1. Problem confirmation

When abnormalities are found during the use of the instrument, the first step is to confirm that the problem has occurred at least twice. If the problem does not recur, it is difficult to confirm its existence.

2. One at a time rule

Change only one factor at a time to confirm the correlation between the changed factor and the problem.

3. Replacement rule

Replacing suspicious components with good ones is the best way to find faults. For example, if you suspect that the detector is causing noise, replace it with a high-performance detector. If the fault is resolved, it indicates that there is a problem with the replaced detector. The scale of application of this rule varies, from replacing the entire component to replacing the integrated block on the printed circuit board.

4. Exchange rule

This rule is used together with the replacement rule. After replacing the suspicious component with a good one, the situation has not improved and the original component should be replaced. This approach minimizes maintenance costs and prevents the accumulation of used components. This rule only applies to a single fault. The principle of replacement does not apply to the following situations:

(1) The new component was damaged when removed (such as the pump sealing gasket);

(2) Low component prices;

(3) There is a risk of damage when reinstalling the original components;

(4) Parts that are regularly replaced.

5. Reference condition rule

Standard reference conditions, also known as standard test conditions, are conditions that are easy to verify from one system to another, and from one laboratory to another. The data measured under this condition helps to identify issues between actual experiments and systems. If the system pressure increases under certain test conditions and the pressure is normal under standard conditions. This indicates that system anomalies are caused by changes in the laboratory

6. Record rule

This rule is often overlooked by people. It should be recorded after each maintenance and troubleshooting. For example, it is impossible to systematically analyze a specific fault in a system without recording it, which is time-consuming and laborious. In the long run, specific failures that occur in the system also have extremely important implications for future operations. Each instrument should have a maintenance record book, which includes the date, location of the malfunction, symptoms, causes, solutions, and results. When a malfunction occurs again, the problem can be resolved as soon as possible based on records.

7. Prediction rule

Personnel with maintenance practices and habits should be able to predict system failures, invest more time in maintenance, and the system will reduce failures as a reward, while also eliminating chain damage. For example, if maintenance is not paid attention to, the sealing gasket of the pump may be damaged, causing leakage of the mobile phase and corroding the pump and other components. Timely maintenance can save time and money. For example, if the baseline drift is caused by the lifespan of the lamp at the beginning or end of each day's work, the lamp should be replaced. If all the lights are broken, the machine needs to be shut down, and the resulting losses may be higher than the cost of a single light.