Fire Pump House

The purpose of a fire pump house is to provide and maintain a reliable water supply for firefighting purposes.

A fire water sump or reservoir is a dedicated storage system designed to ensure a steady and reliable water supply for firefighting. Here’s an overview:
 
1. Purpose: The main function of a fire water sump is to guarantee an adequate water supply for fire protection systems such as hydrants and sprinklers during emergencies.
 
2. Capacity: The sump’s size and capacity are based on the water needs of the facility, calculated from the number and type of fire protection systems. National building codes also set minimum capacity standards to ensure safety.
 
3. Location: Sumps can be located above or below ground, depending on site conditions and space. The location affects the design and construction of the sump.
 
4. Maintenance: Regular maintenance is essential for functionality and reliability. This includes checking for leaks, ensuring water quality, and keeping the sump free from debris.
 
In summary, fire water sumps are crucial for providing a dependable water source in emergencies.
Purpose of Fire pumps are essential components of a building’s fire protection system, designed to ensure that a steady and reliable supply of water is available at high pressure. Their primary role is to deliver water to fire protection systems like sprinklers and hydrants, which is critical for effectively controlling and extinguishing fires. By maintaining high pressure, fire pumps enable these systems to operate efficiently, ensuring that they can deliver sufficient water to combat a fire and protect the building and its occupants.
Fire water pump house consists of 
1.Main Electric motor driven pump 
2.Diesel engine driven pump 
3.Jockey pump 
Purpose of the the main electric motor-driven fire pump is designed to provide a high-pressure water supply to the building’s fire protection systems, such as sprinklers and hydrants. Its primary purpose is to ensure that these systems have a consistent and reliable source of water during a fire emergency. The electric motor drives the pump, which draws water from a storage source and boosts its pressure, enabling effective firefighting capabilities. This setup is crucial for maintaining safety and controlling fires by ensuring that adequate water pressure is available when needed.
 
Starts automatically in response to significant pressure drops but may need manual intervention to stop.
 
Basic parameters are as follows.
Pump Type Main Fire Pump
Capacity 2280 LPM
Net Head Generated 70 MWC
Speed 2900 RPM
Shut Off Head 78 MWC
Power Absorption (KW) 60 Hp Motor / 45 KW
Suction Size As per OEM
No. of Stage Single
Efficiency 73%
Note : Parameters will change based site requirements. 
The fire pump control panel is a robust electrical enclosure designed to manage and protect the electrical system of a fire pump. It is constructed from 14 SWG mild steel sheet, painted with enamel paint for durability, and features double doors with an IP 65 rating for dust and water resistance. 
 
Key Components:
 
– Incoming Section:
  – 1 x 400A FP MCCB (35 KA): A main circuit breaker to protect and control the incoming power supply.
 
– Bus Bars:
  – 1 Set of 3-Phase, 4-Wire, 500A Aluminum Bus Bars: These carry the electrical current from the incoming supply to the various circuits within the panel, protected with color-coded PVC insulation.
 
– Outgoings:
  – 3 x 200A TP MCCBs: Circuit breakers for individual motor circuits, each with a neutral link and rated for 25 KA.
  – 3 x 63A TP MCCBs: Smaller circuit breakers for additional circuits, also with neutral links and rated for 25 KA.
  – 2 x Star Delta Starters with Overload Relays: Used to start large motors (up to 70 HP) in a star-delta configuration to reduce starting current.
  – 1 x DOL Starter with Overload Relay: Direct-on-line starter suitable for a smaller motor (10 HP).
 
– Metering:
  – RYB Phase Indication Lamps: Lights showing the status of each phase, with toggle switches and protection fuses.
  – 0-500V Voltmeter: A gauge for measuring voltage, with a 96mm square display and MCB protection.
  – 0-400A Ammeter: Measures current with a 96mm square display and suitable current transformers (CTs).
  – Energy Meter: Measures electrical energy consumption, also with CTs.
 
– Cables and Additional Components:
  – Aluminum Bus Bars: Equipped with a rated capacity and housed in a chamber with spare chambers for future use.
  – Main Isolation Switch Fuse Unit: Features HRC (High Rupture Capacity) fuses for high-capacity isolation.
  – Individual Isolation Switch Fuse Units: Each motor circuit has its own HRC fuse unit.
  – Automatic Starters: Auto-transformer starters for each motor and “STAR DELTA” starters for the jockey pump, including push buttons for operation.
  – Single-Phasing Preventers: Protect each motor from damage due to loss of one phase.
  – Panel-Mounted Meters and Switches: Includes ammeters, voltmeters, and rotary switches for manual or automatic operation of the fire pump.
  – Color-Coded Wiring: Ensures clear and accurate connections from the main supply to the panel’s components.
  • Purpose of the the diesel engine-driven pump serves as a backup to ensure that firefighting systems continue to function even during power outages. This pump is critical for maintaining water pressure in systems like sprinklers and hydrants when the primary electric supply fails.
  • Starts automatically in response to significant pressure drops but may need manual intervention to stop.
  • The diesel engine-driven pump is made up of several important components:
– Engine Parts: These include the flywheel housing, exhaust manifold, vibration damper, air cleaner, fuel pump, and a mechanical governor to control engine speed.
– Cooling and Fuel Systems: Features like a heat exchanger, fuel filter, and fuel oil pump help manage the engine’s temperature and fuel supply.
– Electrical System: Includes a 24-volt DC starter and a battery charging system to ensure the engine starts reliably.
– Operational Support: Comprises engine support structures, a flexible coupling to connect the engine to the pump, and a tachometer to monitor engine speed.
– Instrumentation: An instrumentation panel with gauges for oil pressure, oil temperature, and water temperature, plus an ammeter to measure electrical current.
– Safety Features: Includes alarms for low oil pressure and high water temperature to prevent engine damage.
– Additional Parts: Such as a silencer to reduce noise, fuel hoses, and a water heater with a thermostat to ensure the engine operates in varying temperatures.
 
The diesel fuel tank is designed to supply fuel to a diesel engine-driven pump. Its size can be adjusted based on the specific needs of the site. The tank is made from mild steel and includes several features:
 
– A manhole cover for access.
– A glass gauge for visual inspection of fuel levels.
– Inlet and outlet connections with gate valves for controlling fuel flow.
– A drain plug for easy removal of any sediment.
– GI piping with a wire mesh vent to prevent debris from entering.
 
The tank is painted in PO red and mounted on a steel angle frame to ensure that fuel flows by gravity. To monitor the fuel level, the tank is equipped with both a glass gauge and a level sensor, which are connected to a control panel. If the fuel level drops below a preset point, the sensor sends a signal to the control panel, triggering an audio-visual alert to notify of the low fuel condition.
The diesel engine exhaust pipe is essential for directing exhaust gases away from the engine. It plays a key role in controlling emissions, reducing noise, managing heat, and ensuring optimal engine performance.
 
For specific site conditions, additional features are incorporated:
 
– Heat-Resistant Aluminum Cladding: Insulation wrapped around the pipe to handle high temperatures.
– Cowl: Positioned at the top of the pipe to better manage the dispersion of exhaust gases.
– MS Clamps: Used to secure the exhaust piping to walls or ceilings.
 
The pump’s starter panel is equipped to automatically start the engine with three attempts if needed. It also includes a battery charger with an ammeter and voltmeter, manual start/stop buttons, and indicators and alarms for various engine conditions. This panel is designed for 230-volt single-phase power, is made of durable 16 SWG sheet metal, and is suitable for floor mounting.
 
Pump Type Fire pump
Capacity 2280 LPM
Net Head Generated 70 MWC
Speed 1800 RPM
Suction Size As per OEM (100/80)
No. of Stage Single Stage
 
Make Kirloskar/EQVT
Model GK 80/40B
BHP 65 BHP
Speed 1800 RPM
 
Note : Parameters will change based site requirements. 
Functions,
a. Auto Mode
b. Off Mode
c. Manual Mode
AUTO MODE:-
Under this mode should provide complete unattended operation. When the mode is put in AUTO position, the operation of the Diesel Engine is as follows,
a. When normal water pressure is above 3.00 Kg/Cm2, the Diesel Engine Driven Pump is at rest.
b. When the water pipe line pressure switch for Diesel Engine is actuated and water pressure dropping to 3.00 Kg/Cm2, the control shall actuate the pumping set.
c. When the Diesel Engine Driven Pump is to be switched off (This shall be done manually), the pump is ready for next operation.
OFF MODE:-
The off mode, as selected on the unit mode switch, all functions from the panel are in OFF condition. Battery charging system however does not remain affected.
MANUAL MODE:-
  • The Manual mode of operation on the unit mode switch is different from the Automatic Mode is that the Diesel Fire Pump has to be started manually by the operator by pressing the ‘START’ push button.
  • To ensure engine stops, the ‘STOP’ push button should remain in pressed position till the engine stops completely, otherwise the engine starts again.
BATTERY CHARGER:-
The Diesel Engine Fire Pump Panel regulates control power supply which is provided from the Fire Pump Set battery. A battery charger is provided in the control gear. This consists of one D.C. Voltmeter, one D.C. Ammeter, and a Trickle boost charge – Rate Selector Switch. Input of the battery charger shall be 220 V A.C. Supply.
 
Purpose of this smaller pump is to maintain constant pressure in the Wet Riser/Hydrant System and Sprinkler System. Initially, the system is brought up to the required pressure. If there are minor leaks or small drops in pressure, the Jockey Pump kicks in to boost the pressure back to the desired level. It operates automatically: starting up when the pressure falls below a preset threshold and shutting off once the pressure is restored. This helps to keep the system stable and ready without the need for the larger main pump to start frequently.
  • Pump Type Fire Pump
  • Capacity 180 LPM
  • Net Head Generated 70 MWC
  • Speed 2900 RPM
  • Shut Off Head 71.5 M
  • Power Absorption (KW) 9.3 KW
  • Suction Size As per OEM
  • No. of Stage Single
  • Efficiency 28%
Note : Parameters will change based site requirements. 
When main Pump installed at Fire Pump House start to fail for keeping the Wet Riser and Sprinkler System in a pressurised state, one Terrace Pump is employed.
The Basic Parameters of Pump are:
  • Pump Type
  • Capacity 900 LPM
  • Net Head Generated 35 MWC
  • Speed 2900 RPM
  • Power Absorption (KW) 9.3 KW
  • Suction Size As per OEM (80/65)
  • No. of Stage single
  • Efficiency 52%
Note : Parameters will change based site requirements. 

The Air Vessel is crucial for maintaining stable system pressure by addressing minor pressure drops and providing an air cushion to absorb surges when the pump operates. It features a 100 mm diameter flanged connection to the pump, a 25 mm drain valve, a water level gauge, and 25 mm sockets for pressure switches. Capable of withstanding pressures up to 10.5 kg/cm², the vessel has a diameter of 250 mm and a length of 1500 mm, with dished ends. It includes both an inlet valve and a drain valve and is mounted on the pump’s delivery side to ensure reliable and consistent system performance.

The systems shall be provided with suitable drainage arrangements with G.I. piping of 40 mm dia., complete with all accessories, and provided with 40 mm dia. drain valve.  
1. Operational and Failure Signals: Connect the pumps’ operational and failure signals to the fire command and control center to ensure real-time monitoring and response.
 
2. Emergency Lighting System: Install an emergency lighting system with backup power to ensure visibility during a fire emergency. This system should cover key areas including:
   – From the building entrance to the fire pump.
   – From the fire command and control center to the fire pump house.
 
3. Signage: Provide illuminated signage for the fire pump house and its access routes to ensure they are clearly visible during emergencies.
 
4. Talkback System: Set up a talkback system to enable two-way communication between the fire pump house and the fire command and control center.
 
5. Adequate Lighting: Ensure that there is sufficient lighting with a backup power supply throughout the fire pump house and its routes to maintain safety and functionality during power outages.
 

The purpose of a pressure switch is to detect pressure and activate a built-in mechanical switch. It includes a provision to set a threshold level. These pressure switches are mounted on the main header at the pump house. Based on the detected pressure, they send signals to the fire pump control panels to enable automatic operation and provide indications.

A pressure gauge in a fire pump house monitors water pressure within the system. It is typically installed at key points such as the pump discharge and suction, providing real-time pressure readings. Accurate gauges are crucial for ensuring the system maintains the proper pressure needed for effective fire protection. Regular maintenance is required to ensure the gauges function correctly.

  • Aluminium conductor, PVC insulated armoured cable 3 x 95 Sq.mm PVC AA cable alongwith 2×6 SWG GI wire.
  • Aluminium conductor, PVC insulated armoured cable 3 x 25 Sq.mm PVC AA cable alongwith 2x8SWG GI wire.
  • Aluminium conductor, PVC insulated armoured cable  4 x 6 Sq.mm PVC AA cable alongwith
2×8 SWG GI wire.
GI slotted cable trays  40 × 100 × 40 × 2 mm
The Butter Fly Valve shall be made of Cast Iron to IS: 210, grade FG 260 body, in circular shape and of high strength to take the minimum water pressure of 16 Kg/ cm2. The disc shall be heavy duty C.I with anticorrosive epoxy or nickel coating. All Butter Fly Valves shall be full lug with internal threading. The rating of valves should be PN 1.6 with flange drilling as per IS: 1538.
 
•  250 mm dia. butterfly valve
•   200 mm dia. butterfly valve
•   150 mm dia. butterfly valve
•   100mm dia. butterfly valve
•   50mm dia. butterfly valve
 
  • 150 mm dia. non-return valve (flanged)
  • 100 mm dia. Gunmetal Non Return valve
  • 80mm dia. Gunmetal Non Return valve
•200mm dia. strainer
•100mm dia. strainer

a) Flushing of Underground Connections:
– Before connecting the underground mains and lead-in lines to the system risers, flush these connections to clear out any debris or foreign materials that might have entered during installation.
– Continue flushing until the water flowing out is clear, indicating that the pipes are clean.

b) Flow Rate for Flushing:
– The flushing process should be performed at a flow rate of at least 1620 liters per minute to ensure thorough cleaning of the underground mains and connections.

c) Disposal of Test Water:
– Arrange for proper disposal of the test water from the flushing process to prevent any damage to property. This could involve directing the water to a drainage system or other suitable area.

d) Acceptance Test:
 i) Jockey Pump Start-Up:
– Set the pressure switch on the Jockey Pump to activate at 7 kg/cm² and to stop at 7.5 kg/cm².
– To test, open the system drain to lower the pressure. The Jockey Pump should turn on automatically when the pressure drops to 7 kg/cm² and turn off once the pressure is restored to 7.5 kg/cm².

This procedure ensures that the system is properly cleaned and functioning before final acceptance. 

ii) Main Electric Pump:
– Set the pump to start at 6.5 kg/cm².
– Open an external hydrant valve with a single hose and branch pipe to cause a pressure drop. The Jockey Pump should start at 6.5 kg/cm². Allow the pressure to drop to 5 kg/cm² to test the automatic start of the electric pump.
– The electric pump should run for at least 5 minutes, raising the pressure to 7.5 kg/cm². The Jockey Pump should then start automatically.
– Manually stop the electric pump using the stop button.

 iii) Standby Diesel Pump:
– After the system is fully charged to 7.0 kg/cm², open an external hydrant valve with a hose and branch pipe.
– When the pressure drops to 6.0 kg/cm², the electric main pump should start automatically.
– After 5 minutes of operation, turn off the power supply to the pump house. The diesel pump should then start automatically.

e) Repetition of Tests:
– All tests must be repeated after a one-hour interval, and results should be consistent. The system can be accepted from the contractor once it satisfactorily passes all tests.

1. Location and Construction:

  • Location: The pump house should ideally be situated outside the building, at least 6 meters away from adjacent structures. It should have natural ventilation with protected windows.
  • Diesel Pump: If it includes a diesel pump, the exhaust must extend outside and discharge at a safe height.
  • Flooring: The floor should slope to drain water from leaks.
  • Lighting: Provide both normal and emergency lighting, either from an alternate source or a generator.
  • Fire Safety: If inside, the pump house must be separated by a 2-hour fire-rated wall and have a 1-hour fire-rated door. Basement pump houses require forced mechanical ventilation, while those on the first floor should have exterior access.

2. Pump Arrangement:

  • Space: Ensure sufficient space for all equipment, with clearances of 1 meter front and back, and 0.75 meters on sides for large pumps (>2,280 l/min). For smaller pumps, clearances should be 0.75 meters front and back, and 0.60 meters on sides. Headroom should be at least 2.75 meters.
  • Control Panel: The panel should include a TPN switch, HRC switch, ammeter, voltmeter, phase indicators, single-phase preventer, start/stop buttons, and auto-manual switches. Use copper busbars of appropriate thickness.
  • Diesel Pump Panel: This should be in the same or adjacent room, with its own battery and charging device, and interlock with the main pump panel to prevent simultaneous operation.
  • Air Vessel: Install a suitably sized air vessel with pressure switches—one for upper and lower limits for the jockey pump, and another for the main pump’s lower limit. Manual control for stopping the main pump should be clearly indicated.

2.1. Terrace Pump:

  • Automatic Start: The terrace pump should start automatically when any hydrant or hose reel is used. Include a manual push button on the ground floor for starting and stopping the pump. Ensure push buttons are clearly marked and colored differently.

3. Pipe Sizes:

  • Minimum Sizes:
    • 450 l/min pump: Suction & Delivery 50 mm
    • 900 l/min pump: Suction 75 mm, Delivery 50 mm
    • 1,400 l/min pump: Suction & Delivery 100 mm
    • 2,280 l/min pump: Suction & Delivery 150 mm
    • 2,850 l/min pump: Suction 200 mm, Delivery 150 mm
    • 4,540 l/min pump: Suction 250 mm, Delivery 200 mm
  • Manifold Size: Must match the cross-section of the main pump’s suction inlets.

4. Priming:

  • Preferred Method: Use positive suction by positioning the pump house below the water tank. If not feasible, use a priming tank with a foot valve and strainer. The tank should be eight times the volume of the suction pipe.

5. Wet-Riser-Cum-Down-Comer System:

  • Pump Setup: Install two pumps—one for the wet-riser and one for the down-comer system. Provide power from both a normal and an alternative source.

6. Wet-Riser System:

  • Pump Configuration: Use two automatic pumps for the wet-riser, with one as a standby. Ensure each pump has a different power source and interlock them to operate one at a time.

7. Alternative Power Supply:

  • Options:
    • A diesel generator capable of meeting the full requirements, including initial start-up currents and other emergency services.
    • A separate sub-station dedicated to emergency services.

8. Pump Mounting:

  • Foundation: Pumps should be mounted on a concrete foundation (minimum 75 mm thick) with vibration-absorbing layers. Foundations must match the dimensions of the pump, motor, and coupling base.
  • Diesel Pumps: Foundations should cover the length of the engine and pump with flexible couplings.
  • Pump Specifications: Use horizontal split-casing centrifugal pumps with cast iron casings, bronze impellers, and stainless steel shafts. All metal parts in contact with water should have anti-corrosive treatment or be of non-ferrous material.

5.1.2.2 Firefighting pump house (NBC 2016)

The requirements shall be as given below:

a) It is preferable to install the pump house at ground level. Pump house shall be situated so as to be directly accessible from the surrounding ground level.

b) Pump house shall be installed not lower than the second basement. When installed in the basement, staircase with direct accessibility (or through enclosed passageway with 120 min fire rating) from the ground, shall be provided. Access to the pump room shall not require to negotiate through other occupancies within the basement.

c) Pump house shall be separated by fire walls all around and doors shall be protected by fire doors (120 min rating).

d) Pump house shall be well ventilated and due care shall be taken to avoid water stagnation.

e) No other utility equipment shall be installed inside fire pump room.

f) Insertions like flexible couplings, bellows, etc, in the suction and delivery piping shall be suitably planned and installed.

g) Installation of negative suction arrangement and submersible pumps shall not be allowed.

h) Pump house shall be sufficiently large to accommodate all pumps, and their accessories like PRVs, installation control valve, valves, diesel tank and electrical panel.

i) Battery of diesel engine operated fire pump shall have separate charger from emergency power supply circuit.

j) Exhaust pipe of diesel engine shall be insulated as per best engineering practice and taken to a safe location at ground level, considering the back pressure.

k) Fire pumps shall be provided with soft starter or variable frequency drive starter.

4.9 (h) From fire command and control center following monitoring facility shall be provided as per NBC 2016.

1) Water level in all tanks.

2) Hydrant and sprinkler pressures of respective zones as provided.

3) Pump ‘ON/OFF’ status.

4) All isolation valves, wherever provided with supervisory switch (non-padlock valves).

5) Other requirements to meet electro- mechanical services interface.

6) Talkback speaker shall be installed to communicate with fire command and control center.

7) Adequate emergency lightning shall be provided.

 Bill of Material for Fire Pump House – Type 1  
Sl.NoDescriptionUnitQty
Pumps
1Main electric pump – 96 Cum/hr. electrically driven horizontal centrifugal (end suction) Common Main & Standby pumpset for Hydrant & Sprinkler system, at 7 Kg/sq.cm and 2900 rpm with all necessary accessor. Pump shall have electrical motor of adequate KW/HP suitable for Electric supply 415V, 50 Hz, 3Phase and cofirm to IS 325 – 1978.No1
2Diesel Engine Pump – 96 Cum/hr. deisel engine driven horizontal centrifugal (end suction) Common Main & Standby pumpset for Hydrant & Sprinkler system, at 7 Kg/sq.cm and 1800 rpm with all necessary accessor. Batteries & battery leads with stand, 200 ltrs. The electric motor shall be of rated HP and speed and suitable for operation at 415V, 50Hz. The pump shall be of cast iron construction with bronze impeller, stainless
steel shaft, flexible coupling and gland packing seal.		No1
3Jockey Pump – 10.8 Cum/hr. electrically driven horizontal centrifugal  (End suction type ) Common Jockey pumpset for Wetriser & sprinkler system at 7Kg/sq.cm and  2900 rpm with all necessary  accessories like providing & fixing bronze impeller, stainless steel shaft and mechanical seal along with anti-vibration mounting  pad and flexible connections at discharge end of the pipes etc. and shall be automatic
in operation.		No1
Fire Pump House Control Panel
1control  panel  for  Electrical  motor  driven  pumps  ,
Diesel engine driven pumps.		No1
Terrace Pump
1450 lpm 35 metres head and 3.5 kg/sqcm pressure monoblock type booster pumpNo1
Control Panel for booster pump
Valves for Fire Pump House
1Sluice Valves(pn-1.6,non rising type)  
 a)100 mm dia – Sluice Valves(pn-1.6,non rising type)No’s2
 b)40mm dia – Sluice Valves(pn-1.6,non rising type)No’s1
 a) 150 mm dia foot valve with strainerNo’s2
 b)50mm dia foot valve with strainerNo’s1
2 C.I NRV slim seal type as per  IS: 5312  
 a) 100 mm dia C.I NRV slim seal type as per  IS: 5312No’s2
 b) 40 mm dia C.I NRV slim seal type as per  IS: 5312No’s1
 a) 150 mm dia C.I. butterfly valveNo’s1
3Ball Valve / gate Valve25mm dia(Gun Metal)No’s10
4GM Air Release valve of 25 mm. dia.No’s1
Instruments
1pressure gauges for pumps in delivery line and common delivery header(0-14 Kg./sqcm)No’s4
2pressure switch (0-15 Kg./sqcm)No’s3
Pipes
1MS “B” class pipes for fire pump house  
 a) 150 mm dia – MS “B” class pipes RMT12
 b) 100 mm dia – MS “B” class pipes RMT12
 c)50mm dia – MS “B” class pipes RMT6
 d)40mm dia – MS “B” class pipes RMT6
 e)25mm dia – MS “B” class pipes RMT6
2Air Cushion vessel(150mm dia)No’s1
3exahust pipe for diesel engineMtrs6
Cable requirement for fire pump house
1PVC  insulated  PVC  sheathed,  steel  armoured,  Aluminium  / copper  conductor,  100v  grade  power  cables.  The  cables  shall  be  laid  in  tray  / Hume pipe / in trenches/on walls/ floor etc. as required.  
 a) PVC  insulated  PVC  sheathed,  steel  armoured,  Aluminium  conductor,  100v  grade  power  cables – 3C x  25 sq.mm copper-for Main PumpMtrs24
 b) PVC  insulated  PVC  sheathed,  steel  armoured,  Aluminium  conductor,  100v  grade  power  cables -3 c X 10 sq.mm Copper for Jockey PumpMtrs24
 c) 2C x 1.5sq.mm copper armourd cable for instrumentationMtrs30
 d) 12cx1.5sqmm copper armourd cable for diesel pumpMtrs24
 e) 100mm wide 50mm depth perforated sheet cable tray. Rate shall include necessary angle iron suspension, anchor fasteners etc., complete.Mtrs24
Earthing Strip
1i)G.I Earthing Strips – 25x3mm ThicknessMtrs12
 ii)G.I Earthing Strips – 50x6mm thicknessMtrs12