Related Discussions on the Basic Rules of Instrument Maintenance

1. One time rule

When the system fails, you can tentatively change certain states, and you can change one parameter at a time. For example, to limit the problem of de-dimensionalization of chromatographic peaks, you can sequentially change the mobile phase, change the guard column, and change the analytical column. A few simple changes may solve the problem.

2. Second comparison rule

The fault has been clarified before the hands-on overhaul, or the solution to the fault has been determined. In other words, you have found the right solution before you start. For example, if the peak value of the internal standard is found to be lower during the injection process, you can repeat the injection to see how the repeatability is. If it is accidentally lowered, whether it is caused by bubbles in the loop. This rule can be used to examine the situation after the system is changed. After changing the flow direction, two standards can be injected before the formal injection to check the stability of the retention time and the stability of the chromatographic peak. If there are redundant peaks in gradient elution, you can elute with no-load gradient once (is there really a problem?). Use this rule to avoid unnecessary changes and determine corrective measures as soon as possible.

3. Replacement rules (Guide: Which three issues should be paid attention to in the maintenance of fasteners)

Replace the suspicious part with a good part is the best way to find the fault. If you suspect that the detector is causing noise, replace it with a good rotorless vulcanizer detector. If the fault is eliminated, it means there is a problem with the replaced detector. The scale of the application of this rule varies from large to small, ranging from replacing entire components to replacing integrated blocks on printed circuit boards.

4. Exchange rules

This rule is used together with the replacement rule. After a good part replaces the suspicious part of the melt flow rate tester, the situation has not improved, and the original part should be replaced. This minimizes maintenance costs and prevents the backlog of used parts from the rotorless vulcanizer. This rule only applies to a single failure. The exchange-back principle does not apply to the following situations:

(1) The new part is damaged when it is removed (such as pump sealing gasket);

(2) The price of components is low (such as column lining filter);

(3) Reinstall the original parts to take the risk of damage;

(4) Parts to be replaced regularly.

5. Reference condition rules

There are usually two reference conditions: ①standard reference conditions; ②test reference conditions.

Standard reference conditions, also called 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 problems between the actual test and the system. If the system pressure rises under certain test conditions, but the pressure is normal under standard conditions. This shows that the abnormality of the melt flow rate analyzer system is caused by the changes in the laboratory. The following table lists the standard test conditions for starting a new column. The standard test conditions can also be used to check the system during use.

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