Safety at Tank Farms and Tanker Loading Areas

Tanker loading safety: why is risk concentrated at the loading point?

A solvent tanker is being unloaded. The site operator steps away for a few minutes to answer the phone, and the driver waits in the cab. The level indicator on the receiving tank is faulty; the tank overflows and solvent starts filling the bund. Tanker loading safety is therefore a matter of discipline before it is a matter of equipment: at the loading point, liquid, vapour, static electricity and human error come together at the same time.

Most accidents during loading and unloading start with one of these four events:

Overfill: No space in the receiving tank, unloading into the wrong tank or a faulty level indicator.
Connection leak: Damaged hose, unsuitable seal, valve not fully closed or hose rupture.
Ignition: Static electricity, the vehicle engine, a telephone or nearby hot work.
Movement: The tanker moving while the hose is connected.

Legal framework

The tank farm and loading area are where several regulations intersect:

Legislation	What it means for this area
Regulation on Fire Protection of Buildings Art. 119–122	Bund volume, distance between tank and bund wall, level indicator, electrostatic measures, hazard zone at the loading point
Regulation on the Protection of Workers from the Hazards of Explosive Atmospheres	Hazardous zone classification and explosion protection document
Regulation on the Carriage of Dangerous Goods by Road	Obligations of the filler and the unloader, dangerous goods activity certificate
Regulation on Health and Safety Measures for Work with Chemical Agents	Exposure during transfer, chemical risk assessment
Regulation on the Prevention and Mitigation of Major Industrial Accidents	Additional obligations for establishments holding dangerous substances above threshold quantities

Under transport legislation, businesses that have filled or unloaded 20 tonnes or more of dangerous goods in the last calendar year must obtain a dangerous goods activity certificate for the relevant activity. For the related safety adviser obligation, see our article on who needs a dangerous goods safety adviser (TMGD).

Tank farm: bunds, level and overfill prevention

The first question in the layout of a tank farm is where the liquid will go if a tank empties completely. Art. 119 of the Regulation on Fire Protection of Buildings sets bund volume as follows:

For tanks of the same size, the bund volume equals the volume of one tank; for tanks of different sizes, it equals the volume of the largest tank.
If crude oil and carbon disulphide are stored, the bund volume is taken as equal to the total volume.
Tanks must be at least 3 m away from bund walls whose height is lower than four-fifths of the tank height.
The bund area must be leak-tight and must remain leak-tight in a fire.

Art. 120 of the same regulation requires an arrangement showing the liquid level in each tank or compartment for above-ground tanks, and flammable liquid tanks to be secured against electrostatic charging. Spilled liquid is also prevented from reaching underground and surface water sources and the sewer system.

For tank overfill prevention, do not rely on a single level indicator; set up a layered structure:

Calculating the free volume before filling: The current quantity in the tank is read, compared with the incoming quantity and the result is written on the form.
Level indicator and high level alarm: Warns the operator.
Independent high-high level switch: Stops the pump or closes the filling valve with a sensor separate from the indicator.
Bund: The last line of defence. The rainwater drain valve is normally kept closed and opened in a controlled way; no combustible materials are kept inside the bund.

For fuel stations, the regulation also requires the unloading unit to be fitted with a valve that closes automatically when the tank is full, or the valve handle to have no locking-open device (Art. 121). For general storage rules for flammable liquids, see our article on storing flammable liquids.

Earthing during filling and static electricity

Liquid flowing through pipes, hoses and filters accumulates static charge. A spark between the tanker body and the filling installation can ignite the vapour at the filling opening. Art. 120 of the Regulation on Fire Protection of Buildings requires measures to prevent the hazard of electrostatic charging in vehicle-mounted tanks and defines the area within a 15 m radius of the filling point, up to a height of 0.8 m above the ground, as a hazard zone. Transport legislation also requires antistatic clothing and equipment to be used during filling.

Rules of practice for earthing during filling:

The earthing clamp is attached first and removed last. No valve is opened and no pump is started until the clamp is attached.
If possible, use an interlocked system that verifies the earthing connection and does not run the pump when there is no connection.
In top loading, the filling pipe is extended to the bottom of the tank; the liquid is not allowed to free-fall and the initial flow rate is kept low.
The conductivity of hoses and connection components is checked periodically.

We explain clamp checks, equipotential bonding and non-conductive containers in our article on static electricity and earthing, and the zone classification of the loading area in our article on ATEX and the explosion protection document.

Tanker unloading procedure: step by step

The following tanker unloading procedure should be turned into a checklist applied jointly by the site operator and the tanker driver:

Acceptance and document check: The substance, quantity and hazard information on the transport document are compared with the order and with the orange plates and hazard labels on the tanker. Transport legislation places this comparison and a check of the tank for damage on the unloader; if there is a problem, unloading does not start.
Confirming the receiving tank: Which tank will be unloaded into is set in writing and the free volume is calculated.
Vehicle positioning: The tanker is placed at the marked loading point, the engine is switched off, the handbrake is applied and wheel chocks are placed. Taking the ignition key is a simple way to prevent movement while the hose is connected.
Earthing: The clamp is attached and the connection is verified.
Closing off the area: Unauthorised entry to the loading area is prevented; the ban on fire, naked lights and smoking is applied and telephones are not used in the area.
Hose and connection check: The hose is checked for cracks, crushing and bulging; the seal for damage; and connection components for incompatibility. Labelling product lines and using couplings that prevent connection to the wrong line prevents unloading into the wrong tank.
Opening valves in sequence: First the receiving side, then the tanker side; leaks are checked in the first few minutes.
Continuous supervision: Throughout unloading, the operator does not leave the loading point and has clear access to the emergency stop button. If they need to leave, unloading is stopped.
Finish: Valves are closed, the hose is drained and emptied, and the drip tray is checked.
Closing the covers: The tanker's valves and covers are closed securely and spills are checked.
Earthing removed: After the hose has been disconnected, last of all.
Record: The quantity, tank, time and the signatures of the driver and operator are entered on the form.

For a facility carrying out filling, the maximum degree of filling of the tank is also taken into account, and after filling the tightness of the covers and filling valves and whether there is contamination on the outer surface of the tank are checked.

Emergency shutdown and the emergency plan

When something goes wrong in the loading area, the first minutes are decisive. The emergency shutdown arrangement should include:

Emergency stop buttons: At the loading point, on the escape route and in the control room; they stop the pump and close remotely operated valves.
Spill response: Absorbent and sealing materials suitable for the substance close to the loading area; covers to close sewer and rainwater inlets. For the steps, see our article on chemical spill response.
Fire-fighting and cooling: Water spray capacity to prevent a neighbouring tank heating up and igniting in a tank fire (Art. 122), and extinguishers suitable for the substance.
Scenarios: Separate response steps for hose rupture, overfill, tanker fire and vapour cloud; the direction of evacuation is set according to the wind.
Drills: Emergency drills are carried out at least once a year. Test the loading area scenario with a drill in which the tanker driver also takes part; you can plan drill and inspection dates with the OHS calendar.

Our articles on the hot work permit for hot work near the site and on neighbouring major accident hazard establishments in Kocaeli for joint planning with neighbouring facilities are complementary. Writing the loading and unloading procedure on site at chemicals and plastics facilities and entering it in the risk assessment document, and testing the scenarios through the emergency plan and drills, are work we carry out together across our service area from Bursa to Kocaeli.

Frequently Asked Questions

How large should the bund be?

Under Art. 119 of the Regulation on Fire Protection of Buildings, it should be equal to the volume of one tank for tanks of the same size, and to the volume of the largest tank for tanks of different sizes. For crude oil and carbon disulphide, the bund volume is taken as equal to the total volume.

When is the earthing clamp attached and when is it removed?

The clamp is attached as the very first step, before the hose is connected and the valve is opened; it is removed last, after unloading has finished and the hose has been disconnected. Interlocked systems that verify the connection prevent the pump from running until the clamp is attached.

Can the operator leave the loading point during unloading?

They should not. Overfills and leaks mostly grow during the minutes when the point is left unsupervised. If the operator needs to leave, unloading is stopped, the valves are closed and it is restarted when the operator returns.

What rules does the tanker driver follow in the loading area?

They follow the facility's loading and unloading procedure: they switch off the engine, apply the handbrake, use wheel chocks, obey the ban on fire and smoking and wait where they are shown. These rules should be explained to the driver at the facility entrance and confirmed by signature on the checklist.