New grounding unit for fuel loading

Maintenance, Test & Measurement, Calibration

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September 2003 Maintenance, Test & Measurement, Calibration

The MT30 grounding unit, from DLM, prevents loading unless the earthing clamp is satisfactorily applied to the vehicle being filled.

Grounding is required in cases where flammable substances are pumped at high speed, thereby generating electrostatic charges that can cause sparks and explosions. To prevent the accumulation of these static charges a device is required to release these charges to ground in a safe manner.

The Isoil MT30 has been designed and built according to the ATEX 94/9/CE directive with type protection EEx-d [ia] IIB T6 and is completely water tight (IP66 enclosure). The MT30 allows safe loading and unloading of rail and road tankers by verifying that the correct connection to ground is performed.

Operation

* The clamp is connected to the tank truck or rail tanker to be protected.

* The electronic circuit measures the electrical parameters (resistance and capacitance) of the connection loop. The device monitors that the clamp remains connected to the truck and not to any other metallic object ie, the gantry, by means of a controlled capacitance circuit.

In the case of a positive connection

Once the clamp has been connected to the vehicle that needs to be protected and a positive result has been achieved through both the resistive and capacitive checks then:

* The ground relay is energised and remains energised during the loading operation.

* The LED indicator on the front panel changes from red to green indicating that loading can commence.

* Two internal relays that can be used for permissives or interlocks are also energised.

* The connection is monitored until the loading operation is completed. Any sudden interruption will result in the MT30 de-energising all relays and interrupting the permissives to other loading devices and ultimately the loading operation will be terminated.

Connection to the clamp is achieved through an intrinsically safe circuit. As the clamp has a simple mechanical contact, no Ex approval is required. This microprocessor controlled device performs resistive and capacitive measurements, controls the LED panel and the permissive relays and has the following unique features:

* External calibration (it is therefore no longer necessary to open the enclosure to calibrate the device).

* An additional row of LEDs indicates the sensitivity level set.

* The system is programmable.

* Two cable clamps can be connected to the MT30.

"Isoil identified that the petrochemical market was in need of a cost effective grounding unit that would provide years of trouble-free and maintenance-free operation", says Wayne Walton, national sales manager for DLM's flow division. "We are delighted to once again provide an economic solution to meet a southern African market need."

Isoil's product range includes control valves, positive displacement meters, strainer air eliminators and accessories, as well as a range of electronic devices consisting of badge readers and small terminal automation software as used at bulk loading facilities.

For more information contact Wayne Walton, DLM, 011 457 0500, [email protected], www.dlm.co.za

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Maintenance, Test & Measurement, Calibration

New grounding unit for fuel loading

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