Replacing a Broken Sampling Tube in a Residual Chlorine Monitor

Residual chlorine online analysers are essential instruments for ensuring the safety of drinking water, swimming pool water, and industrial recirculating systems. Over prolonged operation, the sampling tubing is continuously exposed to chlorinated water samples, fluctuating ambient temperatures, repeated mechanical stress from pump modules, and natural material ageing. 

These factors can cause the tube walls to soften, crack, or even rupture. A broken sampling tube not only leads to sample leakage and unstable flow rates but also directly triggers erratic monitoring data or complete equipment shutdown. Therefore, carrying out a prompt and standardised replacement of the ruptured tube is a critical maintenance procedure for restoring normal analyser operation.

Preparation Before Replacement

Before commencing any replacement work, the analyser must be taken out of service. The operator should disconnect the instrument from its power supply and close the upstream sample isolation valve, then drain any residual water from the tubing to eliminate electrical hazards and prevent spillage that could contaminate internal components or cause moisture damage to circuitry. 

During the preparatory phase, a new sampling tube of identical specifications and material to the original should be obtained according to the instrument model, and necessary tools — such as scissors, wrenches, and hose clamps — should be assembled. The operator must wear protective gloves to prevent injury from sharp edges on the damaged tubing or contact with residual chemical reagents in the sample.

Removing the Damaged Tubing

Once the power supply has been disconnected and the system drained, removal of the old tubing can proceed. The operator should first open the instrument's front cover or tubing compartment door and identify the connection points at both ends of the sampling tube — one end is typically attached to the inlet of the peristaltic pump or sampling pump, while the other connects to the flow cell or sample conditioner. During disassembly, the appropriate tool should be used to gently loosen the hose clamps or compression nuts at the fittings, and the old tubing should be withdrawn steadily from the ports. 

Excessive force or abrupt pulling must be avoided to prevent damage to the fitting threads, seals, or mounting bases. If the aged tubing has adhered to the fittings, it may be loosened gently with the aid of a tool; brute force should never be used. After removal, any scale, debris, or aged tubing fragments remaining at the connection ports should be carefully cleaned to ensure that the ports are clean and unobstructed, providing favourable conditions for installing the new tube.

Installing the New Sampling Tube

Before installation, the new tube should be verified to have exactly the same material, inner diameter, and length as the original. It should be routed along the original pathway, ensuring that the tubing lies flat without excessive bends or tension that could cause stress concentration and subsequent rupture. 

After precisely aligning both ends of the new tube with the instrument ports, hose clamps or cable ties should be used to secure the connections, ensuring a tight seal without looseness or play. The tightening force must be moderate — overtightening may strip the threads or damage the tube wall. 

For tubing located in the peristaltic pump section, special attention should be given to correct positioning of the soft tube within the pump module to ensure proper aspiration of both sample and reagents.