Chemical engineer and industrial engineer by education.

After my undergrad in chemical engineering, I designed large vessels for specialty chemicals, O&G, petrochemicals, fragrance, and then developed bulk powder system for plastic, which ultimately found more success in food industry, specifically baking operations, which led me more and more deeper into the food industry.

For your standardized equipment (I am assuming the company has standardized equipment which has been designed and done, and is not custom built for each customer) you need to bring down the variability in BillofMaterials (BoM). This method won't work for custom designed and built equipment. Once variability in BoM is brought down to a specific level, it will become more profitable to hold inventory of inputs (steel plates, pumps, paddles, bushings, pipes, tubing etc.) rather than having an inventory of standardized equipment. From a small number of basic ingredients you can make multiple different dishes kinda theory, like Taco Bell. For example, instead of having 6 different pump sizes across 10 standardized equipment and each having 5 different sizes, so ultimately 50 standardized equipment, only have 3 different pump sizes. Standardize the pipe diameters and thickness you use, to 3-4 different types. Standardize the stand types for each, so each stand is same, other than it's height or width or length. Similarly, on the control box side, standardize the wire diameters/gauges, ferrule colorings (if applicable), relays, and if possible the PLC computer too. HMI screens are the easiest to standardize. Once you bring down the total variability of individual components low enough, it is easier and cheaper to stock these basic ingredients, and be able to quickly fabricate required dishes.

Nozzles and nozzle paddings. I'm assuming there are not many nozzle types or are there? And if there are, to ease the cleaning procedure, they're clamp type nozzles instead of flange type nozzles? If there is anything high pressure, there will be nozzle paddings. Or if anything's acidic or basic enough, the nozzles will probably be of 304L/316L while other nozzles will be 304/316. The usage of nozzle pipes and others is small enough sometimes that it makes more sense to make everything of the L variant, rather than storing different kinds of nozzle pipes. Obviously, a strong cost estimation is needed.

Welding, rolling, straightening, plate cutting, acid cleaning, buffing, passivation - batching, order pooling and scheduling always has a better more efficient way of doing where savings in changeovers or labor can be achieved. Don't schedule repeating stuff of carbon steel and stainless steel. First do carbon steel all of it, and then go to stainless. Acid cleaning and passivation is horrible to do, so one batch/order should be as large as possible, assuming you do it in-house.

I don't know if these are possible at YOUR place of work, but I'm assuming they should be.