Commissioning a diaphragm valve

Abstract

A method for determining the end-of-travel positions of a diaphragm in a diaphragm valve having an actuator: initiating displacement of the diaphragm into a first end-of-travel position; ascertaining the first end-of-travel position of the diaphragm, wherein said first end-of-travel position is ascertained by monitoring an actuating current value, wherein the first end-of-travel position is reached when a predefined current value is reached; saving the first end-of-travel position; moving autonomously, preferably in the opposite direction, towards a second end-of-travel position of the diaphragm; ascertaining the second end-of-travel position of the diaphragm, wherein said second end-of-travel position is ascertained by means of a predefined travel length (a) of the diaphragm from the first end-of-travel position; saving the second end-of-travel position.

Claims

1. A method for determining the end-of-travel positions of a diaphragm (11) in a diaphragm valve (10) having an actuator, comprising: initiating displacement of the diaphragm into a first end-of-travel position (1); ascertaining the first end-of-travel position (1) of the diaphragm, wherein said first end-of-travel position (1) is ascertained by monitoring an actuating current value, wherein the first end-of-travel position (1) is reached when a predefined current value is reached; saving the first end-of-travel position (1); moving autonomously, preferably in the opposite direction, towards a second end-of-travel position (2) of the diaphragm; ascertaining the second end-of-travel position (2) of the diaphragm, wherein said second end-of-travel position (2) is ascertained by means of a predefined travel length (a) of the diaphragm from the first end-of-travel position (1); saving the second end-of-travel position (2); and preferably detecting the actuating current value (I) at the second end-of-travel position (2) in order to verify and ensure the reached second end-of-travel position (2).

2. A method for determining the end-of-travel positions of a diaphragm (11) in a diaphragm valve (10) having an actuator, comprising: initiating displacement of the diaphragm into a first end-of-travel position (1); ascertaining the first end-of-travel position (1) of the diaphragm, wherein said first end-of-travel position (1) is ascertained by monitoring an actuating current value, wherein the first end-of-travel position (1) is reached at a predefined current value; saving the first end-of-travel position (1); moving autonomously, preferably in the opposite direction, towards a second end-of-travel position (2) of the diaphragm; ascertaining an advance end-of-travel position (3) of the diaphragm, wherein said advance end-of-travel position (3) is ascertained by monitoring an actuating current value, wherein the advance end-of-travel position (3) is reached when a predefined current value is reached; reaching and ascertaining the second end-of-travel position (2) by additionally completing a predefined adjustment length (c) of the diaphragm; saving the second end-of-travel position (2).

3. A method according to claim 1, wherein the actuating current value (I) for detecting and ascertaining the first end-of-travel position (1) of the diaphragm changes as a result of a mechanical resistance, wherein the actuating current value (I) rises to a specified maximum current value.

4. A method according to claim 1, wherein the first end-of-travel position (1) of the diaphragm (11) defines the maximum opening state of the diaphragm valve (10).

5. A method according to claim 1, wherein the second end-of-travel position (2) of the diaphragm (11) constitutes the closed state of the diaphragm valve (10).

6. A method according claim 1, wherein a running current (IL) establishes itself during the travel length (b) of the diaphragm between the first end-of-travel position (1) and the second end-of-travel position (2) or respectively the advance end-of-travel position (3), wherein the running current (b) is not meant to exceed a specified current value.

7. A method according to claim 1, wherein the position of the diaphragm (11) is adjusted by means of a threaded stem, and the diaphragm is moved towards the first end-of-travel position (1) by clockwise or anticlockwise rotation of the threaded stem, and the adjustment of the diaphragm into the second end-of-travel position (2) or into the advance end-of-travel position (3) is performed in the opposite direction.

8. A diaphragm valve (10) comprising a positioning actuator (12), wherein during commissioning according to the method according to claim 1, the diaphragm valve (10) self-adjusts the end-of-travel positions (1, 2) of the diaphragm (11).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a graph of the variation in actuating current of the positioning actuator of the diaphragm valve;

(2) FIG. 2 shows a cross-section through a diaphragm valve in which the diaphragm is in the open position; and

(3) FIG. 3 shows a cross-section through a diaphragm valve in which the diaphragm is in the closed position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

(4) The drawing illustrated in FIG. 1 shows a graph which depicts the actuating current (I) with respect to the length or distance (s) by which the diaphragm (11) in the diaphragm valve (10) is displaced. As a result of the diaphragm displacement being initiated or, for instance, as a result of an actuating pushbutton on the positioning actuator being pressed, the diaphragm moves towards a first end-of-travel position (1). The actuating current (I) is monitored during this process, or throughout the method according to the preferred embodiment of the invention. If the actuating current then reaches an already predefined current value, which has been predefined as the value for ascertaining the first end-of-travel position, this position is ascertained as the first end-of-travel position (1) and saved, preferably in the firmware or in software of a controller, wherein the first end-of-travel position (1) preferably constitutes the open position of the diaphragm valve (10). In order to ascertain additionally the second end-of-travel position (2), the diaphragm moves autonomously in the opposite direction. There are two variants for ascertaining the second end-of-travel position (2). In one variant, the diaphragm moves towards the second end-of-travel position (2), which is to be ascertained, wherein the diaphragm has a predefined travel length (a) or distance assigned, and hence travels from the first end-of-travel position (1) along this travel length (a), and once arrived there, this is saved as the second end-of-travel position (2), and the actuating current is detected at the position ascertained as the second end-of-travel position (2). This detected actuating current at the second end-of-travel position (2) is preferably used during normal operation as the verification value. Hence, for example if the diaphragm has reached the second end-of-travel position (2) and the actuating current does not match the saved value, an error message is output or the diaphragm is re-adjusted autonomously. This can be used during commissioning or even during normal operation.

(5) As a variant for commissioning a diaphragm valve (10), there is also the option to ascertain the second end-of-travel position (2) by monitoring the actuating current (I). Once the first end-of-travel position (1) has been reached and ascertained, the diaphragm moves in the opposite direction, and when a predefined current value is reached that corresponds to an advance end-of-travel position (3), at which a low resistance is already noticeable, a predefined adjustment length (c) is still completed, wherein the current value of the advance end-of-travel position (3) can be calculated by the system or the controller from detected values or can be stored as a fixed value. The second end-of-travel position (2) is reached by completion of the adjustment length (c) from the advance end-of-travel position (3), and is saved. The actuating current values detected are preferably used again in this case during normal operation and commissioning for verifying and ensuring a correctly operating diaphragm valve, in the same way as the other detected actuating current values could be used for this purpose. In addition, the running current (IL) during the positioning of the diaphragm over the distance or travel length (s), in which positioning there is no additional resistance acting on the diaphragm, is used to allow monitoring of whether the diaphragm valve is free of dirt or other foreign bodies that would obstruct or even block the displacement or movement of the diaphragm, wherein the running current (IL) during commissioning and during normal operation lies at a different level, because in normal operation a certain resistance acts on the diaphragm as a result of the medium, although this should not be viewed as the aforementioned additional resistance, which primarily relates to mechanical end stops, or to when the diaphragm is at the valve curve or the end stop.

(6) FIGS. 2 and 3 show a diaphragm valve (10) comprising a positioning actuator 12, wherein FIG. 2 shows the open position and it is clearly evident that a mechanical end stop 13 prevents further opening or limits the prevailing opening. FIG. 3 shows a fully closed diaphragm valve 10.