EDS Ball Valves 101. Concerns about debris, damage, interstitial

Transcription

1 EDS Ball Valves 101 Concerns about debris, damage, interstitial cavity contamination, and leakage relative to Effluent Decontamination System application of a ball valve vertically subpositioned in the tank drip leg

2 Background Cook Tank Drip Leg The common practice in EDS design is to place the cooker s discharge valve vertically in a short stub (drip leg) as shown above, so that there will be no cold spot during the cooking process. Bio-Response takes issue with this practice. Understanding cookers, solids in effluent, and ball valves are important for the designers and purchasers of EDS equipment to make the correct design choices. This presentation addresses this very simple but normally over looked issue. The result of this practice is a leaking cooker valve that routinely drains a portion of untreated material into the sewage system, and such leakage is virtually impossible to detect using any methods that are commonly employed.

3 A typical two piece type 316-SS Full-Flow Ball Valve is shown. It features Teflon seats and seals.

4 Looking through the full flow valve with the ball fully opened. Ball vent hole goes to interstitial cavity (see slide #10) Primary Teflon Seat Location

5 Ball partially opened. Note scoring lines on the ball already and this is a new valve. Dirt line forms at this point on the ball (already forming) Seat to ball interface where dirt can invade both the ball and the seat Teflon seat is very exposed at this point

6 Every time the ball closes, this dirt line is forced through the seat seal and can inflict damage on the seat if it contains hard materials such as sand, glass, metal pieces, mop string, and even a feather shaft. The solution is proper flushing prior to closing.

7 This fully closed valve is in the position it would occupy when materials are filled on top of the valve. Gravity will carry heavy materials such as staples, sand, silt, soil, string, paper, and other items that may be put in the EDS tank. When the ball valve is opened, the soil will push against the side of the ball that moves through the seat and will score the seat and, if it is sand, silt, or glass, score the ball itself. Resulting leakage goes into the interstitial space of the valve.

8 This is the ball valve seat (seal). It is soft Teflon. Already, you can see fine soil on the seat and recall, this is a brand new valve.

9 The seat (right) and housing seal (left) are soft Teflon construction. When hot the Teflon is even softer. This (hot period) is when the valve is opened to drain with the solids laying on the surface of the ball if a vertically oriented drip leg ball valve.

10 This is the interstitial space (cavity). This will become contaminated unless the system design heats the valve sufficiently; an important consideration in a heated drip leg design. This must be decontaminated using the Bio-Response provided Steam Decontamination Hose Kit. This requires extensive exposure to heat to achieve conductive sterilization of this cavity. The ball has a pressure relief vent hole in the top key (slot) where material can also enter the interstitial space. You can see this hole in the top of the ball port (see slide #4).

11 This is the shaft packing Teflon seal. The shaft rotates at this point on the seal with a tapered contact seal point. Fortunately, this does not interact with the seal as with the ball and seat and this seal is much more reliable in presence of soil.

12 If the ball valve is mounted vertically in the drip leg as shown at right, then the soil that is routinely deposited on the valve will cause it to fail prematurely. This failure and leakage can begin occurring within the first few days of operation of this type of system, particularly where sand or grit is prevalent. A vessel air pressure test uses a lot of air and therefore does not have the resolution to show leakage until it has become major (due to the compressibility of air) Cook Vessel Alternatively, a double drip leg ball valve set (Standard on any Bio-Response system), located past the drip leg bend, will require a heated drip leg but the seals are now protected from sand and grit due to the location of the valve. An air test between the two valves assures that the seals on both valves are absolutely tight (high resolution due to low air volume Right design Ball valve Sediment Wrong design required).

13 Contact: Joseph H. Wilson 762 Northampton Row Danville, IN U.S.A. P M