Castlet Holdings Limited

What Castlet Holdings Limited does

Castlet Holdings Limited, trading as Castlet Ltd, is a UK-based engineering company headquartered in Lincoln, England, founded in 1974 and operating as an Employee Ownership Trust since March 2025. The company designs, manufactures, and services bespoke industrial and defense engineering solutions organized across three divisions: ESP Power and Control (electrostatic precipitator power supplies and controllers, including the proprietary MCS III controller family with a 16-bit 40MHz CPU, dual CAN bus, and fiber optic communications, plus the MIGI Rapper Control Panel for ESP cleaning); High-Power Control and Automation Systems (transformer rectifier units and industrial power distribution); and Aerospace, Marine and Defence Solutions (Mk.8 and Mk.9 military ventilator respirator systems certified to Mil Std 810F and Mil Std 461E for fast jet and rotary wing aircraft such as the F35 Lightning II and Eurofighter Typhoon).

The company's commercial model is built on custom-engineered, quotation-based hardware sales supported by a comprehensive aftermarket services portfolio covering commissioning, optimization, calibration, planned maintenance, emergency callouts, remote/online support, spares and repairs, and environmental chamber testing. Distribution is executed through a direct enterprise sales team alongside a global agent and distributor network spanning 40+ countries across Europe, Asia, Latin America, Africa, Oceania, and the Middle East. Pricing is bespoke with no public list prices; payment terms are 30 days per published conditions of sale, and distribution follows EXW Incoterms 2020.

Castlet serves Tier 1 enterprise customers across power generation (including nuclear), steel manufacturing, cement, glass, waste-to-energy, and military aerospace, with named references including BAE Systems, a Brazilian steel producer, a UK waste-to-energy facility, a UK nuclear power station, and a Turkish coal power station. The company employs a long-tenured engineering team and, as of 2025, operates under employee ownership with Managing Director Tim Eagles, Business Development Director Ian Melton, and EOT Director Andrea Plumpton in the leadership team. Recent strategic actions include a brand refresh and website relaunch, a four-day working week introduction, and ongoing digital marketing partnership with Fantastic Media.

Name

Castlet Holdings Limited

Legal name

Castlet Ltd

Website

https://castletltd.com

Company type

Private

Founded year

1974

Operating status

Operating

Short description

Castlet Ltd is a UK-based, employee-owned engineering company founded in 1974 that designs and manufactures bespoke ESP power and control systems, high-power industrial automation, and military ventilator respirator systems for Tier 1 clients across 40+ countries.

Ownership category

akta.pro rank

Product category

Industrial Air Pollution Control & Power Systems

NAICS

Industrial and Commercial Fan and Blower and Air Purification Equipment Manufacturing (333413), Relay and Industrial Control Manufacturing (335314), Power, Distribution, and Specialty Transformer Manufacturing (335311)

SIC

Industrial & Commercial Fans & Blowers & Air Purifing Equip (3564), Electronic & Other Electrical Equipment (No Computer Equip) (3600), Switchgear & Switchboard Apparatus (3613)

akta.pro primary industry

Air Quality & Filtration Equipment (IAQ) (IMAHAKAI)

akta.pro secondary industries

Industrial Control Cabinets & Power Distribution (Panels, Switchgear for Automation) (IMAHAHAK), Military Aerospace Fuel, Hydraulic & Environmental Control Systems (IMABAMAJ), Plant Electrical Systems Upgrades (Aux Power, MCCs, Cabling, Earthing) (EUAEALAJ)

Keywords

• ESP power control
• Electrostatic precipitator controllers
• High-voltage transformer rectifiers
• Military ventilator respirators
• Industrial control automation

Headquarters

HQ city

Lincoln

HQ country

United Kingdom

HQ region

Europe

Offices1 record

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Personnel, Operations, Technology or R&D, Supply Chain, Infrastructure, Marketing or Sales

Revenue model

1. Hardware Products: Manufacture and sale of ESP power controllers (MCS III family), transformer rectifier units, MIGI rapper control panels, high-voltage power supplies, and aerospace defense equipment (ventilator respirators Mk.8 and Mk.9). Products are bespoke and tailored to customer specifications.
2. Aftermarket Services: Commissioning, optimization, calibration, remote/online services, spares and repairs, planned maintenance, emergency callouts, and environmental chamber testing services. These services support the installed base of equipment globally.
3. Spares and Components: Supply of replacement components including microprocessor cards, HMI modules, cooling fans, surge suppressors, and other spare parts for existing and legacy control systems.

Pricing tiers

Go-to-market motion1 record

Distribution channels3 records

Marketing channels6 records

Core offering

Castlet designs, manufactures, and supports bespoke industrial engineering hardware and electronic systems, with three core lines: (1) ESP Power & Control products including the MCS III automatic voltage controller family, MIGI rapper control panels, and high-voltage transformer rectifiers for electrostatic precipitators used in industrial air pollution management; (2) High-Power Control & Automation Systems providing transformer rectifiers and bespoke industrial automation solutions; and (3) Aerospace, Marine & Defence Solutions comprising Mk.8 and Mk.9 military ventilator respirator systems for fast-jet and rotary-wing aircraft. The hardware is complemented by recurring aftermarket services such as commissioning, planned maintenance, spares & repairs, calibration, optimization, remote support, emergency callouts, and environmental chamber testing.

Product overview

Castlet Holdings Limited offers an integrated portfolio of industrial engineering solutions organized around three core divisions: ESP Power & Control (electrostatic precipitator power supplies and controllers including the MCS III family and MIGI rapper control panels), Power Control & Automation Systems (high-power transformer rectifiers and automation), and Aerospace Marine & Defence Solutions (Mk.8 and Mk.9 ventilator respirator systems for military aircraft). The company provides these products alongside supporting services including commissioning, planned maintenance, spares & repairs, calibration, optimisation, environmental chamber testing, and remote/online support. Castlet operates as an employee-owned company since March 2025, serving clients across 40+ countries in sectors including power generation, steel, cement, nuclear, glass manufacturing, and military aerospace.

Differentiator

Problem solved

Functional benefit

Products and services

• MCS III Controller Family Automatic voltage controller family for electrostatic precipitator power supplies featuring a 16-bit 40MHz Near-RISC CPU, CAN-bus networking, USB and fiber-optic communication ports, and configurable digital I/O; used by industrial plant operators for emissions compliance and ESP optimization.
• MIGI Rapper Control Panel Microprocessor-based control panel for ESP cleaning that programmatically energises rapper devices such as impulse hammers, electric vibrators, and air solenoids, with fault detection, CAN-bus communication, and storage for multiple rapping programmes.
• Mk.9 Ventilator Respirator System Military-grade ventilator respirator system for fast-jet aircraft providing filtration against biological and chemical agents, with intelligent controlled airflow that maintains breathing performance as altitude increases and integration with aircraft oxygen supply systems; qualified to Mil Std 810F environmental testing and Mil Std 461E EMC standards.
• Mk.8 Ventilator Respirator System Military ventilator respirator system for rotary-wing and fast-jet aircraft providing respiratory protection and emergency oxygen delivery during decompression scenarios.
• ESP Power & Control Systems Bespoke engineered power and control solutions for electrostatic precipitators used in air pollution management across power generation, steel, cement, glass, nuclear, and waste-to-energy facilities, encompassing MCS III controllers, MIGI rapper panels, and HV transformer rectifiers.
• Power, Control & Automation Systems High-power industrial automation and control solutions including bespoke transformer rectifier units and control panels for demanding industrial applications outside the ESP core.
• Aerospace, Marine & Defence Solutions Electro-mechanical and electronic design solutions for military aerospace applications, including the Mk.8 and Mk.9 ventilator respirator systems and related safety equipment engineered to military specifications.
• Planned Maintenance Services Preventative maintenance programmes for ESP power and control systems including annual inspections, cleaning, calibration, and component testing to ensure optimal performance and continued emissions compliance.
• Commissioning Services On-site installation and commissioning services for ESP power systems, transformer rectifiers, and control equipment, delivered by Castlet engineers at customer sites worldwide.
• Spares & Repairs Supply of replacement components and repair services for industrial ESP equipment, including controllers, rectifier parts, cooling fans, and surge suppressors for both current and legacy control systems.

Quantifiable outcome

• ≥99.9% collection efficiency achievable with properly maintained ESP systems
• +2 more outcomes

Named customers7 records

Segments3 records

Ideal customer profiles2 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature5 records

Partnerships

One partnership is on record.

• Fantastic MediacoreGTM or Marketing Partner · 1 April 2025Partnership with Leeds-based integrated marketing agency for strategic consultancy, brand refresh, website redesign and rebuild, logo redesign, digital and traditional marketing planning, PR, content creation, email marketing, and decal design for office refurbishment. Ongoing marketing consultancy and media relations support to strengthen operations and online presence.

Scale indicators7 records

Recent moves7 records

Expansion highlights5 records

Broad incumbents

• Siemens: Diversified industrial automation, electrification, and digital industries leader with products spanning power distribution, industrial control, and factory automation — a broad benchmark for Castlet's high-power automation offerings.
• Honeywell: Major aerospace and industrial conglomerate with life-support and environmental control systems for military and commercial aircraft — broad incumbent comparable to Castlet's ventilator respirator defense electronics line.
• Andritz: Austrian industrial group with air pollution control and separation divisions serving power generation, pulp & paper, and metals — comparable to Castlet's ESP and industrial air quality control offerings.
• Schneider Electric: Global specialist in energy management, industrial automation, and power distribution with products overlapping Castlet's transformer/rectifier and industrial control scope — relevant broad incumbent for benchmarking.
• ABB: Global industrial automation and power distribution leader with overlapping capability in HV transformer/rectifier systems, switchgear, and industrial control — relevant broad incumbent peer across Castlet's automation and power distribution scope.
• Babcock & Wilcox: Established US power generation and emissions-control equipment supplier offering ESPs and air quality control systems as part of a broader thermal and environmental portfolio serving power and industrial customers.

Direct peers

• Hamon: Belgian thermal engineering firm with a dedicated air quality systems division that supplies ESPs and related components to power and industrial customers. Directly comparable niche ESP equipment peer.
• FLSmidth: Danish supplier of air pollution control and material handling equipment, including electrostatic precipitators used in cement, minerals, and power generation. Directly comparable to Castlet's ESP power and control business for industrial emissions customers.
• Curtiss-Wright: US defense electronics and industrial systems specialist supplying ruggedized electronics, controls, and life-safety equipment for military aerospace platforms — comparable to Castlet's ventilator respirator and defense electronics business.

Regional players

• Mitsubishi Hitachi Power Systems (MHPS / Mitsubishi Power): Asia-leading power plant systems supplier with air quality and emissions control capabilities serving thermal power and industrial customers in Japan, Asia, and the Middle East — comparable broad peer for ESP/power generation applications outside Castlet's primary UK footprint.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat5 records

Key risks6 records

Key highlights7 records

Customer concentration

• LinkedInlinkedin.com/company/castlet-limited

Revenue estimate

Valuation estimate

Number of profiles

Profiles7 records

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Castlet Holdings Limited