DRY ROOMS WHY ARE THEY NEEDED?
Any manufacturer of moisture sensitive or hygroscopic products can often realize substantial productivity increases in an economical way by utilizing a dry room instead of a glove box or inert chamber for production. Lithium battery manufacturers, pharmaceutical diagnostic firms and other firms have all been using dry rooms successfully for many years. The special advantages a dry room, built by Harris Environmental, provides to you include:
HARRIS DRY ROOM DESIGN
Our philosophy is to design dry rooms and systems around your requirements rather than making you accept a pre-packaged system.
The four critical variables from which dry room design begins are:
The control level and the personnel moisture load in the space dictate the requirements for the size of the dehumidification air handling system required to maintain the room at specifications. With careful design, desiccant dehumidification systems capable of delivering air to a minimum of .47 gr/lb. (-76ºF. dewpoint, 10.6 ppmv) can be integrated into the dry room construction thereby allowing room operating levels as low as 1% R.H. to be maintained.
Where floor space is available, a Harris D/H series skid adjacent to the dry room reduces the possibility of moisture infiltration into the conditioning system and eliminates long runs of ductwork. If this design cannot be utilized, dehumidification systems can be skid mounted and located above the dry room inside the main building or a rooftop D/H skid can be constructed.
The room structure and layout are best depicted in the illustration below which shows a typical production dry room with two D/H series systems.
|Use the key below to identify components|
|A||Return air plenum wall & barrier eliminates high moisture areas by sweeping air across the entire room.|
|B||Makeup air duct.|
|C||Reactivation exhaust through building wall or roof. Can provide low grade heat in the winter.|
|D||Redundant D/H system can provide 50% to 100% system backup for production dry rooms.|
|E||Harris custom D/H Series dehumidification system with desiccant wheel and all heating/cooling for dry room. All systems use double wall construction with double wall access for controls and valves. This eliminates leakage at piping connections.|
|F||Water cooled condensing unit piped to remote drycooler. Air cooled remote units and screw compressor systems are also provided.|
|G||All welded aluminum ducting to prevent moisture infiltration or leakage.|
|H||Harris 3" modular wall panels with smooth white aluminum skin on both sides.|
|I||Airlocks for personnel entry/exit and gowning when also a clean room.|
|J||Dry air supply ducts to machine enclosures for provision of ultra-dry air to critical processes.|
“DRYWARE” DDC CONTROL = EASIER SYSTEM MAINTENANCE
The Harris “Dryware” touch-screen control system replaces traditional discrete controls, mechanical interfaces and relay logic, providing the operator with access to all D/H Series functions via a single interactive touch-screen.
Developed by Harris to enable worldwide service access to our dry rooms, the “Dryware” DDC control system can be modified or expanded as additional D/H Series systems are added. The Windows based software can provide a graphical presentation of the D/H Series system to access and track all dry room variables including room temperature, coil temperatures, compressor discharge temperature, and multiple point dewpoints. With a dedicated modem access installed, Harris can provide online consultation, system service and trouble shooting from our headquarters to help reduce maintenance costs and insure that systems always perform at optimal conditions.
DRY ROOM SELECTION PROCEDURE
When the selection procedure on the attached card is completed by the end user we have all the information necessary to provide you with a Harris dry room proposal. Our expertise in this application has enabled us to prefabricate many of the components utilized, thus placing all dry room requests on fast track construction schedules.
THE HARRIS “SINGLE SOURCE QUALITY GUARANTEE”
Working with a multitude of manufacturers and contractors requires hours of internal planning, coordinating subcontractors and equipment expediting for any construction project. When Harris is turnkey contracted for a dry room we coordinate and control the design, manufacture, installation and startup of the room. We place the burden of working with several sources off your shoulders and onto ours and provide you with one important additional benefit – that the room and all mechanical components will meet the specs for temperature and humidity control for one full year after startup. The Harris “single source quality guarantee” – we only offer it because we know we can conquer any dry room challenge you present to us.
A WORD ABOUT HARRIS ENVIRONMENTAL
Harris Environmental Systems has been a turnkey contractor of environmental rooms for over forty years. We originally specialized in working cold rooms, incubators, and blood storage rooms utilized in hospitals and universities for medical research. In the 1960’s, Harris began designing low temperature refrigeration systems and burn-in chambers for the electronic industry. Today we specialize in dry rooms, clean rooms, wide range temperature and humidity cycling rooms, and 0º, 30% R.H. archival storage vaults in addition to our institutional cold rooms and incubators. Our environmental room division is complemented by our refrigeration service division and our highly skilled pipefitters, carpenters, and electricians, who install, test and start up all components to assure a quality installation. Please call or write Harris Environmental Systems with your requirements for a dry room or other environmental room.
Dry room shall utilize prefabricated, metal clad panels for all walls, and roof to allow future room expansion or disassembly for relocation. Room shall be furnished and installed by Harris Environmental Systems, Inc. as a completely self-contained unit, with all essential mechanical conditioning equipment, controls, and plenums/ductwork designed to maintain the dry room at 72ºF, ±2º, 2% R.H. (1.8 gr/lb) or drier, as specified by the end user.
SUBMITTALS AND OPERATION MANUAL
Submittals shall include shop drawings which indicate (1) all room dimensions and construction features, (2) electrical wiring diagram and electrical parts list, (3) mechanical system schematic with refrigeration circuit and a complete vendors’ parts list for all components. The operating and maintenance manual shall indicate sequential operation, startup and shutdown with all pertinent control data and schematics.
At completion of room installation and startup, the room manufacturer shall provide an engineering representative for complete instruction in the operation of the room including controls and all related systems.
The installation and its ability to maintain the specified control level for temperature and humidity will be guaranteed on year from the date of startup and/or customer approval that the room meets specifications.
Wall & Roof Panels
Wall and roof panels shall be constructed of 3” thick rigid boardform isocyanurate urethane or polystyrene with .032” smooth tempered aluminum skins bonded to each side of the foam core with a two part epoxy. The wall and roof aluminum surfaces shall be coated with a baked epoxy paint and covered with a strippable polyethylene film which shall remain adhered to the panel until the room is assembled, to protect against accidental scratches or markings.
Panel Fastening System
Panels will be assembled using linear tempered anodized aluminum extrusions, which pull the panels firmly together to form a tight seal. Fastener extrusions shall provide a sheath-type closure over the full length of all joined sections. All 90º corners and edges of the panels shall be sealed with silicone to prevent air and moisture infiltration along cracks.
Floors shall consist of the existing surface covered with an appropriate conductive, vapor barrier material. Floor covering consisting of conductive tiles to eliminate static electricity shall be installed.
Doors & Airlock
Standard doors shall be built of the same panel construction as the walls and shall have a clear opening of 80” high and 36” wide. A 9” x 30” or 24” x 24” viewing window will be included in each door. The door perimeter and frame shall be made of anodized aluminum with double gasketing on three sides and a wiper gasket seal on the bottom. Oversized doors and double doors will be provided if required. An airlock or room vestibule shall be included to prevent moisture infiltration. The airlock will e built of and will be kept at a positive pressure no less than .02” pressure, to prevent infiltration.
The dry room conditioning system shall consist of the following major components assembled to provide continuous dewpoint and temperature control: (a) Rotary wheel desiccant dehumidifier, (b) air or water cooled condensing unit(s) utilizing Copeland semi-hermetic compressors, (c) cooling coils, (d) centrifugal airfoil fans, (e) filters.
Whenever possible, the conditioning system should be located directly adjacent to the dry room with the exception of any condensers or wet coils, which shall be located outside the room. This concept reduces leakage possibilities from long runs of ductwork, and allows the mechanical room to be used as a plenum. If an adjacent mechanical room is precluded by space requirements, a skidded D/H Series System can be built and located elsewhere without compromising the systems ability for precise temperature and dewpoint control.
A rotary wheel composite desiccant dehumidifier shall be utilized because of its ability to achieve a delivered air condition of .047 gr/lb. of dry air (-76ºF dewpoint) while utilizing less reactivation energy than other desiccant systems. This unit provides continuous dewpoint control without desiccant channeling, attrition or carryover. All units shall be continuously reactivated to provide a reactivation outlet temperature of 120ºF as a minimum. Reactivation energy can be either electric, indirect fired gas. Or steam (50 PSIG minimum)
The condensing unit shall include a semi-hermetic Copeland compressor and shall be air cooled or water cooled. Air cooled condensers shall be located remotely from the skidded D/H System to prevent possible moisture infiltration. All condensing units shall e spring mounted. Each condensing unit shall be equipped with high-low pressure control, vibration eliminating device on the suction and discharge line, fusible plug, liquid line dryer, moisture indicating sight glass, suction line filter, crankcase pressure regulating valve, magnetic contactor of all three phase units, modulating water regulating valve, and all other safety mechanical devices. Capacity control will be achieved by either compressor unloading through a hot gas bypass valve, an EPR valve or through compressor shutdown.
Coils shall be copper tube, aluminum fin design with an aluminum housing. The coils shal have not less than eight fins per inch with a minimum of four rows deep. Air velocity design shall be less than 500 FPM.
Process dry air fans and dehumidifier reactivation fans shall be of the centrifugal airfoil design. Belt driven fans with motors rated below 1800 RPMs should be utilized whenever possible to reduce noise and vibration. (Fractional horsepower motors may be direct drive). All process dry air fans shall be mounted on vibration isolators.
All refrigerant lines shall be ACR-type hard drawn copper tubing, Type L, soldered with silver bearing solder with the exception of the discharge lines, which shall be silver or silfos brazed. All suction lines shall be sized for a velocity of 500 – 750 FPM in horizontal runs and show a slight pitch towards the condensing unit. The same is required in instances where the condensing unit is located below the evaporator and there is no possibility of trapping oil. All vertical runs on this type of suction line shall be sized identically to the horizontal suction lines on all vertical runs. Where the condensing unit is located above the evaporator, vertical rise suction lines shall be sized for a velocity of 1,000 to 1,500 FPM. An all instances proper “P” traps shall be installed in the suction line on vertical runs and shall be spaced not greater than ten feet apart on all tubing risers. All discharge tubing shall be sized at the same velocities with the same “P” trap requirements as indicated for the suction line when the condensing unit is remote. All liquid lines shall be sized for a maximum pressure drop of 2 PSIG. All refrigeration suction lines shall be covered with Armstrong Armaflex insulation or equal. F & M ring type hangers or Unistrut assemblies with appropriate tubing clamps shall be used to support the liquid, suction, and discharge lines individually. Hangers or clamps shall be spaced not greater than 8 ft. on centers. All condensate drains shall be equipped with 7/8” O.D. Type L copper tubing lines or larger.
Humidity Control and Recording
Room operating humidity shall be sensed using an aluminum oxide current inducing sensor or comparable industrial control sensor. The output of this sensor will then be recorded with a 10” dual pen temperature and humidity recorder mounted in each control panel as an integral component. Chilled mirror type dewpoint sensors with digital readout can also be utilized as an option. Control panels will always be equipped with audible and visual high humidity alarms, which can be set to bring on any backup dehumidification equipment provided if the room goes into high humidity alarm. The alarm shall be automatic and resetting so that once the room humidity is lowered to the desired level, the instrument is able to respond accurately in the future.
Harris “Dryware” DDC controls for full system monitoring can be provided as an option.
Room temperature control shall be accomplished using refrigeration and/or reheat. A PID controller shall modulate final cooling or heating based on actual conditions versus setpoint. Room temperature will be recorded on the dual pen recorder and automatic resetting high/low temperature alarms will be provided.
The air circulation and air distribution system shall be uniform throughout the room utilizing a tee-grid plenum ceiling with metal perforated air distribution ceiling tiles and fire-rated fissured filler tiles. Air shall return to the conditioning system through grills in the walls or by installing a 3” standoff wall along one surface. The ceiling plenum also houses lighting troffers and required ducting. Clearance below the flush ceiling plenum shall be unobstructed within the working area.
Interior troffer-type fluorescent lighting shall be included to provide 70-footcandles evenly distributed throughout the room. The fixture shall include a door mounted acrylic lens. Incandescent or high intensity discharge lighting can also be provided if required.
Electrical supply for room power, lighting, condensing units and dehumidifiers will be brought into the control panel by the electrical contractor.
Water for any water-cooled condensing units will be provided by the end user. A drain for the water discharge and the coil condensate pan will be provided within 5 ft. by the end user or general contractor.
Harris Environmental Systems, Inc. • 11 Connector Road • Andover, MA 01810
|tel: (978) 470-8600 • fax: (978) 475-7903|