Hydraulic passenger lifts are essential for providing accessible and safe transport in South Africa, especially when accommodating wheelchair users or medical‑transport scenarios. Selecting the right control system, whether open‑loop or closed‑loop, can make a substantial difference in comfort, efficiency and compliance. This article explores how these philosophies differ, the implications for system components, and the criteria that specifiers and operators in South Africa should consider.

As vehicle fleets and infrastructure evolve locally, it’s critical to align with South African regulations, standards and best practice rather than simply importing generic global solutions. By focusing on hydraulic passenger lifts through a South African lens, including relevant legislation and standards, we can ensure clarity, relevance and value for local fleet managers, specifiers and engineers.

Basic Principles of Hydraulic Control Loops

Open‑loop and closed‑loop control philosophies underpin how hydraulic passenger lifts are managed. Open‑loop systems deliver hydraulic flow or pressure based on preset values without continuous feedback; closed‑loop control adds sensors and real‑time adjustment so actual actuator behaviour follows the commanded motion more precisely. These differences shape performance, maintenance, energy use and integration.

  • In an open‑loop system the pump supplies fluid to an actuator (such as a lift cylinder) via a directional control valve, the fluid returns to a reservoir, and no real‑time measurement of the actual lift motion is used to adjust the system.
  • In a closed‑loop system sensors measure parameters such as platform displacement, actuator pressure or speed; a control unit compares actual vs commanded motion and dynamically adjusts the pump or proportional valves to correct for deviations.
  • Open‑loop systems are simpler, rely on fixed settings and may suffice for moderate applications; closed‑loop systems are more complex but deliver higher precision, smoother motion and adaptability.
  • Closed‑loop control helps account for changing loads (for example a wheelchair plus occupant), variations in fluid temperature or viscosity and hydraulic friction or wear; open‑loop cannot self‑correct for those variations.

In the South African context, where vehicles may operate under a wide range of load, terrain and environmental conditions, choosing a control philosophy for hydraulic passenger lifts is not simply a matter of cost but also of operational robustness and performance. For example, a lift used frequently in high‑cycle wheelchair transport will benefit from closed‑loop architecture, while a light‑usage platform might function adequately with an open‑loop. Understanding these principles gives you the foundation to evaluate system suitability for your fleet and compliance environment.

System Components and Architecture Differences

Understanding system architecture helps operators and specifiers evaluate which hydraulic control system best suits their requirements.

Open-Loop System Components

  • Fixed or variable displacement pump delivering fluid to the actuator.
  • Directional or flow control valves that set fluid speed and direction.
  • Large hydraulic reservoir to allow fluid cooling and contaminant separation.
  • Minimal sensors or electronic feedback; typically only end-of-travel switches.
  • Simple electrical logic or relay-based control modules.

Closed-Loop System Components

  • Variable displacement pumps or proportional valves capable of dynamically adjusting flow and pressure.
  • Sensors including displacement encoders, pressure transducers, flow meters, and speed sensors.
  • Electronic control unit (ECU or PLC) that continuously monitors sensor inputs and adjusts hydraulic outputs.
  • Smaller reservoir with recirculation loops; charge pump to maintain pressure.
  • Integration capability for vehicle electronics via CAN bus or similar networks.

Closed-loop architecture allows real-time adjustment to load and motion changes. For example, if a wheelchair plus occupant increases platform weight, the system automatically adjusts pump flow and valve openings to maintain a smooth, controlled lift. In open-loop systems, the same scenario could result in slower lifting, jerky motion, or inconsistent platform leveling.

In South Africa, where accessibility is a legal requirement under the National Building Regulations and SANS 10400 Part T (for disabled access), ensuring precise and reliable operation is essential. Fleet operators installing hydraulic passenger lifts need to consider how system architecture affects not just comfort, but regulatory compliance and safety documentation.

Response Accuracy and Passenger Comfort

Comfort and ride quality are key when hydraulic passenger lifts serve vulnerable users or need to provide a premium experience. The right control system directly influences smooth motion, precise platform leveling and minimal jerk, which all contribute to the passenger experience.

  • Closed‑loop systems dramatically improve motion consistency by using feedback to maintain speed and position regardless of load or fluid changes. Case studies in hydraulic lift systems show that closed‑loop control achieved precise positioning and smoother motion compared to open‑loop.
  • Open‑loop systems are more prone to deviations because they cannot monitor actual position or speed and therefore cannot correct overshoot, speed variation or levelling errors.
  • For wheelchair users, consistency of platform entry‑exit height and minimal tilt are critical. Closed‑loop control allows the system to actively correct platform levelling, whereas open‑loop systems may drift.
  • Closed‑loop systems reduce jerks and sudden acceleration changes by dynamically controlling pump and valve flow, leading to improved comfort for passengers and reducing risk of discomfort or safety incidents.

In a South African fleet environment where vehicles may carry mobility‑impaired passengers or operate in uneven terrain or variable conditions, the superior comfort and accuracy of closed‑loop‑controlled hydraulic passenger lifts can provide a competitive advantage. Specifiers should request performance metrics, such as leveling error in millimetres or acceleration profiles, when assessing lifts, and consider how often the lift will be used, under what loads and user‑types.

Regulatory and Safety Implications

In South Africa, regulatory compliance for lifting equipment is a critical factor when installing hydraulic passenger lifts. Ensuring that your systems meet national standards and regulations helps protect passengers, operators and your organisation’s liability. The choice of control architecture plays into how easily you can demonstrate compliance and maintain safe operation.

  • Under the Occupational Health and Safety Act No 85 of 1993 and the associated Driven Machinery Regulations and Lift, Escalator and Passenger Conveyor Regulations, operators must ensure that passenger lifts are installed, maintained and tested by competent persons and comply with the relevant standards.
  • For example, the Lift, Escalator and Passenger Conveyor Regulations require installation and use only after a comprehensive report, and that inspection, testing and examination occur according to incorporated standards.
  • Closed‑loop hydraulic passenger lifts support compliance more readily by offering diagnostic data, fault logging and real‑time monitoring, making fault‑detection, reporting and documented safety performance easier to manage.
  • Open‑loop systems may still comply but require more frequent manual inspection, and they lack the automated feedback and logging capabilities that support modern safety governance and fleet management practices.

For South African fleet operators and specifiers, aligning hydraulic passenger lifts with local regulations means asking about inspection intervals, documentation, competent service providers (per South African national standards such as SANS 10295 for inspection of lifting platforms), and ensuring that the control architecture enables timely fault detection and smooth compliance audits. A closed‑loop system may raise upfront cost but simplifies ongoing compliance burden and enhances safety assurance.

Energy Efficiency and Power Management

Energy efficiency is an increasingly important consideration for vehicle-mounted hydraulic passenger lifts, especially in South African fleets where fuel costs and operational efficiency are key metrics.

Open-loop systems typically operate pumps at a fixed flow rate, often exceeding the actual load requirement. This can lead to:

  • Excessive energy consumption.
  • Heat generation in hydraulic fluid, requiring additional cooling.
  • Faster wear of pump and valve components.

Closed-loop systems dynamically adjust pump output and valve settings based on load and motion feedback. Studies show that closed-loop systems can reduce pump energy usage by up to 25% under variable load conditions, improve platform speed consistency, and minimise heat buildup in the hydraulic circuit.

For high-cycle fleet vehicles, closed-loop hydraulic passenger lifts reduce fuel usage, lower maintenance costs, and extend component life. This is particularly relevant for South African operators managing long routes with frequent passenger entry and exit, where repeated lift operation can significantly impact energy and maintenance budgets.

Choosing the Right Control System

Selecting the optimal control system for hydraulic passenger lifts involves balancing performance, comfort, energy efficiency, maintenance capabilities, and regulatory compliance. Open-loop systems may suffice for moderate-use lifts with lower precision demands, but closed-loop hydraulic passenger lifts deliver superior accuracy, smoothness, and operational reliability.

In the South African context, where legislation, accessibility requirements, and fleet management are critical, closed-loop systems provide clear advantages. They facilitate compliance with the Occupational Health and Safety Act, Lift, Escalator and Passenger Conveyor Regulations, and SANS standards while supporting predictive maintenance, real-time monitoring, and improved passenger experience. At Dhollandia SA, we specialise in both open-loop and closed-loop hydraulic passenger lifts designed for South African conditions. Contact us to ensure your fleet benefits from lifts that are safe, efficient, and comfortable for all passengers.