By Mark Rosenzweig
How much of your shopping for the holidays have you done? If you haven't starting stockpiling gifts yet, have you at least begun deciding what you need to buy? I can't imagine many engineers among the last-minute shoppers crowding the aisles at Target, Best Buy, Toys "R"Us, etc. After all, we have a hopefully deserved reputation for being disciplined and methodical.
I already have several gifts surreptitiously stored around the house. Some stem from not-so-subtle hints or even "I've bought this for you to give to me."
Anyway, a DVD player ranks high on the list of gifts still to be bought. But that poses a problem. Space for new units is tight in our entertainment center. So, I'm leaning towards buying a combination unit -- a component that includes a DVD player and a VHS videocassette recorder. Such a unit takes little if any additional space compared to our aging VHS unit. Plus, it eliminates the need to string cables between a DVD player and a VCR.
However, the very advantages that make a combined unit attractive also pose potential disadvantages or at least tradeoffs. For instance, a company that makes an excellent-performing and reliable DVD player may not offer a comparable quality VCR in a combination unit. Or the DVD player may include all the features that you want, while the VCR may lack some desirable ones, or vice versa.
Even if you can find a unit you like, can you tolerate losing the use of both the DVD player and VCR, if either requires repair? In addition, while fewer external cables are needed for connecting the unit to others, this simplification may pose some sacrifice in flexibility that may be useful as you further update your system.
"Packaged" units long have been an option for process plants. As Dan Hebert points out in the article "Avoid Assembly Hassles" (Chemical Processing, November 2003) such skid-mounted systems can offer a host of advantages. The units may allow plants to employ proprietary technology not available otherwise. Because they are built offsite, usually under a factory roof, skid-mount systems can boost the safety, efficiency and quality of construction, while avoiding interfering with ongoing plant operations. Doing testing right at the factory rather than at the plant site also may be easier and speedier. In addition, the units often require only simple piping, electrical and other hookups and enable faster startups. Factor in their compact size and the single-source responsibility for their performance, and it's clear that skid mounts have a lot in their favor.
However, they also pose some tradeoffs. Vendors of the units caution about the need for more and better upfront planning than for comparable on-site construction. In addition, skid-mount builders generally rely on specific suppliers for, say, control systems, and using the plant's preferred vendor instead may pose economic or technical problems.
So, careful analysis is crucial to make sure they will be a welcome package at your plant.
Mark Rosenzweig is editor in chief of Chemical Processing magazine. E-mail him at firstname.lastname@example.org.