NZ331111A - Pressure relief valve, typically for dairy tanker, able to accommodate some pressure and/or vacuum fluctuation without discharge of product, by movement of valve element while maintaining sealing effect - Google Patents

Abstract

The valve is typically attached to a milk tanker. Valve element 17 moves upwards but is maintained in sealing contact with valve sleeve 10 a predetermined distance before uncovering ports 16 to allow venting. This is stated to allow for some liquid surge before venting occurs. Optionally vacuum relief is also provided for by valve elements 25 uncovering ports 22 during vacuum conditions.

Description

No: 331111 Date: 28 July 1998 NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION A PRESSURE RELIEF VALVE We, MERCER STAINLESS LIMITED a New Zealand company of Corbett Road, Bell Block, New Plymouth, New Zealand do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- 75opwr®cFl I o FN.Z. otj _1" / 2 ? JUL 1999 I '—5ICEIVED 2 A PRESSURE RELIEF VALVE BACKGROUND OF THE INVENTION This invention relates to a pressure relief valve.

With the road transport tankers (as, for example, used in the dairy industry for transporting milk) there is a need to have a pressure relief valve which provides tank protection both for vacuum and pressure (ie. negative and positive pressures). For example the valve must routinely be able to allow air or liquid to move in or out of the tank during the performance of typical operations such as filling, emptying and clean in place ("CiP").

When filling the tank a flow rate may, for instance, be 1,600 litres per minute when the filling is carried out at the farm using the truck mounted pumping system. However, when filling at a factory site via a bottom outlet of the tank the flow rate could be as high as 2,000 litre per minute. With emptying operations discharge is normally 2,000 litres per minute.

SPEC226 23 July 1999 3 During CiP operations the valve is required to compensate for changes in air volumes due to temperature changes or due to fluid entering or exiting the tank.

Also during any period where due to temperature change in either the product or air in the tank, a volume change may occur and therefore pressure or vacuum relief is required. Such a situation can arise with post CiP cooling and hot AMF product cooling in transit.

Still further situations can arise where the vent function may fail to operate normally or where due to valve failure on product transfer valving, an already full tank may continue to be filled.

Also product surge during transportation may cause overflow or leakage of product via the relief valve.

SUMMARY OF THE INVENTION The present invention therefore has, as a prime objective, the providing of a pressure relief valve which allows for normal volume changes in a tank during routine operations and SPEC226 23 July 1999 331111 provides pressure and vacuum protection in potential failure situations as well as accommodate liquid surge during transportation.

Accordingly in one broad aspect of the invention there is provided a pressure relief valve including a valve body, an inlet port, outlet port means, a first valve element within the valve body and movable to bring the inlet port into communication with the outlet port means, said first valve element being movable while maintaining a sealing effect a distance before said communication occurs.

In a preferred form the valve includes biasing means, the first valve element being thereby biased to a first position where the inlet port is isolated from the outlet port means.

According to the preferred form of the invention there is provided at least one second valve element mounted with said first valve element, the first valve element having at least one vent passage therethrough and normally closed by said second valve element. The second valve element is biased by second biasing means to the closed position.

In the preferred form there is provided actuating means for the second valve element such that upon the first valve element moving a determined distance from said first position, the second valve element is moved to an open position.

In this preferred form the outlet port means includes at least one port opening which communicates with the inlet port when said second valve element is in an open position.

According to one form of the invention there is also included actuation means for actuation of the first valve element.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of the pressure relief valve according to one embodiment, Figure 2 is a section taken on line A-A of Figure 1, Figure 3 is a cross-sectioned view of a second embodiment of the invention shown in the closed position, and Figure 4 is a similar view to Figure 3 but with the valve in an open position.

SPEC226 23 July 1999 6 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring firstly to Figures 1 and 2 of the drawings, the valve comprises a valve sleeve 10 which at one end is provided with an outwardly projecting flange 12. This flange 12 is engaged with a threaded collar 11 by the collar having an inwardly directed lip 11a (see Figure 1).

The valve sleeve 10 is closed at its other end by an end plate or cap 14 from which downwardly depends a skirt 13. The skirt 13 terminates short of the threaded collar 11. As can be seen in Figure 1, the skirt 13 is spaced from the external wall surface of sleeve 10.

The sleeve 10 is provided with a plurality of spaced apart outlet ports 16. The ports 16 are positioned above the top surface of a movable first valve element 17 when the valve element 17 is located in a so called "first position". In this first position valve element 17 engages on a seating 18 in the vicinity of flange 12 (see Figure 1).

SPEC226 23 July 1999 7 Extending upwardly from first valve element 17 is a rod 19. This rod 19 is slidingly engaged in a collar 20 mounted with end plate 14. Located about rod 19 and extending between collar 20 or end plate 14 and first valve element 17 is a biasing spring 21. This spring 21 biases the first valve element 17 to the first position where the valve element 17 seals on seat 18. The distal end of rod 19 projects beyond collar 20.

A plurality of vent passages 22 extend through first valve element 17. As can be seen in Figure 2 these vent passages 22 are of arcuate shape spaced equi-distant apart and at a radius from the central longitudinal axis of a bore 23 which also extends through the first valve element 17. Slidingly located within this bore 23 is a stem 24. At the lower end of stem 24 is a second valve element 25 which normally engages against the bottom surface of the first valve element 17.

Stem 24 projects beyond the upper surface of the first valve element 17. A biasing spring 26 is located on the projecting part of stem 24. Spring 26 applies a biasing force which results in the second valve element 25 normally assuming a SPEC226 23 July 1999 8 closed position as can be seen in Figure 1. The distal end of each stem 24 has an end cap 27 to retain spring 26 on the stem. Second valve element 25 can have sealing rings or the like (see seals 25a in Figure 3).

In use the pressure relief valve is mounted to a threaded annular wall (not shown) which locates about an opening in the tank barrel. In its normal position the first valve element 17 seats on seat 18 while the second valve elements 25 close the vent passages 22.

Upon a pressure build up in the tank the first valve 17 is caused to move against the biasing force of spring 21 until it moves past the lower end of the outlet port 16 whereupon venting to atmosphere (through the space between sleeve 10 and skirt 13) can take place. When the first valve element 17 has moved sufficient to cause the end caps 27 of stems 24 to engage with the underside of closure plate 14, the second valve elements 25 are moved away from the first valve element thereby opening vent passages 22. This permits venting through at least one but preferably a number of openings 28 in the end cap 14.

SPEC226 23 July 1999 9 The position at which the first valve element 17 is located within sleeve 10 can be visually observed by observing the amount by which the stem 19 projects beyond collar 20.

Upon the pressure within the tank being relieved the first valve element 17 returns to its seated or first position.

If a surge of liquid within the tank takes place (eg. during transportation) and this surge is sufficient to lift the first valve element 17 from its seat 18, there will be a "dwell time" before the first valve element 17 can reach a venting position. However, prior to this venting position being reached the surge will have generally ceased or at least discontinued a lifting action on the first valve element 17 thereby preventing liquid leakage through the valve from occurring. Nevertheless during filling of the tank and in the situation where the pump has not shut down when the tank is full, liquid will be able to force the first valve element 17 from seat 18 so that liquid can vent through the outlet openings 16.

During CiP operations the actuation of the second valve elements 25 by the end caps 27 engaging with end plate 14 SPEC226 23 July 1999 provides the ability to wash the top side of the first valve element 17 by directing the washing solution through the vent passageways 22.

When a negative pressure occurs in the tank the second valve elements 25 are drawn away from the first valve element 17 thereby opening the vent passages 22. The interior of the tank is thus vented to atmosphere via outlet ports 16.

In Figure 3 there is shown an embodiment of the invention which is intended for situations where flow rates are higher than would normally be experienced when using the valve of the first embodiment. With this form of the invention like parts carry the same reference numerals used for the first embodiment.

According to this second embodiment the distal end of the rod 19 is located within a chamber 29 formed by housing 30. This housing 30 extends upwardly from the end plate 14 with the skirt 13 in this embodiment extending from the cap 30 rather than end plate 14.

SPEC226 23 July 1999 11 Located within chamber 29 is a piston 31. Rod 19 slidingly extends through piston 31 to engage in a threaded manner in a collar or disc 32. A biasing spring 33 extends between end cap 14 and the piston 31.

Positive pressure can be applied via inlet port 34 to act on the disc 32 to apply a closing pressure on the first valve element 17. As the piston rod 19 is not mechanically fixed to the piston 31 the first valve element 17 is still permitted to rise against the positive pressure on disc 32. Valve element 17 can thus move past the annular outlet ports 16 in the valve body 10 in the event of an over pressure situation. Thus the valve element 17 can move even if the valve is held closed by actuating pressure via chamber 29.

An air bleed or exhaust passage 28 is provided and communicates with the chamber 37 defined by piston 31, the wall of housing 30 and end wall 14.

A spring 38 if included in the valve construction between end wall 14 and the first valve element 17 would maintain a set lower limit seal pressure. However, it is not necessary to include this spring.

SPEC226 23 July 1999 12 Because in this embodiment of the invention the distal end of the rod 19 is not readily visible an indicator rod 35 is mounted with the first valve element 17 and projects through end cap 14 at the top of skirt 13 to be readily visible externally of the valve.

An additional benefit of the present invention is that use of the valve requires only one penetration into the tank barrel. This is of conventional form and is provided by a threaded annular wall with which the threaded collar 11 inter-engages to fit the valve to the tank barrel.

The pressure relief valve according to the present invention provides venting for normal volume changes during routine operations and provides pressure and vacuum protection in potential failure situations.

Also the problem associated with on road surge and consequential leakage has been overcome by the valve sleeve 10 and the arrangement therein of the biased first valve element 17 giving a dwell time should surge within the tank be sufficient to lift the first valve elements 17 from its SPEC226 23 July 1999 13 seal 18. In other words the first valve element 17 can be pushed off its seat by liquid movement in the tank and by being free to float to a pre-determined limit can do so without discharging product.

Furthermore when the first valve element 17 is driven to its limit by liquid pressure (or in the actuated embodiment of Figure 3) moved to the limit position, the opening of the second valve elements 25 provides a greater exhaust area by virtue of the exhaust area being comprised of not only the outlet port 16 but also the exhaust ports 28.

SPEC226 23 July 1999 14

Claims (14)

WHAT WE CLAIM IS:-

1. A pressure relief valve including a valve body, an inlet port, outlet port means, a first valve element within the valve body and movable to bring the inlet port into communication with the outlet port means, said first valve element being movable while maintaining a sealing effect a distance before said communication occurs.

2. A valve as claimed in claim 1 further including biasing means, the first valve element being thereby biased to a first position where the inlet port is isolated from the outlet port means.

3. A valve as claimed in claim 2 wherein a stem extends from the first valve element and is journalled for sliding movement by bearing means, the biasing means being a spring located on the stem between the first valve element and the bearing means.

4. A valve as claimed in claim 3 wherein the stem extends through the baring means such that a distal end thereof is visible externally of the valve body. 33111 SPEC1255 intellectual property office of n.z. 1 8 OCT 2000 RECEIVED ■lTOfcTOBER 2000 15

5. A valve as claimed in any one of claims 1 to 4 wherein the outlet port means are shrouded by a skirt spaced from a valve body wall in which the outlet port means are located.

6. A valve as claimed in any one of claims 1 to 5 wherein the valve body is provided with a threaded collar for mounting of the valve body to an annular threaded mounting wall.

7. A valve as claimed in any one of claims 1 to 6 wherein the valve body include a seat with which the first valve element sealing engages.

8. A valve as claimed in any one of the preceding claims further including at least one second valve element mounted with said first valve element, the first valve element having at least one vent passage therethrough and normally closed by said second valve element. SPEC226 23 July 1999 16

9. A valve as claimed in claim 8 wherein the second valve element is biased by second biasing means to the closed position.

10. A valve as claimed in claim 8 or 9 wherein there is provided actuating means for the second valve element such that upon the first valve element moving a determined distance from said first position, the second valve element is moved to an open position.

11. A valve as claimed in any one of claims 8 to 10 wherein the outlet port means includes at least one port opening which communicates with the inlet port when said second valve element is in an open position.

12. A valve as claimed in any one of claims 1 to 11 wherein there is also included actuation means for actuation of the first valve element.

13. A valve as claimed in claim 12 wherein the actuation means includes a piston slidingly engaged in a cylinder and pneumatic means to move the piston, said piston being coupled to the first valve means. SPEC226 23 July 1999 17

14. A pressure relief valve substantially as herein described with reference to Figures 1 and 2 or 3 of the accompanying drawings. MERCER STAINLESS LIMITED By its Attorney DON HOPKINS & ASSOCIATES per: & SPEC226 ,IIILLLLUU1T2PER1Y 2 7 JUL 1999 I --RECEIVED 23 July 1999