Pump skid panels for a process cooling specialist, from a one-off to a repeat

The requirement

Control panels for the pump skids the customer builds alongside their chillers. The first was a twin-pump skid: two 2.2kW pumps, each on its own inverter, with duty changeover, an emergency stop, and a switch to start an external chiller through a volt-free contact, with the chiller's run and fault shown on the door. The next skids needed a single 2.2kW inverter-driven pump started and stopped by the customer's own controls, with two preset speeds selected by volt-free contacts, hand/off/auto on the door and a temperature display for monitoring only.

The constraints

• Pumps on inverters, with the drives fitted in the panel and set up before delivery, so the skid runs when it is wired.
• A safety-rated emergency stop, with the door showing when it is active.
• Simple volt-free interfaces to the customer's chiller and controls, nothing that needed a BMS.
• Indoor, skid-mounted enclosures: compact, with a fan and thermostat to keep the drives cool.
• For the repeat design, a price that made sense to order again and again.

What we built

The twin-pump panel uses two Invertek drives, a Siemens LOGO! with an expansion module for the duty changeover and chiller enable logic, a Pilz safety relay for the emergency stop, interface relays and a door laid out in plates for power, each inverter and the chiller. For the single-pump design we left the PLC out: the two speeds are preset in the Invertek drive's own parameters, a Schneider safety relay handles the emergency stop and three relays do the rest, in a smaller enclosure. We also offered a cheaper route, a wall-mounted IP66 drive with no panel at all. The customer preferred a traditional panel for this job, and we built the panel.

Delivery

The single-pump drawing was approved within an hour of us sending it, and the first two were built and despatched about three weeks later. The third was ordered as a straight repeat of that drawing number, needed no redesign and went out three weeks from the order, works tested at full supply voltage with no faults.

The outcome

A small, repeatable panel the customer can order by drawing number and fit to each skid as it is built. Approving the drawing, the customer replied: "That's perfect … thanks very much. They can be put into production." Six months later the order was one line: a repeat of the same panel.