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It is very easy to check for air in a submersible piping 3) Is the leak detector slow in the morning at station system. Install test equipment shown in Fig.3. Observe start up time? warning shown in Fig.3. Turn the pump on and let it run Similar to the discussion above,thermal contraction until the leak detector opens to the unrestricted flow over several hours of station quiet time or overnight can position. This can be determined by simply opening a cause vapor pockets to form that will make the opening nozzle into a suitable container and determining that full time of the leak detector long enough to last several flow is available. Shut the pump off and open the ball minutes in extreme conditions. The longer the station valve on the test fixture (Figure 3). quiettime,the greaterthe last volume dispensed ancithe Diaphragm Model - No more than 1 to 3 oz. (about 1/2 temperature difference, the greater the vapor pocket cup),or 501 to 110 ml of product should becomes and the slower the leak detector becomes in drain from the line. opening. Piston Model - No more than 11 to 14 oz. (about 1-1/2 One other vapor condition that can affecttheopening cups),or350 to 410 ml of product should time of the leak detector is that of flashing. When high drain from the line.' volatility gasoline flows through a small orifice such as `Leave the valve open for approximately 60-90 seconds the one found in the metering fluid circuit of a leak after zero line pressure is obtained.This allows the piston detector, a rapid pressure drop from pump pressure to reset. occurs. The pump pressure is usually 27-30 PSI and the If larger amounts of product are measured, it is possible downstream pressure may be nearzero aswhenthe leak air is present in the system.The amount of product which detector begins pressurizing the line. High ends of the will flow out of the opening will depend completely upon gasoline can instantly vaporize or flash as the result of the volume of air which was compressed in the piping. this rapid depressurization. This results in a condition There have been cases where as much as 5 gallons of where the line is now being pressurized, not with incom- product were removed before the system pressure went pressible liquid but with a mixture of liquid and vapors. to zero and product quit flowing from the opening. While The line pressurization process is slowed down as a it is very easy to check for trapped air, it can be difficult to result. Vapor pockets and flashing will disappear when eliminate the air from the piping. Some of the things that the system is pressurized. we have found, however, may help you in removing the 4) Are internal seals in the leak detector causing a air. Dispensing product is the best way of eliminating air from the system since,in most cases,the flow of product longer opening time? will carry the air along with it. Turn the pump on and make Diaphragm leak detectors with ruptured diaphragms sure that the leak detector is in the unrestricted flow will display gradually increasing opening times and ulti- position. Starting at the nozzle furthest away, pump mately will stay in the trip position permanently. Fluid approximately 20 to 30 gallons through each dispenser, gradually fills the dome through the rupture eventually into a suitable container, working back toward the making it impossible for the diaphragm to move. (Fig.4) submersible pump. On installations that have separate If piston leak detectors have a leak around the lines to different individual dispensers, or a "Y" in the metering piston seal (Figure 413), it will be viewed by the piping, you must pump product from all branches. leak detector as a leak. Minor leaks will prolong the In stations where a line is stubbed off for future opening time while larger seal leaks will cause the piston expansion,it is not possible to get the airout of the system leak detector not to open up. This condition can be by dispensing product. In this case, it is necessary to observed by disconnecting the copper vent tube on the locate the end of the pipe, and dig down to it and install leak detector and creating a leak in the product line,using a snifter valve or some other air releasing type of valve to the test equipment in Fig.3. After the pump is turned off, bleed the air from the line. Air will reaccumulate with the bleed the pressure to zero and allow the leak detector to above situation. It is best to remove the stub if possible. go into the trip position. Turn on the pump with the When testing for resiliency using DIAPHRAGM LEAK DETECTOR the Red Jacket Field Test Appara- tus, refer to publication #RJ 20, page 4,section II, or#RJ 21, Appa- ratus to Verify Operation, page 4 FLUID — section IV. 2) Is vapor present in the system? �< As discussed in the introduction, vapor pockets can be introduced into the piping system by thermal proc- ` \ DIAPHRAGM esses. If thermal contraction of a sufficient magnitude is present in a piping system, the pressure can actually drop to a negative value or vacuum. Under these conditions,the high end components of the fuel will flash s '' from a liquid to a vapor state creating a vapor pocket in the line. This can happen within a matter of minutes after 'i dispensing. The next leak check performed may be slowed to the point that 5 seconds or more may be required to perform the leak test. ��:"% /%� FIGURE 4A