BlueInGreen 4375 N. Vantage Rd., Suite 202 Fayetteville, AR 72703 United States BlueInGreen: +1 304 825 5244 AdEdge: +1 678 835 0052 ChartWater India: +91-9717032880, +1-330-805-2615

The water pressure will be reduced by the amount of pressure it takes to open the first check spring loading. The 1st check of an RP can have a loading of anywhere between 5-15 PSI depending on the make, model and size. In our generic RP, we will assume our relief valve spring generates a 2.0 PSID and the first check spring has a 10.0 PSI Loading.

The test procedure for the second check is different than the first check. The 2nd check test is a backpressure test, while the 1st check is a direction of flow test. In our field test of the 2nd check, we take the higher inlet pressure form test cock #2 upstream of the first check (100 PSI), and with needle valves and hoses, place it into our number four test cock (85 PSI) causing the pressure on the downstream side of the second check to rise until it is higher than the upstream side of the second check. When the field test is performed on a working 2nd check, the check disc will be embedded farther into the check seat. This can cause a condition known as disc compression as previously mentioned. When the second check fails, the higher pressure would go past the leaking second check into the area between the two checks. As the pressure in this area increases, the relief valve senses the differential. When the pressure in the area between the two checks increased to 98.0 PSI (relief valve opening point 2.1 PSID), then the diaphragm would move, causing the relief valve to open. The causes of failure on a second check are similar to the first check.

Howden Air and Gas India Private Limited Survey No. 127 & 130, NH-207 Sarjapur-Bagalur Road Hosur Taluk, Tamil Nadu 04344 2556 India         Products: Centrifugal Blowers Compressors - Centrifugal Compressors - Reciprocating and Diaphragm Compressors - Screw Centrifugal Fans Cooling Fans Heaters - Gas Gas Heater Howden Aftermarket Axial Fans Turbo Fans

CPI France 95 Rue de Neuf-Mesnil, Batiment A8 Feignes, 59750 France France: +33 (0)327 63 16 64 Spain: +34 (0)91 651 9355 Germany: +49 6152 9316 0 United Kingdom: +44 (0)1488 684 585 Netherlands: +31 (0)1816 63149   Products: Howden Aftermarket Compressors - Reciprocating and Diaphragm

3415 Earl B. Wilson Rd New Iberia, LA 70560 United States Telephone: +1 337 369 9195   Products: Brazed Aluminum Heat Exchangers Air Cooled Heat Exchangers

Let us see what happens when we apply backpressure to a non-working 2nd check. Once the pressure begins to increase on the outlet of our assembly, the 2nd check cannot maintain the separation of pressures between the inlet and outlet of the 2nd check, and the pressure will equalize on both sides. As the pressure increase begins (from 85 PSI in our illustration) the area between the 2 checks will also increase. Remember that the area before the 2nd check is where our low pressure is applied to the low pressure side of our relief valve elastic element. As the pressure increases above our starting pressure of 85 PSI, and goes to the point equal to the inlet pressure minus the relief valve opening (100 PSI - 2.0 PSI = 98) of 98 PSI, the relief valve will open.

There is a variation of a DC called a (DCDA). This is a double check created for fire sprinkler applications. A DCDA consists of an approved DC with a bypass arrangement that consists of a by-pass water meter and an approved by-pass DC. This by-pass is piped around the mainline DC. The purpose of this by-pass arrangement is to detect and register the first 3 gallons per minute (GPM) of flow across the backflow preventer into the fire system.

Let us assume we have a proper working RP, and we apply backpressure to the outlet side of our RP. In our illustration, the normal upstream pressure is 100 PSI and the downstream pressure is 85 PSI. If the starting downstream pressure (85 PSI) increases to105PSI for example, and the second check is working properly, the 2nd check closes and keeps the 105PSI pressure from migrating into the area (90 PSI) between the 2 check valves.

CPI Netherlands Harregatplein 17 Zuidland, 3214 Netherlands France: +33 (0)327 63 16 64 Spain: +34 (0)91 651 9355 Germany: +49 6152 9316 0 United Kingdom: +44 (0)1488 684 585 Netherlands: +31 (0)1816 63149   Products: Howden Aftermarket

Backsiphonage is a condition that causes a sub-atmospheric pressure to be applied to the upstream side of the assembly. Backsiphonage can happen for several reasons; one of the more common is excessive water demand in the distribution system.

Now let us look at how an RP reacts when components of the assembly are not working properly and how we can diagnose the condition. Let's assume we perform a field test on an RP and generate a 1.5 relief valve opening point. Does this mean the assembly is "leaking" or will not prevent backflow? The answer is probably no. We know from our tester training that 2.0PSID is the minimum acceptable relief valve opening point. If the relief valve opens at 1.5PSID, the relief valve will open and keep the pressure in the area between the two checks 1.5 PSI lower than the upstream pressure, if subjected to a backflow condition. An RP with a 1.5 PSID relief valve opening point will still prevent backflow, but does it at a value lower than the minimum accepted value of 2.0 PSID. For the assembly to perform optimally, it must operate at or above this minimum standard, in this case 2.0 PSID.

Howden Americas 7204 Harms Road Houston, TX 77041 United States Telephone: +1 716 817 6900

403 35 Libouchec Decin, 403 35 Czech Republic Telephone: +420 412 507 343

Many testers think a DCDA is simply any small by-pass DC piped around any main line DC with a meter attached, and because the by-pass DC is smaller, the first flow will go through it. This is not true. In order for the by-pass to detect and register 3 GPM, the two DC's and the water meter must be engineered so that the larger assembly will have a slightly higher differential at the low flow condition of 0-3 GPM. This will ensure that the first 3 GPM travel through and are registered by the water meter in the by-pass. Then, if the fire system demands more than 3 GPM, the main line assembly will open up and flow will commence up to the designed flow requirements of the system.

Howden Africas 5A Rand Street, Vaalbank Middelburg, 1050 South Africa Sasolburg: +27 16 986 0795 Middelburg: +27 13 246 8400 Johannesburg & Cape Town: +27 11 240 4000

Howden Africa 5 Van Biljon Industrial park Cape Town, 7530 South Africa Sasolburg: +27 16 986 0795 Middelburg: +27 13 246 8400 Johannesburg & Cape Town: +27 11 240 4000

918 S Park Ln, Suite B-104, 1st Floor Tempe, AZ 85281 United States BlueInGreen: +1 304 825 5244 AdEdge: +1 678 835 0052 ChartWater India: +91-9717032880, +1-330-805-2615

AdEdge Water Technologies 2055 Boggs Rd Duluth, GA 30096 United States BlueInGreen: +1 304 825 5244 AdEdge: +1 678 835 0052 ChartWater India: +91-9717032880, +1-330-805-2615

Once the 1st check opens, water will travel past and pressurize the area between the 1st and 2nd checks. When this area is pressurized, it will also pressurize the low pressure side of our relief valve. The higher inlet pressure (100 PSI) is placed on the high pressure side of the elastic element in the relief valve, and the lower pressure past the 1st check (90 PSI) is placed against the low pressure side of the elastic element.

Watts Under Sink Hot Water Mixing Valve. • Lead free brass body • Field adjustment range 80 to 120º F • For residential and commercial applic ...

Most fire protection systems do not have a mainline water meter at their point of service from the water purveyor, and that is why it is important to detect this low flow of water. Because a fire system is an emergency connection, water purveyors do not want the expense or extra flow loss of going through a full size water meter. Because a fire system is considered an emergency connection, there should be no flow to detect across a mainline water meter anyway. Water purveyors use this bypass to ensure that water users with fire systems do not flow water through this emergency connection, and with the ability of the bypass to detect small flows, they can also detect if there are any small leaks that may be underground and out of sight.

Howden Korea Ltd. & CPI South Korea Ltd. 12-1, Sanan-Ro, Nam-gu Ulsan, 44781 Republic of Korea Seoul Head Office: +82 (0)2 6022 2393 Ulsan Workshop: +82 (0)52 266 1011   Products: Howden Aftermarket

Howden Allegade 6 Helsingoer, 3000 Denmark General Enquiries: +45 4921 1400         Products: Centrifugal Blowers

In this way, water seeking the path of least resistance will close the air inlet before it can open the check valve, thus minimizing any discharge (spill resistance) from the air inlet. In the SVB, water does not have to travel past the check valve to pressurize the air inlet as it does in the PVB. For this reason, the SVB will not discharge from the air inlet on initial start up. Once the SVB is pressurized, the SVB will perform similar to a PVB. The causes of failure of a SVB are similar to those of a PVB as discussed above.

The check valve opens, and water travels past the check valve, and causes an air inlet poppet (spring biased open) to travel up an air inlet guide, compressing an air inlet loading (it's not always a spring), which is designed to generate a load of at least 1 PSI. The air inlet is kept closed by the normal water pressure in the piping system and is designed to open when the force from the air inlet (1.0 PSI Minimum) is greater than the water pressure in the area downstream of the check valve. The PVB is designed to prevent backflow from backsiphonage only, and must be installed 12" above the highest point of use or piping on the downstream of the assembly.

The minimum criteria in a test procedure is set at a point that will trigger a repair before the assembly can degrade to the point where it cannot prevent backflow (0.0 PSI). As long as our check valve has a positive loading, it can prevent backflow, but only when it is above 1.0 PSI does it meet the minimum criteria as established in the test procedure. So once the test procedure generates data that the check is maintaining less than 1.0 PSI, we must repair the check valve and return it to its original working specifications.

Chart has domestic operations located across the United States, international engineering and manufacturing in Europe, India and China and a global network for sales and service.

Howden Hua Engineering Co. Ltd Unit 1807 "Square One" Building, No 18 Dongyu Street Chengdu, Jingjiang District 610016 China

Corporate Headquarters: 2200 Airport Industrial Dr. Suite 100 Ball Ground, GA 30107 United States Main: +1 770 721 8800

IMB Strada Paullese, 2 Bagnolo, Cremasco 26010 Italy IMB: +39 0373 237611       Products: Hairpin Heat Exchangers SPINTUBE LABLEX

There is also a Reduced Pressure Principle Detector Assembly (RPDA). This has a main line RP with a bypass arrangement containing a smaller RP and detector meter to register the 1st 3 GPM of flow. These RPDA's are used on high hazard fire systems, and the DCDA is used for low hazard fire systems, when the detector function is needed.

Howden Korea Ltd. #320, C Bldg. H Business Park, 26, Beobwon-ro 9-gil, Songpa-gu Seoul, 05836 Republic of Korea Seoul Head Office: +82 (0)2 6022 2393 Ulsan Workshop: +82 (0)52 266 1011 Products: Howden Aftermarket

SUEZ

Ustecka 30 Decin, 405 30 Czech Republic Telephone: +420 412 50 7111         Products: Bulk CO2 Carbonation Bulk Storage Tanks Europe Aftersales Liquid Cylinders LNG Fueling Stations MicroBulk Storage Systems

CPI Germany Robert Bosch Strasse 3 Buettelborn, D-64572 Germany France: +33 (0)327 63 16 64 Spain: +34 (0)91 651 9355 Germany: +49 6152 9316 0 United Kingdom: +44 (0)1488 684 585 Netherlands: +31 (0)1816 63149   Products: Howden Aftermarket

1725 Graham Road Franklin, IN 46131 United States Telephone: +1 317 535 4315   Products: Brazed Aluminum Heat Exchangers Air Cooled Heat Exchangers Vaporizers

No. 11, Fu Kang Road, New District Changzhou, Jiangsu 213032 China Telephone: +86 519 8596 6000     Products: Cryogenic Transport Trailers

Howden South America - Brazil Av. Osvaldo Berto, Distrito Industrial, Alfredo Rela Itatiba, CEP 13255-405 Brazil Telephone: +55 11 4487 6250

Calle 124 No. 7-35 - Officina 703 Calle 124 No. 7-35 Officina 703 Bogota, 110111 Colombia Telephone: +57 (1) 214 2822

Howden Vietnam Company Limited 1E Nguyen Van Thu Street, Da Kao Ward Ho Chi Minh City , District 1 Vietnam   Products: Howden Aftermarket

The normal path of water for a PVB is for water to enter the body, then open the check valve with a minimum 1.0 PSI loading, proceed past the check valve, and seal the air inlet with a minimum 1.0 PSI loading. The SVB is a little different. The check and air inlet have the same 1.0 PSI check and air inlet minimum loading requirements, but the order of the operation of the components is different.

8665 New Trails Drive Suite 100 The Woodlands, TX 77381 United States Telephone: +1 281 364 8700

Howden Air and Gas India Private Limited 147 Poonamallee High Road, Numbai Chennai, 6000077 India         Products: Centrifugal Blowers Compressors - Centrifugal Compressors - Reciprocating and Diaphragm Compressors - Screw Centrifugal Fans Cooling Fans Heaters - Gas Gas Heater Howden Aftermarket Axial Fans Turbo Fans

The cause of a relief valve opening below the 2.0 PSID minimum can vary greatly between different models. Usually, the incorrect assumption is made that a spring has worn out and that is why the relief valve will not open. The most common cause of low relief valve opening points is a restriction on the travel of the relief valve stem mechanism. Either the guide of the relief valve becomes damaged, or a scale or corrosion will cause the guide to not travel optimally leading to a low relief valve opening point.

Sustainable Energy Solutions 1489 West 105 North Orem, UT 84057 United States Telephone: +1 801 528 9509         Products: Cryogenic Carbon Capture

CPI Spain Calle de los Aragoneses, 2 Alcobendas Madrid, 28018 Spain France: +33 (0)327 63 16 64 Spain: +34 (0)91 651 9355 Germany: +49 6152 9316 0 United Kingdom: +44 (0)1488 684 585 Netherlands: +31 (0)1816 63149   Products: Howden Aftermarket

Dormont A75 3/4" SnapFast Quick Disconnect in Home. ADD NOW. $86.88. Quantity: 0. OUT OF STOCK. CALL 330-775-7577 FOR LEAD TIME & SHIPPING QUOTE.

CPI 19520 Rancho Way, Suite 206 Rancho Dominguez, CA 90220 United States Baton Rouge: +1 225 752 4272 Los Angeles: +1 310 223 1101 Stafford (Houston): +1 281 207 4600 Philadelphia: +1 215 946 0845

As the inlet shut-off is opened, water enters the upstream side of the backflow prevention assembly body ahead of the 1st check valve. Once in this area, the water enters a relief valve sensing line. Some sensing lines are external hose or pipe, and some utilize an internal passageway. The water travels through this sensing line to the elastic element in the relief valve. The elastic element is either a diaphragm, or a rolling diaphragm. This pressure will build up on the high pressure side of the elastic element, which will deflect and cause the relief valve stem to compress the relief valve spring, and move the relief valve disc to seal against the relief valve seat. The function of the relief valve spring is to constantly try to open the relief valve.

GOFA Am Mooshof 15 Goch, D-47574 Germany GOFA Sales: +49 (0)2823 328 224 GOFA Service & Repairs: +49 (0)2823 328 185 GOFA Spare Parts: +49 (0)2823 328 0         Products: Cryogenic Transport Trailers Non-cryogenic Transport Trailers Europe Aftersales

Howden GmbH Naundorfer Strasse 4 Coswig, 01640 Germany Aalen Ebnat: +49 3523 940 Coswig: +49 7321 5504 900 Olpen: +49 2761 7029 600         Products: Howden Aftermarket

Panasonic [SD3-A1], Safety Laser Scanner Type 3 SD3-A1(Discontinued), Part number detail page. Detailed specification of is here.

The check valves of a DCDA are similar to the DC and the repair process will be similar. In many cases, the spring loading of the mainline assembly or the by-pass may be different from the standard DC, but the repair procedures and the test procedures to diagnose its workings are the same. Before we can repair any assembly, it is important to have correct data on the workings of the assembly to be sure we know what we are fixing, and just as importantly, that it really does need to be repaired.

16 Feb 2014 — What is Hydronic Radiant Heating? Have you ever walked past a large brick building long after the sun goes down, and felt warmth all over your ...

Veolia north america

Sometimes the air inlet will fail, in which it will not fully unseat itself when the water pressure in the body past the check valve is below 1.0 PSI. This can occur when the air inlet disc adheres to the air inlet seat, caused by temperature or water quality conditions.

BlueInGreen-Manufacturing 1201 W Sunchase Ct. Fayetteville, AR 72701 United States BlueInGreen: +1 304 825 5244 AdEdge: +1 678 835 0052 ChartWater India: +91-9717032880, +1-330-805-2615

299 West Huanghe Road New District Changzhou, Jiangsu Province 213032 China Telephone: +86 519 8596 6000     Products: Bulk Storage Tanks MicroBulk Storage Systems Liquid Cylinders ISO Containers

CPI 6308 Davies Road NW Edmonton, Alberta T6E 4M9 Canada Brantford: +1 519 753 8671 Edmonton: +1 780 468 5145   Products: Howden Aftermarket

Flow Instruments, GmbH Siemensstr 19 Monheim am Rhein, 40789 Germany Telephone: +49 2173 96059 0         Products: Flow Measurement Europe Aftersales

48 Pine Road Brentwood, NH 03833 United States Toll Free (from US): 855 LEASE 00 Main US: +1 855 532 7300 New Hampshire: +1 603 505 6380 Europe: 00 800 2796 4413     Products: Cryo-Lease Equipment Repairs & Services

Find strainer at a store near you. Order strainer online for pickup or delivery. Find ingredients, recipes, coupons and more.

Conditions that can cause a check to perform below its optimum level are many. The main cause of check failure is due to the failure of the disc to seal with adequate force against the check seat. Many times the check spring is blamed for this lack of force but this is usually not true. The more common causes of failure are dirt and debris between the disc and seat. Another common problem is disc degradation where the disc will not seal tightly against the check seat. The third common cause is a restriction in the travel of the guide, limiting the movement of the check valve and prohibiting it from sealing properly.

Thermostatic mixing valve for mixed water from 30 to 60°C, 5 - 33 lpm M1/2", rough finish.

FEMA Via Tibet, 5 Busto Arsizio, Varese 21052 Italy Sales & Enquiries: +39 0331 1646099       Products: Safety Valves

L.A. Turbine 28557 Industry Drive Valencia, CA 91355 United States Global Consult & Service (24/7): +1 855 FX-TURBO or +1 855 398 8726 Sales & Engineering Office: +1 661 294 8290 24/7/365 Helpline: +1 855 FX-TURBO         Products: Turboexpanders

The first check rarely fails where there is no differential. The usual case is that instead of a 10 PSID, as shown in our example, the differential begins to fall as the first check begins to wear out. Let us assume we know our relief valve has a 2.1 PSID opening point. Let's add further that our first check is starting to degrade and it can only generate a 2 PSID. In other words our upstream pressure is still 100 PSI and the downstream pressure of the first check is 98 PSI and we know we have a 2.1 relief valve opening point, what would happen to our relief valve? The relief valve would open up and begin to discharge. If we have a 100 PSI inlet pressure and a pressure of 98 PSI after the first check, you can see where the 98 PSI along with the 2.1 PSI from the relief valve spring loading would cause the diaphragm to move, causing the relief valve to open, because there is a greater pressure on the downstream side of the relief valve diaphragm (98 +2.1 =100.1 PSI) than on the upstream side (100 PSI).

407 Seventh Street NW New Prague, MN 56071 United States Telephone: +1 952 243 8800 Sales/Customer Service: +1 800 400 4683 Technical Service: +1 800 253 1769 Repairs: +1 800 231 8276         Products: Bulk Storage Tanks Repairs & Services MicroBulk Delivery Systems Vacuum Insulated Pipe LNG Fueling Stations

Howden Maintenance Partners Vithoekstraat 6 Zwijndrecht, 2070 Belgium Enquiries: +32 3541 7140       Products: Howden Aftermarket

In order to determine how well a backflow prevention assembly is working, it is important to understand how it operates when it is in a working condition and a non-working condition. It is important that we can diagnose various conditions by performing an accurate field test with an accurate test kit to generate accurate data to make a true assessment of the workings of our assemblies.

VRV Asia Pacific Pvt Ltd 220 Pelto Way Sri City, Andhra Pradesh 517 646 India         Products: Bulk CO2 Carbonation Bulk Storage Tanks Cryogenic Transport Trailers Liquid Cylinders MicroBulk Storage Systems

Conditions that can cause the check in a PVB to perform below its optimum level are similar to the check failures in an RP or DC. In addition, there is a common cause of failure unique to the PVB and SVB, which has to do with the alignment of the check spring. Many models require the spring to be installed with a spring retainer that, if not properly installed, will exert a side pressure on the spring, preventing it from delivering the proper load to the check valve.

Disc compression is one of the most common errors made by a backflow prevention assembly tester when performing a field test. Once the relief valve discharges when testing the second check, you must open the low bleed one more time to determine if the 2nd check is actually working or not. A disc compression scenario may occur, and the tester may incorrectly assume the 2nd check is not working.

CPI 11997 Airline Hwy Baton Rouge, LA 70817 United States Baton Rouge: +1 225 752 4272 Los Angeles: +1 310 223 1101 Stafford (Houston): +1 281 207 4600 Philadelphia: +1 215 946 0845   Products: Howden Aftermarket

Howden Air and Gas India Private Limited Eco Tower, Office 301, Third Floor, Baner Pashan Link Road Pune, 411045 India         Products: Centrifugal Blowers Compressors - Centrifugal Compressors - Reciprocating and Diaphragm Compressors - Screw Centrifugal Fans Cooling Fans Heaters - Gas Gas Heater Howden Aftermarket Axial Fans Turbo Fans

Howden Turkey Dap Yapi Bumerang Ofis, Seckin Sk. No:3 Kagithane/Istanbul, Kat:1 D:34 Turkey Telephone: +90 8502 165 859     Products: Howden Aftermarket

Just because a relief valve discharges water, does not always mean the RP is not working. Pressure fluctuations can simulate conditions that can lead a person to assume the assembly is not working properly. To be sure whether the assembly is working or not, a test kit must be attached and proper test procedures applied to determine the working condition of the assembly.

4075 Hamilton Boulevard Theodore, AL 36582 United States Main (Auto Attended): +1 251 800 6300     Products: Cryogenic Transport Trailers Hydrogen Energy

In order to repair any assembly, RP, DC, PVB or SVB, it is important that the repair technician first understand how the backflow prevention assemblies are supposed to work, so that when they are not working, the problem can be properly identified. The purpose of the repair process is to return the assembly back into its original factory specifications.

Howden Japan Ltd 3-19-11 Ryogoku, Sumida-ku Tokyo, 130-0026 Japan Telephone: +81 3 4540 0390

Howden Solyvent-Ventec 143 Rue de la Republique Meyzieu, 69330 France Telephone: +33 4 72 45 13 00         Products: Axial Fans Centrifugal Fans Tunnel Ventilation

The cause of check failure tends to be due to the failure of the disc to seal against the check seat easily. Many times the check spring is blamed for a check failure but this is usually not true. The more common causes are dirt and debris on the disc, disc degradation where the disc will not seal, or a check guide restricting the travel of the check component.

Chart facilities, services and products offered by region. For invoice queries please send an email to corpaccountspayable@chartindustries.com

Howden Singapore Pte. Ltd 28 Ayer Rajah Crescent, #06-06 Singapore, 139959 Singapore   Products: Howden Aftermarket

In our field test procedures, when we perform the 2nd check test of an RP, we are simulating a backpressure condition by bringing the higher inlet pressure (100 PSI) around to test cock 4 (85 PSI). If you remember from your field test procedures, when an apparent 2nd check failure is observed, you are required to open your low side bleed valve on your test kit. This will draw the elevated pressure from the area between the 2 check valves, while the second check disc stays embedded into the 2nd check seat from the applied backpressure. When the low bleed is opened, you are reestablishing the pressure in the area between the 2 checks back to its normal pressure of 90 PSI while the elevated 100 PSI is maintained after the second check.

Let us see what happens when the check valves are not working properly. Let us talk a little about the first check. In this example we show an upstream pressure of 100 PSI. The pressure downstream of the first check shows us 90 PSI, which means we have an 10 PSID across the 1st check valve. This is the load the first check is generating on a properly working first check. If the first check was completely fouled and there was no differential produced, that means we would have 100 PSI before and after the first check (0 PSID); then the relief valve spring would cause the relief valve to stay open.

Tekmar Thermostat Programable ; Brand: Tekmar ; Display Type: Backlit ; Voltage Rating: 10 to 30 VAC/VDC ; Dimensions: 3 in W x 15/16 in D x 3-11/16 in H ; Domestic/ ...

CPI 124 Shaver Street Brantford, Ontario N3T 5M1 Canada Brantford: +1 519 753 8671 Edmonton: +1 780 468 5145   Products: Howden Aftermarket

Backflow is the hydraulic condition that can cause an RP to stop working in the described normal flow pattern. Backflow can happen by either backpressure and or backsiphonage. Backpressure is a condition where a greater pressure is generated on the downstream than the upstream side of the assembly. This condition can happen for many reasons, pumps, thermal expansion, etc.

The PVB consists of an inlet and outlet shut off, two test cocks, a check valve, and an air inlet component. The normal flow of water goes from the upstream side of the body into the check valve. The check valve (which is spring biased closed) is designed to hold 1 PSI in the direction of flow, similar to the check in a DC.

68A Stiles Rd Unit 2 Salem, NH 03079 United States Telephone: +1 603 382 6551     Products: Hydrogen Energy Cryogenic Transport Trailers ISO Containers

There is a variation of the PVB called an SVB. The SVB has an inlet and outlet shut off, a check valve and an air inlet valve, a single test cock, and a bleed screw. The SVB performs similarly to the PVB except when initially pressurized.

CPI UK Unit 5 Smitham Bridge Road Hungerford, RG17 0QP United Kingdom France: +33 (0)327 63 16 64 Spain: +34 (0)91 651 9355 Germany: +49 6152 9316 0 United Kingdom: +44 (0)1488 684 585 Netherlands: +31 (0)1816 63149   Products: Howden Aftermarket

What happens when our field test data presents an excessively high relief valve opening point, something above 5.0 PSID? A high relief valve opening point can happen for different reasons depending on the make, model and size. The most common cause of a high relief valve opening point is when the relief valve disc does not completely embed itself into the relief valve seat, usually because the relief valve stem assembly is not traveling its full length; for example, if a rolling diaphragm in the relief valve is pinched or twisted, it will restrict the relief valve from traveling its full designed length. If the stem does not travel its full length, the relief valve disc cannot fully embed into the relief valve seat. If this disc is just barely touching the relief valve seat, and not fully embedded, then the relief valve opening point will be excessively high.

Howden Turbo - DE Hessheimer Strasse 2 Frankenthal, 67227 Germany Telephone: +49 6233 85 0         Products: Centrifugal Blowers Compressors - Centrifugal Steam Turbines Turbo Fans Howden Aftermarket

Howden Indonesia Marquee Pondok Indah Office Tower 3, 17th FloorJI. Sultan Iskandar Muda Kav TA Pondok Indah, 12310 Indonesia

Some administrative authorities require the loading on the first check to have a minimum of 3.0 PSID higher value than the relief valve opening. By having a buffer greater than 3.0 PSID, this would help minimize relief valve discharge from a small pressure fluctuation in a static condition. This would mean that if our relief valve opening point is 2.1 PSID than we would have to have a first check loading of at least 5.1 PSID to pass the field test. If a 3.0 PSID buffer was not required in your area, then any first check value greater (above 2.1 PSID) than the relief valve opening point would keep the relief valve closed and would be a passing check value.

Howden GmbH Habsburgerstrasse 7 Aalen-Ebnat, DE 73432 Germany Aalen Ebnat: +49 3523 940 Coswig: +49 7321 5504 900 Olpen: +49 2761 7029 600   Products: Howden Aftermarket

To understand what happens inside an RP, let us flow water through a generic backflow prevention assembly. An RP consists of inlet and outlet shut-off valves, four properly located test cocks, a first and second check valve component, and a relief valve component. Let us hook up our RP to a water source, which delivers 100 PSI, and begin to pressurize the backflow prevention assembly.

521 Business Park Dr. Richburg, SC 29729 United States Telephone: +1 803 724 3939 Toll Free: +1 800 231 8276   Products: Cryo-Lease Equipment Repairs & Services

1300 Airport Drive Ball Ground, GA 30107 United States Telephone: +1 770 479 6531 Repairs: +1 800 231 8276       Products: Bulk CO2 Carbonation MicroBulk Storage Systems Liquid Cylinders Laser Assist Gas Systems Fuel Systems

28 Mar 2024 — 1. The PRV manual says to set the pressure when the system is at ambient temperature, but the pressure has always read zero after the boiler is ...

In conclusion, the field test is the way we generate the data needed to determine which part of the assembly is performing below the accepted minimal standard. When the numbers fall below the minimum standards established by the accepted test procedure, a repair must be facilitated to bring the working condition of the assembly above the minimum standards and back to its original factory working specifications. The generation of accurate data is very important and this means using an accurate test kit and proper test procedures and techniques to ensure that the data we generate properly reflects the working condition of the assembly.

Howden Service Centre Park Road, Holmewood Industrial Park Chesterfield, S42 5UY United Kingdom Telephone: +44 (0)1246 859053     Products: Howden Aftermarket

VCT Vogel Industriesstr. 6 Gablingen, 86456 Germany Telephone: +49 8230 891 5060   Products: Europe Aftersales

2191 Ward Avenue La Crosse, WI 54601 United States Telephone: +1 608 787 3333         Products: Brazed Aluminum Heat Exchangers

Howden Old Govan Road Renfrew, PA4 8XJ United Kingdom Telephone: +44 141 885 7500     Products: Centrifugal Fans Compressors - Screw Howden Aftermarket Heaters - Air Preheater Heaters - Gas Gas Heater

9660 Grunwald Road Beasley, TX 77417 United States Air-X-Changers, Hammco, Cooler Service Company: +1 918 619 8000 Hudson Products: +1 281 396 8100 Smithco: +1 918 446 4406         Products: Air Cooled Heat Exchangers Axial Flow Fans

Howden Africa 1A Booysens Road, Booysens Johannesburg, 2091 South Africa Sasolburg: +27 16 986 0795 Middelburg: +27 13 246 8400 Johannesburg & Cape Town: +27 11 240 4000

If a water hammer condition happens on the downside of a properly working RP because of a quick closing solenoid, this increase in pressure would create a backpressure condition, which could cause the relief valve to open by disc compression.

An inexperienced installer may install a mainline DC and pipe in a small by-pass that looks similar to the DCDA. These unapproved DCDA's cannot guarantee that they will detect this first 3 GPM because they are not factory engineered assemblies with the proper pressure differentials, but rather a collection of 2 DC's and a water meter assembled to look like a DCDA.

Howden Thomassen Compressors Havalandseweg 8-a Rheden, 6991 AB Netherlands Telephone: +31 26 497 5200         Products: Compressors - Reciprocating and Diaphragm

Howden Africa 12 Silver Street Sasolburg, Sasol Chemcity Eco-Industrial Park 1947 South Africa Sasolburg: +27 16 986 0795 Middelburg: +27 13 246 8400 Johannesburg & Cape Town: +27 11 240 4000

Karapellontie 12 Espoo, 02621 Finland General Enquiries: +358 102874000   Products: Turbo Fans

Once this area between the two checks and the low pressure side of the relief valve is pressurized, the pressure will now cause the 2nd check to open. The loading of the 2nd check spring will be anywhere between 1-5 PSI depending on the make, model, and size. The pressure after the 2nd check will be reduced by the amount of pressure it takes to open the 2nd check. For our illustration, we will give the 2nd check a 5.0 PSI loading.

Sometimes the air inlet poppet will not seal on the air inlet seat completely, and will leak. This unwanted discharge from the air inlet can be caused by several reasons. The usual is when some dirt or debris is located between the air inlet poppet disc and the air inlet seat. If the disc becomes damaged from this debris or becomes worn for other reasons, it could inhibit its ability to seal. Another cause of leakage can happen if the air inlet guide is damaged in such a way as to not allow the air inlet poppet to seat squarely on the air inlet seat.

Even if we have a working 2nd check, and backpressure is applied, we can get a discharge from our relief valve. A condition called disc compression can cause discharge from a properly working RP. When backpressure occurs, this increase in pressure placed on the downstream side of the 2nd check causes the 2nd check disc to embed farther into the 2nd check seat. The volume of water in the body between the 2 checks is being squeezed as the 2nd check disc embeds farther into the seat. Water is a not a compressible fluid in these pressure ranges, so this squeezing of this water causes an increase in pressure in the area between the 1st and 2nd check valves. If this increase in the pressure between the 2 checks, which started at 90 PSI in our illustration, increases to the point where it is greater than the inlet pressure minus the relief valve spring loading (100 - 2.0 = 98), the relief valve will open.

Howden ČKD Compressors s.r.o. č.p. 1101, Nehvizdy Prague, 250 81 Czech Republic General Enquiries: + 420 3170 75075     Products: Compressors - Centrifugal Compressors - Reciprocating and Diaphragm Howden Aftermarket

46441 Landing Parkway Fremont, CA 94538 United States Toll Free: +1 800 400 4683 Service: +1 800 253 1769       Products: Carbon Dioxide Enrichment Nitrogen Dosing Vacuum Insulated Pipe

CPI China 28-3 Rongle East Roads Shanghai, 201612 China Telephone: +86 (0)21 6787 1990   Products: Howden Aftermarket

VeoliaWater Technologies& solutions

B385, Lot G02-G07, Level 3, Spaces, Platinum Sentral, Jalan Stesen Sentral 2, Kuala Lumpur Sentral, Kuala Lumpur, 50470 Malaysia Telephone: +60 3 2722 4676 Fax: +60 3 2722 4601

Earthly Labs 1305 W Oltorf St, Suite 300 Austin, TX 78704 United States Toll Free: +1 833 728 3202 Telephone: +1 737 309 3300       Products: Small Scale Carbon Capture

The relief valve of an RP can only open for the two backflow conditions of backpressure or backsiphonage or the simulation of these two conditions. One of the more common simulations of backpressure happens when there is a pressure fluctuation at the inlet of the RP. If there is no flow going through the assembly, and then the upstream pressure drops quickly from 100 PSI down to 80 PSI, this can cause the relief valve to open. This would happen because there would be higher pressure on the low pressure side of the relief valve elastic element versus the high pressure side (high pressure side would be 80 PSI and the low pressure side would be 90 PSI plus the relief valve spring loading).

Cryo Technologies 241 N Cedar Crest Blvd Allentown, PA 18104 United States         Products: Helium Liquefiers Hydrogen Liquefiers

In other cases, the canopy that covers the bonnet is missing, which can also cause direct sunlight onto the air inlet, also causing a problem with deterioration from the ultraviolet rays of the sun. Lastly, On some models of PVB's, the air inlet spring can easily be removed or inserted in such a way as to lower its loading below the 1.0 PSI minimum requirement. There is one brand of PVB that does not use a mechanical spring in the usual sense but rather a fold of rubber on the poppet that generates the load, and if you are not familiar with this brand, you could erroneously assume the spring is missing.

1995 Peru Drive McCarran, NV 89434 United States Telephone: +1 775 343 1813 Repairs: +1 800 231 8276   Products: Repairs & Services Cryo-Lease Equipment

Howden Spain Lo Vilagran s/n, Ctra. F40 Km 1 a Los Camachos La Union, 30360 Spain Telephone: +34 968 32 00 64     Products: Heaters - Air Preheater Heaters - Gas Gas Heater Howden Aftermarket

Our plumbing courses cover a number of specialisations including roof plumbing, gasfitting, drainage, and hydraulic services design.

Howden Air and Gas India Private Limited No. 302, 3rd Floor, Tower B|WTT, C-1, Sector-16 Noida, Uttar Pradesh 201301 India         Products: Centrifugal Blowers Compressors - Centrifugal Compressors - Reciprocating and Diaphragm Compressors - Screw Centrifugal Fans Cooling Fans Heaters - Gas Gas Heater Howden Aftermarket Axial Fans Turbo Fans

Howden Turbo - UK 85 Papyrus Road Peterborough, PE4 5HG United Kingdom General Enquiries: +44 (0)1733292200   Products: Compressors - Reciprocating and Diaphragm Steam Turbines Compressors - Screw

CPI 107 William Leigh Drive Tullytown, PA 19007 United States Baton Rouge: +1 225 752 4272 Los Angeles: +1 310 223 1101 Stafford (Houston): +1 281 207 4600 Philadelphia: +1 215 946 0845   Products: Howden Aftermarket

55 Southbelt Industrial Dr. Houston, TX 77047 United States Telephone: +1 713 413 3000 Repairs: +1 800 231 8276   Products: Repairs & Services Cryo-Lease Equipment

When we are field testing any of these assemblies, we are making a diagnostic analysis at one point in space and time. From this data, we cannot say how the backflow prevention assembly worked yesterday or if it will work tomorrow, only what it is doing right now. When we perform the field test, we are generating data on the workings of the assembly, which we must compare to the minimum acceptable performance data as established in our accepted test procedure. For example, two (2.0) PSID is the minimum acceptable relief valve opening point, but few assemblies are designed to open at 2.0 PSID. For this reason, when we get a performance value from a field test, whether it be a relief valve opening point, or a check valve value, we must understand what is happening in the backflow prevention assembly.

Let's examine the effect of backsiphonage on our RP and see how it functions. When the inlet pressure to our assembly (100 PSI in our illustration) goes down to sub-atmospheric, or negative, the 100 PSI is reduced to a negative pressure. The pressure at the inlet of the RP is what keeps the relief valve closed. When the pressure at the high pressure side of the elastic element in the relief valve is reduced to a negative, the relief valve will open because of the relief valve spring load, and any pressure remaining in the area between the 2 check valves is now applied to the low pressure side of the relief valve elastic element.

Howden Italy Via Nino Bixio, 3 Mornago, 21020 Italy Telephone: +39 0331 903890     Products: Centrifugal Blowers Compressors - Centrifugal Howden Aftermarket Europe Aftersales

When water first enters the SVB, instead of causing the check valve to open first, as in a PVB, the air inlet closes before the check valve opens. This is accomplished by the air inlet having a lighter loading (1.0 PSI minimum) than the check valve (1.0 PSI minimum). Even though they have the same minimum loading requirement, there will always be a pressure differential between the load of the check and the air inlet, with the check valve having a higher loading than the air inlet.

Howden Solyvent-Ventec Chalon 12 rue Alfred Kastler Chalon sur Saône, 71530 France Telephone: +33 3 85 41 73 22       Products: Centrifugal Fans Howden Aftermarket

The criteria for the workings of the second check, like the first check, must maintain a higher pressure upstream of the check than the downstream pressure. This differential is established by the spring loading of the second check spring, which is designed to be a minimum of 1.0 PSID.

CPI 4410 Greenbriar Drive Stafford, TX 77477 United States Baton Rouge: +1 225 752 4272 Los Angeles: +1 310 223 1101 Stafford (Houston): +1 281 207 4600 Philadelphia: +1 215 946 0845   Products: Howden Aftermarket

Chart VRV Via Burago, 24 Ornago, 20876 Italy VRV S.r.l. (E&C Products): +39 039 60251       Products: Bulk Storage Tanks Liquid Cylinders MicroBulk Storage Systems Bulk CO2 Carbonation Europe Aftersales Specialty Heat Exchangers

The upstream pressure (100PSI) of the RP in our illustration is reduced by the combined pressure load of the 1st and 2nd check spring (100 - 10 - 5 = 85PSI), producing our downstream pressure of 85 PSI into our piping system. Don't forget that the relief valve spring is continually trying to open the relief valve, which the inlet pressure is keeping closed, and that a properly working relief valve can only open when the pressure downstream of the 1st check plus the relief valve spring load is greater than the upstream pressure to our RP. In our illustration, the pressure past the 1st check (90 PSI) must increase to 98.1 PSI, so that the value of the relief valve opening point (2.0 PSID) and the pressure after the 1st check (90 PSI) is now greater (98.1 + 2.0 > 100PSI) than the inlet pressure.

Sievers

Howden Netherlands Haaksbergerstraat 67 Hengelo, 7554 PA Netherlands Telephone: +31 74 255 6000       Products: Cooling Fans

Howden Hua Engineering Co. Ltd Room 1004 Tower B, Poly Grand Plaza, No 26 Chenyue Road Guangzhou, Haizhu District 510310 China

Howden Fan & Compressor Service Centre No 25 - 27, Ln 296, Xinya Road Kaohsiung City, Qianzhen Dist 806 Taiwan   Products: Compressors - Centrifugal Compressors - Reciprocating and Diaphragm Compressors - Screw Centrifugal Fans Cooling Fans Axial Fans Turbo Fans

Cryogenic Service Center Knipplekullen 3A Gothenburg, 417 49 Sweden General Enquiries: +45-(0) 49 21 14 00   Products: Europe Aftersales

Howden Americas 2933 Symmes Road Fairfield, OH 45014-2099 United States Telephone: +1 866 771 6266         Products: Centrifugal Fans Cooling Fans Axial Fans Turbo Fans

Define Reduced pressure detector assembly (RPDA. means an assembly which operates and functions exactly as a reduced pressure backflow assembly, ...

The check valves in a DC will open when something downstream of the DC in the piping system opens a water-using fixture, and as the water begins to flow to that fixture, the pressure drops. The pressure upstream of the fixture begins to drop as the water flows through the fixture. Because of this flow of water, the pressure upstream of the DC is now great enough to cause the check valve to open and flow water to the fixture demanding water. Check valves only open enough to fill the demand for water; they do not open fully but usually modulate to fill the demand for water.

Howden Americas, Compressors 600 Day Hill Road Windsor, CT 06095 United States       Products: Compressors - Centrifugal Compressors - Reciprocating and Diaphragm Compressors - Screw

Howden Axial Fans ApS Industrivej 23 Naestved, DK-4700 Denmark General Enquiries: +45 5577 6292     Products: Axial Fans

Howden Americas 411 Independence Drive Medina, OH 44256 United States Telephone: +1 330 867 8540

If the pressure downstream of the 1st check rises to where it is a minimum of 2.0 PSI less than the inlet pressure upstream of the 1st check, then the 2.0 PSI loading from the relief valve spring would cause the relief valve to open. In a properly working relief valve, the opening point can be anywhere from 2.0 - 5.0 PSID depending on the manufacturer, model and size. Once the water pressure has closed the relief valve, then the pressure will increase to the next point, which will cause the first check to open, and allow the water to travel past the first check valve.

Howden GmbH Raiffeisenstrasse 12 Olpe, 57462 Germany Aalen Ebnat: +49 3523 940 Coswig: +49 7321 5504 900 Olpen: +49 2761 7029 600     Products: Howden Aftermarket

Howden BC Compressors Rue Roland Vachette Nogent sur Oise, 60180 France General Enquiries: +33 3447 44100   Products: Compressors - Reciprocating and Diaphragm

ChartWater India C-521A, Executive Villas Lane, Sushant Lok, Block C, Sector 43 Gurgaon, Haryana 1222002 India BlueInGreen: +1 304 825 5244 AdEdge: +1 678 835 0052 ChartWater India: +91-9717032880, +1-330-805-2615

A DC is simply two approved independently operating check valves that can hold a minimum of 1 PSI in the direction of flow with the outlet of the check valve open to atmosphere. These checks must be located between an inlet and outlet shut-off and have 4 properly located test cocks. The check valves in a DC must hold a minimum pressure (1.0 PSI minimum) in the direction of flow. The two check valves (1st & 2nd Check) will have similar spring loadings.

During the normal flow of water through a properly working RP backflow prevention assembly, the relief valve will be pressured closed, and the check valves will modulate between an opened and closed position to fill the water demand of the plumbing system. The two check valves (1st & 2nd Check) will have different spring loadings. The check valves in an RP will open when something downstream of the RP in the piping system opens a water-using fixture, and as the water begins to flow to that fixture, the pressure drops. The pressure upstream of the fixture begins to drop as the water flows through the fixture. Because of this flow of water, the pressure upstream of the RP is now great enough to cause the check valve to open and flow water to the fixture demanding water. Check valves only open enough to fill the demand for water; they do not open fully, but usually modulate to fill the demand for water.

If a check valve is holding less than 1.0 PSI, for example, 0.5 PSI, testers have been known to incorrectly state, "The check valve is leaking." This leads some people to believe that this check valve would not stop a backflow condition. In fact, the check valve is not leaking at 0.5 PSI because it is still sealing off the area upstream and downstream of the check valve with a 0.5 PSI loading; however, the check valve is performing below the minimum criteria as established in the test procedure (1.0 PSI).