Below you will find a summary of the most common rejection points for combustion plants at carrying out SCIOS – first/special inspection, periodic maintenance and periodic inspection.
Thermeta Service BV has composed a 'TOP 10' of frequently recurring deviations in combustion plants in boiler houses of horticulturists. Also a short explanation is given of what the standard/model should be, any calculations and the deviations that occur.
This information is applicable to combustion plants with ventilator burners installed in boiler houses of horticulturists.
In view of readability and overview, this information has been made in the form of an extract and therefore it is not complete. It is still important to keep testing manuals, technical documentation, valid standards and legislation when implementing projects.
Thermeta Service BV does not accept any responsibility with respect to this document and no rights can be derived from this.
Air Supply Device
Standard
Practical standard Burner load [nom] in kW x 2 the number of cm2 net air supply grate.
Grate minimally 30 cm above surface level.
Draught height: The top of the grate minimally 170 cm below the bottom of the air discharge device
Position: together with the air discharge a good draught must be achieved in the heater room.
Remark.
If the CO2 fan extracts air from the heater room for e.g. pure CO2 dosing / OCAP / modulating thermostat for cooling or otherwise, the ventilation supply openings must be enlarged (discuss this with the EBI employee)
Example / calculation
Burner 3480 kW must have 3480 x 2 = 6960 cm2 net air supply device + any extra for CO2 set, see Remark.
Attention: The passage factors of the grates deviate for each shape or manufacture!
Remark
Often too small
The practical standard deviates from Standard 3028.
Air exhaust device
Standard
Practical standard Burner load [Nom] in kW x 1 the number of cm2 net air supply grate.
Draught height: Top of grate minimally 170 cm above the top of the air supply device
Position: together with the air supply a good draught must be achieved in the heater room.
Example / calculation
Burner 3480 kW must have 3480 x 1 = 3480 cm2 net air exhaust device.
Attention: The passage factors of the grates deviate for each shape or manufacture!
Remark
Often too small
The practical standard deviates from Standard 3028.
Safety valves boiler heating
Standard
It must be possible to blow off the power of the boiler in kW in steam with the set relief pressure of the safety valve(s)
Example / calculation
If the power of boiler 3000 kW safety valve pressure relief capacity is 1700 kW at 2 bar, then install 3000/1700 = 1.8 = 2 valves of this type.
Remark
Often too small
Safety valves boiler LP steaming
Standard
It must be possible to blow off the power of the boiler in kW in steam at the set relief pressure of the safety valve(s). Pay attention: the set pressure with LP steam is formally 0.5 bar!
Example / calculation
If the power of boiler 3000 kW safety valve pressure relief capacity is 588 kW at 0.5 bar, then install 3000/588 = 5.1 = 6 valves of this type.
Remark
Often too small
Safety valves boiler condenser
Standard
Must have been provided with a safe outlet.
The tube on the valve has max. 1 bend, is max. 3 m long and may not have been renewed or have a smaller diameter than the connection to the valve.
Example / calculation
N/A
Remark
Often not provided
Do not make this of plastic
In practice a somewhat longer pipe will be approved as well.
Fire emergency switch
Standard
Emergency switch with clear text outside the heater room that at least switches off the control power system of the burner.
Example / calculation
N/A
Remark
Often not provided
Ventilation time
Standard
Installations must have been provided with a 5-fold purging time.
Example / calculation
Calculation (rule of thumb: if the burner and boiler capacities correspond
Purge at Bmax: Required purging time [sec] = Flue gas side volume [m3] x 5 / (Bmax [kW] x 10 / 3600)
Purge at 30 Hz = ca. 50% Bmax: Required purging time [sec] = Flue gas side volume [m3] x 10 / (Bmax [kW] x 10 / 3600)
Remark
Often too short
This can be avoided by mentioning the flue gas side volume of the boiler to Thermeta Service BV when placing the order.
CO2 set closing position monitoring
Standard
If the CO2 set does not run (because of operation or failure), the CO2 valve must be switched off if the burner is not closed.
Example / calculation
This rule also applies with several sources (total energy or extra boiler). This may then be carried out by the source valve of the boiler involved.
Remark
Often does not work
To prevent flue gas leakage towards the heater room/greenhouse
Flue gas leakage smoke box
Standard
No flue gas leakage is allowed in the heater room
Example / calculation
Any flue gas leakage must be sealed or be provided with a solid water seal.
Steam tube is allowed if it is suitable for the temperature concerned.
Remark
Often open connections from the condensate discharge to the heater room
DA / AV = pressure limit safety / pressure relief valve
Standard
Pressure limit safety / pressure relief valve provided if the supply pressure exceeds the allowed pressure of the burner.
Example / calculation
Thermeta burners usually have max. 200 mbar allowed gas pressure. (SKP)
Remark
Often not provided
Pressure relief pipe / pressure relief valve often not provided.
Often incorrectly adjusted and no tools available for adjustment.
