The Upgraded Gas & Electric Self-Contained Kettle
Frequently Asked Questions and Operating Procedures
1. Why is LEGION now using a 316L stainless steel steam jacket for gas self-contained kettles instead of 304L stainless? What is the difference between 316L stainless and "regular" 316 stainless?
The quality of water has continued to decrease throughout the U.S. Water, today, may contain high levels of chlorides which are very corrosive to 304L stainless! In addition, some states allow distilled water with tap water added to be sold as "distilled water"!
LEGION has now replaced 304L stainless with the more expensive 316L stainless to significantly increase the corrosion resistance of the steam jacket and to reduce "stress corrosion cracking" caused by chlorides. However, extremely high levels of chlorides will also attack 316L, and any water added to the jacket must be pure distilled water. The chlorides that attack the steam jacket will also corrode the kettle liner and draw-off tube unless it is 316 stainless!
316L is identical to 316 stainless (17% chromium, 12% nickel, 2.5% molybdenum) with the exception of carbon. "L" designates "low carbon" with a maximum of 3%; standard steel allows a maximum of 10% carbon. Low carbon content improves the corrosion resistance of stainless, and is also required by ASME for pressure vessels exposed to combustion products.
2. What problem does air cause in any self-contained kettle?
A kettle will not operate properly if it contains air. Steam (water molecules in a gaseous state) and air cannot occupy the same space. The air must be removed from the steam jacket in order to allow the steam to transfer the heat from the boiling water to the kettle liner, quickly and efficiently.
3. How does air get into a kettle?
A kettle always contains air after it is built at the time of "start-up". Once the air is removed during the start-up procedure, a kettle will have air only if leakage has taken place through faulty seals, joints and fittings.
LEGION uses Teflon pipe dope to seal pipe threads and couplings to prevent leaks. All kettles are checked before shipment to verify that they are air tight.
4. How can I tell if air is in the kettle?
Check the pressure gauge to determine the presence of air. For an accurate reading, the kettle’s temperature must be below 125°F.
If air is leaking into the kettle, the gauge will show a pressure at or slightly below "0". Only a qualified technician should determine the cause of the leak and repair the kettle.
Note: This section applies only to kettles manufactured before 10/97 without air eliminator valves, and all TEH kettles regardless of date.
5. How can I tell if the kettle is working properly and does not contain air?
When a kettle is void of air and is working properly, the gauge will show a "negative" pressure (below 0) with a reading of approximately 25 Hg (Hg represents inches of mercury). The kettle temperature must be below 125°F.
In a properly running kettle, the steam contained in the steam jacket will condense to water as it cools creating a vacuum. The integrity of this vacuum will remain unless air is leaking into the kettle jacket.
The pressure gauge is the most important device on a kettle. Since it is so essential to the operation of the kettle, LEGION uses only the highest quality of pressure gauges. The gauge is oil filled and sealed to provide vibration and shock dampening thereby assuring long, accurate life.
LEGION also provides a connecting tube between the gauge and the kettle to serve as a steam trap and shock absorber. It is commonly called a "pig tail", and further protects the pressure gauge.
6. How do I remove the air from the kettle?
Air must be removed carefully to prevent burns caused by the escaping steam. Only trained, qualified individuals should purge the kettle. The procedure is as follows:
- Set the thermostat @ 230°F
- Observe the pressure gauge - when it reaches 5 psi, open the safety valve to allow air to escape. The pressure will drop to 0 psi. CAUTION - do not exceed 5 psi. Opening the safety valve at higher pressures is a severe burn hazard.
- Repeat the process several times until steam and droplets of water exit consistently from the safety valve.
- Allow the kettle to cycle several times @ 230°F after the last purge. If all the air is removed from the kettle, the pressure will cycle between 4 - 10 psi.
- Your kettle is now ready to operate very efficiently!
7. How often should a kettle be "burped" (purged) ?
The kettle should be "burped" (purged) only after filling with distilled water or when started for the first time.
Do not burp the kettle to compensate for an air leak! Opening the safety valve to remove air will either allow more air to enter or release moisture from the kettle. Continuous release of moisture will ultimately require the refilling of the kettle with distilled water which increases the risk of introducing chlorides.
8. What should I check before I start the kettle?
Always check the pressure gauge as outlined above. The pressure must be negative to assure there is no air in the kettle.
9. What happens to the pressure when I add cold products to a kettle?
Cold products placed in the kettle will cause the temperature and pressure to drop quickly. The resulting pressure drop could be as low as a negative 25"Hg.
Note: This section continues after Item 4 and applies only to kettles manufactured after 10/97 with air eliminator valves as part of the safety valve assembly.
5. What is the purpose of the air eliminator valve?
An air eliminator valve eliminates the need to burp a kettle by completely removing the air as the kettle warms up to the operating temperature. Without air in the steam jacket, the condensing steam achieves maximum heat transfer to the food in the kettle.
Small air leaks caused by fittings accidentally loosened can be troublesome and difficult to find - the result is some air always remains in the kettle creating poor performance (slow heatup and cooking).
6. How does an air eliminator valve work?
The air eliminator valve allows the air in the kettle to escape as it heats up. Once steam starts to pass through the valve, it will condense in a chamber causing a float to both expand and rise closing a needle valve. Steam can no longer escape through the valve and pressure will start to build in the kettle.
When the kettle is turned off and starts to cool, a vacuum is formed inside the kettle. Condensate inside the air eliminator valve and air are drawn into the kettle, opening the valve, and allowing air to enter the kettle.
7. What problems does an air eliminator valve create?
As the kettle heats up and air is driven out of the kettle, some of the kettle water is also driven out. Depending on the frequency of startup and shutdowns, distilled water will be need to be added more frequently.
Note: This section applies to all kettles regardless of manufacturing date and with or without air eliminator valves.
1. What happens if the low water light is on? What should I do?
If the low water light is on, it is necessary to add distilled water before the kettle will operate. Water should be added by a qualified individual.
The safety valve, water fill device, and sight glass are now located at the rear of the LEGION kettles to allow easy viewing and filling when needed. They also are out of easy reach to prevent accidental or "experimental" tampering. A low water light has been added to the front of the control panel to clearly show a low water condition.
2. Is it necessary to use pure distilled water to fill a kettle?
Absolutely! Pure distilled water is free of chlorides.
LEGION has done it’s part by providing you with the highest quality kettle that now includes:
- The 316 Kettle System
- 316L stainless steam jacket (gas kettles only)
- A low water light in addition to a sightglass
- Teflon pipe dope to seal all pipe fittings
- An oil filled shock dampening pressure gauge
- Relocated safety valve, water fill device, and sight glass to prevent tampering
- New baffled enclosure to keep water out while allowing the components to operate at lower temperatures.
You do your part ... USE PURE DISTILLED WATER WHEN THE KETTLE NEEDS WATER!