Twenty-two-year-old hydraulic power unit replaced to enhance efficiency and reliability

04 July, 2024

The original hydraulic panel with the oil reservoir sunken into a pit in the floor under the unit in the right of the photo.

Pressure Hydraulic & Controls was asked to quote on replacing an existing 22-year-old hydraulic power unit for a refractory plant. The hydraulics run a dual-purpose system, one is to operate a special pendulum cylinder that controls the crushing force of raw Magnesium Oxide that is being ground down on a conveyor system into a usable powder and the other is to lubricate the cylinder due to the large amounts of heat generated by the manufacturing process.

Several other companies had declined to quote due to the nature of the environment and general lack of information on both the existing hydraulics and the electrical controls that were in place. A photocopy of the original hand typed system overview sheet and a photocopy of a barely legible circuit were provided by the customer as the only source of information, but they had no electrical schematics available but knew they did not have any PLC controls in place. The customer’s one major requirement that was repeatedly mentioned was that the new HPU had to be ’Plug & Play’ to keep downtime to an absolute minimum when the new unit was installed.

One of Pressure Hydraulic & Controls’ field engineers went to site to carry out an initial assessment and get an overview of what might be involved. While onsite the engineer gathered as much information about the fitted components, but due to the age of much of the equipment, many part numbers either were not visible or were now obsolete making the customers ‘Plug & Play’ request even more of a challenge. While onsite it was discovered that the filter elements had been removed from the main pressure filters ‘as they keep getting blocked and slowing production down’, so they were removed. What information could be gathered was passed to the company’s sales team for review for them to put a costing together to be able to quote the customer. With a large degree of guesswork, the customer was quoted, and an order received from them at which point the project was passed to the design team.

Pressure Hydraulic & Controls’ Group Design Manager then went to visit the site and get a better understanding of the project, meet the customer, get their full wish list from them, and conduct a more detailed site survey. While carrying out the survey, the customer mentioned they would also like to future proof the system and may want to add full automated PLC control in the future so any of the sensors must not only be backwards compatible, they must also be able to work with any new PLC if it was ever implemented and they also wanted additional sensors to monitor the water usage for the cooling loop and oil temperature before and after the cooler, adding to the ‘Plug & Play’ challenge that was quickly becoming a nightmare. The customer also showed him where they wanted the unit that meant the company had limited space to make the new HPU fit into, especially height to add to the mounting challenges.

Due to the nature of the product the factory manufactures, he decided that to protect the new HPU as much as possible, an enclosed cabinet would be required and that if the cabinet was positively pressurised then it would help keep the product dust getting in the system and another major concern was the amount of product literally everywhere in the plant so he decided that to get the clean air the cabinet needed both for pressurisation and for the general HPU function that outside ducting would also be required.

The design started to develop and after many hours of research, reading old datasheets scoured from all over the internet and the back of a lever arch file and then cross referencing the functionality between old parts and possible new alternatives, a new hydraulic circuit was drawn up using Pressure Hydraulic & Controls’ HyDraw CAD software along with a parts list that would meet the customers’ requirements including the various fan controls and sensors to keep the cabinet pressurised @ 15pa (which is around the same level as a hospital operating theatre). Now that the company had a circuit to work from, the CAD work could start using its full Solidworks Premium design package. Some of the challenges of the design included making everything fit inside the restricted size of the cabinet and still be accessible for servicing and having any sensors visible without having to open the cabinet door to stop the product residue getting in. Pressure Hydraulic & Controls’ designer took the approach very similar to an industrial freezer utilising a door seal and handles commonly used in that sector to keep the unit pressurised and even added bonded seals and acorn nuts to every external fixing through the outside of the cabinet to ensure it stays sealed and the only way for air to get in or out is through the fans.

Once a complete set of drawings were produced along with various 3D renders of what the unit would look like they were presented to the customer for their approval along with the new hydraulic circuit. Once the drawings were approved, manufacturing and parts ordering began and despite various delays on parts and a sensor screen damaged in transit from the USA, the new HPU was built in the company’s Liverpool facility and successfully completed factory acceptance testing mid-May 2024 and is currently being prepared to ship to site for installation

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