35 Dealing with Type II and N Pattern Assemblies Pete Chapman

Transcription

1 35 Dealing with Type II and N Pattern Dealing with a Type II Detector Assembly Bypass Single Check An Obstruction In the Pipeline to Slow OR Divert Flow Function Mainline Non Testable single check Swing check no closing force Spring or weight loaded to a Closed Position NOT considered an Approved Backflow Preventer Single Detector Check, Flow Detection, BUT NOT A BACKFLOW PREVENTER! Function To Recognize Unauthorized Water Flow on an Unmetered Fire Sprinkler System Mainline Single Check Acts an Obstruction to Force Low (?) Flows Thru a Bypass Meter Bypass line No Check Valve on Bypass Typically ¾ x 5/8 Residential Water Meter Indicates Unauthorized Water Usage No Hydraulic Balance Backflow Preventer With Bypass Cross Connection ASSE 1993 (& Earlier) DCDA Description th Edition. Foundation for Cross Connection Control and Hydraulic Research at The University of California Original Double Check Detector Assembly (DCDA) Specification 4 April

2 35 Dealing with Type II and N Pattern th Edition. Foundation for Cross Connection Control and Hydraulic Research at The University of California ASSE 1993 (+ Earlier) RPDA Description Original Reduced Pressure Detector Assembly (RPDA) Specification Typical Early ( s) DCDA Early DCDA W/ Heavy loaded 2 nd Check Spring Typical Early DCDA with Compression Spring Checks with Heavy Loaded 1st (could be 2 nd check) Check Mainline Spring Later Model Lower Pressure Drop DCDA Design With Standard Double Check Spring Loads Allows Accurate Metering of Low Flows up to 3 GPM Thru the Bypass ONLY, W/ Mainline Closed Detection Mode Bypass Checks Open Mainline Checks Closed 4 April

3 35 Dealing with Type II and N Pattern Later Model Lower Pressure Drop DCDA At Fire Flows 3+ GPM Main Line & Bypass Both Open Meter Reading, but Inaccurate Fire Suppression Mode Bypass Checks Open Mainline Checks Open ASSE DCDA Section of ASSE states: "The bypass line shall include either a water meter, an alarm signaling assembly, or both. The bypass line shall bypass either the first and second checks, or the second check only. A bypass line that bypasses the first and second checks shall include an ASSE 1015 double check assembly. Flow rates up to and including 2.0 GPM (0.13 L/s) shall be directed through the bypass. A bypass line that bypasses the second check shall include a bypass check assembly with a shut-off valve upstream and downstream in the bypass line. The bypass line shall include two test cocks, one between the upstream shut-off and the bypass check and one downstream of the bypass check but before the downstream shut-off. Flow rates up to and including 2.0 GPM (0.13 L/s) shall be directed through the bypass." ASSE RPDA USC FCCC & HR 10 th Ed DCDA Type 2 Bypass Section of ASSE states: "The bypass line shall include either a water meter, an alarm signaling device, or both. The bypass line shall bypass either the first and second checks, or the second check only. A bypass line that bypasses the first and second checks shall include an ASSE 1013 reduced pressure principle assembly. Flow rates up to and including 2.0 GPM (0.13 L/s) shall be directed through the bypass. A bypass line that bypasses the second check shall include a bypass check assembly with a shut-off valve upstream and downstream in the bypass line. The bypass line shall include two (2) test cocks, one between the upstream shut-off and the bypass check and one (1) downstream of the bypass check but before the downstream shut-off. Flow rates up to and including 2.0 GPM (0.13 L/s) shall be directed through the bypass." USC FCCC & HR 10 th Ed RPDA Type 2 Bypass Double Check Detector Assembly DCDA (Type 2) Protects Against Backflow & Tests Identical as Type 1 Mainline DC Each check holds minimum 1 psi Bypass line Water Meter & Single check Measures low flows (<2 gpm) Bypasses only 2 nd check (Double Check Protection!) Each Check Still holds 1 psi Minimum 4 April

4 35 Dealing with Type II and N Pattern Type II Bypass Single Check Type II Bypass Check example Testable Repairable Includes Serial Number Type 2 & Type 1 Bypass Detector DCDA Type 1 Bypass Both Meet all National Standards Both Provide the Same Backflow Protection Both Test the Same Way Both Provide 2 Serial numbers DCDA Type 2 Bypass DCDA Type II Detector Flow <2GPM 4 April

5 35 Dealing with Type II and N Pattern DCDA Type II Detector Fire Flow 2>GPM DCDA Type II Fouled 1 st Mainline Check RPDA Type II Fire Flow 2> GPM RPDA Type II Both Checks Fouled with both Backsiphonage And Backpressure Type 2 & Type 1 Bypass Detector Both Meet all National Standards Both Provide the Same Backflow Protection Both Test the Same Way Both Provide 2 Serial numbers Questions? 4 April

6 35 Dealing with Type II and N Pattern N Shape Backflow Preventers Dealing With n shape Flow Pattern Backflow Preventer What is an n shape Backflow Preventer? The History of Approved n Shape Backflow Preventers What are the Advantages of an n shape? Any Disadvantages? Traditional Inline Backflow Preventer n Shape Internal Checks Positioned to Provide n Flow Path Toro Orion, Original n Shape Backflow Preventers ¾ Double Check Reduced Pressure Febco 825YA n Shape ¾ Current Reduced Pressure 4 April

7 35 Dealing with Type II and N Pattern Febco Master Series n Shape 2 ½ Current Double Check Double Check Detector Reduced Pressure Reduced Pressure Detector Zurn Wilkins 975XLSEU n Shape ¾ Current Reduced Pressure Assembly Zurn Wilkins 400 Series n Shape Current Double Check Assembly Double Check Detector Assembly Reduced Pressure Assembly Reduced Pressure Detector Assembly Apollo Valve 4An Series ¾, Current Reduced Pressure Assembly Apollo Valve 4An Series 2 ½ Current Double Check Double Check Detector Reduced Pressure Reduced Pressure Detector n Shape Advantage Smaller Footprint 4 April

8 35 Dealing with Type II and N Pattern Advantages: Space Saver! Advantages: Smaller Installation Space Required Traditional Inline Lay Length 2 ½ New n Shape Assembly Width 2 ½ n Shape Advantage Space Saver Remember OS&Y Shutoff Valves Open Dimensions Example: 4 A = 14 Example: 4 = 18.6 Advantages: Vertical Reduced Pressure N Shape Advantages Vertical RP Installations 4 April

9 35 Dealing with Type II and N Pattern n Shape Advantage Same Repair Kits as Traditional Straight Inline n Shape Advantage: Ease of Installation Optional Setters No Concrete Necessary No Thrust Blocks Necessary Prefabrication Ability n Shape Assembly With Setter Installation n Shape Advantage: Smaller, Less Costly Enclosures n Shape Advantage: Similar Pressure Loss Performances n Shape Backflow Preventer Disadvantages New! My Daddy Didn t use Them No Direct Connection Ability to Fire Department Connections Additional Height Makes Vault Installations Awkward 6 8 Y Strainer Adds Height (Rather than length) 4 April

10 35 Dealing with Type II and N Pattern n Shape Disadvantage Fire Department Connection n Shape Disadvantage Fire Department Connection n Shape Disadvantage Vault Installations n Shape Disadvantage Y Strainer Added Height Requirement, Flushing Ability Additional Height Required Additional Length Required Space Saving n Shape Backflow Preventer Thank you! Questions? 4 April