BENSON JETSTREME 4+ - Two Pipe System

Two Pipe System
Where it is not possible to install a gravity oil supply system then a two pipe pumped system
must be installed. The oil in this arrangement is drawn from the tank by the pump on the burner,
and any excess is returned via the second pipe to the tank If a two pipe system is to be fitted, the
pump on the burner will require to be modified from that supplied (See Burner Manual).
The
diagrammatic layout of the pipe work for a two pipe system is shown below. Where the
tank is below the level of the oil pump the two pipes should each be the same length into the oil. If
the return pipe is shorter than the flow, then it will be necessary to fit a spring loaded non-return
valve to this pipe.
On a two pipe system the pump vacuum should not exceed 0.4 bar (30cm Hg). If this is not
observed then dissolved gas will be released from the oil resulting in oil starvation to the burner
and repeated boiler 'lockouts'.
A filter
of the metal bowl type with a micronic filter should be installed in the oil return pipe. If
this pipe should become blocked it may cause the pump to fail.
The installer MUST supply and fit a fire check valve in the oil supply line, and this valve must
comply with BS 799: part 5: 1977 Specification for Oil Storage Tanks.
The pipe size requirement is given in the table below.
TWO PIPE OIL SYSTEM - TANK OUTLET BELOW BURNER
JETSTREME 4 +
FIRE CHECK
VALVE SENSOR
VENT
.-------------;;::::~~F=F::r::F1 '.::t:J[j.Lf-jf----- RETURN PORT
A
NON RETURN
RETURN PIPE
FILL
SLUDGE
COC~K~~~~~~~~~~~~L-~
FL OW ----Il1o-
FILTER
VALVE
Fig. 2
20 mm PER METRE FALL
-- RE1\.lRN
TABLE GIVING MAXIMUM SUCTION PIPE LENGTH 'L'
HMETRES 0
0.5 1.0 1.5 2.0
3.0 3.5
MAXIMUM
L
PIPEI0mmOD
35 30 25 20 15 8 6
METRES
PIPE
12mmOD
100 100 100
90
70 30 20
Table 4
7