OSV Emergency Generator Specialists
Allen-Bradley MicroLogix Repair
Siemens S7-1200 New Build
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Emergency Generator PLC Control System — Atlantica Duke (ex-Highland Duke / Standard Duke), Aberdeen & Teesside
Between October 2022 and February 2024, Ashmit Engineering supported the same offshore support vessel through three service visits — as the vessel changed names from Highland Duke to Standard Duke to Atlantica Duke across different operational phases. The work spanned two UK ports: A&P Teesside shipyard in Middlesbrough and Aberdeen Harbour.
The vessel presented a sequence of escalating challenges across the engagement: a password-locked Allen-Bradley MicroLogix 1200 PLC that could not be accessed on the first visit, a complete emergency generator control system built from scratch with a new Siemens S7-1200 and KTP700 HMI on the second visit, and a safety relay interlock logic fault corrected in a live MicroLogix session on the third visit at Aberdeen Dock — restoring normal generator operation and completing comprehensive alarm testing.
This ongoing relationship illustrates Ashmit Engineering's continuity of support across a vessel's operational life — spanning emergency generator control, new-build panel commissioning, and live PLC logic fault correction.
Project Overview — Atlantica Duke (ex-Highland Duke / Standard Duke)
- Vessel
- Atlantica Duke (formerly Standard Duke, formerly Highland Duke) — Offshore Support Vessel
- Operator
- Ffolkes Offshore Ltd / Blackwell Automation
- Locations
- A&P Teesside Shipyard (Middlesbrough) · Aberdeen Harbour
- Industry
- Marine / Offshore Support Vessels (OSV)
- Systems
- Allen-Bradley MicroLogix 1200 PLC · Siemens S7-1200 (CPU1212C) · KTP700 HMI · Emergency Generator Control Panel
- Scope
- Locked PLC diagnosis, new Siemens S7-1200 emergency generator control panel design, build and commissioning, MicroLogix safety relay interlock logic fault correction and comprehensive alarm testing
- Dates
- 12 October 2022 (as Highland Duke, Teesside) · 20–23 October 2022 (as Standard Duke, Teesside) · 6–7 February 2024 (as Atlantica Duke, Aberdeen)
Site Photography — A&P Teesside (vessel as Standard Duke)
Siemens KTP700 HMI commissioned at A&P Teesside when the vessel was named Standard Duke — Emergency Generator control screen
The Challenge: One Vessel, Three Names, Three Control System Problems
Offshore support vessels operating in the North Sea face demanding electrical environments. Emergency generators must be available at all times — a failed auto-start or a locked control system can hold a vessel in port, delay a North Sea departure, and generate significant charter penalties.
On the first visit (vessel then named Highland Duke), the emergency generator PLC had become inaccessible — the Allen-Bradley MicroLogix 1200 was password-protected with no password on record. Without the ability to read or modify the program, any future fault in the control logic could not be diagnosed or corrected.
On the second visit (vessel then renamed Standard Duke), the requirement was a complete new emergency generator control panel — designed, wired, programmed, and commissioned to the vessel's operational requirements, with a modern HMI for crew operation and full alarm integration.
On the third visit (vessel now named Atlantica Duke, at Aberdeen Harbour), the symptom was clear but the root cause was embedded in the control logic: the engine was shutting down approximately 15 seconds into Local Mode operation. PLC diagnostics revealed the safety relay output was asserting immediately after start — before the engine could stabilise — triggering the safety shutdown prematurely.
One Vessel · Three Names · Three Service Visits · Two Years
The work below is presented in chronological order. Visit 1 (Highland Duke) and Visit 2 (Standard Duke) were carried out at A&P Teesside in October 2022. Visit 3 (Atlantica Duke) was carried out at Aberdeen Harbour in February 2024.
Technical Work — Step by Step
1
Visit 1 — Vessel as Highland Duke · A&P Teesside · 12 October 2022
Locked Allen-Bradley MicroLogix 1200 — PLC Diagnostic Assessment
On arrival at A&P Teesside, Ashmit Engineering was presented with an Allen-Bradley MicroLogix 1200PLC controlling the vessel's emergency generator. The PLC was password-protected with no password available from the vessel or operator's maintenance records. An RSLogix 500 connection was attempted to assess whether any program data could be recovered, but the hardware lock prevented access. Control power was applied locally to bring the system online for observation. Following assessment, Ashmit Engineering confirmed that the locked PLC represented an unacceptable operational risk — any future fault could not be diagnosed or rectified without replacing the controller. A full PLC and HMI replacement was recommended, scoped, and approved for the vessel's next yard period.
2
Visit 2 — Vessel as Standard Duke · A&P Teesside · 20–23 October 2022
New Siemens S7-1200 Emergency Generator Control Panel — Design, Build & Commissioning
Returning to A&P Teesside with the vessel now named Standard Duke, Ashmit Engineering designed and built a complete new emergency generator control panel installed into the existing enclosure. The hardware specification was: Siemens S7-1200 CPU1212C (6ES7212-1AE40-0XB0), SM1223 digital I/O relay output expansion module, SM1231 analogue input module for sensor integration, and a Siemens KTP700 7" HMI (6AV2123-2GB03-0AX0) touchscreen at operator level. A Mean Well DC-DC converter provided an isolated 24 V DC supply for the control circuit. Ashmit Engineering wrote the complete PLC control software and HMI screens from scratch — covering engine start/stop sequencing, local and remote mode switching, all alarm inputs (Lube Oil Low Pressure, Cooling Water Temperature High, Fuel Leakage, Engine Overspeed), and the auto-start interlock logic. The panel was commissioned with the Chief Engineer and signed off on 27 October 2022.
3
Visit 3 — Vessel as Atlantica Duke · Aberdeen Harbour · 6 February 2024
Allen-Bradley MicroLogix — Safety Relay Interlock Logic Fault Diagnosis
In February 2024, Ashmit Engineering was called to the vessel — now operating as Atlantica Duke — at Aberdeen Harbour. The reported fault was engine shutdown approximately 15 seconds after starting in Local Mode. An RSLogix 500 online session was opened with the Allen-Bradley MicroLogix PLC. Live monitoring of the control logic showed that the safety relay output was being asserted immediately after engine start — before the engine had time to build oil pressure and stabilise — triggering the safety shutdown circuit prematurely. This was a logic fault, not a hardware failure.
4
Visit 3 — Vessel as Atlantica Duke · Aberdeen Harbour · 6–7 February 2024
PLC Logic Correction, Local Mode Verification & Full Alarm Testing
The interlock sequence for the safety relay output was corrected within the MicroLogix program — adjusting the enable logic so that the safety relay output was held off for the appropriate engine warm-up period before monitoring commenced. Following the correction, Local Mode was tested: the engine started, ran through the warm-up window, and entered normal operation without triggering a shutdown. Multiple start cycles were run to confirm consistent behaviour. HMI Start and Stop commands were then verified. Full alarm testing followed — Lube Oil Low Pressure, Cooling Water Temperature High, Fuel Leakage, and Engine Overspeed were all triggered individually and confirmed to initiate the correct engine protection response and alarm annunciation. All results were documented in the service report.
Outcomes
🔒
Locked PLC Risk Mitigated
Password-locked MicroLogix assessed and the operational risk documented. Full replacement recommended and scoped — eliminating the risk of an unrecoverable failure at sea.
⚙️
New Panel Commissioned
Complete Siemens S7-1200 + KTP700 HMI emergency generator control panel built, programmed, and commissioned at A&P Teesside — signed off by the Chief Engineer.
✅
Engine Fault Resolved
Safety relay interlock logic corrected in a live MicroLogix session at Aberdeen. Engine ran normally in Local Mode through multiple consecutive test cycles.
📋
Full Alarm Testing Passed
Lube Oil, Cooling Water, Fuel Leakage, and Overspeed alarms all tested and documented. Service report delivered to vessel management.
Marine Control System Services — Aberdeen and UK Ports
Supporting OSVs, North Sea support vessels, and commercial fleet operators from Aberdeen Harbour and across UK ports — available 24/7 for emergency generator and PLC control system faults.
OSV Generator Fault? Locked PLC? Control System Down?
Ashmit Engineering provides 24/7 emergency control system support for offshore support vessels, North Sea fleet operators, and commercial marine vessels in Aberdeen and across Scotland. We cover Allen-Bradley MicroLogix, Siemens S7, and legacy PLC emergency generator faults.
Frequently Asked Questions — OSV Marine Control Systems, Aberdeen
- Do you carry out emergency generator PLC work on OSVs at Aberdeen?
- Yes. Ashmit Engineering carries out emergency generator control system work on offshore support vessels, anchor handlers, and platform supply vessels operating from Aberdeen Harbour and the Nigg and Peterhead terminals. We can typically mobilise within 48 hours, and same-day for vessels with an imminent North Sea departure.
- Can you recover or bypass a password-locked Allen-Bradley MicroLogix PLC?
- Where a MicroLogix PLC is password-protected and the password is unavailable, we carry out a full diagnostic assessment to determine whether the logic can be recovered. In cases where recovery is not possible, our standard approach is to design and install a replacement control panel with a modern PLC (such as Siemens S7-1200 or Allen-Bradley CompactLogix) and write new control software from scratch, replicating the required generator control and alarm sequences.
- What does a Siemens S7-1200 emergency generator control panel include?
- Our standard build includes a Siemens S7-1200 CPU (typically CPU1212C), SM1223 digital I/O relay expansion, SM1231 analogue input module for temperature and pressure monitoring, KTP700 or KTP900 HMI touchscreen, Mean Well DC-DC converter for isolated supply, and all marshalling, labelling, and documentation required for class society witness testing if required.
- Can you correct PLC logic faults on an Allen-Bradley MicroLogix without replacing the system?
- Yes — where the MicroLogix is accessible and the existing program can be read, Ashmit Engineering can diagnose and correct logic faults including incorrect safety relay interlock sequencing, timer misconfiguration, and incorrect analogue scaling. On the Atlantica Duke at Aberdeen, we corrected a safety relay output logic fault that was causing premature engine shutdown in Local Mode, without replacing the existing PLC hardware.
- Do you carry out alarm testing for marine emergency generators?
- Yes. Full alarm testing is part of our standard commissioning process for emergency generator control systems. This includes Lube Oil Low Pressure, Cooling Water Temperature High, Fuel Leakage, and Engine Overspeed alarms — tested to confirm both the detection input and the control system response. We document all test results in the service report for owner and class society records.
- How quickly can you respond to an OSV control system fault at Aberdeen?
- Aberdeen is within our regular service coverage area. For emergency generator failures or PLC control system faults, we aim to have an engineer on board or on site within 24–48 hours of your first call. For vessels with a North Sea sailing window, call our 24/7 line on +44 20 3129 5414 and state it is an emergency callout — we will prioritise accordingly.
Related Case Studies and Services
Enquire About Marine Control System Support in Aberdeen
Whether your vessel is at Aberdeen Harbour, Peterhead, Nigg, or any Scottish port — contact Ashmit Engineering for emergency generator PLC fault-finding, control system replacement, and alarm testing.