Automatic approval routing based on equipment number (which identifies the cost centre and the approval route) and the estimated cost
BL In the backlog Approved in principle and in the backlog awaiting planning
PL In planning Detailed planning is in progress or some commitment for materials has been made The change to this status can be automatic as soon as the first purchase requisition against the work order is approved
WL Waiting for re-approval Detailed planning has identified that the cost will exceed the amount initially approved This should be automatic, based on the allowed variance
WM Waiting for materials There is some outstanding material required for the work See RS
RS Ready to schedule All materials are on site and all maintenance equipment is available The change to this status should be automatic, as soon as the last direct purchase item is received and the quantity on hand for required stock materials covers the work order requirements
SC Scheduled The work order has been added to a formal schedule The change to this status should be automatic, if scheduling is performed in the maintenance computer system
IP In progress Some labor has been charged to the work order The change to this status should be automatic
CO Physically complete No further material or labor costs will be incurred The tradesperson or his supervisor should have authority to use this code when their section of the work is complete


CA Cancelled The originator should be advised
CL Closed A formal work order closing process should be established. It is recommended that the use of this code be limited to planners. The originator should be advised
RJ Rejected The originator should be advised
Comment:  – The values for and use of this field is often dictated by the functionality of the maintenance computer system, and the above list is just one possibility

– The number of values for describing the status should be minimized, especially if the maintenance computer system lacks the functionality for the automatic updates suggested above. Manual updating of many values is time consuming and may be of little value.


WO – Resources

Work order characteristic described by this field(s): The title of the labor and other resources required to complete the work are defined.
Comment: – There may be two fields required to define the labor resources to be used to complete a work order. The lists below are typical examples, and these must be adapted to suit each plant.

– Of course, the quantity (effort-hours) required for each resource must be entered in the appropriate fields during planning.

Skill or trade Crew
Mechanic (or millwright) Utilities area mechanical crew
Electrician Utilities area operating crew
Instrument technician Process area #1 electrical/instrument crew
Welder Process area #1 operators
   ….other trades….     …etc….
Gas tester
Vendor’s representative
Safety watch



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© Veleda Services Ltd

Don Armstrong, P. Eng, President