We’re more than happy to answer any questions that you might have about our test tunnels. Here are some responses to the most commonly asked questions. If you can’t find what you’re looking for, please don’t hesitate to get in contact with us.
Can addressable detectors be tested?
In addition to 6 interfaces for conventional detectors, the tunnel control electronics all include 6 opto-isolator inputs. These can be connected to repeat LED outputs in the base of addressable detectors, which will indicate to the tunnel system when the detectors go into alarm. This will freeze the aerosol/heat reading for each detector as a measure of sensitivity.
Are the tunnels easy to use?
For general use the tunnels are very easy to use. A client engineer can create a custom menu of test profiles, specific to a product range. After the required test profile is selected the test is carried out following the press of one button. The test cycles are fully automatic, and include: checking of tunnel sensors/system, ramping of aerosol or temperature, monitoring of detectors, logging of results, and clearing/cooling of the tunnel. The test can be stopped at any time if required, and the tunnel will then clear or cool to revert to the correct starting point.
What do the tunnels test?
The AW Technology test tunnels measure the sensitivity of smoke and/or heat fire detectors (depending on version selected). In the case of smoke detectors the tunnel will gradually increase the concentration of a paraffin aerosol until the detectors indicate an alarm state. The concentration at alarm is recorded on the PC screen, and in the results log file. In EN standards this concentration is called the 'response threshold value'. For heat detectors the principle is the same, but the temperature of the tunnel is gradually increased at a controlled rate until the detectors indicate an alarm state. The time to alarm and the temperature is recorded.
How is the aerosol concentration measured?
When testing optical detectors an obscuration meter measures the reduction in intensity of a beam of infra-red light, which is caused by scatter and absorption by the paraffin aerosol. The concentration is described in units 'dB/m'. It is calculated, using the equation in EN54-7, from the beam path length (d), and the ratio between the received power of the beam in clean air (Po) and in aerosol (P):
m = 10/d * log (Po/P) dB/m
If ionisation detectors are to be tested an interface to an MIC reference, as defined in EN54-7, can be supplied with the tunnel. The MIC references are available from Delta (www.madebydelta.com) as model number EC-912.
How are the tunnels calibrated?
The obscuration meters used when testing optical detectors are effectively self calibrating for two reasons: the clean air reading is automatically measured before each test starts, and the aerosol concentration is described by the ratio between clean air and in aerosol readings. This gives a reading of detector sensitivity which complies with the requirements in EN54-7. There are however differences in readings between major test laboratories, particularly for different designs of detector. It is therefore recommended that individual manufacturers use 'Golden' sample detectors to check the correlation with the main test laboratory used, and this can be adjusted if necessary in the tunnel software settings.
How much do the AW Technology tunnels cost?
We will provide an indicative price list on application. However we believe that the AW technology tunnels are very good value. The client will benefit from the years of development and operational experience within AW Technology. The tunnels are supplied virtually ready to use, and are a complete and professional package that is reliable and easy to operate. If the client were to design and build a tunnel for their own use, the cost and timescale would be significantly larger.
What is the maximum temperature of the heat tunnels?
In EN54-5 the maximum temperature at the end of a fast ramp test for class C detectors is 144oC (20K/min test from maximum application temperature). The fastest ramps for class C detectors of 30K/min could reach 127oC if the detector does not go into alarm. The more powerful heaters in 2000 series tunnels can reach these temperatures before the maximum power is applied. Series 1000 tunnels can carry out these tests for the vast majority of compliant detectors. Static tests can be carried out in all tunnels up to 100oC (maximum for class C).
Can the AW Technology tunnels test to UL standards?
The UL standards define very specific test methods which are different from those in the EN and ISO standards. For example the smoke used by UL is generated by burning cotton wick, and is measured using an obscuration meter based on a car headlamp bulb and photocell. The AW technology tunnels are designed to meet the testing requirements of EN and ISO standards, and therefore cannot be used in for type testing to UL standards. However is is usually possible to get a good correlation between, for example, dB/m in EN to %/foot in UL. This means that the AW Technology tunnels can be used for calibrating, factory test and quality control when manufacturing UL approved detectors. As the AW Technology tunnels are easier to use, faster and cleaner than UL type tunnels this is a significant advantage.
Is an airspeed meter required for testing?
The motor which drives the main fan in the tunnel duct is fitted with a tachometer as standard. The motor rpm is always displayed on the main display of the tunnel software. If an airspeed meter is not fitted to the tunnel then the software will control to a target rpm, which should always result in a constant airspeed. This can be checked with a separate meter, and the target adjusted if necessary. If the optional airspeed meter is fitted the airspeed meter is also displayed, in units of m/s, and the user can set a target airspeed in m/s. Note that the airspeed meter is only used during smoke detector testing, as a rapid temperature ramp will adversely affect the reading.
