Vent Testing and Repair
As I mentioned in the discussion "Gorton Air Vent Quality", I had so many vent failures that I found it necessary to not only pre test Vents before installation but to repair the existing failed vents because the high number of replacement vent failures. First, I will explain the components of steam vents. Second, how they operate. Third, Requirements
for their proper operation. Finally, Testing typical failures and repair.
Components:
Each vent regardless of type has:
1] Input opening
2] Case or Housing
3] Seat with air port
4] Pin/head and float
5] Thermal element
6] Output opening
[See Vent Diagram]
The operation:
1] Low Temperature position:
The thermal element which is attached to the case, is in a contracted position and the pin
or head attached to it is not blocking air from passing out of the seat air port. The
amount of air entering the input and leaving the radiator is determined by the output
opening size. This opening can be fixed, interchangeable or adjustable.
2] Closed position:
The steam and or heated air entering the input will heat up the case and the thermal
element attached to it. This transfer of heat will cause some of the steam to condensate
and flow back through the input opening. The case and thermal element will heat up to
a higher temperature. The thermal element will expand forcing the pin / head into the
seat with enough force to close the air port and preventing steam from escaping. In the
case of a bellows system, the expansion and force is determined by it’s volume and the
amount of and type of chemical [usually alcohol] contained in it. In the case of a bi
metal system, the expansion is determined by it’s length and the closing force is
determined by it’s thickness and with.
Requirements:
1] A vent when attached to a mains pipe or radiator must pass cold air within a specified
pressure level without and below closing temperature without closing. In most cases this
should not be more than 3 psi. The closing temperature is normally 140F and is close
to the case temperature. Within 4 to 5 degrees.
2] The thermal element must be positioned so that when the closing temperature is
reached it’s expansion distance is equal to the closing distance which is the difference between the low temperature position and the closed position of the pin / head. The case temperature with steam present is determined by the ambient temperature, the temperature transfer coefficient of the vent, the transfer of heat between the input opening and the radiator or pipe and the steam temperature [212F to 218.5F between 0 and 2psi]. The proper closing distance cannot be determined accurately unless the tolerance or deviation of the pin / head dimensions is known.
3] The movement of the pin / head into the seat should be with little friction
Test Setup: [See Test setup and options]
1] Induction Cooktop: heat source
2] Induction adapter plate: non iron heating
3] Pressure cooker 1930 15 Qt: Steam generator
4] Pressure release valve: protection
5] Siphon SS 1/4" with loop: protection
6] Gauge 3 psi 1/4": Monitor pressure levels
7] Tee 1/4 SS: Connections
8] Valve ball SS 1/4": Steam flow control
9] Adapter M/F SS: 1/4" to 1/2 or 1/4" to 3/4" or 1/4" to 1/8:
10] Elbow 90 SS: 1/4 to 1/2, 1/4 to 3/4"
11] Coupler SS 1/4"
12] Type K thermocouple and meter: monitor case temperature
Using this test set up each Vent type can have its shut off case temperature which is
close to the thermal element temperature by throttling the valve and watching the
gauge needle fluctuate with steam turbulence passing through the tee to the vent and
looking at what temperature the turbulence stops. The shut off temperature can also be
determined if the vent closes too fast to monitor the temperature by turning off the
pressure cooker after the vent closes, and wait to see at what temperature the vent opens.
This can even be a negative temperature as the pressure cooker cools it makes a vacuum.
This setup can determine the Shut off temperature of any vent and if mains vents would pass or fail in the field. It will not determine pass or fail for radiator vents which are
apparently affected by the connection to the cast iron radiator. Pass or fail for radiator
vents were determined by their operation when connected to actual radiators. I have
obtained a small radiator for this purpose in the future. Must determine how to connect it
to the pressure cooker.
Common Failures:
1] Will not Pass air:
For out off box [OB] vents that do not pass cold air the cause is the pin / head is
stuck in a position blocking the seat hole. Members of this site have mentioned that
Gorton #2 vents will not rattle when this occurs. For in service vents foreign substance
blocking the seat hole. [See G#2 OB]
2] Will not close:
For OB vents that will not close the cause is the expansion distance or force created
by the thermal element is not long or great enough respectively for the pin / head to
reach the closing position or force
3] Will not stay close during the steam cycle:
For OB vents, the vent is closing partly do to pressure not just temperature and will
open as the case temperature and pressure drops
Test and Repair: Gorton vents
I do not at this time whish to go into details as to how the units were unsealed
[Un soldered] and resealed. Here is a summary of the repair procedure:
1] Open unit on hot plate. Examine head and post position in bi metallic strip. If the
head and float are dislodged, replace it in strip hole. For in service vents clean heads
and seat holes with CLR.
2] Measure the closing distance using the bottom of case as reference. Mark the float
bottoms so that you measure from the same location. Example: Low temp = 0.76",
Closed position = 0.92", Closing distance = 0.16"
3] Attach sensor to bi mettallic strip and freeze the vent to determine the fall out
temperature. Example: 53F was measured.
4] Heat the vent and determine the closing temperature of strip. 162F was measured.
5] Cool vent strip to 85F and adjust the strip to close at 140F. A change of Low temp
position from 0.76 " to 0.83" was made. The vent was heated to verify 140f closing.
6] Cool unit to determine new fall out temperature. 30F was measured.
7] Seal vent and rest for leaks, closing pressure and closing temperature.
Conclusions:
I was able to repair 18 of 32 Gorton radiator vents. 3 could not be repaired because of
physical damage and soldering issues. Some were in service so their was corrosion issues that were not reversible. All were purchased within the last 5 months.
1] All OB Gorton vents that closed when turned upside down and would not close when
when they reached 160F case temperature or at all, have closing distances that are
greater than the expansion distance.
2] All OB Gorton vents that had head float fall outs, were due to closing distances that are
greater than the expansion distance.
3] There is no way to know the correct closing distance without knowing the head / float
tolerance. However, If you repair enough vents you can guess the distance consistently.
4] The G#2 vent I referred to was sent as a replacement for a OB failed vent.
I would like to thank the members of heatinghelp for their information on steam heating. You saved me a lot of time money and more important, reputation.
