Vapour pressure device
This type of device is commonly used on cookers and typically does not have a closed position. Instead it has a low fire rate, or bypass used to light a burner on low flame.
The low flame is positioned on to the probe containing a volatile vapour. As the flame heats up the probe, the vapour expands to move a bellows, thus opening a gas valve to main flame.
If the flame is extinguished the vapour pressure reduces, the valve then closes the main gas supply to the burner , aid by the spring. The valve then reverts to the low fire position.
Faults
Flame stays on low flame probe wrongly positioned
Flame go’s to full flame gas valve stuck open dirt on seat of valve
No pilot gas blocked injector
Liquid expansion thermostat
This type of thermostat can be found on gas cookers.
The phial is positioned in the area to be heated and is filled with liquid, and connected to the bellows. The bellows move a lever which in turn moves the spring loaded gas valve up and down.
The lever is pivoted on the adjustment screw. Turning the thermostat knob will move the fulcrum and will alter the distance of the valve from its seating.
When the bellows expands due to the heat, the valve begins to close and gas passes through the by-pass to keep the burner alight at low rate. If the phial cools, the valve will reopen to maintain a constant temperature.
Faults
Flame go’s out by-pass blocked
Overheating out of calibration
Under-heating out of calibration or gas rate to low
Please any help would be great as started to get stressed abit
Taking acs at a BPEC center
Cheer Paul
This type of device is commonly used on cookers and typically does not have a closed position. Instead it has a low fire rate, or bypass used to light a burner on low flame.
The low flame is positioned on to the probe containing a volatile vapour. As the flame heats up the probe, the vapour expands to move a bellows, thus opening a gas valve to main flame.
If the flame is extinguished the vapour pressure reduces, the valve then closes the main gas supply to the burner , aid by the spring. The valve then reverts to the low fire position.
Faults
Flame stays on low flame probe wrongly positioned
Flame go’s to full flame gas valve stuck open dirt on seat of valve
No pilot gas blocked injector
Liquid expansion thermostat
This type of thermostat can be found on gas cookers.
The phial is positioned in the area to be heated and is filled with liquid, and connected to the bellows. The bellows move a lever which in turn moves the spring loaded gas valve up and down.
The lever is pivoted on the adjustment screw. Turning the thermostat knob will move the fulcrum and will alter the distance of the valve from its seating.
When the bellows expands due to the heat, the valve begins to close and gas passes through the by-pass to keep the burner alight at low rate. If the phial cools, the valve will reopen to maintain a constant temperature.
Faults
Flame go’s out by-pass blocked
Overheating out of calibration
Under-heating out of calibration or gas rate to low
Please any help would be great as started to get stressed abit
Taking acs at a BPEC center
Cheer Paul
