The KKS identification system is the way power stations name every system, item of equipment and component unambiguously, using the Kraftwerk-Kennzeichensystem (KKS) of the German association vgbe energy, known until 2022 as VGB PowerTech. A KKS code of up to 17 letters and digits states, in a fixed order, which unit, system, equipment unit and component you are dealing with. Because mechanical, electrical, instrumentation and civil engineers all use the same code, one pump can be found on the P&ID, in the control system, on its label in the field and in the maintenance system.
What the KKS identification system is and where you will find it
KKS was developed in the 1970s by the association of German power station operators and has been used worldwide to identify power plants since the middle of that decade. The current guideline and key part is the eighth edition of 2018 (VGB-S-811-01), supplemented by application explanations in VGB-B 106. The system is meant for every type of power station, from coal and gas to hydro. You will also come across KKS codes in waste-to-energy plants; the function key even has its own code for grate firing. On its page about its identification systems, vgbe gives an overview of the documents, the licences and the successor RDS-PP.
The guidelines rest on a few principles you can see in every code:
- one way of coding for all types of power station and the processes connected to them;
- enough capacity to code every system and component, including for new technologies;
- one code for all disciplines, with separate codes for function, point of installation and location;
- language independence, so that a code means the same thing in every country.
What KKS does not cover matters just as much. The guidelines say nothing about how to make labels, how to combine KKS with another coding scheme or how to abbreviate descriptions. Those belong in your own coding manual.
The three types of KKS code
KKS has three types of code, which can be used together or separately. A prefix symbol shows which type you are looking at.
| Type of code | Prefix | What it identifies | Examples |
|---|---|---|---|
| Process-related | = | Systems and equipment by their function in the process | Pump, valve, measurement, motor |
| Point of installation | + | Where electrical and C&I components sit in cabinets and panels | Fuse or terminal block in a cabinet |
| Location | + | Structures, floors, rooms and fire areas | Boiler house, floor, room |
The prefix may be left out if the code is unambiguous without it. In a point of installation code, a full stop always separates levels 1 and 2. For maintenance, the process-related code matters most: it appears on the P&ID, on the work order and on the label next to the pump. The rest of this article is about that code.
How a KKS code is built: four levels
A process-related KKS code has four levels, each pointing to a smaller part of the plant from left to right. Every character has a fixed position. Letters classify, digits count.
| Level | Name | Characters | Format |
|---|---|---|---|
| 0 | Total plant | G | 1 letter or digit |
| 1 | System code | F0 F1 F2 F3 FN | (digit) + 3 letters + 2 digits |
| 2 | Equipment unit | A1 A2 AN A3 | 2 letters + 3 digits (+ letter) |
| 3 | Component | B1 B2 BN | 2 characters + 2 digits |
Level 0: the total plant
The first character (G) identifies the unit, usually the unit number of the power station. Some coding manuals use 0 for plant shared by all units.
Level 1: the system code
The three letters F1, F2 and F3 come from the KKS function key. The first letter is the main group, and the next two refine it step by step. The two digits that follow (FN) number systems or system sections, usually in the direction of flow; some plants count in tens (10, 20, 30) to leave room for extensions. An optional leading digit (F0) distinguishes identical systems, such as two identical water-steam cycles.
| Letter | Main group | Example from the function key |
|---|---|---|
| B | Power transmission and auxiliary power supply | BAT generator transformer |
| E | Fuel supply and residues disposal | ET ash and slag removal |
| H | Conventional heat generation | HHC grate firing |
| L | Steam, water and gas cycles | LAC feedwater pump system |
| M | Main machine sets | MAA high-pressure turbine |
| P | Cooling water systems | PAC main cooling water pump system |
| U | Structures | UHA boiler house |
Other main groups include A (grid and distribution), C (instrumentation and control), G (water supply and disposal) and W (renewable energy plants). Not every letter is in use: vgbe keeps some in reserve.
Level 2: the equipment unit
Two letters from the equipment unit key say what kind of unit it is, and three digits (AN) count identical units within the system. The first letter is the group: A for mechanical equipment such as pumps, fans and valves, B for apparatus such as tanks and piping, C for direct measuring circuits, D for closed-loop control circuits and G for electrical equipment. Examples are AA (valve including actuator), AN (compressor or fan unit), AP (pump unit), BB (tank or vessel), CP (pressure measurement) and CT (temperature measurement). An optional extra letter (A3) adds a further distinction, for instance between two drives on one conveyor.
So in KKS, measurements are equipment units too. Where a drawing to ISA-5.1 shows a TT, a KKS plant might call the temperature measurement CT002, with the sensor and the thermowell as components below it. For valves the number often carries meaning as well: the key part and many coding manuals reserve number ranges for particular kinds of valve, drains for example. Which ranges apply is set out in your plant's manual.
Level 3: the component
The last level splits an equipment unit into individual parts. Two digits (BN) count the components; the characters B1 and B2 in front of them come from the component key:
- a dash plus a letter for electrical components, such as -M for an electric motor;
- K for mechanical components in the process, such as KA for a valve and KP for a pump;
- M for auxiliary mechanical components, such as MK for a coupling;
- Q for non-electrical C&I components, such as QT for a thermowell;
- X, Y and Z for signals.
How deep you code is set by the coding manual: one client requires every part down to level 3, another uses level 3 only where the distinction is needed.
A KKS code taken apart: the feedwater pump
The diagram below takes the code 1 LAC10 AP001 KP01 apart.
- 1 is unit 1 of the power station.
- LAC10 is the system. L stands for the steam, water and gas cycle, LA for the feedwater system and LAC for the feedwater pump system. The number 10 identifies that system; if the plant counts in tens, a second pump system might be LAC20.
- AP001 is the equipment unit: AP is a pump unit, meaning the pump with its drive and accessories as a whole, and 001 is the first one in this system.
- KP01 is the component: the pump itself.
Within the same pump unit, the electric motor is 1 LAC10 AP001 -M01 and the coupling 1 LAC10 AP001 MK01. Pump, motor and coupling each get their own code and their own maintenance history, yet remain recognisable as one pump unit. If the station has two identical water-steam cycles, the leading digit F0 goes in front of the system code: 1 1LAC10 AP001 KP01 in the first cycle and 1 2LAC10 AP001 KP01 in the second.
Notation and common pitfalls with KKS codes
- Spaces between levels. KKS puts a space between the levels so the code cannot be misread. On drawings and in control systems you will often see the same code run together. That makes little difference to a technician, but a great deal to searching and matching. Agree on one format and make sure your systems recognise both. How recognising codes on drawings works is shown under technical document management.
- No I or O. The VGB guidelines exclude the letters I and O. If you find an I or an O in a code, it is almost always a 1 or a 0 that was mistyped or misread by text recognition.
- Changing numbers afterwards. Once the numbering is fixed, leave it alone. Every change affects drawings, labels, the control system and the history at the same time.
- A variant for every contractor. Many clients have a coding manual with their own conventions, such as always filling in F0 (0LAC10). That is fine as long as it is written down. It becomes a problem when every contractor brings its own interpretation.
- Drawing and register drifting apart. After a change, the new code appears on the P&ID but not in the maintenance system, or the other way round. Always update them together.
KKS and RDS-PP: the successor
RDS-PP (Reference Designation System for Power Plants) is the system vgbe regards as the further development of KKS. It is built on the international IEC 81346 series for reference designations. Power supply systems have their own part, ISO 81346-10, which became a full International Standard in 2022, replacing the 2015 technical specification. RDS-PP is object-oriented, with separate aspects for function (=), product (-) and location (+), and was also developed with newer technologies such as wind and solar power in mind. According to vgbe, about 90 per cent of the letters in the KKS function key carried over into the RDS-PP system key, so anyone who knows KKS will recognise much of it.
Even so, many existing power stations stay with KKS. Switching means recoding drawings, labels, the control system and the maintenance system, while KKS itself is still maintained: the eighth edition dates from 2018 and vgbe still issues amendment sheets. For an existing plant, the benefit of switching often does not outweigh the cost and the risk of errors. For a major extension or a new wind or solar farm, RDS-PP is a realistic option.
Applying KKS in your own plant
When you code an existing plant or an extension, this order helps:
- Write the coding manual. Which edition of the guideline you follow, which local conventions apply, which notation, how deep you code and what labels look like.
- Start on the P&IDs. Mark the systems and their boundaries on each drawing and give them a system code. An up-to-date P&ID is the foundation.
- Code equipment units and components down to the agreed level, following the direction of flow.
- Check in the field and label. In its guidance on safe isolation (HSG253), the UK's Health and Safety Executive advises a scheme that uniquely identifies all process plant, piping and valves, with the same references on the P&IDs and permanent labels on key items. KKS is exactly that kind of scheme.
- Enter the codes as positions in the asset register, with the physical item and its serial number underneath. How to set that up is covered in setting up an asset register, and you can see how positions and assets come together in a tree structure under asset management software. If you are introducing a new maintenance system, that is a good moment to clean up the codes in the register and align them with drawings and labels.
- Link drawings and documents to the codes, so that an asset leads you to the right drawing. There is more on this in technical document control.
- Secure ongoing control. One administrator issues new codes, every change updates drawing, label and register together, and contractors receive the manual before they start work.
KKS tells you which object it is. What went wrong with that object is recorded with failure codes; together they make failures comparable per object.
Frequently asked questions
Can you use KKS outside power stations?
Yes, the principles are more widely applicable. Waste-to-energy plants have a boiler and a water-steam cycle like a power station, and KKS codes turn up there too. Derived systems have been developed for other sectors, such as aluminium smelters. For a factory without a boiler, the international IEC 81346 series is often the more natural choice, because it was not written for a single sector.
What is the difference between a KKS code and an ISA-5.1 instrument tag?
An ISA tag such as LIC-101 names an instrument function within a measurement or control loop. A KKS code names every object in the plant in a fixed hierarchy, from unit and system down to component. In KKS a measurement is an equipment unit, CT for a temperature measurement for example, with the sensor and the thermowell as components. That is why the P&IDs of power stations that use KKS show KKS codes where a chemical plant would use ISA tags.
How long is a KKS code?
Up to 17 letters and digits. The example code 1 LAC10 AP001 KP01 has 15, not counting the spaces. With a leading digit for identical systems and an extra letter at level 2, you reach 17. Not every code is complete: for a system as a whole you stop after level 1, and for a pump unit after level 2.
Which documents do you need to apply KKS?
The basis is the KKS guideline and key part, VGB-S-811-01 (eighth edition, 2018), available in German and English. It contains the rules and the keys for systems, equipment units and components. The application explanations in VGB-B 106 show how to apply the rules discipline by discipline, and there is a separate part for hydro power plants. If you are just starting out, vgbe's free KKS pocketbook gives a good overview.