CMMS

What is a CMMS?

A CMMS (Computerized Maintenance Management System) is software that lets an organisation plan, execute, record and analyse all maintenance work on its plant, machines and buildings digitally, with the aim of increasing the reliability, availability and service life of those installations at the lowest possible cost. In essence it is a database of maintenance activity: which assets exist, what maintenance they need, what was done, by whom, with which parts and at what cost. A CMMS is indispensable in production and infrastructure environments where planned and corrective maintenance determine continuity, from a factory floor to the pumping stations of a water authority.

🧠 What does a CMMS do?

A CMMS supports the entire maintenance cycle, from notification to analysis:

• Asset register and hierarchy - records installations down to component level (location, functional location, serial number, supplier, documentation)
• Creating and assigning work orders - for preventive and corrective maintenance, including scheduling, required skills and work permits
• Logging and following up on faults - notifications with cause codes, which makes root cause analysis possible
• Preventive maintenance plans - tasks triggered by calendar interval, running hours, meter readings or measured condition, including inspections and calibrations
• Managing spare parts - bills of materials per asset, minimum stock levels and links to inventory management and purchasing
• Maintaining maintenance history - a complete record per asset, which also serves as evidence for regulators and auditors
• Measuring KPIs - such as Mean Time To Repair (MTTR), Mean Time Between Failures (MTBF) and availability

A CMMS does not decide how you maintain your plant; it executes the strategy you choose and supplies the data to refine that strategy.

🔄 Which types of maintenance does a CMMS manage?

The European standard EN 13306 (current edition 2017) defines the maintenance terminology that most CMMS packages follow. Broadly, you distinguish preventive maintenance (before a failure) from corrective maintenance (after a failure).

In EN 13306 terms, predictive maintenance is a form of condition-based maintenance: the difference lies in forecasting when the limit will be reached. Which type you choose per asset depends on its criticality. Methods such as FMEA and reliability-centred maintenance determine that; the CMMS captures the outcome in maintenance plans.

🧱 What is the difference between CMMS, EAM and ERP?

The terms are often used interchangeably, but their scope differs:

EAM historically grew out of the CMMS. Where an organisation implements asset management according to ISO 55000, the CMMS or EAM system supplies the data on failures, costs and condition that underpins asset management plans. ISO 55001 itself does not prescribe a maintenance method or software.

🏭 How does a CMMS fit into the OT architecture?

In the ISA-95 model, maintenance operations management sits at level 3, alongside MES and the historian; ISA-95 Part 3 (IEC 62264-3) describes a separate activity model for it. In practice the CMMS usually runs in the IT domain or as a cloud application, while the data on failures and running hours comes from the OT environment. Typical integrations:

• SCADA or MES - pass on fault notifications, alarms and running hours so that the CMMS updates notifications or meter readings
• PLCs and field equipment - supply counters and diagnostics, usually not directly but via SCADA, a historian or an edge device using standard protocols such as OPC UA or MQTT
• Asset and inventory systems - synchronise installation data; an OT asset inventory with firmware versions complements the CMMS asset register
• ERP - for purchasing parts, cost accounting and labour hours; in SAP, maintenance is the Plant Maintenance (PM) module

Because the CMMS sits at a higher level of the Purdue Model, data flowing out of the OT zone should pass through a controlled intermediate zone (IDMZ), preferably in one direction only: OT delivers data, and the CMMS never sends anything directly back to a controller.

🔧 How do you implement a CMMS step by step?

A CMMS implementation rarely fails on the software and often on data and discipline. A proven sequence:

1. Build the asset hierarchy - site, installation, system, component. Align it with the ISA-95 equipment hierarchy or, in oil and gas, the ISO 14224 taxonomy.
2. Determine criticality - rank assets by consequences for safety, environment, production and cost; only critical assets get extensive preventive plans.
3. Define maintenance plans - tasks, intervals, required skills, parts and safety measures per asset class.
4. Link parts and bills of materials - which spare parts belong to which asset, with minimum stock levels.
5. Set up the notification and work order process - who reports, who assesses, who schedules, who closes; with mandatory cause and action codes.
6. Enable mobile working - technicians record work directly on a tablet or phone, for example by scanning barcodes or QR codes on the equipment.
7. Integrate with OT and ERP - only once the core process runs reliably.
8. Manage by KPIs - review monthly and adjust the plans.

Common target values in maintenance practice are rules of thumb, not requirements of a standard:

The European standard EN 15341 (2019 edition) defines a standardised set of maintenance KPIs so that you can compare results across sites and companies. In manufacturing, these figures are often linked to OEE and TPM.

📊 How does a CMMS handle a fault at a pumping station?

A practical example at a Dutch water authority:

• The SCADA system detects that a pump at a pumping station has tripped and raises an alarm.
• Through an integration, the CMMS automatically creates a notification against the right asset; a planner or the on-call team assesses it and converts it into a work order. This prevents every flickering alarm from becoming a work order.
• The on-call engineer receives the work order in a mobile app, together with the asset history, drawings and recent failures.
• After the repair, they record the work performed, cause code, hours spent and parts used.
• The CMMS updates stock levels, MTTR and failure frequency; repeated failures trigger a root cause analysis and possibly a revised preventive plan.

🔐 Which cybersecurity risks come with a CMMS?

A CMMS holds sensitive information: an overview of critical installations, firmware versions, drawings and sometimes credentials or remote access for suppliers. For organisations subject to NIS2 and the Dutch Cybersecurity Act (Cyberbeveiligingswet), the CMMS therefore falls within the duty of care. Points of attention:

• Segmentation - keep the CMMS outside the OT zones and route integrations through an IDMZ (network segmentation)
• Access - MFA for administrators and external users, with role-based permissions
• Suppliers - a SaaS CMMS requires agreements on hosting, backups and incident reporting
• Data quality - an inaccurate asset register also undermines patch management and incident response

🧾 Which CMMS systems are commonly used?

❓ Frequently asked questions

What does CMMS stand for?

CMMS stands for Computerized Maintenance Management System. A CMMS is software you use to plan, execute, record and analyse maintenance on plant and equipment. It is sometimes also called maintenance management software.

What is the difference between a CMMS and an EAM system?

A CMMS focuses on executing maintenance: work orders, preventive plans, faults and spare parts. An EAM system includes those CMMS functions and also manages the entire asset lifecycle, including investments, contracts and replacement across multiple sites.

Can a CMMS communicate directly with a PLC?

Technically a CMMS can retrieve counters or faults via protocols such as OPC UA or MQTT, but a direct connection from the CMMS to a PLC is unwise from a security perspective. The usual approach is for SCADA, a historian or an edge device to collect the data and deliver it to the CMMS through an IDMZ.

Which KPIs can you get from a CMMS?

A CMMS provides, among others, MTTR, MTBF, availability, PM compliance, planned work share, backlog and maintenance cost per asset. The European standard EN 15341 describes a standardised set of maintenance KPIs that makes those figures comparable.

Do you need a CMMS for ISO 55001?

ISO 55001 does not require any specific software, but it does require demonstrable information about assets, risks and performance. In practice a CMMS or EAM system is the main source of that maintenance and failure data.

Does a CMMS fall under NIS2?

A CMMS is not regulated as a product under NIS2 or the Dutch Cybersecurity Act, but an essential or important entity must secure all network and information systems that support its services. Because a CMMS contains asset data, maintenance schedules and often supplier access, it belongs within that organisation’s risk assessment and duty of care.

📌 In summary

A CMMS records which assets exist, what maintenance they need and what actually happened. Integrated with SCADA, MES and ERP, it connects the OT reality of failures and running hours with the IT world of planning, purchasing and cost. Success depends on a sound asset hierarchy, disciplined recording and secure integrations.

A CMMS is the digital heart of maintenance management: it improves the reliability of assets, reduces unplanned downtime and gives maintenance teams the data to move from reactive to planned and predictive maintenance.