A Clean Start For Cleanrooms
Optimum Manufacturing Corp. is a very precise machine shop that specializes in complex, critical-tolerance components, CNC jig boring, and parabolic mirror housings. Using the most modern and precise machines, the company manufactures optical housings, mirror blanks, and optics-related prototypes for customers serving a wide range of industries such as aerospace, scientific, medical, communications, and defense.
Last year, the company decided to move some of its manufacturing processes to an existing facility in Charlestown, NH. Their new space was formerly a warehouse, so major renovations were needed to meet Optimum’s needs, which included extremely close space temperature (±0.5°F) and space humidity (±;1% rh) controls, and very clean spaces in order to maintain their manufacturing tolerances.
There were other needs, too: One of the company’s manufacturing processes had extremely sensitive vibration requirements, so that particular machine required installation on an isolated, 39-in., reinforced, concrete slab. The walls and ceilings of the manufacturing room had to be constructed of an insulated metal skin, due to the need for temperature, humidity, and dust control. And, for even more dust control, the space had to be designed to maintain a slight positive pressure relative to the surrounding area.
The requirements for the new facility were obviously extensive, so Optimum asked an expert in this area - Bonhag Associates, PLLC of Lebanon, NH - to provide the MEP and process engineering to turn the old warehouse into two clean process rooms and an open manufacturing space.
Noisy NeighborsOptimum Manufacturing Corp. had been happy in its previous location in Claremont, NH, but a nearby neighbor made it necessary to move. “At our other plant, there was a recycling company located about a quarter mile away. In their process of crushing cars and other items, they’d occasionally hit gasoline or something flammable, and there would be an explosion,” said Brian Murphy, vice president of sales and engineering for Optimum Manufacturing. “Imagine you’re milling a part that requires a 50-millionth flatness tolerance, and the ground shakes. You just scrapped a very expensive part.”
Company president Tim Donovan started looking around and settled on an existing 18,000-sq-ft warehouse, which is located in the pastoral setting of Charlestown, NH. Out in the country, there are no neighbors that could possibly disrupt the company’s new $1.2 million Yasda horizontal precision machining center, which is one of the most accurate machines in the world and the only one of its kind in America.
The Yasda center required its own isolated concrete slab, its own special room, and tight environmental controls. The room housing the Yasda center is an approximately Class 10,000 cleanroom that required precise temperature and humidity controls. The room next door, used for tooling, had similar environmental requirements.
The Charlestown facility was a very basic warehouse, and according to Wayne T. Bonhag, P.E., P.P., LEED AP, principal, and chief engineer for Bonhag Associates, PLLC, virtually no mechanical systems could be used for the new Optimum facility. “All we reused was the electrical service coming in. Everything else was ripped out and we started over. We basically built our own mechanical room in the space to service the two cleanrooms.”
Donovan’s requirements for the new facility included a space temperature of 68° ±0.5° and an rh of 50% ±1%. Murphy noted that expandability and remote monitoring were also key requirements for the new facility.
“We have been approved to add on another 9,000 sq ft to our facility, and we did not want to have to go through another major engineering feat to make that happen,” said Murphy. “Remote monitoring was also critical, because we have to be able to monitor the temperature when no one is around.”
If the machines overheat at night or on weekends, it can cause a tremendous disruption in the manufacturing process. Should the ambient temperature increase to a certain point, the security company is notified, and the general manager is then alerted to the situation.
Machines Need Precise EnvironmentBonhag has designed numerous cleanrooms over the years, so he knew the types of heating, cooling, and humidification systems that Optimum would require. For the cooling system, he specified a 25-ton Trane air cooled chiller with dual scroll compressors, that were configured in a lead-lag arrangement. The two chilled water pumps were outfitted with VSDs for energy efficiency.
The new chiller was placed on a pad outside the building, and piping manifolds and supports run from the building to the chiller pad. Because of its location, the metal building can shed snow onto the chilled water piping and conduit, so a special rack assembly was designed to protect the piping during year-round operation.
The two air handlers, sized at approximately 6,500 and 5,600 cfm, were designed with fully modulating 100% enthalpy economizers. This permits free cooling in the fall, winter, and spring in the process spaces, which can require cooling year-round due to the heat generated by the machinery. VSDs modulate the air handlers in order to optimize energy savings, and high-efficiency, 99.7% filters were installed on both units.
“One of the interesting things we did was to take the ventilation air into the mechanical room,” noted Bonhag. “The mechanical room gets warm, so there’s an option to either take that warm air in the wintertime and move it into the general warehouse, or else we can exhaust it directly out of the mechanical room to the outside.”
Two Nortec variable output electronic humidifiers were installed in the ductwork in order to provide the proper amount of humidification to each room. The water is prefiltered before it reaches the humidifiers in order to keep the particulate level low. Bonhag paid special attention to the ductwork, making sure it was tight, insulated, and sealed before it reached the processing rooms.
“We also had to make sure all the ductwork was tight and sealed coming back out of the rooms to the mechanical room,” said Bonhag. “If you spend all this money to put moisture into the air, you don’t want to lose it when you’re moving the air into another space.”
Two propane-fired Buderus boilers - one primary, one standby - provide hot water for three different heating purposes at the Optimum facility. First, they supply the heating coils in the air handlers, which are in the reheat position in order to maintain proper rh levels. Second, they feed the radiant heating system that was installed in the floors of the Yasda and tooling rooms. Third, they deliver hot water to several unit heaters that are used for space heating purposes elsewhere in the facility.
The radiant floor heating system has five temperature zones, and the floors are programmed to stay at a constant 66°. “With this massive piece of equipment sitting on a slab, you can’t afford to have that floor change temperature,” explained Bonhag. “The tolerance on this equipment is probably .0001 millimeters, so there can’t be any expansion or contraction. In the Yasda room, the floor is totally isolated from the rest of the building. The radiant heating in that slab had to also move independently with the slab, so it has its own zone.”
The radiant heat is sampled in numerous locations throughout the facility to ensure a constant temperature is being maintained. Each of the five manifolds has a three-way valve and a pump, so the amount of water going to the manifold loops can be controlled based on the current requirements.
The radiant heating zones have a minimum of two infloor temperature sensors, and each sensor also has a backup. “Before we poured the concrete slab, we put a spare sensor at every sensor point in the concrete. The spare sensor isn’t being used, but if something goes wrong with the primary sensor, we can just connect to the auxiliary sensor,” said Bonhag. “We were trying to anticipate problems that might occur, so we thought the back-up sensor system was prudent.”
Keeping ControlSince the process spaces at the Optimum facility operate every day, 24 hours a day, 365 days a year, the building systems are always operational. Therefore, it was critical to specify and install a completely integrated BAS that could monitor and control all process systems in order to maximize efficiency and minimize power consumption. In addition, the BAS DDC system can be accessed remotely, including by those at the Bonhag Associates offices.
To that end, Bonhag specified a Johnson Controls Metasys® BAS to monitor and control the approximately 300 points located around the facility. The BAS has all the normal start-stop functions that would be expected, as well as failure alarms on just about every piece of equipment. It also measures outside air temperatures and controls the air handlers by monitoring heating, cooling, and discharge temperatures. The chilled water supply and return, as well as all the chilled and hot water pumps, chiller, and boilers are controlled by and provide feedback to the BAS.
All did not go smoothly initially, as the chiller and the BAS didn’t communicate the way Bonhag would have liked, so he changed the algorithms to compensate. “I kept getting a lock-out situation at 2 a.m., so I looked at all the parameters and realized the chiller was not allowing the DDC system to talk to it. Fortunately, we were able to override the internal system and let the DDC system control what’s going on in that chiller.”
The BAS is also able to change over from chiller operation to outside air for the economizers. “We wanted to optimize the humidification system, so we had to be sure that even though the system may indicate there’s nice, cool dry air available, the economizer would stay off so we wouldn’t have to put more moisture in with the humidifier,” stated Bonhag. “We needed the BAS to look at all those different functions.”
There are very few employees working at the Optimum facility, but several CO2 sensors were installed anyway and are monitored by the BAS. Bonhag said that due to the lack of people, there are very few outside air requirements for the space, but he wanted to make sure adequate outside air is maintained at all times.
The cost for all the mechanical systems totaled about $550,000, and Optimum expects to receive a rebate of $50,000 from the local utility. Bonhag stated he’s very proud of the way the Optimum facility turned out, even though the deadlines were “horrific” and coordinating all the contractors was a bit of a challenge. In the end, though, he added, “It was a lot of fun. It was a fussy job, but that’s what we do best.”
Murphy couldn’t agree more, noting, “When you stop and look at the number of variables that were engineered into maintaining the temperature and relative humidity, it’s pretty amazing. Wayne did a terrific job here, and people are blown away when they come and visit our facility.”