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Appendix and Glossary
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Appendix and Glossary - 1

Float Type Level Switches Installation and Maintenance Orientation A standard NPT female boss in tank top, bottom or side is all that is required for rapid installation. Units operate normally in any attitude — from the vertical to a 30° inclination — with lead wires up or down. Standard IPS pipe extends units to any intermediate level in the tank. Figure 1. Accuracy and Repeatability The accuracy of many GEMS level switches is ±1/8˝ (3.2 mm) of true liquid level. In order to assure the proper accuracy for your liquid, please specify the specific gravity of the media. GEMS will automatically calibrate for the submergence of the float, based on this specific gravity information. Furthermore, accuracy may be enhanced by specifying whether the circuit condition should be measured on decreasing or increasing liquid level. The repeatability of the actuation point is approximately 1/32 inch (.79 mm). Moisture Protection When moisture exists in conduit and extension pipes, the potential for this moisture to wick down the wire leads and into the switch assembly exists. Should this happen, the switch may fail to close due to a high resistance path through the moisture. There are several means that can be used to prevent this from happening. 1. Pitch conduit away from the level switch when possible so that condensation will drip away from the level switch assembly. Figure 2. 2. When a vertical run of extension pipe is used to extend a level switch down from the top of the tank, a non-conductive silicone oil should be used to fill the vertical run. Alternatively, an appropriate potting may be used to fill the vertical run to occupy the space in which condensation will normally form. Figure 3. By working closely with your GEMS representative, there are many design considerations that can help lessen the effects of moisture. 1. Consider a product such as the GEMS LS-270 Single Level Switch which has a water-tight molded cable. 2. Consider using a unit with a connector and gasket seal. 3. Consider using moisture resistant heat shrink tubing on the switch capsule assembly. 4. Consider using Scotchcast® 2114 sealing compound and electrical insulator. Part No. 157636. A WORD OF CAUTION: Most of GEMS level products incorporate a potting cap or are fully potted. Due to the bonding characteristics of the potting to the wire leads, there is no way of assuring a water tight seal at the potting joint. Our potting cap will resist moisture to some degree, but the precautions mentioned above should be used to assure moisture doesn’t enter the switch and cause a short. Please refer to Gems Instruction Bulletins for detailed installation and maintenance procedures. Instruction Bulletins are available at www.GemsSensors.com X-1 Visit www.GemsSensors.com for most current information.

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Appendix and Glossary - 2

THREAD TREATMENT Thread Treatment Tightening When threading a plastic level switch into a metal coupling, the installer should use a suitable wrench and tighten the threads 1 to 1-1/2 additional turns past hand tight. Over torquing of the threads will result in damage to the plastic mounting plug. Sealing When threading metal threads into a metal coupling, pipe sealant or Teflon® tape is recommended. Due to potential compatibility problems, when sealing plastic threaded units, a compatible pipe sealant such as No More Leaks™ from Permatex® is recommended. Examples: To solve for “L” use the...

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Appendix and Glossary - 3

REED SWITCH PROTECTION Reed Switch Protection APPENDIX X The hermetically-sealed reed switch used in GEMS level switches are extremely rugged and designed to operate reliably for many years – 2 million cycles under ideal conditions. To achieve the maximum service life, reed switches benefit from protected electrical supply. The dependable reed switch is at the heart of most level switch shown in this catalog. IMPORTANT: • Don’t be misled by the resistive ratings of the switches. Most applications involve inductive loads. • Don’t be misled by the wattage ratings of loads. Low wattage loads...

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Appendix and Glossary - 4

JUNCTION BOXES Junction Boxes APPENDIX X GEMS offers optional CSA Listed and FM Approved, explosion-proof junction boxes for many level switch models. Compatible level switches are indicated throughout this catalog by the small icon– . NOTE: Explosion-proof ratings are available only when J-boxes are part of factory assembled sensor unit. J-boxes below, when ordered separately, do not carry explosion-proof ratings. Pyromation® 3-1/16˝ DIA. REF. 1-3/4˝ 3-1/8˝ HEX. REF. REF. Cast Iron Stainless Steel Chain and Pin EPDM Rubber Gasket (300°F/149°C Max. Service Temp.) Finish Electroless Nickel...

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Appendix and Glossary - 5

ELECTRICAL DATA Electrical Data APPENDIX X Standard reed switches in GEMS level and flow switch units are hermetically-sealed, magnetically actuated, make-and-break type. Switches are SPST or SPDT, and rated 20 VA. See the chart below for maximum load characteristics of GEMS level switches. GEMS Sensors Inc. would be pleased to run life tests on our level or flow switches with your specific load, and issue a report indicating the approximate number of cycles that can be expected. U.L. Recognized Units: Switches showing a U.L. listing are rated for 10 VA or 20 VA as shown below. Typical...

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Appendix and Glossary - 6

Glossary of Terms De-energized Valve: The "normal" state of a valve. The condition of an electrically operated valve when no current is being applied. Air, Dry: Air that has most of the moisture removed and has not been lubricated with oil. Differential Pressure: The difference in pressure between two different pressures one of which is not usually defined as absolute zero pressure or atmospheric pressure. Air, Lubricated: Air or gas that has had an oil mist injected into the system. Alternator: A device that alternates between two or more pumps or solenoid valves. Ampere: The basic unit of...

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Appendix and Glossary - 7

GLOSSARY Intrinsically Safe: Control unit that is incapable of generating a spark. This type of control is typically used to interface with equipment which is exposed to hazardous atmospheres. Inverse Mode: Indirect (inverse) mode controls energize relays when the liquid level drops below the lowest probe (typically used in pump up applications to refill vessels). Plunger Seal: A material that is used on the end of a plunger assembly to seal an orifice or fluid path in a valve. Point Level: Type of level control that turns a device On or Off when liquid rises or falls below a single preset...

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