PTL Glow Wire Test Apparatus
The test procedure is used to examine the fire resisting properties of products if, during the application or in the case of a fault, heated or glowing parts could be considered as a short-time ignition source. Loose connections or bad contacts cause
punctually high temperatures on electrical articles, their components and their parts. Attention should also be paid to the fire risk in connection with textile seat coverings, table-cloths, or curtains, e.g. after coming into contact with a lighted cigarette.
For this reason, prototypes of all articles which could be a source of danger if they con-tact with ignition sources should be subjected to the Glow-wire Test.
The ignition source is imitated by an electrically heated wire loop against which the sample is pressed with a
constant force. A miniature jacket thermocouple serves
as a sensor for the loop temperature.
The sample has to be fastened to a carriage on which, by means of a tensioning cord, a weight with a force of 1 N is effective in the direction of the wire loop. Scales enable the reading of the flame height and the depth of penetration. Approx. 200 mm below the wire loop a board of pine wood, covered with a layer of tissue paper, is mounted. This device enables to judge the danger of a fire spreading through burning drops or glowing parts falling from the sample.
The specimen and, if necessary, a base shall be attached relative to the wire loop in such a way to represent the most unfavourable practical case. The scales of the measuring device shall be adjusted and the penetration depth of the loop shall be limited by the adjustable stop. After returning and covering the specimen the loop shall be heated up to the specified temperature.
When the loop has maintained the testing temperature for at least 60 seconds, the specimen can be briskly led up to the loop. From the moment of contact, an operation time of exactly 30 seconds must be kept. Then the penetration depth is read and the specimen is slowly returned to its starting position. During and after the operation the burning behaviour of the specimen and the tissue paper on the wooden board has to be observed.
S t a n d a r d o u t f i t :
1 wire loop of nickel-chromium, with clamping mechanism,
1 carriage with Cardanic holding device for the specimen, five-fold adjustable,
1 rail system with ground running surfaces,
1 fine rope pull mechanism with weights for loads of 1 ?0,2 N,
1 indicating device for the depth of penetration, with maximum pointer and stop,
1 scale to measure the flame height, multiple adjustable,
1 high current isolating transformer to heat the wire loop, with series connected
variable ratio transformer, to set the temperature up to 960℃
1 miniature jacket thermocouple Chromel-Alumel, with plug almost free from thermoelectric voltage and with compensating lead,
1 temperature indicating instrument to indicate the temperature of the glow-wire loop, with digital display, measuring range 0...1000℃, class 0,5, built-in operable, see Fig. 1 and 3, can be recalibrated, with compensation of the ambient temperature. 1 housing, desk shaped, with all necessary
electrical components, with safety switch and 2 keys.
D e s i g n : testing device as Fig. 2, moun-ted on housing of sheet steel, papyrus-white structure varnished, plan dimensions approx. 400 mm x 400 mm, total height approx. 570 mm, carriage and specimen holding device of corrosion-protected material, including 2 cm2 foil of fine silver 99,8 %, 0,06 mm thick, for
calibration of the temperature indicating instrument, board of pine wood, 10 mm thick, wrapping tissue and mains connection cord set, for connection to A.C. 230 V, 50 to 60 Hz,other voltages or frequencies: on request
S p a r e p a r t s :
The articles T 03.81 to T 03.93 are wearing parts and have no guarantee
T03.81 Glow-wire loop 0,5
T03.82 Glow -wire loop 1 , 0
T03.84 Miniature -jacket - thermocouple 1 , 0
T03.86 Miniature -jacket - thermocouple 0 , 5
T03.89 Silver foil , 2 cm
Fine Wire Brush
Board of Pine Wood