PNEUMATIC TUBE SYSTEMS
trigger could cause the control system to issue an eject command for a carrier that is only just leaving a plant room. The system will then initiate a purge because the RFID identification cannot be verified. If the underlying fault remains, the system may repeat the sequence – purge after purge – while staff experience what appears to be an unreliable or non-functioning system. Eventually, staff may contact the helpdesk and report that the system is not operating correctly. A member of FM staff investigates the problem and may halt the affected zone. However, if the section is not manually purged before the system is restarted, the underlying problem may remain. And this is how previously lost carriers can become rogue elements, creating further problems for subsequent sends. This is just one of many possible scenarios
in which the PTS may actually be behaving correctly according to the information being provided to it.
Linear Coupler.
zone and display a fault condition requiring human intervention. Ultimately, if the system determines that a carrier cannot safely reach its destination, it must stop. This becomes particularly important where the PTS is being used for sample handling or pharmaceutical delivery. From the early 2000s onwards, RFID verification was added to PTS technology. Initially, this allowed laboratories to scan carriers and return empty carriers to their tagged home address. This technology subsequently developed into a secondary method of carrier tracking and traceability.
RFID tracking and carrier identification RFID tagging and tracking is essential to the operation of a modern multi-destination PTS within a hospital. A tagged carrier can be scanned at the sending station
and then travel through several zones before reaching its destination. However, it cannot simply be assumed that because the system records a carrier as having been dispatched, the correct physical carrier has actually arrived at the intended destination. The carrier must also be verified on arrival. This becomes particularly important when considering
the number of carriers that can be in transit within a large, multi-zone PTS. Modern systems incorporating advanced technology, including robotic linear coupler zone-transfer devices, can have up to 100 carriers in transit at any one time.
Intermediate scans can be made as carriers pass
through linear couplers at transfer points. However, it is not possible to completely rule out the presence of a carrier that has been lost or misrouted somewhere within the system. If that carrier is physically ahead of another carrier that the control system believes is destined for a particular receiving station, the rogue carrier could potentially arrive first. That creates an entirely different level of risk from the simple point-to-point systems of the past.
How can a rogue carrier become lost within a PTS? There are numerous possible scenarios. A faulty sensor or limit switch, for example, can cause the control system to receive an incorrect indication of the exact location or status of a carrier. Consider a major destination station within a laboratory
where a sensor is intermittently switching between open and closed states. When a carrier enters the zone, a false
44 Health Estate Journal November 2026
The control system can correctly identify an abnormal condition, attempt to protect the network by stopping the affected zone, and generate an alarm. The problem can arise afterwards. Human intervention can override the system’s response without addressing the original cause.
System alarms and fault recovery The stand-alone PC systems supplied for the past 25 years can raise an alarm when it suspects or identifies a fault, either through a BMS relay or by email notification. If the control system cannot complete a transport for any reason, it will normally attempt to purge the affected zone and recover or discharge the carrier. If this is unsuccessful, the zone may be suspended and an error condition reported. At this point, the fault cannot normally be resolved without human intervention. And this is where the problems can begin. If the person responding to the alarm is trained and familiar with PTS operation, they can either attend the system directly or access the control system remotely and investigate using the available diagnostic and statistical software.
In most cases, a trend or recurring pattern can be identified, directing an experienced operator towards the root cause of the problem. The operator can then locate the source of the fault, repair or replace the defective component, manually purge the affected section, and restore the zone to service under observation until they are confident that the problem has been resolved. That is how an alarm should work: identify the problem, investigate the cause, take the appropriate corrective action, and then return the system to service.
The risk of inexperienced intervention But – and it is a significant but – if the person attending to the fault has little or no practical experience with the PTS, they may be able, at the click of a mouse, to override the system’s protective response and restore the affected section to service. In many situations, the system will then appear to
operate normally. However, it may only continue to do so until the original fault occurs again. This can potentially create a situation that is more dangerous than the original fault. The system has identified a problem, taken action to
protect itself, and reported that problem to the operator. Human intervention has then overridden that protection without identifying or correcting the underlying cause.
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