A novel formula to oil mist system design doubling the collectors while strategically reducing air velocity, is clearing the air on machining lines at compressor plants in three different countries. Filter life has increased three-to-four times, reducing annual filter costs by 75% and more. Filter changes can now be made with systems on-line, eliminating up to a shift of machining line downtime and lost production.

Developed by Kirk & Blum, an innovator for nearly 90 years in industrial process ventilation the system design was originally conceived for a machining area addition at an automotive compressor plant, installed in 1995. Seeing the improvements in air quality in the new area, the plant had K&B retrofit similar systems into the oldest of the machining areas during summer vacation shutdown in July, 1996.

Exporting the Design

Pleased with those results, the client decided to export the oil mist design, having Kirk & Blum engineer, fabricate and package systems for installation at its plant in Mexico, and then a new compressor plant in Portugal.

Installation was handled by local contractors on those projects, using comprehensive plans and numbered components provided by K&B. The Palmela Plant required that all systems be engineered for CE mark compliance.

Kirk & Blum's Indianapolis plant handled all four oil mist system projects. Headquartered in Cincinnati, Kirk & Blum specializes in engineering, fabrication, installation and repair of chip, dust and fume control systems, and all types of process ventilation. It has along history of involvement with automotive plants, particularly major projects installed during plant shutdowns, says R.J. "Rick" Blum, K&B president.

Six Kirk & Blum facilities strategically located in the U.S. industrial heartland enable fast response and close coordination on projects. As manufacturing becomes more global, henotes, Kirk & Blum has increasingly been called on by customers to apply its expertise t ointernational projects, as with the oil mist systems here. In the past couple of years, cites Blum, K&B has been involved in projects in Korea, Latin America, Europe and Egypt, as well.

Innovative Systems

Each plant produces aluminum compressor bodies and other compressor parts for automobile air conditioners. The first oil mist project was designed for a new machining area addition at the plant. The system captures coolant mist from five different machining lines inthe new area so that the coolant can be cleaned and reused.

"Each machining line has its own ductwork and collector, so the project actually entailed five separate oil mist systems," says John Witkowski, Kirk & Blum project engineer. The project involved 1500 ft. of ductwork ranging from 6" to 52" in diameter. The five collectors filter out cutting fluid from 4000 CFM of air for the smallest system to 18,000 CFM for the largest.

While the systems for the first oil-mist project were installed sequentially over about five months, a retrofit project the following summer needed to be installed during plant vacation shutdown. Similar in size to the original project with five separate machining lines, the retrofit system had to be installed in just two weeks, while working around other contractors doing other shut-down projects from floor to roof. The job consumed 2750 field man-hours for tear-out of the old systems and installation of the new, but was completed within the two-weekwindow.

First Dual-Collector Systems

The oil mist systems are the first ever built by Kirk & Blum with dual collectors. "Our compressor areas are designed for 24-hour-a-day, 7-day a week machining, so we can't afford to shut down for extended periods," says the client's manufacturing engineer who handled the oil mist projects. "The double-wide, dual collector unit lets one side operate while the other side is off-line."

"Before retrofit of the oldest machining line at the plant", says the engineer, "we were changing filterbags about every three months on some collectors units because they got so saturated. We'd have to shut down the line for about eight hours to pull the bags and filters, clean everything out, then install new bags. With the new system, the dual collectors allow us to keep the line running while we make the change."

The dual collectors also improve filter life and system efficiency. "K&B proposed that media life and performance will be extended if a unit can shut down for a period of time to allow oilto drain out of the filters to self-clean," says the manufacturing engineer, "In fact, we're now averaging 10 months to a year between filter changes."

The system signals when filters need changing. If the pressure drop increases and doesn't recover after the filters drain down, a warning light goes off to signal for a filter change.

Ease of Filter access

The cartridge-type filters are mounted two-deep on racks and can be changed by the operatormerely by reaching arms into the collector unit. By comparison, old collector units had bags mounted four-deep. Personnel had to crawl into the units to remove the rear bags, which were far heavier and dirtier than the cartridges. "It was nasty work," the client stresses.

The cartridges are comparable in cost to the bags about $120 each. "And, sincewe're getting three times the filter life we did before, we're actually realizing a considerablecost savings on filters," the client adds.

The 4" thick cartridge filters are stacked in four stages of progressively finer mesh 90% and 95% respectively for the last two.

Avoiding Power Trap

Unlike most machining systems, where high velocities are needed to capture and air convey chips, K&B found that chip and mist entrainment contributed to the problem. The original ducts in the retrofit project, installed around 1987, were found on tear-out to be 50% or more constricted by chips and sludge in some locations.

K&B carefully reduced transport velocity to eliminate entrainment of chips into the ductwork. As further barrier to entrainment, K&B created large cone-shaped hoods to cover circular machining stations, such as large dial-type machines, in place of individual hoods and ducts for each machine. The hoods are fitted inside with a smaller-diameter disk that intercepts chips,so they drop back to the machining area for capture by chip-collector systems. The coolant mist migrates along the disk to the hood circumference, entering into the gap between disk and cone for up-take into the duct.

The largest hoods 14 ft. diameter with 10 ft. diameter interior disk were mounted by K&B on a steel platform and fitted with rollers, so that they can slide out of the way for maintenance access to the machining area. K&B worked out the arrangement in planning meetings withplant maintenance personnel.

Drain, Not Entrain

In trapping oil, as with chips, K&B found less power worked better. By carefully backing offon duct velocity, oil droplets aren't entrained all the way to the collectors, but fall out along the way and condense on the inner walls of the duct. The ducts are hung with a gradual slope (1" in 40 ft.) toward the collectors. The fluid drips down the duct walls, collects into a thin stream, and flows toward the collector, helped along a bit by the airflow. Before getting to the collector, the stream encounters a drain pipe in the bottom of the duct and is carried directly into a sump.

"The duct design removes a large percentage of the oil droplets before they ever get to the collector, so the collectors aren't doing as much work," says the client's manufacturing engineer. "They're seeing minor stuff, rather than heavy oil loading, for greatly improved filter life."

Solution Fits Needs

"The dual-collector design is a cost-effective solution within the context of the client's large-scale, around-the-clock machining operations," stresses Blum. "the client wanted a system that they could turn on and only have to check once in a while. If anything needs attention, operators get an alarm. The systems represent a strong commitment to air quality, while supporting the objective of continuous, high-volume production."

NO MORE MIST Clear view across five machining lines shows effectiveness of retrofit oil-mist collection system, engineered and installed by Kirk & Blum in machining department at a large air-conditioner compressor plant. The system was installed over a two-week plant vacation shutdown. Pleased with these results, the client has since ordered oil-mist collection systems from Kirk & Blum for compressor plants in both Mexico, and Portugal.

DOUBLE-WIDE, DUAL COLLECTOR eliminates shut-downs for filter change, which previously took up to eight hours. One side of collector operates while the other is off-line, permitting continuous around-the-clock machining. Dual collectors also extend filter life three-to-four times and improve system efficiency by allowing shutdown for a period of time so oil can drain from filters self-clean. Kirk & Blum "tuned" duct velocities so mist is not entrained all the way to collector, but falls out along the way, and condenses into thin stream in bottom of duct. White pipe in photo drains oil stream directly to sump for cleaning and reuse. A large percentage of oil is captured this way, greatly reducing oil loading for extended filter life.

OIL-MIST SYSTEM DESIGN was jointly developed by the client Kirk & Blum's full service design/build Indianapolis facility. On largest machining line (shown), 14 ft. diameter hoods were mounted by K&B on a steel platform fitted with rollers, enabling them to be slid out of the way for maintenance access to the machining area.