Do you know Building material combustion calorific value calorimeter?

With the continuous advancement of building materials technology, most materials currently in use can meet market demand. However, this presents a challenge: the combustion performance of many building materials fails to meet requirements, potentially leading to significant casualties and property losses in the event of a fire. Consequently, the combustion performance of building materials has received increasing attention in recent years, and the importance of calorific value, a mandatory parameter for assessing the Class A combustion performance rating, is undeniable.

A building material calorific value tester is an instrument for measuring the calorific value of building materials. It is primarily used to determine the calorific value of combustible materials such as stone, wood, concrete, uniformly dispersed mineral wool, and polymers. It is widely used in construction research and technical supervision departments. This method measures gross and net calorific values ​​and can be used to evaluate the potential fire load of building products. It is one of the test methods for evaluating whether the combustion performance of composite (sandwich) materials meets Class A standards.

Test Principle and Features

This test specifies the equipment for measuring the calorific value of a sample of a specified mass in a constant-volume oxygen-nitrogen calorimeter under standard conditions. Under standard conditions, the test is based on the measured temperature rise, taking into account all heat losses and the latent heat of vaporization, to calculate the calorific value of the sample.

The standard used is GB/T 14402-2007. "Combustion Performance of Building Materials and Products - Determination of Calorific Value." The Building Materials Calorific Value Tester is a new analytical instrument developed based on similar previous products. It utilizes a state-of-the-art single-chip microcontroller, a large LCD display, and a fully Chinese user interface. It features high measurement accuracy, a compact size, easy operation, and automatic ignition, water addition and discharge, stirring, calculation, and printing.

Test method

The determination of the calorific value of building materials is based on the provisions of the standard GB/T14402-2007 "Determination of the calorific value of combustion performance of building materials and products". The specific test method is as follows:

1. Test preparation

(1) Sample preparation

Select representative samples and cut samples of the tested components of homogeneous or heterogeneous products. If the tested component is the main component of the homogeneous product or heterogeneous product, the minimum mass of the sample is 50g. If the tested component is the secondary component of the heterogeneous product, the minimum mass of the sample is 10g. After cutting the sample, grind it into powder.

(2) Mass determination

Weigh 0.5g of the tested sample and 0.5g of benzoic acid. If necessary, weigh the ignition wire, cotton thread and "cigarette" paper.

(3) Sample preparation method

Crucible test

a. Place the weighed sample and benzoic acid mixture into the crucible;

b. Connect the weighed ignition wire to the two electrodes;

c. Adjust the position of the ignition wire so that it has good contact with the sample in the crucible.

Cigarette test

a. Adjust the weighed ignition wire to hang down to the center of the mandrel;

b. Wrap the mandrel with the weighed "cigarette paper" and glue the overlapping edges with glue. If the "cigarette paper" has been glued, it does not need to be glued again. Leave enough paper at both ends to twist it together with the ignition wire;

c. Twist the paper and the ignition wire at the lower end of the mandrel together and place them in the mold. The ignition wire should pass through the bottom of the mold;

d. Remove the mandrel and place the weighed sample and benzoic acid mixture into the "cigarette paper";

e. Take out the "cigarette paper" containing the sample and benzoic acid mixture from the mold and twist the two ends of the "cigarette paper" together. f. Weigh the "cigarette" sample to ensure that the difference between the total weight and the mass of the components does not exceed 10 mg; g. Place the "cigarette" sample in a crucible. (4) Conditioning Before the test, the powder sample, benzoic acid, and "cigarette paper" should be conditioned in accordance with the specified requirements. (5) Water equivalent calibration The water equivalent of the calorimeter, oxygen bomb, and accessories should be calibrated by measuring the total calorific value of 5 groups of standard benzoic acid samples of the same mass. The water equivalent should be the average of the 5 calibration results, and the deviation of each calibration result from the water equivalent should not exceed 0.2%.

2. Standard test procedure for calorific value of combustion The test should be carried out under standard test conditions (temperature 23±2℃; humidity 50±5%). The temperature difference between the test room and the water temperature in the calorimeter cylinder shall not exceed ±2 K. (1) Weigh five quantitative samples and mix them with benzoic acid (total amount is 1g), accurate to 0.1mg. (2) Install the sample and ignition wire, ensure good contact and avoid the ignition wire from contacting the edge of the crucible. (3) Add 10mL of distilled water to the oxygen bomb to absorb the acid gas generated during the test. Tighten the oxygen bomb sealing cap, connect the oxygen bomb and oxygen cylinder valve, and fill the oxygen bomb with oxygen until the pressure reaches 3.0~3.5Mpa. (4) Add the same amount of distilled water as used in calibration to the inner cylinder of the calorimeter, place the oxygen bomb into the inner cylinder of the calorimeter so that it submerges the oxygen bomb (use 2L of water, accurate to 1g), and check to ensure that the oxygen bomb does not leak. (5) Place the inner cylinder of the calorimeter into the outer cylinder. (6) Turn on the instrument, install the temperature sensor, and start the mixer and timer.

(7) Adjust the water temperature in the inner cylinder to make it basically the same as the water temperature in the outer cylinder, until the continuous reading deviation within 10 minutes does not exceed ±0.01K. The temperature at this time is taken as the starting temperature.

(8) After the temperature is balanced for 10 minutes, the sample is automatically ignited. During the rapid heating stage of the inner cylinder of the calorimeter, the water temperature in the outer cylinder should be kept as consistent as possible with the water temperature in the inner cylinder, until the continuous reading deviation within 10 minutes does not exceed ±0.01K. The temperature at this time is taken as the highest temperature and the test is automatically terminated.

(9) Remove the oxygen bomb from the calorimeter, leave it for 10 minutes, and then slowly release the pressure. Open the oxygen bomb and observe the sample sediment to determine whether the sample is completely burned.

3. Calculation of total calorific value

Calculate the total calorific value of the sample combustion according to the standard.

(1) For homogeneous materials, three samples should be taken and the average of the three test results should be taken (the deviation between the maximum and minimum values ​​is ≤0.2MJ/kg, and the effective range is 0~3.2MJ/kg).

(2) For non-homogeneous materials, the total calorific value of each individual component should be calculated (the deviation between the maximum and minimum values ​​is ≤ 0.1 MJ/kg, and the effective range is 0~4.1 MJ/kg).

Daily Inspection and Maintenance

1. Oxygen bomb for building materials product combustion calorific value tester: In addition to cleaning and drying the oxygen bomb after each test, the following points should also be noted and inspected:

① The oxygen bomb should only be turned by hand. Stop when you feel resistance. Never force it with tools. Clean it after each test.

② The bomb cap and valve seat should be rinsed and wiped dry after use.

③ Rinse the bomb cup, clean the threads, and inspect the cup for mechanical damage. Be careful not to invert the cup.

④ Inspect the sealing ring for wear and combustion damage. If it is leaking, replace it.

⑤ Check the insulation pad and insulation sleeve for damage and whether they are in good condition. Regular insulation performance checks can be performed.

⑥ Regularly perform a 20.0 MPa water pressure test on the oxygen bomb. After each water pressure test, the oxygen bomb must not be used for more than one year.

2. Building Materials Product Combustion Calorific Value Tester's Graduated Cylinder: After the test, drain the water from the cylinder into the outer cylinder, wipe it dry, and keep it clean.

3. Building Materials Product Combustion Calorific Value Tester's Test Water: It is best to use purified water and replace it regularly to ensure test reliability and success rate.

Note: For safe use of this system, the computer equipment must be reliably grounded.

In summary, building material calorific value testers play a vital role in ensuring building fire safety, accurately measuring the calorific value of various building materials. Through rigorous test preparation, precise standard testing procedures, and meticulous calculation methods, reliable results are obtained to evaluate the combustion performance of building products. Furthermore, regular routine inspection and maintenance of the tester's components, such as the oxygen bomb, graduated cylinder, and test water, are crucial to maintaining its accuracy, reliability, and service life. By adhering to these practices, construction research and technical supervision departments can effectively assess and mitigate potential fire hazards, thereby protecting lives and property.