Most printing facilities use vacuum for one process or another. I recently spoke with Jesse Krivolavek, (a vacuum system efficiency specialist with IVS, Inc.) about his recent adventures in the world of printing:
Where do you see the most vacuum efficiency opportunities in printing?
Many of the printers we visit have tremendous vacuum efficiency opportunities. But recently, we have seen a spike in interest and opportunity in vacuum efficiency from the envelope manufacturers.
The two types of envelope manufacturing machines we see the most of are "FL Smithe" and "W+D" machines. In these machines, vacuum is applied to small holes in large metal rollers which hold and convey the envelopes through the machine. The deeper the vacuum, the more holing force is generated. Unfortunately, running too deep unnecessarily wastes energy. Also, in this application there is always a leak. But, it varies depending upon how many and which holes are covered with paper. This is why it is important to isolate machines that are going through a "change out".
Can you be more specific on the type of efficiency opportunities?
Sure. Usually, the primary driver for a vacuum audit at an envelope factory is energy reduction. This is because many utilities and state governments are offering grants and rebates for energy reduction studies, as well as energy reducing projects.
Other reasons we are asked to look at an envelope manufacturer’s vacuum system include; increasing reliability, providing redundancy, increasing production and reducing operating costs.
Energy reductions mean operating cost reductions and we’re all trying to save money right now. What makes our job really fun is when clients discover additional operating cost reductions by reducing consumables like oil, water, and parts. This is usually accomplished by implementing operational changes or technology upgrades.
What type of operational changes?
Sometimes, we see operators cranking the vacuum as deep as possible, usually fearful of operating anywhere less than “their standard”. We’ll see plants with a central vacuum systems operating at 24”Hgv at the furthest machine (26”Hgv at the pumps), when they only needed 18”Hgv (or 20”Hgv at the pumps). The energy consumed to create about 4”Hg-absolute (26”Hgv), when they could be creating 10”Hg-absolute (20”Hgv), is more than twice as much necessary. The potential energy saving can be a big deal.
We’ll also see several machines on a central system that do not having working isolation valves and when one or more machines is going through a “set-up” or “change-over” their cylinders are just open to atmosphere. It can become expensive if it causes cascading slippage on all the surrounding machines.
Decentralization of the vacuum system can help with this issue and also save energy through on-demand vacuum when only select machines are in production. Let’s say it is third-shift and three out of twelve machines are running on a central system that uses throttling to balance the pressure level. The client is only utilizing about 25% of what he’s paying to create.
What types of technology upgrades are being implemented?
In the field we usually see liquid ring pumps, oil-flooded screw pumps, dry vane pumps, rotary lobe blowers, side channel blowers, and claw pumps. They all have different energy efficiency characteristics and operating requirements.
The simplest unit of vacuum supply efficiency is cfm/hp at a given pressure. It’s a lot like your miles per gallon at a specific speed in a car. Depending on your required pressure level, you can easily have a 5:1 difference in or say 5 cfm/hp versus 25 cfm/hp. So upgrading to a more efficiency technology automatically saves you energy and money. It all depends on the payback. Some technology upgrade paybacks where water or oil usage is removed from the equation, and kW reduction rebates are available, bring the “simple payback” conversation from how many years or months, to how many days.
Other upgrades may include VFDs on point-of-use pumps, VFDs for a trimmer pump on a central system, cell-based systems or cabinets that serve two to three machines and can provide two different vacuum levels simultaneously. Even efficient central systems that have an extra pump and use lead-lag are being installed to always have redundancy. Eliminating down-time can be a big cost savings.
Anything else you would like to add for BVBP readers?
Yes, if you’re using vacuum for making envelopes or any printing application, please ask yourself three things: (1) Are we operating deeper than necessary? (2) What’s our cfm/hp at the required pressure level? (3) Is there money available from our utility or state for energy efficiency studies or improvements?