Sealing of Petrol/Diesel Dispensers

Sealing Basic

If the tampering of the seal or sealing wire cannot be detected, it is as good or bad as non-sealing.

Precautions to be exercised

  • Do not use single thin wire and round seals.
  • Multi threaded lead wire and square seals are to be used.
  • Ensure that locking pins (if any) are in place and cannot be drawn out.
  • The fixing should be tight so that no part can be moved or opened after the sealing.
  • Indicate the points sealed on the Verification Certificate.

Components that require sealing

Component To prevent Remarks
Meter Sensor i) Removal
ii) Opening
Mechanical Adjustment Device Opening Located just outside or inside the meter box. (Wheel or rod)
All mechanical connections between sensor and pulsar Inserting additional device
Connection between Pulsar and Electronic Indicating Devices Manipulation
Electronic Adjustment Device Unauthorized calibration Dip Switch Box
Electronic Indicating Devices i) Opening
ii) Removal
Volume Indicator
Total Price Indicator
Name Plate Removal
Data Sheet Plate Removal

NOTE: A printer is not an indicating device because it does not show the delivery continuously but only the end result.


After the calibration (if required) and the verification is completed stamping is done to authenticate the verification.

  • The unit must have a name plate which will be stamped.
  • The unit number should be mentioned in the V. C.

A fraudulent device - the bypass

An additional device is planted on the PCB to create an additional path for spurious signal passing to the CPU so that display will show more quantity than delivered actually. The device is operated through an on-off switch located in the manager's room.

Look carefully for any additional device and connecting wire on the PCB. The connecting wire will run from the device, come out of the upper chamber of the dispenser and then run underground to the operating room.


An instance of Additional Device

The planted device is not likely to match with other components in finishing and color. The wiring will be rough and should be visible to a searching eye.

Some Components and their Sealing Example

Dip Switch Boxes / Electronic Calibrating Mechanism

Calibration Card is the most vital component of a dispenser. The dispenser cannot be electronically calibrated unless the dip switch is set on first. The Dip Switch is housed inside a box commonly known as Black Box or Calibration Switch Box. Adequate care should be taken to locate the box and sealing it to prevent any access to the switch.

The wiring should be followed so that the box cannot be opened without breaking the verification seal.

The figure shows two black boxes, each containing a Dip Switch for calibrating two separate nozzles.

Follow the wiring to prevent access to the Dip Switch.

Electronic Display unit and Totalizer (Registering Unit)

The sealing, made with a thick multi threaded wire should prevent opening of the Display Unit and the Totalizing Unit. They should also be not allowed to be removed from their site.

In some units Totalizer are connected to the PCB by a male-female connector. Sealing the connector by a cross wire prevents removal of the Totalizer.
All Printed Circuit Board (PCB / Mother board) are to be sealed in this way so that it cannot be taken out for unauthorized calibration or insertion of a bypass to the Processing Unit from the sensor.

In some models, the totalizer itself bears points through which a wire may be passed and the end point may be sealed.


Sensors / Pulsar

Seniors and Pulsar are gateway to the Registering Unit in digital display type pumps. They are normally found just above the meter casing.
The sensor is used to measure the quantum of liquid flowing though the meter. The information is passed to the Central Processing Unit (CPU)

For sealing a sensor, a wire is passed through perforated screws A and B. and the ends are twisted together and sealed.

In some MPD, a number of sensors are used for each type of fuel dispensed. All the sensors need to be sealed individually by placing a wire across it so that it cannot be changed or opened.

Today's MPDs use Pulsars in place of back dated sensors.

This type of sensors are used in many units.

Sealing should not only prevent removal of the component, it must also prevent access inside the sensor.

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