BS EN 777-3:2009 pdf download
BS EN 777-3:2009 pdf download.Multi-burner gas-firedoverhead radiant tubeheater systems for nondomestic usePart 3: System F一Safety.
5.2.ll.2 Common duct
The common duct shall be fitted with a suitable device for proving adequate ar-flow during the prepurge. ignition and operation of the system (see 6.6.1 e and 6.7)
The sensor shall be located at a specified point in the common duct and shall not rely on static pressure measurement.
The air-proving device shal be proved in the no air-flow state prior to start-up of the system. Failure to prove the device Ii the no al-flow state shall prevent start up of the system.
Air-flow failure in the common duct at any time during the pre-purge. ignition and operation & the bumer shall cause non-volatile lock-out of the system.
The system control shall be designed such that there is at least one check & the pressure switch in the no air-flow state every 24 h,
5.2.11.3 Burner units
Each burner unit shall be fitted with a suitable device for proving adequate air-flow in its branch duct during the pro-purge, ignition and operation of the burner unit (see 6.6.1.5 and 6.6.2).
The sensor shall be located at each burner unit and shall not rely on static pressure measurement, The air-proving device shall be proved In the Inadequate air flow state prior to start up. Failure to prove the device Ni the Inadequate air-flow state shall prevent start up of the burner unil
Air-flow failure at any time during the pre-purge, ignition and operation of the burner shall cause:
a) non-volatile lock-out; or
b) volatile lock-out; or
c) safety shut-down of the burner unit sud’i that re-start rnay only take place following autornatic recyding.
Each bumer unit shall be designed such that there is at least one check of the pressure switch in the no air-flow state every 24 h.
5.2.12 AutomatIc system control
&2.121 System operating sequence
The following sequence of events shall occur to initiate the system:
a) Stage 0: complete shut down of the system;
b) Stage 1:
1) call for heat;
2) all air proving switches checked In the no air-flow state:
3) common duct tan on:
4) check of adequate aIr-flow In the common duct.
c) Stage 2:
1) on a signal to operate a burner unit, check that the air provrng switch on the burner is in the insufficient air state:
2) burner unit tan on;
3) pre-purge and check that there Is adequate air.flow through the branch te:
4) ignition;
5) running conditrnn.
Following a signal to shut down a burner unit in the course of normal operation, the burner unit shall
return to a state of readiness between events 5.2.12.1 c4) and c5) above, or stage 0 as appropriate
5.2.12.2 Automatic burner control system
5.2.12.2.1 General
Each burner unit shall be fitted with an automatic burner control system complying with EN 298:2003.
5.2.12.2.2 Manually operated devices
The operation of manually operated devices (e.g. push buttons and switches). incorrectly or out of sequence shall not adversely affect the safety of the automatic burner control system.
Under the test conditions described in 7.2.1. the rapid (on and off) operation of any start switch shall not set up a hazardous condition.
5.2.12.2.3 Pre-purglng
Immediately before any attempt at igniben or the opening of automatic shut-off valves, the branch
duct shall be purged.
Under the test conditions described in 7.2.2. the purge penod shall be at least 10 S.
5.212.2.4 Flame detector
On each burner unit, the flame detector system shall incorporate a means to prevent the energization of any gas valve and of the ignition device it a flame or flame simulating condition is present during the start-up period.
Upon flame (allure in the running condition the flame detector shall either cause:
a) non-volatile lockout; or
b) volatile lock-out: or
c) one of the following provided that such attempts cannot give rise to the hazardous cndiLn,
1) safety shut-down followed by automatic recyding; or
2) spark restoration.
The time for the flame detector system to de-energize the burner automatic shut-off valves upon flame failure shall not exceed 2 s. This shall be verified under the test conditions described in 7.2.4. Notwithstanding this requirement, where a spark restoration system is used, this time may be extended to allow for the re-ignition attempt but shall not exceed the first safety time.
