Conditioning
Chamber air is recirculated by a balanced, high volume, stainless steel blower discharging through a guard and diffuser baffle to create a uniform environment around your test object and grips. The blower is driven by a vertically mounted motor with dual ball bearing races connected by an extended stainless steel shaft. Sheath type heaters behind a radiation baffle raise chamber temperature as required.
Cooling, LN2
For operation to -73 C (-100 F) either liquid nitrogen or liquid carbon dioxide (CO2) cooling is provided. For cryogenic operation down to -184 C (-300 F) liquid nitrogen cooling is provided. We normally recommend the selection of Liquid Nitrogen due to its higher reliability for all temperature ranges.
Liquid nitrogen systems include dual liquid solenoids, one for proportional control and one to act as an interlock to prevent run away in the event of a solenoid failure. A liquid line strainer and a relief valve are also included.
Cooling, Mechanical
When relatively frequent cold tests down to -73 C (-100 F) are required, mechanical cooling using a Bemco cascade, dual compressor, mechanical refrigeration system is recommended. Mechanically cooled systems typically require a "Counterbalanced Stand."
For mechanically cooled systems, a proportionally controlled cascade, two compressor, refrigeration system utilizing modern environmentally friendly refrigerants cools the workspace. The system includes automatic hot gas bypass and suction cooling unloading as well as Bemco’s exclusive, high performance coaxial cascade heat exchanger.
All systems have thermal and current sensors on the compressor, charging valves, and a sight glass as well as numerous safety and reliability protection systems for dependable operation.
Construction
FTU
chambers include 300 Series stainless steel welded liners with
high temperature fiberglass (316 C, 600 F) units) or ceramic wool (638
C, 1000 F units) insulation. No asbestos is used in chamber construction.
Outer cases are fabricated from cold rolled steel finished in Bemco Blue.
Chamber doors feature Bemco’s high aspect ratio plug to minimize problems with expansion and contraction. The door is sealed by a Bemco over-center cam type latch. 638 C (1000 F) chambers are furnished with double articulating hinged doors and dual latches so that the door can be opened with the face away from the operator. Double articulating doors, a space saving feature, can also be specified as an option on other models.
Strain Rod Sleeves
Stainless steel sleeves centered on the top and bottom of the chamber workspace for passage of strain rod sleeves to internal upper and lower jaws or grips are standard. A dual size insert is provided for each sleeve with an internal pilot hole that can be opened up to a maximum standard diameter of 3-1/2 inches.
To prevent damage to the chamber in the event of over travel of the Universal Test Machine, a breakaway plug is installed in the chamber floor. The plug is provided with gaskets and a stainless steel thermal breaker strip. Standard sizes are 6 inches x 6 inches and 8 inches x 8 inches. Larger sizes are available.
Slotted break away plugs are also optionally available. Slotted plugs allow removal of the chamber from the Universal Test Machine without first removing the machine grips and strain rods. The slots and the slot plugs extend through the door face plug. The slot plug piece remains with the Universal Test Machine. Additional slot plug pieces can be specified to allow a single FTU's use on more than one machine. Standard slot plug widths are 6 inches and 8 inches.
Electrical Wiring
All electrical wiring meets the United States National Electric Code. UL and CSA approved components are used where possible.
Controls
Each Bemco FTU chamber is furnished with a microprocessor based, programmable 1/4-DIN, solid state 256-step ramping controller which includes a 4-line LCD interface display and a large red LED display.
Controls are mounted in a separate control console connected with a 10 foot control cable to maintain thermal isolation. Temperature inside the chamber is sensed by a precision thermocouple. An RS232 and RS485 interface is standard. Heaters are interlocked with a separate heavy duty power contactor and a factory preset high temperature safety control.
Thermal Performance
Standard heating and cooling time on -73 to 316 C chambers from 23 C to -73 C and from 23 C to + 316 C (-100 to +600 F) is 30 minutes. Standard time for -184 to +638 C (-300 to +1000 F) chambers is 60 minutes. These times are with expendable refrigerant systems.
Standard time from 23 C to -73 C with mechanical cooling is 55 minutes.
Optional Equipment
- Window and interior light. Window sizes are 6 ” x 15 ” and 12” x 12” clear viewing area. This option is available on systems with ranges up to 316 C (600 F). 6" x 15" windows are available for +538 C models (1000 F).
- Hand ports in the door with sealing plugs and glove rings.
- Slotted, removable, upper strain rod sleeve grip port and slotted, removable, lower strain rod grip port and break away plug. See discussion above.
- Oversize, upper and lower strain rod sleeves.
- Upper and lower strain rod boots to seal the strain rods and isolate the chamber interior environment. This option is recommended when low humidity or a gas purge is to be maintained around the test specimen.
- Double articulating door, standard with +538 C models (1000 F).
- Door cutoff switch.
- GN2 gas purge with pressure regulator, gauge, flow measuring and regulating valved rotameter, and vent.
- Desiccant drier purge with dual tower 10 cfm desiccant drier, pressure regulator, gauge, flow measuring and regulating valved rotameter and vent.
- Mechanical cooling to -73 C. See description above.
Optional Instruments
- Microprocessor-based, FM Approved high over-temperature safety control.
- Set of two, one high and one low microprocessor-based, FM Approved temperature safety controls.
- Remote control over an Ethernet Link.
- 12 inch, chart printing, circular recorder.
- Strip chart recorder.
Available Literature Includes:
Bemco FTU Series, Universal Test Machine Temperature Chambers. Document
is triple fold front and back, 2 pages, 373 KB download.
Bemco Temperature Conversion Table. Temperature conversion chart
for -273.15 C (absolute 0) to +548.89 C (1020 F) in 10 degree increments.
Document is 1 page, 336 KB download.
The systems described above are our Standard Models. We make custom equipment to your specifications. If you have any questions, need assistance in preparing a specification, or have a technical problem you want help with, we are ready. Our quotations and advice are free.
