GB2038032A - Control of a valve - Google Patents

Abstract

In controlling the operation of a drain valve, in which a sensing element triggers the electronic circuit operating the valve when a predetermined condition in the system is sensed, the electronic circuit includes a delay means imparting a desired minimum period between successive particular operations of the valve. In one use in a steam system the predetermined condition is that a condensate level is below the sensing element. In another use, there are two temperature sensing elements at high and low levels respectively and the predetermined condition is that steam is present at both these levels.

Description

SPECIFICATION Condensate drain valves This invention relates to condensate drain valves.

According to the present invention there is provided an electrically operated condensate drain valve arrangement for draining condensate from a fluid transfer system, the arrangement comprising a condensate drain valve, an electronic circuit for controlling operation of the valve, and at least one sensing element for insertion in the fluid transfer system to trigger the electronic circuit for operating the valve when a predetermined condition in the system is sensed by the sensing element; the electronic circuit including a delay means imparting a desired minimum period between successive particular operations of the valve.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the drawings accompanying this specification and in which: Figure 1 is a schematic illustration of a condensate drain valve arrangement in a steam system, Figure 2 (drawn on two sheets in parts "(A)" and "(B)") is a circuit diagram of an electronic circuit of the drain valve arrangement of Figure 1, Figure 3 (drawn on two sheets in parts "(A)" and "(B)") is a circuit diagram of another electronic circuit that can be incorporated in a drain valve arrangement such as that of Figure 1, Figure 4 is a logic diagram illustrating operation of the electronic circuit of Figure 3, Figure 5 is a schematic illustration of another form of steam trap arrangement, Figure 6 (drawn on two sheets in parts "(A)" and "(B)") is a circuit diagram of an electronic circuit of the arrangement of Figure 5, and Figure 7 (drawn on two sheets in parts "(A)" and "(B)") is a circuit diagram of an electronic circuit of a condensate trap for a compressed air system.

The condensate drain valve arrangement of Figure 1 consists of an electrical sensing probe 1 inserted in a condensate drain line 2 of the steam system upstream of a solenoid operated condensate drain valve 3 and so as to be electrically insuiated from the wall of the drain line. Electrical leads 4 connect the probe 1 and the wall of the drain line 2 to an electronic circuit 5 which has voltage supply leads 6 and which is connected to the solenoid of the valve 3 by leads 7.

As shown in Figure 2, the electronic circuit 5 includes a first integrated circuit 9 which serves to compare the signal from the probe 1 with an internal resistance of the circuit 9; a second integrated circuit 10 that is a solid state timer; an opto-isolator 1 1; and a triac 1 2. The coil of the solenoid of the valve 3 is represented at 13. Operation is as follows. An AC signal is passed to the sensing probe 1. If there is no condensate at the level of the probe 1 the output at pin (12) of the integrated circuit 9 oscillates at a frequency of 6 KHz. If the probe is covered by condensate there is a steady positive output at pin (12). The output from pin (12) is taken to pin (2) of the timer integrated circuit 10.Taking timer circuit pin (2) to zero volts (i.e. by feeding the 6 KHz oscillating signal to it) initiates a timing cycle during which timer circuit pin (3) is held at +V and in this condition the solenoid coil 13 is de-energised. At the conclusion of a timing cycle, and until initiation of the next timing cycle, timer circuit pin (3) is at zero volts and the transistors and solid state switches generally referenced 14 in the electronic circuit 5 switch the coil 1 5 to its energised condition.

At start up, if there is no condensate at the probe 1, the oscillating output of the integrated circuit 9 initiates a timing cycle (as the first excursion down to zero volts triggers the timer circuit 10). The solenoid valve is held shut. If, at the end of the first timing cycle, there is still no condensate at the probe, another cycle is initiated. When condensate has built up to submerge the probe during a timing cycle, the output of the integrated circuit 9 changes to a steady positive voltage and, at the end of this cycle, the output at the timer circuit pin (3) changes to zero volts. The solenoid valve opens and the condensate is discharged.When the probe is no longer submerged the output from the integrated circuit 9 changes back to the 6 KHz oscillation which initiates a timing cycle, simultaneously taking timer circuit pin (3) positive and de-energising the coil 1 3 of the solenoid valve, which closes.

Thus in the condensate drain valve arrangement of Figure 1 incorporating the circuit 5 of Figure 2, a single sensing element (the probe 1) sensing a predetermined condition In the steam system (condensate level below the probe 1) serves to trigger the circuit 5 to operate the valve with at least a desired minimum period between particular (valve opening) successive operations of the valve being imparted by a delay means (the timer integrated circuit 10) in the electronic circuit 5.

The operation described above can be illustrated as follows:

Timing Cycle F -When power initiated 1 I first switched I ON cycle may I be entered anywhere in Timing Cycle I this band Running t secs Timing Timing Cycle completed - - No No oondensate Condensate at at Probe | | Probe I Opens 1 Condensate I Discharged No condensate at Probe Valve closes In the above the time oft. seconds can be preset, or provision can be made for adjusting this time over a wida range, see resistor 100 in Figure 2.

in operation of the drain valve arrangement of Figure 4 incorporating the electronic circuit 5 of Figure 2 the solenoid is energised continuously when the drain valve is open. In the case of the electronic circuit 5A of Figure 3 short electrical pulses are used to open and close the valve so that the electrical energy required is minimised.

In Figure 3 components that are the same as are used in the circuit of Figure 2 are given the same reference numerals. Principle changes are that a pair of CMOS integrated circuits 1 4A, 1 4B and associated components replace the transistors and solid state switches generally reference 1 4 in Figure 2; and the solenoid valve has two coils 1 3A, 1 3B. Respective NAND gates of the pair of CMOS integrated circuits are referenced A1, A and A3 and B1, B2 and B3.

Operation of a drain valve arrangement incorporating the electronic circuit 5A of Figure 3 is as follows, reference also being directed to the logic diagram that constitutes Figure 4.Withno condensate at the probe 1 the output at pin (12) of the integrated circuit 9 is oscillating as described with reference to Figure 2 and pin (3) of the integrated circuit 10 is held at +V. Consider NAND gates As and Bt, pins (9) of each are at +V (connected via resistor-capacitor network 15to pin (3) of the integrated circuit 10) and pin (8) of NAND gate A, receives a small oscillation near zero volts (connected via resistor-capacitor network 1 6 to pin (12) of the integrated circuit 9). As NAND gate A, has +V on pin (9) and, because of the RC filter, near zero volts on pin (8) its output at pin (10) is high level. This output is connected to pin (8) of NAND gate B, and as pin (9) of this gate is at +V the output at pin (10) of this gate is low level. No puises are fed to the solenoid coil 1 3A, which is the valve-opening coil, and the valve is shut.

If the probe 1 is submerged in condensate when a timing cycle concludes, pin (3) of the integrated circuit 10 goes to zero volts as previously described and hence pins (9) of the NAND gates AT and B, are taken to zero volts. Taking pin (9) of gate B1 to zero volts takes pin (10) of this gate to high level and this signal is used together with NAND gate B3 and a resistor/capacitor network 1 7 to provide a 1 5ms pulse for energizing the valve-opening solenoid coil 1 3A. The drain valve opens.

When discharge of condensate uncovers the probe 1, pin (3) of integrated circuit 1 O, and hence pins (9) of NAND gates A, and B1, go to +V, as does pin (2) of NAND gate A2 which is used together with a resistor/capacitor network 1 8 and NAND gate A3 to provide, in these circumstances, a 1 sums pulse for energising the valve-closing solenoid coil 1 3B. The drain valve closes.

Should there by no condensate at the probe at the end of a timing cycle (as illustrated in the logic diagram of Figure 4 at the end of the second timing cycle) another timing cycle is initiated as described for the circuit of Figure 2. Although as this occurs pin (3)-of integrated circuit 10 is taken to zero volts, this is only for an extremely short time and does not initiate valve opening as the signal is damped out by the resistor-capacitor network 1 5.

In place of the condensate level sensing probe, a temperature sensing element such as a thermistor or a thermocouple can be provided so that the valve will open at a condensate temperature at or below a temperature which can be an absolute temperature or some set temperature below steam temperature at the operating line pressure.

Figure 5 illustrates one such possibility. In the steam trap arrangement herein illustrated low and high level temperature sensing elements 19,20 are inserted in the condensate drain line 2 with the element 20 in a zone normally always occupied by steam (or the high level element 20 can be in the steam supply line that the condensate line is branched off). These elements 1 9,20 are connected via leads 4A, 4B to a common electronic circuit 21 which is connected to the solenoid valve 3 by leads 7 and which has voltage supply leads 6.

Referring to Figure 6 one portion of the circuit 21 is substantially the same as a portion of the circuit of Figure 2. In the remainder of the circuit the temperature sensing elements 19,20 connected in a bridge network, replace the probe 1 of Figures 1 and 2 and are connected via an instrument amplifier 22 and an operational amplifier 23 to the timer integrated circuit 10.

In operation the differential temperature which can be adjusted by the 5K potentiometer 24 is detected by the instrument amplifier 22. The signal from the instrument amplifier 22 is amplified by the operational amplifier 23 before being fed to the timer 10. If the set differential temperature exists, i.e.

the condensate has cooled sufficiently to be discharged, then pin (2) of the integrated circuit 10 is taken to +V which, at the end of the timing cycle, causes the solenoid valve to open as described previously.

When hotter condensate, or steam, covers the lower temperature sensor 1 9 (the upper sensor 20, as the reference, is always in steam) pin (2) is taken to zero volts which initiates a timing cycle and closes the solenoid valve.

The condensate drain traps so far described have been foruse in steam systems. Condensate drain traps are also utilized in compressed air systems and the electronic circuit 25 of Figure 7 will now be described.

This circuit has a portion that is substantially the same as a corresponding portion of the circuit of Figure 6. In the remainder of the circuit a self-heating thermistor 26 replaces the sensors 19 and 20 and the instrument amplifier 22 of the circuit of Figure 6. The thermistor 26 serves as a condensate level sensor.

In operation, with no condensate present the thermistor warms up and its resistance is such as to cause pin (2) of the timer integrated circuit 10 to be held at zero volts. A timing cycle is initiated and the solenoid valve is held shut. When the thermistor is submerged in condensate this has a cooling effect and the thermistor's change in resistance is detected by the operational amplifier 23 taking pin (2) of circuit 10 to +V. At the end of the timing cycle the solenoid valve is opened as described above, closing again when the condensate level drops away from the thermistor.

Claims (10)

1. An electrically operated condensate drain valve arrangement for draining condensate from a fluid transfer system, the arrangement comprising a condensate drain valve, an electronic circuit for controlling operation of the valve, and at least one sensing element for insertion in the fluid transfer system to trigger the electronic circuit for operating the valve when a predetermined condition in the system is sensed by the sensing element; the electronic circuit including a delay means imparting a desired minimum period between successive particular operations of the valve.

2. A drain valve arrangement as claimed in claim 1, wherein the sensing element is a single electrical probe; wherein said predetermined condition is that condensate level is below this probe, the circuit being triggered to close the valve when this condition is sensed and the probe serving to trigger the circuit to open the valve when condensate level above the probe is sensed; wherein said successive particular operations occurring with said desired minumum period between each are valve opening operations; and wherein said delay means is a timer integrated circuit.

3. A drain valve arrangement as claimed in claim 2, wherein the elecronic circuit includes a first integrated circuit which serves to compare the signal from the probe with an internal resistance of this first integrated circuit, and a second integrated circuit that is said timer integrated circuit; the probe receiving an AC signal in operation of the arrangement and the electronic circuit operating such that in the no condensate at the level of the probe condition there is an oscillating output from the first integrated circuit whereas in the condensate at the level of the probe condition there is a steady positive output from the first integrated circuit; the second integrated circuit being connected to receive the output from the first integrated circuit so as to initiate a timing cycle upon receiving said oscillating output, an output from this second integrated circuit being positive during this and any subsequent timing cycle but changing to zero at the end of any timing cycle if the output then being received from the first integrated circuit is steady positive; and wherein the valve is a solenoid-operated valve having its solenoid coil connected in the electronic circuit such that the valve is shut when the output from the second integrated circuit is positive and is open when this output is zero.

4. A drain valve arrangement as claimed in claim 2, wherein the electronic circuit includes a first integrated circuit which serves to compare the signal from the probe with an internal resistance of this first integrated circuit, a second integrated circuit that is said timer integrated circuit, and two further integrated circuits each comprising NAND gates; the probe receiving an AC signal in operation of the arrangement and the electronic circuit operating such that in the no condensate at the level of the probe condition there is an oscillating output from the first integrated circuit whereas in the condensate at the level of the probe condition there is a steady positive output from the first integrated circuit; the second integrated circuit being connected to receive the output from the first integrated circuit so as to initiate a timing cycle upon receiving said oscillating output, an output from this second integrated circuit being positive during this and any subsequent timing cycle but changing to zero at the end of any timing cycle if the output then being received from the first integrated circuit is steady positive; and wherein the valve is a solenoid-operated valve having a first solenoid coil for opening the valve and a second solenoid coil for closing the valve, these coils being connected to the NAND gates of said two further integrated circuits, via resistance/capacitor networks, and the NAND gates ofthe two further integrated circuits being connected to receive the output of the second integrated circuit, such that an output from the gates of one of these two circuits which is low level when the output of the second integrated circuit is positive changes to high level when this last-mentioned output is zero to provide in conjunction with one of the resistance/capacitor networks a pulse for energising the valve-opening solenoid coil to open the valve, whereas when the output from the second integrated circuit goes to positive there is an output from the NAND gates of the other of the two further integrated circuits which in conjunction with the other of the resistance/capacitor networks provides a pulse for energising the valve-closing solenoid coil to close the valve.

5. A drain valve arrangement as claimed in claim 3 or 4, wherein the electronic circuit includes a variable resistor associated with said second integrated circuit for adjusting the length of said desired minimum period.

6. A drain valve arrangement as claimed in claim 1, for use in a steam system and wherein there are two sensing elements that are temperature sensing elements serving as low and high level temperature sensing elements the high level one of which in use of the arrangement is at a zone normally always occupied by steam; wherein said predetermined condition is that the zone at which the low level element is disposed is also occupied by steam, the circuit being triggered to close the valve when this condition is sensed and being triggered to open the valve when a temperature differential is sensed between the two zones indicating that condensate has cooled sufficiently to be discharged; wherein said successive particular operations occurring with said desired minimum period between each are valve opening operations; and wherein said delay means is a timer integrated circuit.

7. A drain valve arrangement as c!aimed in claim 6, wherein said two sensing elements, connected in a bridge network, are connected to said timer integrated circuit such that this integrated circuit initiates a timing cycle whenever said predetermined condition is sensed, an output from this integrated circuit being positive during this and any subsequent timing cycle but changing to zero at the end of any timing cycle if said temerature differential is then being sensed; and wherein the valve is a solenoidoperated valve having its solenoid coil connected in the electronic circuit such that the valve is shut when the output from the timer integrated circuit is positive and is open when this output is zero.

8. A drain valve arrangement as claimed in claim 6 or 7, wherein the sensing elements are thermistors.

9. A drain valve arrangement as claimed in claim 6 or 7, wherein the sensing elements are thermocouples.

10. A drain valve arrangement as claimed in any one of claims 6 to 9, wherein the electronic circuit includes a potentiometer for adjusting the range of the sensed temperature differential.

1 A drain valve arrangement as claimed in claim 1 for use in a compressed air system, the sensing element being a self-heating thermistor that warms-up, in use, when no condensate is present at its level, and that cools when immersed in condensate, said predetermined condition being that no condensate is present at the level of the thermistor and the circuit being triggered to close the valve upon warming-up of the thermistor and being triggered to open the valve upon cooling of the thermistor; said successive particular operations occurring with said desired minumum period between each being valve opening operations, and said delay means being a timer integrated circuit.

1 2. A drain valve arrangement as claimed in claim 11, wherein the self-heating thermistor is connected to said timer integrated circuit such that this integrated circuit initiates a timing cycle whenever said predetermined condition is sensed, an output from this integrated circuit being positive during this and any subsequent timing cycle but changing to zero at the end of any timing cycle if the thermistor is then cooled; and wherein the valve is a-solenoid-operated valve having its solenoid coil connected in the electronic circuit such that the valve is shut when the output from the timer integrated circuit is positive and is open when this output is zero.

1 3. An electrically operated condensate drain valve arrangement, substantially as hereinbefore described with reference to Figures 1 and 2, or Figures 1, 3 and 4, or Figures 5 and 6, or Figure 7 of the accompanying drawings.