DV diaphragm valve series application ideas APPLICATION BRIEF-03

Transcription

1 AB-03 DV diaphragm valve series application ideas AB-03 APPLIATION BRIEF-03 Analytical Flow Products, Division of Mecanique Analytique Inc. 33, Jalbert St. W., Thetford Mines, Q, anada G6G 7W Web: *See disclaimer notice available on our website at *The author may be contacted at : ygamache@afproducts.ca A POTPOURRI OF LIQUID APPLIATION USING THE DV SERIES DIAPHRAGM VALVE By Yves Gamache, Pres. Analytical Flow Products The unique feature of the DV series diaphragm valves makes them an excellent choice for liquid application. Their unique patented dynamic flow path eliminates problems related to dead volume and carry over. No inboard / outboard contamination, no friction allow extended lifetime compare to rotary design. Tight shut off port design give a tremendous level of sealing at high pressure. Sealing level is by far superior to rotary shear valve design. The intelligent electronic integrated drive makes integration work really easier. Each port is control independently allowing complex fluid control path to be done easily. Wide range of material valve head availability, port connection type, number and orientation allow then to retro-fit existing design base on rotary valves improving their performances with little effort and investment. They found their use in HPL application, auto-sampler system, syringe base pumps with higher pressure and life performance and many more other liquid control application. Application includes : linical diagnostics Genomic Sample preparation / purification Proteins science solution Drug discovery ell biology solutions Forensics Fluidic and microfluidic control devices EDV GENERAL DESRIPTION info@afproducts.ca opyright 05 Analytical Flow Products *Please see EDV brochures for complete description and option The EDV series has the same flow configuration as the DV series. The only difference is the actuator. This one is based on miniature gear head motor. The EDV is available in 3 actuation configurations. In its simplest form, the EDV may be supplied without any built in controller. The user has direct access to the valve motors. The next level is the standard one. The EDV is supplied with minimal electronic circuit that allows control as a simple solenoid valve by using the digital control line or through serial RS-485 port. The third configuration has a complete drive and microcontroller built-in into the valve assembly. It is possible to download switching event table and many other parameters. The EDV moves away from the traditional electrically controlol solenoid valve. To get the same amount of performance, a solenoid valve will consume anywhere between 8 to watts of power. It s a lot of power and heat generation when working with multiple channels system. The EDV is a diaphragm valve having a high level of port sealing, available with diaphragm agm purging option, eliminating diffusion and permeation. Ideal for high purity sampling. 37

2 DV diaphragm valve series application ideas AB-03 EDV ATUATION MEHANISM The port closing or opening is done by controlling the power of a miniature D motor gear head drive, as shown in Figure. When the power is applied to the motor, the output shaft of the gear head rotates in one direction or the opposite, depending on applied voltage polarity. This shaft has a flat side, and it s inserted into the threaded coupling. The threaded coupling is free to move up and down on the shaft when it rotates. The threaded coupling transfers the rotational torque into a vertical displacement. Then it pushes on a self-aligned plunger. The plunger do not rotate, thank to the anti-rotation dowel pin. The other side of the diaphragm is facing the valve s seat. Pressing the diaphragm against the valve s seat shuts off fluid flow. Lifting it restores the flow. The plunger is self-aligned and free to move. When the threaded coupling is going up, the plunger will be lifted by the return spring, removing any force on the sealing diaphragm. This makes sure that there is no flow restriction when the valve port is fully open. ontrolling the speed of the motor controls the speed of operation of the entire system. This allows valve operation in a controlled speed mode that could be advantageously used to control the rate of rise of pressure or flow of a system. Figure Mechanical assembly FLOW PATH The unique patented flow path make sure that there is no dead volume effect, eliminating the carry over problem. There is always a flow around a closed port. The Fluid could be set to flow from or into a port. Pressure drop is extremely low. The independently controled port make easy to wash the internal channel. Figure A PORT a OPEN AND b LOSED Figure B PORT a LOSED AND b OPEN Figure BOTH PORTS OPEN 38 opyright 05 Analytical Flow Products info@afproducts.ca Figure D BOTH PORTS LOSED

3 AB-03 DV diaphragm valve series application ideas Here some ideas of applications. TYPIAL HPL APPLIATION SAMPLE LOOP INJETION / BAKWASH PUMP V HPL OLUMN V PUMP V DV V HPL OLUMN SAMPLE V3 SL SAMPLE V3 SL WASTE WASTE A) Sample flowing through sampling loop B) Sample loop injection PUMP V HPL OLUMN V PUMP V HPL OLUMN V DV SAMPLE V3 SL SAMPLE V3 SL WASTE WASTE ) Sampling loop cleaning or flush D) Alternate flowpath sample injection for dead volume cancelation n effect. Here the section DV is swept. TIP: This L sample injection use only 3 valves. However such configuration create an unswept dead volume upon sample injection. This dead volume is show in fig. B and identified as DV. Such dead volume may cause peak tailing base on HPL system operating parameters. If your system fall in this categorie, an alternate sample injection as show in fig. D may be considerated. By opening both ports of V at sample injection, the DV section is also swept. info@afproducts.ca opyright 05 Analytical Flow Products 39

4 DV diaphragm valve series application ideas AB-03 LIQUID APPLIATION, SHAVE / REYLE SYSTEM L DETETOR V PUMP SAMPLE INJETION VALVE SET UP HPL OLUMN V V, V, V3 : EDV-3 V3 NOTE: There is no valve stem or circular seal in the wetted part of the valve flowpath that can contaminate or generate leak of the fluid being controlled. WASTE OLLET LIQUID APPLIATION / PROPORTIONING VALVE GRADIENT SYSTEM L DETETOR MIXER SELETION VALVE PUMP SAMPLE INJETION VALVE SET UP HPL OLUMN V A B ONTROLLER WASTE V: EDVS-3 RESERVOIRS 40 opyright 05 Analytical Flow Products info@afproducts.ca

5 AB-03 DV diaphragm valve series application ideas AUTOMATION OF SYRINGE APPLIATION All the application shown below are done with an EDV-3. EDV-3 DISPENSER / DILUTER SAMPLE DILUTION A) Fill the syringe with diluting solution B) Aspirate some amount of sample with syringe info@afproducts.ca opyright 05 Analytical Flow Products ) Load Vial with sample and diluting solution 4

6 DV diaphragm valve series application ideas AB-03 REAGENT DILUTION A) Load Solution A and B in their respective syringe. B) Addition of Solution A and B to a commercial or reservoir. SIMPLE DISPENSE OF SOLUTION A) Dispense precise amount of reagent into vials. 4 opyright 05 Analytical Flow Products info@afproducts.ca B) Dispense precise amount of reagent into vials.

7 AB-03 DV diaphragm valve series application ideas ALIQUOT DISPENSE A) Fill in the syringe B) Repetitive dispense of fixe volume ) Repetitive dispense of fixe volume D) Repetitive dispense of fixe volume info@afproducts.ca opyright 05 Analytical Flow Products 43

8 DV diaphragm valve series application ideas AB-03 HIGH PRESSURE SYRINGE PUMP HIGH PRESSURE PROESS 500 PSI EDV-3 MULTIPLE HANNEL SYRINGE PUMP EDV-6 common port 6 controlable Syringe ports Precise and Pulsation-free dosing of fluids. Easy washing cycle, eliminating carry over. 44 opyright 05 Analytical Flow Products info@afproducts.ca

9 AB-03 DV diaphragm valve series application ideas FLUIDI AUTOMATION PURIFIATION SYSTEM PURIFIATION REYLE SYSTEM opyright 05 Analytical Flow Products 45

10 DV diaphragm valve series application ideas AB-03 PURIFIATION ENHANED SYSTEM 46 opyright 05 Analytical Flow Products

11 AB-04 Things you should know about G diaphragm valve AFP 33, Jalbert St. W., Thetford Mines, Q, anada G6G 7W info@afproducts.ca Web: *Disclaimer notice is available on our website *The author may be contacted at : ygamache@afproducts.ca Today, AFP G diaphragm valves are more frequently specified than the one developed years ago. Thank to the technical improvements done by AFP, now these valves are really reliable and are often used to replace rotary valves in gas chromatograph. They also provide self diagnostic feature, a World premier. In order to get full benefit out of them, some technicals details must be taken into consideration for some specific applications. The purpose of this paper is to provide the information necessary to understand these technical details and possible impact on your system. Mixing or not mixing?.0 Flow mixing, what is this? When it is not desirable? When it is desirable to have it? Flow mixing is a phenomenon that occurs in a G diaphragm valve upon actuation. For a short period of time, all the ports of the valve become in communication, i.e. all ports are open at the same time. This means that any high pressure stream can flow back in any lower pressure port or stream. Figure shows the simplest gas chromatographic configuration. Imagine a liquid sample at a pressure of 500 psig, or even higher, flowing into the sample loop, being injected into carrier circuit to be allowed to be separated by the gas chromatographic column. olumn olumn arrier gas Inlet arrier gas Inlet : Plunger Down : Plunger Up : Plunger Down : Plunger Up Sampling Injection Figure : The simplest G configuration info@afproducts.ca opyright 05 Analytical Flow Products 47

12 Tips info Here the mobile phase or carrier is gas while sample is liquid. This is a common situation in gas chromatography. Do not confuse this situation with liquid chromatography i.e. HPL. Many hydrocarbon samples will vaporise or evaporate at the atmospheric pressure. It is therefore required to maintain them at higher pressure to avoid sample fractionation or distillation, leading to inaccurate measurement. The most volatile compound will vaporise when the heavier or less volatile ones will still be in liquid phase. Such sample under high pressure condition must be quickly injected into the carrier circuit as a slug and then vaporised in the gas phase. This is done by allowing the sample liquid slug to flow through a heated zone. When the liquid sample is vaporised, its volume will increase anywhere from 300 to 900 times its original volume. For this reason, the sample loop size is very small to take this phenomenon into account. A larger liquid sample volume will generate a too high volume of gas sample after vaporisation step, causing separation column overloading. Now coming back to Figure, imagine during sample injection step i.e. when introducing the sample loop volume into carrier circuit, that for a short period of time during that process, all valve s ports are open because all valve s plungers are retracted. This situation will allow the high pressure liquid sample to flow back into low pressure carrier circuit and into column inlet. These parts of the system become momentary connected to the high pressure sample source. This will have a negative impact on system performance, since the volume injected will not be repeatable and also larger dependent on actuation time, that itself depends of the pneumatic actuation line and solenoid valve size and V. Furthermore, depending on sample vapor pressure partial, fractionation will occur during this process. Figure shows typical plungers displacement related to the actuation pressure rise, for typical G diaphragm valve available on the martket. NOT AJUSTABLE Figure : Typical actuation step for commercial valve. ADJUSTABLE DEAD BAND Figure 3: Actuation step but for AFP valve. When used for such application, our valves are generally tuned to have a dead band of 5 psig, when the pressure rises into the actuator. This is done with the help of pressure adjusting screw mounted in the center of bottom cap. This screw is not used to hold the cap on the cylinder body like the valve found generally on the martket. Dead band zone may be defined as the zone where all plungers are up for a certain actuation pressure range. This value is adjustable between 5 to 5 psig. Generally the valve dead band is set at 5 psig, as show in Figure 3. This will prevent any flow mixing or cross port flow into the valve, improving system performance when operating under these conditions. It maintains the slug type injection. In such application, flow mixing is not desirable. 48 opyright 05 Analytical Flow Products info@afproducts.ca

13 .0 When a controlled level of flow mixing is desirable? When sampling at the atmospheric pressure and the sample volume is small i.e. about 00 microliters or less, it may be desirable to retune the valve to get a little bit of flow mixing upon actuation. This will effectively eliminate the dead volume effect generated by the space between the plungers and their adjacent ports. Pressure adjusting screw with fine pitch thread Rotary Valve Washer Diaphragm Valve Washer Spring (Temperature compensated) Preload assembly Locking screw Ball bearing Hardened thrust transfer disc Treated rotor Preload ass y housing Stator Dowel Pin oated drive/ bushing adaptor Mounting collar P5 P6 P5 P6 Figure 4 P4 P4 P3 P P P3 P PURGE IN PURGE OUT P Groove (Displacement Volume used to connect two ports) Tips info One of the differences between a diaphragm and rotary valve is the method used to divert the flow between ports. The rotary valve is a volume displacement valve i.e. to control the flow direction, a volume is aligned to allow flow path between two adjacent ports. This space or this volume is displaced, generally between two positions. This way, there is no dead volume because this volume, or more precisely a groove machined on a rotor surface, is precisely put in line with the two adjacent ports. Things are different for a G diaphragm valve. Indeed the flow direction is controlled not by introducing a volume between two ports, but by closing or reducing it, interrupting the flow path, as shown in figure 4. For this reason, mixing could occur only in a diaphragm valve. info@afproducts.ca opyright 05 Analytical Flow Products 49

14 Referring to figure 5, we can see where those small dead volumes are located. These small dead volumes could in some situation, like mentioned here above, generate a second, but with much less sample volume, injection. Indeed, when operating the G.. diaphragm in a non mixing mode and the sample volume is small this phenomenon could appear. It is all dependent of sample solubility and diffusion speed. It will be much more apparent with small liquid sample than gas, this is due to volume gain upon liquid sample voparisation. The sample pressure and temperature also plays a role. So, in short, this phenomenon shown in figure 6 may not appear at all. When the valve of figure 5 is actuated and injecting the sample into carrier circuit, there could be an accumulation of sample fluid in the dead volume DV-. This volume is not place directly into the carrier flow path but may diffuse slowly or rapidly into the carrier. olumn olumn P arrier gas inlet PL P PP33 arrier gas inlet PL3 PL P PL5 PL4 PL5 P5 Plunger Down olumn Plunger Up B: When actuated olumn DV DV PP PL PP33 PP arrier gas inlet PL3 PL P PP4 PL4 PL6 PP66 PL5 P5 PL6 Plunger Up A: Ready to inject filled sampling loop 50 PL3 Plunger Down arrier gas inlet PP33 PL PP66 P55 PP4 PL4 PP66 PL P PP4 PL6 DV DV PP33 PL PL3 PL6 PL4 P PP4 PP66 Plunger Down Plunger Up PL PL5 P55 Plunger Down Plunger Up : Almost completely injected D: When switched back to refill sampling Figure 5 loop. DV is partly filled with sample, which will create a second injection opyright 05 Analytical Flow Products info@afproducts.ca

15 H O 0.94 mvolts Re-Injection mvolts injection Switch Back V O N O N H Figure Now, when the valve is restore to its original position, this volume will be swept by the carrier and introduce into the carrier circuit, generating a second injection and a set of twin and smaller peaks. This issue could be resolved in two ways. The first solution it by choosing the right time to set back the valve in sampling position in order to get this set of small twin peaks between the real ones, and samply ignoring them. It hurt nothing to do so. The next method is to allow a controlled mixing upon injection. This could be done at the factory or by the end user, after reading proper instruction sheet about this. Allowing a little flow mixing will force the dead volume to be swept by the carrier gas, moving the accumulated sample away through separation column. This way, when the injection valve is returned to sampling position, there will be no second injection. Figure 7,8 and 9 are showing what happens in such case. olumn olumn arrier gas Inlet arrier gas Inlet : Slightly leaking Plunger : Plunger Down : Plunger Up : Plunger Down : Plunger Up Sampling Injection Figure 7: The simplest G configuration info@afproducts.ca opyright 05 Analytical Flow Products 5

16 olumn olumn DV P arrier gas inlet PP33 PL P arrier gas inlet PL3 PL P PP4 PL4 PL6 PP66 PL5 PL6 PL4 PP4 PL5 Slightly leaking Plunger P5 Plunger Down Plunger Up A: Ready to inject filled sampling loop Plunger Up B: When actuated olumn DV DV PP arrier gas inlet (P) PP33 PL3 PP66 Plunger Down olumn PL PL P Slightly leaking Plunger P55 P P DV PP33 PL PP arrier gas inlet PL3 PL P PP4 PL4 PL6 PP66 PL5 PL6 PL4 PP4 PP66 Plunger Down (P) PL3 P Slightly leaking Plunger P5 PP33 PL PL PL5 Slightly leaking Plunger P55 Plunger Down Sample p Inlet Plunger Up : Transient state upon injection that allows tune-mixing. This step occurs upon actuation. Plunger Up D: When switched back to refill sampling loop, DV is now filled with carrier gas H V h Ba ck injection Sw itc N O 4 H Figure 9 5 opyright 05 Analytical Flow Products info@afproducts.ca mvolts 0.9 O No second Injection mvolts Figure 8

17 Tips info If required and if the application is critical, AFP could provides specific valve and plunger assemblies (patented technologies). These plungers could be actuated at different speed or at different moment in time during the actuation sequence. Such arrangement makes sure that carrier gas always sweeps the dead volume space DV at all time. 3.0 Port pressure drop One characteristic that differs the diaphragm valve from a rotary valve is the port pressure drop between the two valve operating states, i.e. normally open sections in the unactuated state and normally closed sections when the valve is actuated. In the rotary valve, the pressure between the two rotary valve operational positions is the same. Indeed, as previously said, a volume is displaced when the valve when the valve is switched between positions. The volume in the groove machined into the rotor surface is always the same whatever is the valve position. So is the pressure drop. In a diaphragm valve, things are different. The diaphragm is lifted up against the valve head in order to interrupt the flow between two adjacent ports. When the plunger is retracted, the diaphragm will take back its place into the valve actuation body groove in order to restore the flow. Normally, the diaphragm memory effect is enough to reseat it. Furthermore, the line pressure will help to re-seat the diaphragm and clear the flowpath between ports. However, there are some situations where the diaphragm will not re-seat completely causing a difference in pressure between valve positions. At high temperature, the diaphragm mechanical behaviour changes and the diaphragm loses some of its spring back capacity. Operating at low or sub-atmospheric pressure (not vacuum), for example when pulling the sample through the valve with the help of a sample pump, the diaphragm will have a tendency of being lifted of a little causing a slightly higher pressure drop. When working with capillary columns, the column head pressure is very low and in some cases almost equal to the valve pressure drop. However the velocity is relatively high. So, in such case, any slight variation of valve port pressure drop upon actuation will affect carrier flow velocity into the column. Most of the time, the slight pressure drop variations between valve positions is not an issue and doesn t affect system performance at all. info@afproducts.ca opyright 05 Analytical Flow Products 53

18 However, if required, it is possible to cancel this phenomenon. Figure 0 shows how to reduce flow perturbation upon actuation by increasing the impedance of the source of carrier. During sampling mode, the valve pressure drop for the carrier flowpath is equal to P A. During sample flow injection, this value is now P B + P + P SL, so a higher pressure drop or restriction is put in series with the column P R ΔP B apillary column PR ΔP A arrier gas Inlet ΔP SL ΔP Figure 0 This extra pressure drop or flow restriction may reduce column head pressure and carrier velocity through it. This is because the valve pressure drop is close to the column pressure drop. It s like adding two restrictions almost of the same value is series. Now by adding a restriction R between the valve and the column, and tuning R in order to get the required flow through the column at a substantially higher pressure value P will cancel any negative impact of the slight pressure drop change upon valve actuation, or a temperature change like in a temperature programmed environment. ΔP B apillary column ΔP A arrier gas Inlet ΔP SL P PR R Or Sample Figure ΔP P Sample pump Sample vent Typical value for P has been set from 30 to 90 psig. This system configuration allows also monitoring the carrier flow by crossreferencing it to pressure P. It is easy to set up a look-up table in the software to do so. We did test this configuration with great results. No velocity change at all through the column, so peak timing and shapes unaffected at all. 54 opyright 05 Analytical Flow Products info@afproducts.ca

19 Figure shows how to eliminate problem on the sample side of the system. In some reactor or catalyst performance monitoring, it is really important to not modify any operating parameters when sampling the effluent. This necessitates maintaining the flow and sampling pressure of the system constant. The best way to achieve that is by adding a miniature sample pump in the sample vent of the valve. A miniature by-pass control valve could be added to maintain the pump inlet pressure at a constant pre-set value. This is achieved with an inexpensive pressure sensor and an independent PID controller. All this costs less than 300$ and performs exceptionally well. In the case that the sample is higher than the atmospheric pressure, a restriction R, as shown in Figure could be added. By properly tuning R relatively to P, the internal part of the valve and the sampling loop are maintained at a constant higher pressure. This eliminates the effect of any slight variation in valve pressure drop. Sample flow will be constant during injection and sampling. Same philosophy could be followed when using the valve for a column switching application. Slightly increasing column pressure or back pressure seen by them will improve in such application the performance of the system. onclusion Most of the time, this slight changes in pressure drop doesn t affect at all system performances. Knowing diaphragm valve behaviours make it easy to correct them in case of impact on your system. This is application dependant. info@afproducts.ca opyright 05 Analytical Flow Products 55

20 NOTES 56 opyright 05 Analytical Flow Products