Fuel interception valves

FUEL INTERCEPTION VALVE WITH POSITIVE ACTION, APPROVED
AND CALIBRATED INAIL (EX ISPESL)
The advantages off ered by using fuel interception valves are considerably greater than those for thermal discharge valves, as defi ned in the Standard Index denominated “R“ which, when the request for fuel interception valve is indicated, confi rms the alternative possibility to use the thermal discharge valve (self-activating valve, with positive safety, where the shutter opens due to the excessive high temperature and closes again when it decreases. This means that an amount of the produced heat is transferred to the outside, by the discharge of water, in order to reach the preset temperature limit of the same water).
The most signifi cant advantages are outlined as follows:
• Installation is far easier (the thermal discharge valve is in fact also connected to a solenoid fuel valve and /or a valve that allows the reinstatement of the discharged fluid).
• When a thermal discharge valve is foreseen “with reinstatement” when operating the introduction of cold water causes drawbacks to the generator (thermal shock).
• When the thermal discharge valve is foreseen “without-reinstatement” when operating
the amount of discharged fl uid can, in most cases, fl ood the boiler room.
• The interception valve makes it easier for the plant designer to choose, as the sizing is per formed entirely according to the sizes of the fuel adduction pipes.
• The fuel interception valve is also a much cheaper solution.

OPERATION
The valve consists in two parts:
• The body of the valve through which the liquid or gas fuel fl ows.
• The control device fi tted with a sensitive (diathermic fl uid) element.
• The valve shutter rod is connected to the control device so the valve can be closed (blocked) when:
• a) the temperature of the generator exceeds the set value;
• b) there is a leak of diathermic liquid (positive action).
In the case of a block, the valve closes and can only be operated by manual intervention. This operation can occur when the temperature of the heat generator decreases below 87°C.
The positive action occurs whatever the temperature of the sensitive element.
Under normal conditions (temperature less than 97°C) the rod (4) rests on the control piston (6) and the valve remains open.
If the piston moves to the left due to the expansion of the fl uid content in the sensitive element (9) it will cause the valve to close instantly.
If the piston moves to the right due to a leak of fl uid from the capillary (breakage) it will cause the valve to close instantly.
To perform manual resetting (when the temperature decreases below 87°C) use the reset latch (1).


COMPONENTS
1 Reset latch
2 Valve body
3 Shutter seal
4 Control rod
5 Connection ring nut
6 Control piston
7 Control device body
8 INAIL/I.S.P.E.S.L. seal
9 Capillary tube
10 Sensor pocket
11 Sensor



COSTRUCTIONAL FEATURES
The valve is patented and totally conforms to all INAIL (ex ISPESL- National Institute for prevention and safety) Standards and Specifi cations (Appendix 3)
• Valve body and the control device in forged and chromed brass CW617N
• Bellow in phosphorous bronze
• Copper capillary and probe (length 5m)
• Stainless steel control rod
• O-ring seal ring in nitrilic rubber
• Steel springs
• Other details in brass CW614N


CODE DN A B C D
WP8030 1/2" 65 165 105 90
WP8031 3/4" 65 180 110 105
WP8032 50 mbar 65 180 110 105
WP8033 67 mbar 65 180 110 105
WP8035 100 mbar 65 205 120 122




TECHNICAL FEATURES
Set temperature 97°C ± 3°C
Temperature for manual resetting 87°C
Maximum environmental temperature 50°C
Maximum working pressure 6 bar (Kg/cm2)
Capillary length 5 m
Sensor pocket connection G 1/2” M
Valve body connections G 1/2”; 3/4”; 1”; 1”1/4 e 2” FF

Diagram 1: Loss of valve load with gas-methane
The diagram has been experimentally drawn, using methane gas, with a pressure upstream of the valve of 390 mm c. d’a.

THE CHOICE
The valve is produced in fi ve diff erent versions:
Art. 8030 DN 1/2” Kv = 1,8
Art. 8031 DN 3/4” Kv = 5,0
Art. 8032 DN 1” Kv = 5,3
Art. 8033 DN 1” 1/4 Kv = 16
Art. 8035 DN 2” Kv = 31
To choose the right valve, it is not necessary to refer of to the generator power or to the static pressure, etc., it is enought choose the model with the same diameter equal to that of the fuel supply pipe. The DN 1/2” version is particularly suitable for gas-oil fuel; the loss of capacity provided by the valve during the flow gas-oil, with density 10,3 cSt, is:
100 Kg/h : 4 mm c. d’a.
150 Kg/h : 8 mm c. d’a.
200 Kg/h : 14 mm c. d’a.
Negligible losses in capacity, for the normal pipe lengths and burner suction pressures. The valve to be used when the fuel is thick oil is generally the DN 3/4” or DN 1” version. The DN 1” version can be used with maximum capacities of 200 Kg/h of naphtha (density 100 cSt). The 1”1/4 and 2” versions are normally used in gas systems.
It is renowned that the most commonly used gaseous fuel is methane gas; this fuel is distributed at a relatively low pressure and therefore the interception valve has to provide a limited loss of capacity. To assist in this choice, we have indicated the features of the valves in Diagram 1. The diagram has been prepared, under an experimentation form, using methane gas; the drop in pressure in the valve can reach diff erent values, according to the available pressure.
Generally methane is available at a pressure which varies from 6/700 and 150 mm c. d’a. from area to area and, very often, the pressure tends to decrease in the winter period when the request for fuel is at its highest. To avoid that the drop in pressure in the valve prevents the correct functioning of the burner, it is recommended to limit the loss of capacity in the valve. We consider that, in most cases, is not possible to foresee a drop in pressure over 40 mm c. d’a. for a valve; with this loss in capacity the level in N m3/h will be:
DN 2” = 41 m3/h ≈ 350.000 Kcal/h.
DN 1” 1/4 = 20 m3/h ≈ 170.000 Kcal/h.
DN 1” = 7,5 m3/h ≈ 65.000 Kcal/h.
Evidently the verifi cation of the pressure available upstream of the valve and the minimum level required by the burner will allow you, with the help of diagram 1, to make a precise choice of the loss of capacity of the valve.

NOTES ON INSTALLATION
The copper sheath that receives the probe has to be completely submerge into the fl uid (fig.1 and 2). Avoid excessively small curve radiuses (R min=70 mm) (fig. 3). A green colour seen through the transparent cap means the valve is in the open position (fig. 4); in the case it is activated (block) the green latch will descend and will no longer be visible through the transparent part of the hood. To perform manual resetting, proceed by unscrewing the cap to raise the rod using the reset latch (fig. 5 and 6).