When a control panel component is discontinued, the best replacement is usually a current model that the plant already uses elsewhere, ordered together with the other parts that are about to become obsolete. In a series of quotations for ammonia stripping plants at landfills in East Asia, the same pattern repeated: a level probe, drives, a touch-screen display, a network switch and thermocouples, all superseded, all replaced in one batch.
The challenge: parts that outlive their manufacturers’ support
Ammonia stripping plants for landfill leachate run for decades. Their panels were built with the best equipment available at the time. Eventually the maker withdraws the model, and a failed part cannot be replaced like for like. Ordering after a failure is the worst time to find out.
The approach: group the obsolete parts and choose proven replacements
One order for one panel
A quotation for one stripping plant gathered a number of superseded items into a single supply:
- A level probe and pre-amplifier for the steam generator, both superseded by newer models.
- Five variable speed drives, from 11 kW to 30 kW, including two of the 18.5 kW size.
- A 10.4 inch touch-screen operator display, replacing an earlier model.
- An industrial Ethernet switch.
- Four N-type thermocouples with a 150 mm sheath.
Delivery was three to four weeks. The supplier also flagged one knock-on change: the level controller in the panel would have to change its input from a voltage to a milliamp signal. A drop-in replacement is rare. There is usually a configuration change to find.
Choose what the plant already runs
Other quotations show the principle. When a differential pressure transmitter on an air flow orifice plate was discontinued, with no direct replacement available, the supplier offered a model already used elsewhere on all the stripping plants at that site. It is proven there and it means the site holds fewer different spares.
The same happened with a steam generator water feed valve and a level transmitter. The valve had been superseded by a newer model from the same maker. The level transmitter could no longer be sourced from its original manufacturer, so a transmitter from an alternative manufacturer already used on the supplier’s leachate treatment plants was proposed.
Drives need the right rating
The drives in these quotations were matched to the motor size, from 11 kW up to 75 kW for a large blower. One 75 kW drive for a blower came with a thermistor card, so that the motor’s temperature sensor can trip the drive. The rating and any extra card should be checked against the existing motor.
Why it works
Grouping avoids repeated procurement, repeated freight and repeated shutdowns. Choosing a model the plant already uses means one type of spare serves several lines. It also means the maintenance team has seen it before.
What to consider for your own project
- Audit the panel for obsolete parts before they fail. Ask the supplier which are discontinued.
- Look for knock-on changes, such as signal types, mounting, communications and software.
- Prefer common spares. Fewer different models make a smaller spares holding.
- Replace related parts together, for example a pre-amplifier with its controller.
- Allow time for configuration and testing after the new part arrives.
For the level control part of this story, see our post on replacing an obsolete steam generator level control. The Environment Agency’s landfill operator guidance is the starting point for UK permit duties.
FAQ
What does obsolescence mean for a control panel?
It means the manufacturer has stopped making or supporting a part, so spares become scarce.
Can I replace a discontinued transmitter with a different make?
Often yes, if it matches the range, output signal and process connection. Choosing a make already used on site reduces risk.
What is an HMI?
A human-machine interface, the touch-screen display operators use to see and control the plant.
Why replace several parts at once?
It saves repeated orders, freight and shutdowns.
Audit your panel
Send us the make and model of the panel components and we will check which are obsolete.