Emerson Rosemount 936 Скачать руководство пользователя

Страница: 4 / 76

Содержание Rosemount 936

Страница 1: ...Reference Manual 00809 0100 4036 Rev AD October 2021 Rosemount 936 Toxic Open Path Gas Detector ...

Страница 2: ...mage to and or misconfiguration of end users equipment This could be intentional or unintentional and needs to be protected against Physical security is an important part of any security program and fundamental to protecting your system Restrict physical access by unauthorized personnel to protect end users assets This is true for all systems used within the facility CAUTION The source and detecto...

Страница 3: ... alternation by line a color encoding system PN Part number ppm Concentration in parts per million Defines the amount of gas molecule parts per million molecules of atmospheric ppm m Integral of concentration in ppm units times the distance in meters RFI Radio frequency interference RTSP Real time streaming protocol SIL Safety integrity level UNC Unified coarse thread UV Ultraviolet Vac Volts alte...

Страница 4: ...4 ...

Страница 5: ...26 4 3 Mechanical specifications 27 4 4 Environmental specifications 28 Chapter 5 Installation 31 5 1 Introduction 31 5 2 General considerations 31 5 3 Preparations for installation 34 5 4 Certification instructions 35 5 5 Install conduits and cables 40 5 6 Mount detector and source to tilt mount 41 5 7 Install detector wiring 44 5 8 Wiring to detector terminals 45 5 9 Wiring to ultraviolet UV sou...

Страница 6: ... 62 8 4 Ratio out of the limit 62 8 5 Voltage less than 16 Vdc 62 Appendix A Wiring configurations 63 A 1 RS 485 communication network 67 Appendix B SIL 2 features 69 B 1 Safety relevant parameters 69 B 2 General conditions for safe use 69 Appendix C Support 71 C 1 Return of material 71 Appendix D Short range model 73 Appendix E Declaration of Conformity 75 Contents Reference Manual October 2021 0...

Страница 7: ...ensors and electronics to the surrounding environment The detector also has a plug interface for connection to a HART Field Communicator which is intrinsically safe This Manual provides a full description of the detector and its features and contains instructions on installing operating and maintaining the detector TheRosemount 936 detects and monitors toxic gases such as NH3 and H2S at ppm m conc...

Страница 8: ...Product overview Reference Manual October 2021 00809 0100 4036 8 Emerson com Rosemount ...

Страница 9: ...mputer PC communication network for a maximum of 247 systems Simple one person installation alignment and calibration ATEX and IECEx per Ex II 2 2 G D Ex db eb ib ib Gb IIB H2 T4 Gb Ex tb ib Db IIIC T135 C Db Ta 55 C to 65 C TR CU approved per 1 Ex db eb ib ib Gb IIB H2 T4 Gb X Ex tb IIIC T135 C Db X 55 C Ta 65 C CSA C US approved per Canada Ex db eb ib ib Gb IIB H2 T4 Gb Ex tb ib Db IIIC T135 C D...

Страница 10: ...y gases in the atmosphere and comparing it ratio to background atmospheric absorption 2 3 1 Spectral fingerprint Each hazardous material is detected at a specific wavelength selected according to its specific spectral absorption or fingerprint The detection process involves two separate sensors one that absorbs a particular gas and one that is not sensitive to it 2 3 2 Optical path The Rosemount 9...

Страница 11: ...lar blind range of 189 nm to 270 nm which enables fast and reliable detection at low concentrations 2 3 4 Ultraviolet UV source The Rosemount 936 employs the latest generation of Xenon UV flash bulbs to provide extended installation distance and maximum reliability 2 3 5 Heated optics The Rosemount 936 includes heated optics for the detector and source The heater increases the temperature of the o...

Страница 12: ...tware and attached by a special harness 2 3 7 Modbus RS 485 For more advanced communications the Rosemount 936 has an RS 485 Modbus compatible output that provides data communication This feature enables simple commissioning maintenance and configuration 2 3 8 Tilt mount The stainless steel tilt mount provides a small installation footprint that can conform to limited space constraints while the s...

Страница 13: ...pliance with the standards ABNT NBR IEC 60079 0 ABNT NBR IEC 60079 1 ABNT NBR IEC 60079 7 ABNT NBR IEC 60079 11 ABNT NBR IEC 60079 28 ABNT NBR IEC 60079 31 and INMETRO decree No 179 as of May 18th 2010 Further details may be found on the Certificate of Compliance Number UL BR 19 0726X 2 4 5 CSA C US The Rosemount 936 is approved per CSA C US for hazardous and ordinary locations Canada Ex db eb ib ...

Страница 14: ...14 m 132 ft 40 m 936 T3 115 ft 35 m 200 ft 60 m Related information Short range model 2 6 Ordering information You can order the Rosemount 936 as separate parts source PN TXT00XXXX detector PN RT12XXXXX and commissioning kit 2 6 1 Online product configurator Many products are configurable online using our product configurator Visit our website to start With this tool s built in logic and continuou...

Страница 15: ...ode Description 936 Toxic Open Path Gas Detector Source Transmitter Transmitter range Code Description T1 Transmitter Range of 17 to 52 ft 5 to 16 m T2 Transmitter Range of 46 to 132 ft 14 to 40 m T3 Transmitter Range of 115 to 200 ft 35 to 60 m Gas calibration Code Description T00 Transmitter Housing style conduit Code Material Measurement 2S Stainless steel in NPT 4S Stainless steel M25 Product ...

Страница 16: ... Description R1 Receiver Gas calibration Code Description T26 Hydrogen sulfide receiver T27 Ammonia receiver Housing style conduit Code Material Measurement 2S Stainless steel in NPT 4S Stainless steel M25 Product certifications Code Description A1 ATEX and IECEx A3 CSA E2 INMETRO EM CU TR EAC Technical description Reference Manual October 2021 00809 0100 4036 16 Emerson com Rosemount ...

Страница 17: ...5 to 10 µsec is very powerful The front of the source unit has an internal reflector that collimates the UV beam for maximum intensity The front window is heated to improve performance in icing condensation and snow conditions Figure 2 1 UV Source A Weather shield B Front window section C Label D Main housing E Mounting plate F Junction box G Indicator light emitting diode LED H Earth terminal I C...

Страница 18: ...conditions The data is sent to the output interface section The front window of the detector is heated to improve performance in icing condensation and snow conditions There is one detector type that is suitable for the H2S version and one for the NH3 version Figure 2 2 Detector A Front window B Handheld fast connection C Weather shield D Front window section E Label F Main housing G Mounting plat...

Страница 19: ...m level 3 1 2 Maintenance call mode 3 mA output This mode indicates low signal that may be caused by a dirty window misalignment or poor source or if one of the detector s parameters is at the limit value The detector continues to function but provides a 3 mA pre warning signal via HART and Modbus that a maintenance procedure is required 3 1 3 Fault mode In the fault status there are three fault t...

Страница 20: ...Field Communicator of host software on your personal computer PC to zero calibrate after installation re alignment and window cleaning In parallel while the detector is connected to the Field Communicator the magnetic mode selector can be used for zero calibration Related information Zero calibrate 3 2 Visual indicators One three color light emitting diode LED indicator is located in the back side...

Страница 21: ...as Channel Current reading Status and description 0 mA 0 2 mA Fault in 0 20 mA loop 1 mA 0 2 mA Zero calibration in progress fault 2 2 mA 0 2 mA Fault 1 non critical 3 mA 0 2 mA Maintenance call 4 mA 0 2 mA No gas present 4 mA 20 mA Continuous measuring of gas concentration at a range between 0 and 500 ppm m or full scale 21 mA Concentration is over the range limit more than full scale concentrati...

Страница 22: ...rature change default When operated in Automatic mode you can define the start temperature below which the window will be heated between 32 and 122 F 0 and 50 C The detector stops heating the window when the temperature is 27 F 15 C above the defined temperature This feature relates to the detector only The source heated optic must be defined within the model structure in two options Heated contin...

Страница 23: ...ble 3 4 Detector Default Setup Function Setup Heat mode Auto Heat on 41 F 5 C You can change the source defaults the same way Reference Manual Operating modes 00809 0100 4036 October 2021 Rosemount 936 23 ...

Страница 24: ...Operating modes Reference Manual October 2021 00809 0100 4036 24 Emerson com Rosemount ...

Страница 25: ... RT126XXXX T3T00XXXX 115 ft 35 m 200 ft 60 m NH3 R1T127XXXX T1T00XXXX 17 ft 5 m 52 ft 16 m R1T127XXXX T2T00XXXX 46 ft 14 m 132 ft 40 m R1T127XXXX T3T00XXXX 115 ft 35 m 200 ft 60 m Response time 3 sec 10 sec to T90 Spectral response 200 to 300 nm Sensitivity range Full scale Warning Alarm 500 ppm m 100 ppm m 300 ppm m Field of view Line of sight Alignment tolerance 1 degree Minimum detectable gas v...

Страница 26: ...ng configurations The maximum permitted load resistance is 500 Ω Communication network The detector is equipped with an RS 485 communication link that can be used in installations with computerized controllers Communication is compatible with the Modbus protocol This protocol is standard and widely used It enables continuous communication between a single standard Modbus controller master device a...

Страница 27: ... for 7 ft 2 m depth for 45 minutes NEMA 250 Type 6p Electrical modules Conformal coated Electrical connection Two options specified at time of order 2 x M25 ISO 2 x in 14 national pipe thread NPT conduits Dimensions Detector 10 5 x 5 1 x 5 1 in 267 x 130 x 130 mm Source 10 5 x 5 1 x 5 1 in 267 x 130 x 130 mm Tilt mount 4 7 x 4 7 x 5 5 in 120 x 120 x 140 mm Weight Detector 11 lb 5 kg Source 11 lb 5...

Страница 28: ...meet DNVGL CG 0339 class B Enclosure The Rosemount 936 is designed to meet DNvGL CG 0339 class C Water and dust IP68 per EN60529 IP66 per EN60529 Dust Completely protected against dust Liquids Protected against immersion between 5 9 in 15 cm and 3 3 ft 1 m in depth Protected against water jets from all directions Vibration The Rosemount 936 is designed to meet DNVGL CG 0339 class B Electromagnetic...

Страница 29: ...otect against interference caused by radio frequency interference RFI and electromagnetic interference EMI the cable to the detector must be shielded and the detector must be grounded Ground the shield at the detector end Reference Manual Specifications 00809 0100 4036 October 2021 Rosemount 936 29 ...

Страница 30: ...Specifications Reference Manual October 2021 00809 0100 4036 30 Emerson com Rosemount ...

Страница 31: ... qualified personnel who are familiar with the local codes and practices and trained for gas detection maintenance Ensure that wiring is only performed and supervised by someone with knowledge of electronics and in particular wiring installation 5 2 2 Required tools You can install the detector using general purpose common tools and equipment Table 5 1 Tools Tool Function Alignment kit Provides to...

Страница 32: ...fshore oil production and exploration reduce this distance to 50 percent Keep the path between the source and detector clear of any obstacles that might hinder the free movement of air in the protected area or block the UV beam 5 2 5 Tips for gas detector locations To provide the best detection coverage install the detector Below potential leak source for gases heavier than air Above potential lea...

Страница 33: ...d be based on the number of detectors used on the same loop and the distance from the control unit The maximum number of wire connections in one terminal is two wire cross sections each 1 mm2 To fully comply with electromagnetic compatibility EMC directive and protect against interference caused by radio frequency interference RFI and electromagnetic interference EMI the cable to the detector must...

Страница 34: ...e and detector B Tilt mounts Detector unit 936R1T2XXXX see Models and types Source unit 936TXT00XXXX see Models and types Two tilt mount bases One base is used for the detector One base is used for the ultraviolet UV source The commissioning kit for H2S or NH3 includes Magnetic mode selector Handle for cover opening Alignment tool kit Function check filter for H2S or NH3 Other accessories are avai...

Страница 35: ...t may exceed 182 F 83 C Take suitable precautions when selecting the cable Only suitably certified cable entry devices or conduit shall be used for connections and unused openings shall be blanked off using suitably certified stopping plugs The marking of the equipment is Ex II 2 2 G D Ex db eb ib ib Gb IIB H2 T4 Gb Ex tb IIIC T135 C Db The equipment may be used with flammable gases and vapors wit...

Страница 36: ...ic chemicals The output of the optical radiation source with respect to explosion protection meets Exception 3 from the scope of UL 60079 28 5 4 1 Intrinsically safe I S outputs Intrinsically safe outputs through the I S ports have the following parameters Parameter Channels Light emitting diode LED 1 LED 2 HART connection RS485 RS485 5 V All combined Uo 6 51 V 6 51 V 6 51 V 6 51 V 6 51 V 6 51 V 6...

Страница 37: ... side of the detector enclosure should be made using equipment that maintains the intrinsically safe levels of protection The Um should be installed in accordance with one of the following The Um is 18 to 32 Vdc in a SELV PELV system Via a safety isolating transformer complying with the requirements of IEC 61588 2 6 or technically equivalent standard Directly connected to apparatus complying with ...

Страница 38: ...ent standard or Directly connected to apparatus complying with CAN CSA C22 2 No 60950 1 CAN CSA C22 2 No 61010 1 or technically equivalent standard or Fed directly from cells or batteries 4 The output of the optical radiation source with respect to explosion protection meets Exception 3 from the scope of CAN CSA C22 2 No 60079 28 16 Ed 1 5 Upon installation remove the plastic transit plug from the...

Страница 39: ...e of the following Where Um does not exceed 50 Vac or 120 Vdc in a SELV or PELV system or Via a safety isolating transformer complying with the requirements of UL 5085 1 or technically equivalent standard or Directly connected to apparatus complying with UL 60950 1 UL 61010 1 or technically equivalent standard or Fed directly from cells or batteries 4 The output of the optical radiation source wit...

Страница 40: ... cable entries facing downwards Use flexible conduits cables for the last portion connecting to the detector When pulling the cables through the conduits ensure that they are not tangled or stressed Extend the cables about 12 in 30 cm beyond the detector location to accommodate wiring after installation After pulling the conductor cables through the conduits perform a continuity test Installation ...

Страница 41: ...same tilt mount by using the upper or lower mounting access Figure 5 2 Mounting the Tilt Mount and Detector Using the Lower Mounting Access A Front shield B Back cover C Security screw D Locating pins E Alternate mounting location Reference Manual Installation 00809 0100 4036 October 2021 Rosemount 936 41 ...

Страница 42: ...ing plate D Horizontal fine alignment screw E Vertical crude alignment tightening screw F Vertical fine alignment tightening screw G Horizontal crude alignment tightening screw H Horizontal fine alignment tightening screw Installation Reference Manual October 2021 00809 0100 4036 42 Emerson com Rosemount ...

Страница 43: ...equisites Prior to mounting the tilt mount to a stable surface verify that the line of site is unobstructed and corresponds to the detector s installation distance Procedure 1 Place the tilt mount holding plate in its designated location and secure it with four fasteners through four holes with diameters of 0 3 in 8 5 mm NOTICE Skip this step if the tilt mount is already installed Reference Manual...

Страница 44: ... Repeat steps Step 1 through Step 4 to install the source 5 7 Install detector wiring Procedure 1 Release the back cover secure bolt and open the detector back cover The chamber is now revealed Figure 5 5 Detector with Cover Removed A Housing B Terminal board C Inlet conduit D Detector holding plate E Earth terminal F Connection to Field Communicator 2 Remove the protective plug mounted on the det...

Страница 45: ...tor cover by screwing the cover and securing it using the secure bolt 5 8 Wiring to detector terminals The detector has six wiring terminals Table 5 5 describes the function of each electrical terminal of the detector Table 5 5 Wiring Options Terminal number Function 1 Power 24 Vdc 2 Return 24 Vdc 3 0 20 mA input 4 0 20 mA output 5 RS 485 6 RS 485 5 9 Wiring to ultraviolet UV source 5 9 1 Install ...

Страница 46: ...e grounding wire to the ground screw located on the exterior of the detector Ensure that the source is well grounded to earth ground Note In case of installation in the US use the internal grounding connection for the equipment grounding connection and the external connection for a supplementary bonding connection where local codes or authorities permit or require such connection The external bond...

Страница 47: ...tector s rear you do not need the periscope In this case remove it by releasing the periscope fastening screw CAUTION Changing factory calibration may prevent optimal alignment Before installing the alignment tool verify that it and its sight mounting are free from any dirt to ensure proper alignment according to factory calibration Do not attempt to change any factory calibration at the alignment...

Страница 48: ...rform fine alignment Refer to Figure 5 4 to see the detector with the alignment tool installed Procedure 1 Remove the front shield and mount the alignment tool on the front of the source using the three screws The alignment tool is supplied in the commissioning kit 2 Aim the source towards the detector within the horizontal access 3 Aim the alignment tool to the center of the front window of the d...

Страница 49: ...Once you have completed fine alignment for both the source and detector you can turn on the power Figure 5 7 View through the Alignment Tool Reference Manual Installation 00809 0100 4036 October 2021 Rosemount 936 49 ...

Страница 50: ...Installation Reference Manual October 2021 00809 0100 4036 50 Emerson com Rosemount ...

Страница 51: ...NING Follow the instructions in this document refer to the drawings and specifications issued by the manufacturer WARNING Do not open the detector source housing while power is applied WARNING Disconnect external devices such as automatic extinguishing systems before carrying out any maintenance tasks 6 3 Power up WARNING Prior to operating or maintaining the detector follow Safety precautions Pro...

Страница 52: ... a Field Communicator to verify the signal The signal verification check determines the proper operation of the open path It checks the alignment and cleanliness of the window and for any problems in the source or detector Operation Reference Manual October 2021 00809 0100 4036 52 Emerson com Rosemount ...

Страница 53: ...nal 1 2 2 V gain 0 1 5 V gain 2 2 V gain 0 1 V gain 1 1 V gain 2 Ratio 1 2 0 6 to 1 4 NQRat 1 2 0 97 to 1 03 ppm m 0 ppm m Temperature Up to 25 C beyond ambient temperature Voltage 32 Vdc V 18 Vdc 1 The minimum distance as defined on the model number 2 Half the maximum distance as defined on the model number 3 The maximum distance as defined on the model number Reference Manual Operation 00809 010...

Страница 54: ...nge E Reference minimum F Signal minimum G Ratio H NQ ratio 6 5 Zero calibrate Prerequisites Zero calibrate after any of the following Installation Realignment Window cleaning Any change in detector or source position Operation Reference Manual October 2021 00809 0100 4036 54 Emerson com Rosemount ...

Страница 55: ...s a clear path between the source and the detector Weather conditions are clear Before zero calibrating align the detector precisely Figure 6 2 Screens shown when Zero Calibrating with WinHost Software Reference Manual Operation 00809 0100 4036 October 2021 Rosemount 936 55 ...

Страница 56: ... Procedure 1 Switch from Normal to Alignment mode 2 Switch from Alignment to Standby mode 3 Switch from Standby to Zero Calibration mode The 0 20 mA output should now be at 1 mA 4 Wait up to sixty seconds until it switches to Normal mode The detector reading is now set to Normal The 0 20 mA output should now indicate 4 mA Operation Reference Manual October 2021 00809 0100 4036 56 Emerson com Rosem...

Страница 57: ...unctional verification procedure is for a standard 0 20 mA output Prior to starting the functional check verify that the power to the detector is on and that the current of the 0 20 mA channel is stable Record the reading Note The R1T26xxxx short range model detects Hydrogen Sulfide H2S gas at a distance of 17 52 ft 5 16 m Unless specified in your purchase order the detecting unit is set by defaul...

Страница 58: ...difference is the 0 20 mA current variance 4 Record the 0 20 mA current variance in the maintenance log book Postrequisites If the variance is more than a 30 percent change when compared to the previous check see delivery form repeat the alignment Operation Reference Manual October 2021 00809 0100 4036 58 Emerson com Rosemount ...

Страница 59: ...red to that of previous alignments Emerson recommends performing this check every six to twelve months Check the signal according to threshold levels See Verifying signal Zero calibrate see Zero calibrate every time the detector or source is realigned or the windows are cleaned 7 2 1 Clean optical surfaces The optical surfaces concerned are the source and detector viewing windows Procedure 1 Turn ...

Страница 60: ...Verify the signal See Verifying signal 9 Zero calibrate see Zero calibrate 10 Do a functional check see Functional check Maintenance Reference Manual October 2021 00809 0100 4036 60 Emerson com Rosemount ...

Страница 61: ...gnment Align Dirt on the window Clean the window Poor light source Replace the light source Detector fault Replace or repair the detector 8 2 NQ Ratio below the permitted limit Table 8 2 Potential Cause and Resolution Potential cause Resolution Gas in path Ensure that the path is clean and the weather conditions are good Reference Manual Troubleshooting 00809 0100 4036 October 2021 Rosemount 936 6...

Страница 62: ...de LED yellow blinking Table 8 4 Potential Causes and Resolutions Potential cause Resolution Poor alignment Align Dirt on the window Clean the window Detector fault Replace or repair the detector 8 5 Voltage less than 16 Vdc The detector is at V fault Table 8 5 Potential Cause and Resolution Potential cause Resolution Low input voltage Check the power supply and installation Troubleshooting Refere...

Страница 63: ...rations Figure A 1 Detector Wiring Terminal A Power 18 to 32 Vdc B Return C 0 20 mA input D 0 20 mA output E RS 485 F RS 485 G Ground Reference Manual Wiring configurations 00809 0100 4036 October 2021 Rosemount 936 63 ...

Страница 64: ...Figure A 2 Source Wiring Terminal A Power 18 to 32 Vdc B Return C Not used D RS 485 E RS 485 F Ground Wiring configurations Reference Manual October 2021 00809 0100 4036 64 Emerson com Rosemount ...

Страница 65: ...Figure A 3 0 20 mA Sink 4 Wire A Detector B Controller C Input power 18 32 Vdc D Return E 0 20 mA meter Reference Manual Wiring configurations 00809 0100 4036 October 2021 Rosemount 936 65 ...

Страница 66: ...Controller C Input power 18 32 Vdc D Return E 0 20 mA meter Figure A 5 0 20 mA Source 3 Wire A Detector B Controller C Input power 18 32 Vdc D Return E 0 20 mA meter Wiring configurations Reference Manual October 2021 00809 0100 4036 66 Emerson com Rosemount ...

Страница 67: ...epeaters the number of detectors can be much larger 32 detectors for each repeater up to 247 on the same four wires When using the RS 485 network it is possible to read the detector status Fault Warning and Alarm For more details consult Emerson Figure A 6 RS 485 Networking for Wiring Option 3 A Controller B First detector C Last detector D Power supply E RS 485 computer port Reference Manual Wiri...

Страница 68: ...Wiring configurations Reference Manual October 2021 00809 0100 4036 68 Emerson com Rosemount ...

Страница 69: ...are and software models Consider the application advice and limitations of the Manual For calibration and maintenance consider the regional and national regulations The 24 V power supply must fulfill the requirements for PELV SELV of EN 60950 The HART and RS 485 interfaces are not allowed to be used for the transmission of safety related data The alert conditions according to SIL 2 can be implemen...

Страница 70: ...calibration checks The operator must switch the Rosemount 936 OFF and ON The connected controller must monitor the 0 20 mA signal current for values below 4 mA and above 20 mA The mean time to repair should be 72 hours SIL 2 features Reference Manual October 2021 00809 0100 4036 70 Emerson com Rosemount ...

Страница 71: ...de the following information when returning equipment a RMA number Emerson provided to you b Company name and contact information c Purchase order from your company authorizing return 2 Pack all items to protect them from damage and use anti static bags or aluminum backed cardboard as protection from electrostatic damage 3 Mark all packages with Return and include the RMA number 4 Ship all equipme...

Страница 72: ...Support Reference Manual October 2021 00809 0100 4036 72 Emerson com Rosemount ...

Страница 73: ... set by default to the mid long range If you require a short range model prior to installation of the detecting unit please connect the unit using RS 485 or HART communication and change the detection range in the setup screen as shown in Figure D 1 and Figure D 2 Visit our website to download the Winhost software for RS 485 communication or the device drivers DD to enable communication with the d...

Страница 74: ...Short range model Reference Manual October 2021 00809 0100 4036 74 Emerson com Rosemount ...

Страница 75: ...E Declaration of Conformity Reference Manual Declaration of Conformity 00809 0100 4036 October 2021 Rosemount 936 75 ...

Страница 76: ... All rights reserved Emerson Terms and Conditions of Sale are available upon request The Emerson logo is a trademark and service mark of Emerson Electric Co Rosemount is a mark of one of the Emerson family of companies All other marks are the property of their respective owners ...

Результаты поиска

Содержание Rosemount 936

Отзывы:

Похожие инструкции для Rosemount 936

Бренды по названию

Популярные бренды

Emerson Rosemount 936, Справочное руководство

Результаты поиска

Содержание Rosemount 936

Отзывы:

Похожие инструкции для Rosemount 936

Бренды по названию

Популярные бренды