INSTRUCTION MANUAL SERIES SAFETY RELIEF VALVES

Transcription

1 ACA 3503 Issue INSTRUCTION MANUAL SERIES SAFETY RELIEF VALVES

2 SAFEGUARDS GENERAL Beside the rules here below listed the plant manager must meet the regulation in force concerning safety and health of workers in jobsites. Qualified staff only must be used to operate on the valve. The Company rejects any responsibility for personal injury and damages to equipment imputable to improper operation, use of non original spare parts or repairs executed by unauthorised staff. Transportation must be performed utilising original packing up to job-site. The Company rejects any responsibility for damages occurred to things and people due to packing because of having been tampered with. USE AND MAINTENANCE WARNING DANGER Safety relief valve, due to its particular function, operate in a discontinuous way. It is therefore necessary to take the necessary precautions when staying near or passing close to the valve, when plant is running. In case of discharge to the atmosphere keep out of discharge duct. The lifting lever must be used for authorised tests or trials only. TEMPERATURE WARNING DANGER In case that hot fluids flow through the valve, the operator must pay attention to not insulated parts. LIFTING AND HANDLING WARNING DANGER When lifting use eyebolts, if any, otherwise sling the valve body. 2

3 LIMITATION OF USE Residual hazards with regard to essential safety requirements of Annex I of European Pressure Equipment Directive no. 97/23/EC If not otherwise specified, the following use limitations have to be considered for PARCOL safety valves. 0 MAXIMUM WORKING PRESSURE AND TEMPERATURE Before placing the valve in pipe line make sure that maximum working pressure and temperature are within the limits of body rating and lower than allowable maximum values indicated on valve serial plate. 1 MINIMUM WORKING TEMPERATURE Valves having Carbon Steel body material (SA-105 or SA216 WCB) are suitable for a minimum working temperature down to 20 C when working pressure is at its maximum rating listed value. If working temperature is down to 29 C, the maximum pressure must be reduced to 1/3 of its maximum rating listed value. Valves having Cr. Mo. alloy steel body material (SA217 WC6, SA217 WC9, SA217 C12A, SA182 F11, SA182 F22, SA 182 F91, etc.), particularly suitable for high temperature services, the minimum working temperature at maximum rating listed pressure shall be +20 C. It is possible to reach a minimum working temperature of 29 C but maximum working pressure must be reduced to 1/3 of its maximum rating listed value at ambient temperature. RATING Rating pressure (1) Pressure at ANSI bar T 20 C (1) (2) - bar (1) Referring to SA217 WC6/WC9 or SA182 F11/F22 (2) Also during hydrostatic pressure test at T 20 C 2 EXPECTED WORKING LIFE IN CREEP RANGE No special limitations are required in the expected service life of safety valve, other than those foreseen afterwards. When safety valves are used at a working temperature within the creep range (as listed on the following table), the guaranteed expected lifetime is in any case not lower than hours of continuous operation at rating listed pressure corresponding to working temperature. Material Tbeginning creep Carbon steels (i.e.: A216 WCB-A105) 343 C CrMo steels (i.e.: A217 WC9-A182 F22) 455 C 300 series cast austenitic steels 510 C 9% Cr Mo V steels (i.e.: A217 C12A-A182 F91) 538 C 300 series forged austenitic steels 538 C 3 SEISMIC STRESSES PARCOL safety valves have been experimentally tested for seismic applications on vibrating table by applying both axial and transversal acceleration up to 5g. Nor damage on pressure containing parts neither performance limitation have been observed after such a test. 4 PIPING STRESSES In general it is not necessary to perform any check and calculation if pipe size is no larger than 1,5 times valve body size (2 times for valve body size up to 3 ). As the safety valve has not to be used as a fixed point, if inlet and outlet pipe sizes are different, it should be considered the smaller one as it is essential for the piping design. 5 SELF GENERATED FORCES DURING FLUID DISCHARGING During operation, due to the high velocity of the discharged fluid, safety valves can generate not negligible reaction forces. The values of these forces are reported on calculation sheet and must be taken into account for holding point and connected piping design. 6 CORROSION In case of local corrosion, particularly with chlorides, such as pitting, interstitial corrosion on gasket seating surfaces and stress corrosion, it is not possible to make any realistic prediction of expected lifetime of valve. In these circumstances it is essential to properly select the material of disk and valve nozzle. 7 EXTERNAL FIRE PARCOL safety valves are not designed to withstand external fire. 8 CYCLIC LOADS OF PRESSURE AND TEMPERATURE For most of installations possible cyclic changes of pressure and/or temperature do not influence the expected lifetime of valves. The above assuming the following working conditions: - maximum working temperature not exceeding 550 C; - fluid temperature change rate 2 K/min or less; - cyclic change of working pressure within 1/3 of maximum allowable rating pressure at corresponding temperature. When working conditions are outside the above specified ones a particular check is necessary to calculate the expected lifetime of the valve. 9 BACKPRESSURE - Unbalanced versions can be used only for constant backpressure applications. In this case the set pressure adjustment is performed taking into account the effect of backpressure. - For variable back-pressure applications, bellows balanced safety valves with vented bonnet must be used. Parcol guarantees the correct operation of bellows balanced safety valves up to the backpressure values listed in the technical bulletins. - When high length discharge piping are connected to the valve outlet, the self-generated back-pressure must be evaluated. The back-pressure value must not exceed 10% of the set pressure for safety valves without balancing bellows (absolute pressures for compressible fluids and gauge pressures for uncompressible fluids). 10 BLOW-DOWN RING SETTING Parcol safety valves are equipped with a blow-down ring screwed on the nozzle for blow-down adjustment. The blow-down ring adjustment is described on this manual and must be performed by skilled personnel only when strictly necessary. 11 BELLOWS Bellows is warranted for high number of valve opening, however it may be accidentally damaged: in this case the balancing function should be compromised. For most severe applications it is suggested to periodically check the bellows integrity by flushing the downstream body and checking any leakage through the vent hole on the bonnet. Be careful to maintain the vent connection on the valve bonnet free to the atmosphere in order to allow the proper balancing function of the bellows. 12 SET PRESSURE Safety valve is supplied after set at the pressure value reported on test valve certificate. Reliability of safety valve set pressure shall always be verified before installation if not otherwise specified. After installation the reliability of safety valve set pressure shall be verified periodically following the prescriptions by laws in force in the country where safety valve is installed. If no prescriptions are available, reliability of safety valve set pressure shall be verified at least every three years in presence of an Authorized Inspector or return the safety valve to manufacturer for overhaul. 13 GUARANTEE If safety valve is supplied with plumbing device, manufacturer guarantee on valve set pressure decays when plumbing device is removed. The User shall then verify safety valve set pressure in presence of a Notified Body Inspector or return the safety valve to manufacturer for overhaul. NTG 76/553E05

4 INSTRUCTION MANUAL SERIES SAFETY RELIEF VALVES 1 HANDLING AND STORING Inside components of safety relief valves are carefully machined and assembled in order to get a perfect alignment. Improper handling of valves may damage seat surfaces or cause misalignment of inside components, thus generating leakage or faulty operation. Safety relief valves must therefore be handled with care. Valves are shipped with suitable protective caps at inlet and outlet, to prevent damages at the sealing surfaces or flanges and to avoid that foreign particles enter the valve body. If valves are expected to remain long time stored before the installation, as in case of new installations, the protective caps should not be removed before the mounting of the valve. Moreover the storage area should be clean, dry and covered. Should the above be impossible valves should at least be protected by suitable and waterproof material. 2 INSTALLATION A correct installation is a key-factor of successful valve operation. Keep utmost clean through all installation steps. Pipes, connecting flanges and valve supporting racks must be carefully cleaned. Prevent foreign particles, such as gasket trashes, slags, dirt, sand, etc., from accumulating during the installation. Pipelines should be blown if possible, to clean the piping upstream the valve. 2.1 INLET PIPING The safety relief valve should be installed in vertical position. The inlet piping from the vessel or the protected equipment should preferably be short and straight. The connection with the vessel should be rounded, to allow a free fluid flow to the valve; sharp bends should be avoided. The pressure drop between vessel and valve should not exceed 3% of the set pressure when the flow rate through the valve is maximum. Beyond this limit chattering of the plug may occur. Inlet piping connection must never have lower dimension than the valve inlet one. 2.2 OUTLET PIPING Trim alignment of a safety relief valve is very important for correct valve operation. Though the valve body can tolerate considerable mechanical overloads, nevertheless excessive pipe length without supports should be avoided. Install where possible piped drainages to prevent water or corrosive liquid collection in the valve body. When two or more valves are piped to discharge into the same header the downstream pressure generated by opening of one valve may cause the set pressure of the other valves to increase by the same amount. Additional recommendations may be found in API RP 520 -"Design and installation of Pressure Relieving Systems in Refineries". 2.3 INSTALLATION In case of vessels containing saturated vapours the safety valve must be installed as far as possible from the liquid surface. Valve location where foreign materials may accumulate should be avoided as well. Since the valve must be inspected and removed for maintenance a suitable free and accessible area should be provided around it. Vibrations of the protected piping or vessel may affect life and tightness of the valve. Excessive fluid turbulences and pressure pulsations upstream the valve may cause plug chattering on the seat during the valve operation, thus reducing valve tightness and life. Where equipment vibrations and upstream pressure pulsations cannot be avoided it is advisable to increase the difference between normal operation pressure and set pressure by more-than the normally recommended 10%. 2.4 LOCKING DEVICE (TEST GAG) When carrying out the pressure test of the plant the valve must remain closed. For this purpose remove the plug (39) and the gasket (40), tighten the locking screw (35) until it gets in contact with the stem (7); then tighten the test gag nut (36), thus preventing the valve to open. After the pressure test remove the screw (35) and replace it with the plug (39) and the gasket (40) to restore the normal valve operation.

5 3 SETTING AND PERFORMANCES All of the valves made and shipped by PARCOL are supplied with a spring suitable for the operation conditions as specified in the order. Using a correctly selected spring is utmost important. Any attempt to use a spring below its rated pressure range will result in a lower lift (and consequently in a lower discharge capacity) and generally in a slower valve action. Similarly using a spring out of its rated temperature range will cause a change in spring behaviour with consequent danger of spring failure. It is however possible to adjust the spring 10% above or below the nominal value for set pressures lower than 17 bar and within ±5% for higher set pressures. Before increasing the set pressure of any valve ascertain that the new set pressure complies with the valve rating; on the contrary, before reducing the set pressure, check that the valve capacity at the reduced pressure is suitable for the protection of the plant. Valves installed on steam, gas or vapour services will relieve with a fast plug lift ("pop-action"). In case that the upstream pressure raises up to 10% above the set pressure the valve will attain the full opening. The valve will reseat only when the pressure, during the discharge, will fall 5 7% under the set pressure. For valves operating on liquid service there will be no "pop-action"; their opening will gradually increase with the pressure rise without any popping. If the upstream pressure will rise up to 25% above the set pressure the valve will attain its full opening. The valve will reseat only when the pressure will fall 5 to 7% under the set pressure. 3.1 BLOW DOWN SETTING The reseating pressure (blow-down pressure) may be adjusted by means of the nozzle ring mounted on the nozzle (see part list). - remove the locking screw (13) of the ring and the gasket (15). - rotate the nozzle ring (6) with a screw driver until it touches the plug (5). Then turn it down until the required blow-down value is reached. - align the nearest nozzle ring notch with the locking screw and reassemble screw and gasket. - to increase the blow-down (i.e. if lower reseating pressure is required) the nozzle ring must be lifted up by moving the notches from left to right (the ring must be rotated counter-clockwise). - to reduce the blow-down (i.e. if higher reseating pressure is required) the nozzle ring must be lowered by moving the notches from right to left (the ring must be rotated clockwise). When valves are used for liquid service or as thermal relief the blow-down ring is not supplied, or it is installed in the lowest possible position. 4 TRIM MAINTENANCE 4.1 DISASSEMBLY To disassemble a series safety relief valve for inspection or maintenance proceed as follows: A - VALVE WITH PLAIN CAP: unscrew the cap (3) from the bonnet (2) and take off the gasket (17). B - VALVE WITH LEVER: place the lifting lever (30) in its lowest position, unscrew the support (24) and remove the lever with support and pin; unscrew the cap (20) and take off the gasket (17), then unscrew the disk (22) from the top of the stem (21) after having loosened the screw (23). C - Before removing the adjusting screw (11) it is suggested to measure the distance between the top ends of the stem and the spring adjustor. This will enable the screw to be replaced in the same position. Loosen the locknut and relieve the spring compression by turning the adjusting screw counter-clockwise. D - Unscrew the bonnet from the body. E - Remove the spring and the spring washers (9). F - After the stem (7) remove the stem guide (8), the gaskets (16) and the plug (5). G - The blow-down nozzle ring (6), if supplied, may be removed, after having unscrewed the locking screw (13) H - To remove the nozzle (4) hold the body in a vice and unscrew the nozzle using a suitable wrench or driving a pin in the existing holes. I - When disassembling the valve remove the gaskets with utmost care, not to damage them. 4.2 SEAT LAPPING When disk seating is slightly scratched, lapping can completely recondition the surface. If lapping is required use a cast iron lapping plate, or a clean and flat ring lap. Spray a thin layer of emery paste on the lapping plate or ring; hold down the component to be lapped and drive it with a figure-eight (8) motion. When lapping apply a light and uniform pressure avoiding any shock. It is recommended the nozzle be removed from valve for lapping. As the nozzle is quite small it is recommended to screw it on a disk, acting as an extension of the nozzle surface to be lapped, to avoid any shock or rocking. Any excess of compound could cause the rounding of seat edges, thus compromising the valve tightness. 5

6 LIFTING LEVER TEST GAG FIG , and SERIES CONVENTIONAL DESIGN , and SERIES BALANCED BELLOWS DESIGN vent PART REFERENCE LIST Item Part name 1 BODY 2 BONNET 3 CAP * 4 NOZZLE * 5 PLUG 5a DISK 5b DISK HOLDER 6 NOZZLE RING (1) 7 STEM ASSEMBLY 7a STEM ROD 7b BALL 8 GUIDE 9 SPRING WASHER 10 SPRING 11 SPRING ADJUSTING SCREW 12 LOCKNUT 13 LOCKING SCREW * 14 NOZZLE GASKET * 15 GASKET * 16 GASKET * 17 GASKET 18 SPHERICAL SUPPORT 20 CAP FOR MANUAL LIFT 21 STEM FOR MANUAL LIFT 22 STOP DISK 23 LOCKING SCREW 24 PACKING HOUSING 25 PACKING GLAND * 26 PACKING 27 CIRCLIP 28 SHAFT 29 DOWEL 30 LEVER * 31 SUPPORT GASKET 35 TEST GAG 36 NUT 37 RIVET 38 WASHER 39 PLUG * 40 PLUG GASKET 41 CHAIN 51 DRAIN PLUG (if required) * 75 BELLOWS * 76 GASKET * Recommended spare parts 1) Not supplied for liquid service 6

7 Lapping compounds vary from coarse to very fine grain. A coarse grain compound is generally used first, then a very fine to finish the piece. Coarse grain compounds must be used only when removing deep scratches and must be followed by finer grains. Clean thoroughly the plate when changing any compound; different plates should therefore be available for different pastes. Important points for good results are: A - Cleanliness of lapping plates B - Flat base surface C - Light and even lapping movement (with no rocking) D - Changing of lapping compounds 4.3 NOZZLE AND DISK MACHINING When scratches are so deep that lapping is not sufficient to completely remove them the components must be remachined on a lathe MACHINING OF SEAT NOZZLE - machine the seat according to data listed in Fig. 2 until the damaged areas are removed; surface finishing should be as smooth as possible. - lap the seat surface until the seat width attains again the original value. - nozzles should be normally discarded when already machined three times DISK MACHINING - machine the disk until the damaged areas are completely removed; surface finishing should be as smooth as possible. The tool rigidity is utmost important. - lap the raised seating surface across the full width. - disks should be normally discarded when already machined three times. 4.4 VALVE REASSEMBLING Remind that gaskets and packing shall be replaced with new ones. Always use Parcol original spare parts. The valve assembling procedure is the reverse of the disassembling one. When assembling the valve the adjusting screw should be loose, so that the spring will not be compressed when tightening the bonnet nuts. Tighten the adjusting screw and prevent the stem to rotate by clamping it with pliers. This will avoid to scratch the reconditioned nozzle surfaces. The measure taken when disassembling the valve should be borne in mind to set the spring adjusting screw approximately in the same position as before disassembling. Aligning the inside components is critical for good operation; it is therefore necessary to handle them and resemble the valve with care. The nozzle ring for blow-down adjustment should be reset in the same position as it was before disassembling (rotate by the same number of notches starting from the contact with the disc). 5 VARIANT FOR VALVES PROVIDED WITH BELLOWS 5.1 DISASSEMBLY FIG. 2 Orifice (1) Φ A Φ B C B(a) C C(a) D D(a) D(a1) (2) E E(a) (2) ) Suffix (a): for liquid service; no suffix: for gas service 2) For application with balancing bellows (both gas than liquid service) Bellows (75) can be removed from the body together with the plug-disk holder group after removing the guide (8). Operate carefully, not to damage the bellows or the plug See points 4.2 and BELLOWS REPLACEMENT Lock disk and disk-holder in a vice USING SOFT JAWS, not to spoil them; then ingage a pin wrench or a round bar in the side holes of the bellows ring nut and turn clockwise to unscrew the bellows. Replace the bellows with a PARCOL original spare; ensure that gasket (76) is in good condition, before screwing it on the disk-disk holder group. Replace it if necessary. Tighten the bellows base against the plug, to properly press the gasket 7

8 5.5 REASSEMBLY See point 4.4, bearing in mind that gasket (16) must be fitted in the body before mounting the bellows assembled with the plug. 6 VALVE TESTING AND SETTING If the valve opens under or above the set pressure remove the top cap (or the lifting lever assembly) making the spring adjusting screw accessible. Loosen the lock nut first, then rotate the adjusting screw clockwise (when a set pressure increase is required, or counter-clockwise for a reduction). When the required value is reached tighten the lock nut and reassemble the cap (or lifting assembly). Test once again the valve opening after having tightened the lock nut. NEVER ADJUST THE SPRING SETTING WHEN THE FLUID PRESSURE IN THE VALVE IS CLOSE TO THE SET VALUE, AS THE SEATING SURFACES OF NOZZLE AND DISK COULD GET DAMAGED. THE FLUID PRESSURE IN THE VALVE SHOULD BE AT LEAST 25% LESS THAN THE SET PRESSURE. BY THIS WAY THE LOAD ON THE SEATING SURFACES WILL PREVENT THEM TO ROTATE AND GET DAMAGED. 6.1 SEAT TIGHTNESS TEST After the final spring setting was made and the valve has been tested sometimes, lower the pressure in the valve to 90% of the set pressure to carry out the air leakage test. The recommended method for closed bonnet type valves, according to API 527, is shown in Fig x 8 mm dia. tube FIG. 3 The valve outlet is blanked off and connected with a water siphon by a tube as outlined in the sketch. When the air pressure in the valve is 90% of the set value the number of bubbles per minute (if any) should not exceed the values plotted in Fig EXCESSIVE LEAKAGE If the procedure has been carefully followed and the leakage exceeds the limits it is necessary to disassembly the valve. Ascertain that no foreign material is within the seating surfaces, or these are not damaged by foreign particles in the testing fluid or imperfectly lapped. If the leakage is due to dirt a good cleaning and polishing are sufficient. If the seating surfaces are scored they must be lapped or re-machined and lapped. 6.3 COLD SETTING Any temperature increase causes a reduction of the set pressure of a safety valve or safety relieve valve. Consequently it is customary to compensate for this effect by increasing the setting pressure when the valve is set at ambient conditions on a test stand and it is intended for a higher operating temperature. Setting reductions for valves intended for sub-zero service are not recommended. The following correction factors should be taken into consideration for valves intended for fluids with temperatures over 100 C. Operation temperature Set pressure increase % Up to 100 C none from 101 C to 250 C 2% from 251 C to 500 C 3% over 500 C 5% When calculating the "differential pressure for cold setting", i.e. the pressure at which the valve must be set on the test stand at ambient temperature and atmospheric back pressure, compensation for the constant back pressure (if any) and for the operating temperature should be taken into account. Example for calculation of "differential pressure for cold setting" with compensation for back pressure and temperature. DATA : set pressure 20 bar, temperature 260 C, constant back pressure 1 bar, steam service. air reservoir - set pressure in service = 20 bar - 1 bar = 19 bar; - correction coefficient for operating temperature between 251 C and 500 C = 3%; - 3% of 19 bar = 0.58 bar (rounded to 0.6 bar); - cold set pressure: 19 bar bar = 19.6 bar. 8

9 7 FAULT FINDING 7.1 DYNAMIC INSTABILITY The most important inconvenience which can occur on a safety valve is the plug instability along the lift. It is not always possible and easy to identify the causes and remedy with simple adjustments or modifications. Instability may occur in two ways: (1) fast alternative plug motion (axial and radial); the plug does not get in contact with the nozzle (fluttering). (2) fast alternative plug motion (mostly axial); the plug gets in contact with the nozzle (chattering). In the first case stem guides may get damaged, seating surfaces in the second one. The above vibratory motions may have the same source and may only occur if the plug does not attain the full lift. When the plug of the safety relief valve gets in contact with the mechanical stop and lays on it plug vibrations hardly occur. On the contrary, if the plug does not attain the mechanical stop it is subject to mechanical stresses due to the fluid turbulence, which may cause it to vibrate. Vibratory motion may occur by one of the following reasons: (1) The valve is oversized. The valve blows-off the maximum capacity without performing the entire rated travel (mostly in case of liquids) or repeatedly opens and closes. A valve with a smaller orifice should be selected. (2) The valve is correctly sized, but the upstream pressure is lower than the design one. Effects are similar to the ones under point (1). Valves with intrinsic overpressure should be selected, or two valves with different capacities could be installed in parallel setting the smaller one at a lower set pressure. (4) The head loss in the pipe connecting the pressure source with the valve is too high. In this case chattering may occur when the valve blowdown is rather low. A maximum head loss at maximum valve capacity equal to 3% of the set pressure is normally recommended; this value is lower than the blow-down of the majority of the safety relief valves. The easiest remedy for such an inconvenience could be to increase the valve blow-down by adjusting the nozzle ring. (5) The overpressure is too low. A low flow is enough to cause the opening and so the chattering can occur. The inconvenience could be caused by a wrong position of the nozzle ring, may be too close to plug, in case that it is mounted on the seat. (6) The leakage is too high. The effect is similar to the one caused by the low overpressure. (7) Fluidodynamic disturbances upstream the valve inlet. If short radius bends, calibrated flanges, globe shut-off valves, compressors or pumps are installed close to the valve inlet, turbulences or pressure fluctuations may occur and produce chattering. Increasing both blow-down and overpressure could be a remedy. Problems related with dynamic instability of safety-relief valves for liquid service are extremely important. If chattering occurs in a safety-relief valve heavy consequences may turn out for the line which the valve is installed in, due to possible resonance phenomena. When for instance a safety relief valve relieves the excess pressure from a pump outlet, it really acts as an upstream pressure regulator. A conventional safety-relief valve cannot be selected for such a use, as the thrust of the fluid on the plug suddenly falls when the plug begins to lift, so that fast opening and reclosing phenomena may occur. To solve the problems of instability at intermediate plug travels the series valve for liquid service has a seat with special shape. Relevant orifices, for conventional design, are identified with "a" letter: B(a), C(a), D(a), E(a). (3) The back pressure is too high. Valves with inlet pressure 10% higher than the set pressure and with 15% back pressure may chatter as the plug never lift completely, due to the closing force on the plug when lifting. When a balanced version of series valves is not available it is necessary to increase the set pressure. 9

10 7.2 EXCESSIVE LEAKAGE CAUSE REMEDY 1) Foreign particles between seat and plug. 1) Operate the valve once or twice subsequently. If leakage does not stop disassemble the valve and clean the trim. 2) Seating surface galled or scratched. 2) Disassemble the valve and lap the seat. 3) The valve is used with a fluid different from the one 3) Lap seat and disk with smoother finishing (if the valve which it was intended for. originally intended for liquid is used for gas). 4) Valve not mounted in vertical position. 4) Change the installation. 7.3 OPENING PRESSURE DIFFERENT FROM SET PRESSURE CAUSE REMEDY 1) The back-pressure is variable. 1) Ascertain that discharge piping diameter is equal or higher than valve outlet diameter and that the discharge piping is not cloggy. 2) The back-pressure is different from the one specified in 2) The valve must be reset for the new back-pressure. the order. 3) The locknut of the spring adjusting screw is loosen. 3) Reset the valve and tighten the locknut. 4) Poor trim alignment. 4) Operate the valve twice or three times in order to allow self-alignment of the trim. 10

11 Max bubbles per minute FIG Φ orifice <= C Φ orifice >= D 20 psi bar NOZZLE RING ADJUSTMENT NUMBER OF NOTCHES FROM CONTACT AGAINST DISK HOLDER SET PRESSURE (bar) ORIF. > 0,5 > 2,5 > 6 > 10 > 16 > 25 > 40 >64 >100 > 160 > 250 2, C D E ) Not supplied for liquid service 2) The blow down ring settings are also valid for alternating service on compressible and incompressible fluids and for service on bi-phase mixtures (1) (2) Table 1 BLOW-DOWN ADJUSTMENT 11

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