Honeywell DBC2000 Series User Manual

ENI7003R8 KO65 2013
18
APPENDIX: Calculations for VPS
General
The maximum allowable leak-rate (according EN676 and
EN746-2) is 0,1% of the maximum burner capacity. The test
time necessary to detect a failing valve is a function of:
- Inlet pressure
- Test volume
- Burner capacity
When the volume between two safety valves is bigger it takes
more time (in case of a leaking valve) to change the status of
the gas pressure switch (GPS).
The switching point of the GPS is set to 50% of the maximum
inlet pressure. The test period Tp is calculated from the
inletpressure Pi, the test volume Vp (see Table a.) and
maximum burner capacity Qm. In a formula:
2 x Pi x Vp
Tp = --------------- [s]
Qm
Pi = inlet pressure [mbar]
Vp = test volume, see also Table a [dm
3
]
Qm = burner capacity [dm
3
/h]
Tp = test time [s]
Important
The total volume Vp has to be calculated with all volumes
between the tested valves: internal volumes of valves and all
pipes.
Calculation examples
Example 1
Calculation of the minimum test time (per valve) in a 2”
threaded pipe train.
Pi = 150 mbar
Qm = 60 dm
3
/h
Gas valves used: 2” size with 0.5 meter pipe.
To be calculated: Tp [s]
Calculation:
From Table a. :
2“ @ L=0.5m  Vp = 2.3 dm
3
2 x 150 x 2.3
Tp = ---------------- [s]
60
Using the formula above, the minimum test time Tp = 11.5s
The DBC2000E2 must be set to 15s test time (see page 11).
Example 2
NOTE: to allow a 3-valve configuration, an external SPDT
relay needs to be added, when used incombination with VPS.
See schematic drawing below.
Calculation of the minimum test time (per valve) in a DN80
flanged pipe train, where a 1” bypass valve is used.
Pi = 150 mbar
Qm = 100 dm
3
/h
Gas valves used: DN80 size with 1 meter pipe (L1).
Bypass valve: 1” valve with 0.5 meter pipe (L2).
To be calculated: Tp [s]
Calculation:
From Table a. :
DN80 @ L1=1m  Vp1 = 6.9 dm
3
1” @ L2=0.5m  Vp2 = 0.44 dm
3
There is only 1” bypass valve, that reduces the total volume
by 0.5x the volume @ L=0m  Vp3 = 0.19 dm
3
Vp = Vp1 + Vp2 – (0.5 x Vp3) = 7.245 dm
3
2 x 150 x 7.15
Tp = ------------------ [s]
100
Using the formula above, the minimum test time Tp = 21.735s
The DBC2000E2 must be set to 25s test time (see page 11).

Honeywell DBC2000 Series Specifications

General

Brand	Honeywell
Model	DBC2000 Series
Category	Controller
Language	English