Pre 2005 Probe Sensor Alert

Is your tanker fitted with pre 2005 Glass Overfill Protection System probes?

Recently a product spill occurred at a terminal when a driver incorrectly connected a loading arm to a compartment that he had already loaded. Failing to recognise the mistake the driver started the loading system and product started entering the compartment, under normal conditions once product has reached or exceeded the compartment Safe Fill Level the Overfill Protection System probe would come into contact with the product and it would activate the Overfill Protection System shutting down the loading system, closing the product flow valves and stoping the loading pumps.

In this case the probe did not detect the overfill and did not shut down the loading system. The driver noticed product flowing from the the top of the tanker and he activated the gantry emergency stop, stopping product flow, the driver then raised the alarm.

Why did this happen?

The compartment was fitted with an Overfill Protection System probe manufactured in July 2004 this probe comes fitted with a heat shrink material that surrounds and protects the glass body of the Overfill Protection System probe. The heat shrink material on this particular probe, over time appears to have dislodged from its original position and has slid down the body of the probe creating a void / shroud at the base of the probe.

During the overfill incident this void/shroud has created an air pocket preventing the rising product in the compartment from reaching the sensor at the base of the probe. This void simply prevented the probe from detecting the product and thus prevented the Overfill Protection System from shutting down the product flow causing the product spill.

Details:

The probe was manufactured in July 2004
The heat shrink surrounding the body of the probe has repositioned to a location lower than specified within the probe design.
Impression markings on the heat shrink indicate the heat shrink was originally located in the correct position.
The heat shrink is tight and cannot be moved by hand
The probe powers up correctly
The probe provides a normal signal
The manufacture and industry has no previous record of the heat shrink material dislodging in this way.
Testing shows the air trapped within the dislodged heat shrink material prevents fluid from contacting the probe activating prism.
The manufacture fitted heat shrink material to all pre 2015 models of this probe

SLP Recommends

Tanker Owners

If you know or suspect your tanker is fitted with these heat shrink covered glass type probes!
We recommend that you have these probes inspected immediately: by removing the probe from the probe holder and inspecting the heat shrink material to ensure the material has not dislodged. If you suspect the heat shrink has dislodged then please contact the probe manufacture for further advice before reinstalling the probe.
If your not sure if your tanker is fitted with these heat shrink covered glass type probes?
We recommend all probes are checked when the tanker receives its next 2 ½ yearly hatch & vent or 5 yearly hydrostatic inspection, by removing the probe from the probe holder and inspecting the heat shrink material to ensure the material has not dislodged. If you suspect the heat shrink has dislodged then please contact the probe manufacture for further advice before reinstalling the probe.
Best Practice: SLP recommends these heat shrink encapsulated glass type probes be replaced, or the heat shrink material be removed from the probe before its returned to service, in doing this we again recommend you contact the manufacture for advice.

SLP Authorised Inspection Locations

When your inspector is completing the probe wet test section of an SLP Pass-2-Load inspection;
- we recommend as much as is physically possible the inspector try to visually determine the type of probe installed in the tanker compartment,
- if you suspect the compartment is fitted with a glass type probe, the probe must be removed and inspected for any fault or movement in the heat shrink material;
- if the heat shrink material has dislodged contact the probe manufacture for further advice.
When inspecting tankers for a 2 ½ yearly hatch & vent or 5 yearly hydro inspection;
- all probes must be removed and inspected for compliance and or physical damage.

Terminals

We know this type of probe is still in service, but we also believe the number in use is low.
During your normal inspections at a terminal, If you discover a tanker is fitted with heat shrink coated glass probes, we suggest you request the tanker owner provide evidence that they have had the probes inspected.