Instrumentation Questions Part One

The oil tanks are protected by Foam tanks fire extinguishing system. Fire Foam Tanks System have some special features, like:

• The fire fighting installation does not require connection to external fire water sources.
• This system is very simple, consists only of foam tanks, main foam valve, the foam distribution and introduction,  pipework, manifold, pressure gauges and PSVs.
• This simplicity provides very high level of reliability, and safe operation. Making human mistake during the operation is unlikely.
• The maintenance is simple, some regular checking is sufficient.
• The burning time of the protected storage tank or processing equipment is less within a minute, almost.
• The short burning time results in negligible air pollution, the system is environment friendly.

Components of Fire Foam Tanks System

The foam tanks or vessels are placed in almost a 20 feet shipping container(Fire Cabin) which is heat insulated and has sun protection shield, These foam tanks or vessels are connected to a common manifold. The manifold has some foam outlet valves, with alarm signal flash light above each outlet valve. The fire extinguishing shall be started by opening the relevant valve of foam tanks and the valve on the manifold, which valves are appointed by the flashing alarm signal light.

The opening of the appointed valves results in leading the foam to the process or storage tank on fire. The manifold and the valves are placed inside the Foam Cabin.( Fire Cabin). The foam pipeline is laid above ground from the Fire Cabin to the process and storage tanks.

There is a 1,0 bar rupture Teflon foil is placed between the flanges at the upper end of the foam riser pipeline on the tanks. It keeps the product vapors in the process and storage tanks, preventing the condensation of the humidity of product vapors. The gas blanketing system remains in the required range on the storage and process tanks.

Working Principle of Firefighting Foam Tanks System

After the fire alarm displays in the control room, the first step is to start the shutdown procedure.Then the operator enters the Fire Cabin (foam tanks system inside the fire cabin), and manually opens the foam valve of the  and also the downstream valve towards the oil tanks on fire. 

The alarm signal lamps of these valves are flashing, to show the operator the appropriate valve to be opened . The two valves opened(the foam valve of the  and also the downstream) then starts the fire extinguishing.

The self expanding foam immediately expands in the pipeline, runs through in the above ground foam pipeline, and breaks through the Teflon foil. The foam enters the inside space of the storage tank, flows down on the inside surface of the tank shell. 

The expanding foam blanket will close on the surface of the liquid, in a very short time and the fire is put out.

What to do after operation of the fire protection system

After fire extinguishing the operators shall close all the valves. The foam pipeline must be flushed with water. Then a new teflon foil is to be inserted between the flanges at the upper end of the foam riser pipeline, replacing the damaged one. Refilling the empty foam tanks or vessels is mandatory.

OPERATING INSTRUCTIONS ACCORDING TO PRESSURE EQUIPMENT DIRECTIVE 97/23/EC

1- General Remarks

• The operation department team is responsible that these instructions are known to the erection, operating and maintenance personnel.
• The operation department team is to ensure through suitable and function-able safety measures that the allowable operation conditions and/or load Cycles are not exceeded.
• Any deviation from the specified operation conditions without the manufacturer's approval.
• instructions nullifies the manufacturer's responsibility. (This is depends on what rules between the company and the manufacture supplier).

2- Operation

• Care is to be taken to avoid surges in the operation parameters.
• For example: The flow line values are not to be exceeded:Pressure: 0.5 bar/min Temperature: 5 °C/min
• Chambers which are completely liquid filled in operation are to be vented.
• All instrument devices should be inspected and checked it's working.
• Should abnormal conditions appear in operation, e.g. pressure increases, drop in pressure and/or temperature, the operation department team is to determine the cause and effect or if necessary. shut down the equipment.
• Also during planned shut downs, surges in the operation parameters are to be avoided.
• The equipment is to be drained through the appropriate nozzles. In order to protect the environment, but also as personnel and material safety. the fluids are to be disposed of as dictated in the applicable ordinance.
• By extended shut downs, it is recommended to protect the equipment with nitrogen. Gasket surfaces are to be coated with a preservation agent and protected from mechanical damage.
• The equipment is to be checked for leaks, e.g. hydro test or leak test before placing in operation again.

3- Maintenance

1. If the equipment has been out of operation for extended periods, e.g. 6 months, as can occur by delayed start-ups or longer shut
2. down - renewed start-up interruptions, soft material gaskets should be replaced.
3. All pressure gauges installed on this equipment should checked, inspected and calibrated on regular planed job.
4. The PSVs installed on this equipment should be certified and checked.
5. The equipment is to be opened and entered with considerable caution and only when permitted by the authorized person.
6. Cleaning materials for use in or on the equipment are to be free of substances damaging to the environment or the equipment
7. or injurious to personnel, protective PPE are to be worn.
8. The interior of the equipment is to be inspected for mechanical and corrosion damage etc.
9. Internals are to be checked for correct installation, e.g. bolting, trays and man ways etc.
10. Gasket surfaces and bolting are to be checked before closing. New gaskets are to be used.
11. A sufficient venting of the system or equipment is to be provided during draining.

4- Regularity Inspections

• The responsible authority determines the intervals between regulatory inspections based on the hazard analysis and applicable laws.
• In general, The Manufacturers recommends internal inspections every 5 years and every 10 years for pressure tests, depending on the material of the made of, types, strength ..etc.

5- Measures for Hazard Control or Reduction

• Use of qualified personnel and reliable programs.
• Assurance of a regular up-dating of documentation
• Material selection based on operation conditions.
• Protection against excessive over-pressure during normal operation (PSVs. pressure switches..etc).
• Protection against excessive over-pressure from thermal expansion.
• Protection against any corrosion on the equipment.

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