BS 799-4:1991 pdf free download.Oil burning equipment Part 4: Specification for atomizing burners (other than monobloc type) together with associated equipment for single burner and multi burner installations.
2.10
limiter
a device which senses the controlled quantity, causing the switching off of the burner. It operates once a predetermined limiting value has been reached
2.11
automatically reset limiter
a limiter which resets itself automatically and allows the restarting of the burner only after a predetermined change of the supervised quantity has occured
2.12
manually reset limiter
a limiter which requires simple manual intervention for the restarting of the burner
2.13
reset limiter with locking device
a limiter which can only be reset by use of specialized tools, by trained personnel, to allow the restarting of the burner
2.14
automatic ignition performed electrically a system in which the ignition necessarily involves the sole use of electrical energy
NOTE The two syima deacrlbed in 2.15 and 2.16 may be ditinguihed
2.15
proven spark ignition
a system which admits no fuel flow unless the presence of the spark is proved
2.16
unproven spark ignition
a system in which the admission of the fuel is not prevented by the absence of the spark
2.17
automatic ignition provided by liquid or gaseous fuels
a system in which the fuel is ignited by a small liquid or gaseous fuel burner known as a pilot burner, and which may be operated continuously or discontinuously
NOTE In the case odimcontinuous operation the two systems indicated in 2.18 and 2.19 may be distinguished.
2.18
ignition by proved pilot burner
a system which admits no main fuel flow unless the presence of flame on the pilot burner is proved
4.2.7 Safety interlocks
Means shall be provided to ensure:
a) that where the oil burner is constructed in such a way that the burner can be swung out or
extracted, these operations shall be possible only with the aid of tools, or an automatic device shall be provided that renders starting-up of the oil
burner impossible in the extended or extracted position;
b) that the burner cycle cannot be started or operated against a closed flue or without
combustion air flow;
c) that the correct conditions for atomization exist (see operation I in Table 1);
d) that the pre-firing purge has been carried out (see operation 2 in Table I).
NOTE Air flow measurement should be preferably by means of a differential measuring device.
The system shall permit connecting of interlocks to protect plant on which the oil burner is fitted.
e.g. additional pressure or temperature limit switches.
4.2.8 Alarms
The control system shall permit the connecting of audible andlor visible alarms to indicate fault
conditions.
5 Purging, ignition and flame failure
5.1 Furnace pre-firing purge
5.1.1 General
NOTE 1 The purpose of the furnace pre-firing purge is to dilute to a safe level the explosive mixture that may be present in the furnace and the gas passages of the plant. and for this reason a source of ignition during a pre.firing purge period is only as
specified in 5.1.2.
There shall be a minimum delay between purging and admitting any fuel into the furnace. The purge shall be sufficient to change the atmosphere of the furnace volume (see 2.44) at least five times.
NOTE 2 The rate of purging should be at least 25 % of the
full-load combustion air mass flow to the furnace. Consideration should be given to increasing the rate of purging to at least 50 % of the full-load air flow when the furnace is very large, e.g. in
water-tube boilers for power generation.
NOTE 3 Normally. the pre-firing purge time should he not less than 15 s except in cases where it has been proved under test that the required five volume changes have been achieved in a shorter pre-purge time. This shorter time period applies to special cases such as flash steam boilers.
NOTE 4 Purging in excess of the minimum air changes
specified for the furnace may be required. e.g. where the relative volume of convective heat transfer sections. flues and chimneys is large, or where there are spaces where explosive gases or
vapours may be trapped.
Seamless copper tubes shall be of appropriate test pressure complying with BS 2871-2. The tubes shall be designed and arranged as steam tubes in accordance with the appropriate requirements of BS 1306, Malleable cast iron fittings (non-galvanized) or cast copper alloy fittings shall comply with BS 143 and BS 1256.
Steel wrought pipe fittings shall comply with BS 1740.
Forged steel pipe fittings, screwed and socket-welding shall comply with BS 3799.
Carbon and stainless steel compression coupling for tubes shall comply with BS 4368-1 and BS 4368-3.
Other types of oil pipe and pipe fittings may he used, e.g. doublewalled tubing processed from strip steel, but they shall be capable of withstanding at least twice the maximum working pressure.
6.1.6 Flexible hoses and fittings
Flexible hoses and their fittings shall withstand at least twice the working pressure at the working temperature of the fluid being conveyed.
NOTE Particular attention should be paid to the hose manufacturexs instructions when installing the hoses and fittings. Flexible hoses are liable to deterioration in service and should be examined periodically. For gas ignition equipment, flexible tubing to BS 3212 may be employed.
6.2 Oil filters
6.2.1 General
6.2.1.1 Means shall be provided of preventing any solid matter that may be present in the oil, or matter that may separate out from the oil, from damaging components or choking valves or orifices.
NOTE Filters and strainers are classified as follows:
a) first stage: a strainer to provide protection for pumps and similar equipment that may handle the oil at the storage temperatures. or at a temperature lower than the final working temperature;
b) second stage: a filter to protect valves, nozzles and similar equipment that incorporate small orifices.
6.2.1.2 Unnecessarily fine filtration shall be avoided.
When clean, the pressure drop across the first stage shall not exceed 7 mbar’3 at the actual maximum flow rate.
6.2.1.3 Filters shall be rated according to their maximum throughput, in litres per hour when clean, at the design pressure drop and design oil viscosity.
6.2.2 Construction
6.2.2.1 Filter bodies and component parts other than the filtering element shall be constructed of materials complying with 6.1.1 and 6.1.2.
10 Marking
All burners shall carry a marking plate securely fixed to one of the surfaces and giving the following minimum information:
a) the name and address of the manufacturer;
b) the serial number, batch number or other distinct means of identification of the burner;
c) the number, Part and year of this British Standard4, i.e. BS 799-4:1991.
NOTE Attention is drawn to certification facilities offered by BSI (see the foreword).