Servo hydraulic test facility – Gaydon Test Centre

Savery Hydraulics was appointed to design and commission the electronically controlled hydraulic ring main system at Rover Group’s servo hydraulic test facility. The solution needed to maintain supply pressure within high tolerances, while operating with maximum economy. 

Prior to the design and commission Savery worked with the Rover group to conduct a failure mode effect and critical analysis of the system, to minimise any potential problems which could have occurred during the design and commissioning phases. 

The pumping system was divided into 2 identical sections, each feeding into the ring main. In the event of major component failure such as a fluid reservoir the system remained operational. The ring main had strategically positioned isolation valves, which allowed sections to be taken out of service and the fluid diverted. System interlocks prevented pressurisation of return lines in isolated sections. 

The fluid was routed around the facility in a 4” nominal bore pressure and return main. This fed isolation and depressurisation manifolds in each of the four test cells, seven in the general purpose test area and one in the small rigs and safety test area. 

Five seal drain power packs were positioned around the facility to collect fluid from drain lines and pump the filtered fluid back into the return main. 

The mains were supplied with the total maximum mean flow requirement of 2.280 l/min at 210bar from a purpose built pump house containing the two independent power systems. The systems were cross connected with isolating valves. Each was subdivided into multiple modules allowing routine servicing to be carried out without affecting system availability. Each power system comprised:

• A 7000 litre fluid reservoir with temperature and level sensors, level gauges and breathers etc.
• A 15kW off line conditioning module passing 430 l/min through a plate heat exchanger and a micron filter.
• Three 90kW electric motor driven A4V variable displacement pumping modules each with parallel controller and swash position indicator, a micron filter and manifold relief and proportional unloading valves.
• Three 90kW fixed displacement pumping modules with control manifolds identical to the variable units.
• A transfer barrier accumulator bank to supply the fluid needed for pump swash operation.
• An isolation manifold to automatically isolate each power system from the ring main and depressurise the accumulators and pipe work.
• A 600kW capacity coo

The control system monitored and controlled the ring main system, minimising the need for human intervention, this comprised of:

• A motor control centre with a PLC section mounted near the hydraulic pump house.
• A PC workstation and control desk approx 70m from the PLC with communication via a serial link. 
• Manifold distribution/isolation control panels mounted near the hydraulic isolation manifolds.

The control system supplied the test cells using minimum power it did this by measuring the flow into the ring main and by deducing and running or loading the required number of pumps. At the same time, full pressure was maintained in the ring main. The life expectancy of the main pump modules was greatly extended as only the minimum number of pumps were run to meet the flow. The system took into account any pumps that were unavailable due to maintenance and if necessary limited the number of test cells in use. It was able to anticipate high instantaneous flows up to 1200 l/min and put the requisite number of pumps on standby.  

Fault tracing was carried out at the PC using mimic screens of the hydraulic circuits of all system modules. A master status screen showed the current status of all test cells, ring main isolating valves etc, as well as numerical values for crucial flows, pressures, temperatures etc, at key points in the system. The system normally ran in automatic mode but could be switched to manual allowing the user to click switches on the screen with a mouse.