Does anyone know the reason why calorimeters often fail to ignite?

Calorimetry|Automatic Calorimeter|Microcomputer automatic calorimeter|Calorific value calorific detector and other experiments commonly used ignition principles and methods:

There are two common ignition methods for calorimeters: the first is a thin metal wire with a known calorific value indirectly from the two electrodes in the oxygen bomb, and the wire is fused and ignited after the electricity is applied.

The second is a section of molybdenum-chromium wire with a diameter of about millimeters on the electrode indirectly, the middle of the wire is wound into a spiral with a diameter of about 2 millimeters, for 3 5 turns, a section of cotton thread is lapped on the spiral, and the cotton thread is in contact with the sample through a hole with a diameter of 1 2 mm in the center of the fire shield, and when there is an electric current passing through, the molybdenum chromium wire is burned into red heat, igniting the cotton thread and the sample.

So why is it easy to fail in experimental ignition?

1. If it only appears once, it is generally that the ignition wire is not installed, if the ignition failure of multiple samples in continuous experiments, you can first check whether the ignition wire is burned out, and the ignition wire is not burned;

Then you should pay attention to the following issues:

a. Whether the crucible frame inside the oxygen bomb is short-circuited.

b. Whether the ignition electrode is in good contact with the oxygen bomb, such as the ignition claw is too open, the ignition electrode is dirty, and whether the ignition electrode rod and claw are elastic.

c. You can use a multimeter to measure whether there is an ignition voltage between the two poles of the ignition electrode (you can manually point the "ignition start" in the "hardware debugging") (AC 24V for the automatic calorimeter, DC 24V for the microcomputer automatic calorimeter), if not, the ignition electrode is loosely connected or the ignition circuit board is broken.

2. Ignition failure, if the ignition wire has been burned:

a. Stirring failure, such as the stirring rod is stuck, and it does not rotate when stirring.

b. If the inner bucket is not filled with water or the amount of water is insufficient, you can observe whether the water is normal at the beginning of the experiment.

c. If the coal sample has been burned, it may be that the calorific value of the sample is too low, and additives can be added for experiments.

d. If the benzoic acid test is done and the ignition wire is melted into the benzoic acid, it may be that the oxygen bomb core seat is not dried after cleaning, the contact resistance between the crucible frame and the ignition wire is too large, or the reason is benzoic acid.

This article is what I saw on the original technical article of Hebi Santai Instrument, I hope it can be helpful to you.

The ignition wire is not tightly tied.

The ignition wire is too far away from the specimen.

When oxygenated, the specimen gets wet.

The screws that fix the stirring blades are loose, the rod rotates, and the blades do not rotate.

The platinum resistance of the probe has moved to the middle or upper part of the probe.

The probe is not inserted into the inner barrel.

Hebi Keli's calorimeter does not have so many faults.

Hebi Keli. They will tell you.

Hebi Keli summarizes some common reasons.

1. Simple Failure - Causes Calorimeter Ignition Failure - Causes of Calorimeter Ignition Failure and Treatment Methods.

1. Forget to fill oxygen.

2. The ignition wire is not tightly tied.

3. The calorific value of the measured object is too low (less than 1500 calories).

4. The oxygen bomb is seriously leaking, and the oxygen has been leaked by the time the experiment begins.

2. Oxygen bomb short circuit - causes calorimeter ignition failure - causes of calorimeter ignition failure and treatment methods.

1. The two ignition electrodes are in contact with each other.

2. The white insulating pad of the oxygen warhead is aging, resulting in a short circuit between the warhead and the projectile body.

3. The ignition wire is installed incorrectly, and the ignition wire touches the crucible or the wall of the barrel.

3. The ignition line is not smooth - causing the ignition failure of the calorimeter - the causes of the ignition failure of the calorimeter and the treatment method.

1. After the equivalent calorimeter is covered, the spring electrode on the cover cannot touch the oxygen warhead: adjust the length of the spring electrode.

2. The contact point between the 24V power supply and the chassis inside the calorimeter is rusted or falling off: open the back cover, find the contact point between the 24V and the interface, polish the contact point with sandpaper, and then connect it reliably. (Coal Quality Analysis Instrument).

3. The triangular bracket of the inner cylinder has scale or rust: use a blade or a stool to brighten the contact point.

4. The two electrode columns in the oxygen bomb are wrapped in dust or rust, and are brightened with sandpaper.

Fourth, stirring failure - resulting in calorimeter ignition failure.

1. The stirring electrode is bad - remove the shell, copy the model of the stirring electrode, and buy and replace it.

2. The shaft of the stirring blade and the stirring motor falls off: you can install it.

When calorimetry determines calorific value, a coal sample is ignited by an ignition wire. The ignition wire is usually nickel-chromium wire, etc., and the electric energy consumed during ignition can be calculated and the heat can be calculated according to the voltage, current and energizing time at the time of ignition. The ignition uses a power supply of (12 24)V, and the 220V AC power supply can be supplied through the transformer.

An adjustable resistor and an ammeter (or indicator light) can be connected in series in the line. The analysis of the calorimeter ignition failure is as follows:

First of all, it should be checked whether the specimen has burned completely, and if it has burned sufficiently, this situation is called a false failure, and the reasons for the failure are as follows:

1) The stirring motor has been damaged, check the stirring system;

2) The screws fixing the stirring blades are loose, the rod rotates, and the blades do not rotate;

3) The temperature measuring probe is broken or the probe line is broken, and the surface of the probe is stained with dirt, which affects its normal operation;

4) Ignition cap oxidation, polish the ignition cap oxide with sandpaper to make it contact well.

Secondly, if the ignition wire has burned off, but the specimen has not burned, or if the ignition wire is fused in benzoic acid, but benzoic acid is not, the reasons for this may be:

1) The ignition wire is not tied to the designated place, or it is not tied tightly;

2) The ignition wire is too far away from the sample;

3) The specimen is wet, and the oxygenation is too fast to splash the wet specimen.

4) The connection of the oxygen bomb itself is not well connected.

Third, if the ignition wire is not burned out, it means that there is a problem between the control part and the ignition electrode, and the possible reasons are:

1) The ignition plate is damaged;

2) The ignition circuit of the instrument is damaged;

3) The ignition line is not passable and the contact is poor;

4) The ignition electrode is interrupted or short-circuited in the interlayer of the barrel cover.

The main reason for the ignition failure of the calorimeter is that the ignition line is not working, the contact is poor or the short circuit.

When the ignition failure occurs in the test, the oxygen bomb should be checked, and the ignition wire should be checked first. First, use a multimeter to measure whether the two ignition electrodes on the oxygen bomb are conductive [for the single-headed oxygen bomb, measure whether the center of the single-head and the projectile body are on], if the line is still not through, most of the two electrode columns are oxidized and rusted [sometimes "white rust", which is not easy to find with the naked eye] causing poor conductivity, at this time, the two electrode columns, especially the parts connected with the ignition wire, should be polished and brightened with sandpaper to make the contact good. If the two electrode columns are still not on after polishing and brightening, check whether the two electrode leads on the calorimeter are on with each other.

If it is not conducted, it may be that there is a false soldering or broken wire in the lead wire. Of course, it is also possible that the operator fails to ensure good contact with the electrodes when connecting the ignition wire. At this time, you only need to replace a new ignition wire [if the old one has been electrified] and reconnect it.

In order to judge whether it is the internal circuit of the instrument or the problem of the oxygen bomb, you can use the ignition wire to test the instrument separately, connect the ignition wire to the ignition head and the instrument shell (on the oval stainless steel plate on the upper cover), and use the ignition function to test, if the ignition is normal, it is the problem of the oxygen bomb. If it is not ignited, it needs to be repaired by the manufacturer. If it is confirmed through inspection that the ignition line of the oxygen bomb and the instrument is on [the ignition wire is red when the oxygen bomb is connected to the instrument and the ignition line is opened], it means that the ignition failure is due to a short circuit.

At this time, the two electrode columns should be checked, mainly to check whether the electrode column with the crucible frame is in contact with the oxygen bomb, whether the insulating sleeve post in the oxygen bomb is damaged, and whether the water in the inner cylinder is clean or mixed with the electrolyte. All of these factors have the potential to cause a short circuit that can lead to ignition failure.

What are the ignition failures and causes of calorimeter failure analysis?

When using a calorimeter to determine the calorific value of the analyte, it is generally easy to encounter, repetitive ignition failure or simply not igniting, this fault is one of the most common problems of calorimeter products

1. The calorimeter itself is not connected or has poor contact.

Solution: Check whether the connection is well connected, whether the oxygen warhead is in good contact with the ignition cap, and whether the inner cylinder of the oxygen bomb is placed?

2. The sample used to test the calorific amount is moist itself.

Generally, the test samples we use for testing should be as dry as possible, if the test object itself has the problem of moisture, it is easy to cause ignition failure;

Solution: Check whether the connection is well connected, whether the oxygen warhead is in good contact with the ignition cap, and whether the inner cylinder of the oxygen bomb is placed?

3. The ignition wire cannot touch the test sample during measurement.

Solution: Reposition the test sample;

Fourth, the two electrodes of the calorimeter are too dirty, and the ignition cap is over-oxidized, resulting in insulation.

Solution: Take a fine sandpaper and gently wipe the ignition electrode or ignition cap until the ignition is successful;

5. The most fatal problem: short circuit between the two electrodes and the crucible.

Solution: When this problem occurs, it is most likely to burn the crucible and electrode, and it is generally good to replace the electrode or reload the crucible immediately if this problem is found.

The above is the fault analysis and solutions of common calorimeter ignition failures summarized by Hebi Huanuo Instrument, hoping to serve as a warning to you.

Here's why:

1) Poor contact of ignition switch or adjustment knob;

2) The ignition wire and electrode fall off;

3) The ignition wire is in contact with the combustion dish or the combustion dish is in contact with another electrode, resulting in a short circuit;

4) Poor contact between the ignition wire and the sample;

5) Low oxygenation pressure;

6) The water content of the sample is too high, the volatile content is too low, and the sample particles are too large;

7) Oxygen bomb leakage.

"Methods for Determining the Calorific Value of Coal" (GB T213-2008). This is the latest.

Which manufacturer's instrument is it, and what model? It is different from manufacturer to manufacturer.

1. Check whether there is ignition voltage.

2. Check whether the oxygen bomb electrode is well connected and whether there is oxidation.

3. Check whether the oxygen bomb is in good contact with the inner cylinder when placed in the inner cylinder.

4. Check whether the ignition wire or cotton thread is in good contact.

5. Coal samples do not need to be mixed with combustibles, but only low-calorific value substances.

Standardized operation, careful and careful, is the basic standard of laboratory testing.