Escalator Technology - Handrail PDF

Unit 4 - Escalator Technology - Handrail A. Handrail On top of each balustrade there shall be provided a handrail moving in the same direction and at a speed tolerance of 0% to 2% of the speed of the steps. Handrails shall receive their motion from main escalator drive through direct gearing and...

Unit 4 - Escalator Technology - Handrail A. Handrail On top of each balustrade there shall be provided a handrail moving in the same direction and at a speed tolerance of 0% to 2% of the speed of the steps. Handrails shall receive their motion from main escalator drive through direct gearing and drive shaft or drive chains, so that handrail and steps operate at the same speed in each direction of travel. Driving and guiding wheels shall have a groove to accept the wedge on the underside of the handrail. The handrail shall have a V-shape wedge. A means to take up handrail slack using a tensioning device, where required, shall be located within escalators. In addition, an approved method of releasing the device for repair or removal of handrails shall be provided pre tensioning of handrail shall be considered unacceptable. Newels meeting the following requirements shall be provided: Newels shall be designed and constructed so that handrail shall return into newel end at a point inconspicuous and difficult for passengers to reach. Newel sheaves shall be provided at upper and lower newels. Handrails, handrail drive system, and guides shall be so designed and installed that handrail cannot be thrown off or disengaged while running, and special design attention shall be given to area where handrail passes from drive system to guides. Handrail rollers shall have sealed bearings rated at 100,000 hours and have provision for retention of lubricant to ensure satisfactory lubrication and operation. Additional lubrication shall not be required. Friction drive sheaves and idlers shall be designed and positioned so that lubricant cannot reach surface of handrail. Marking and spotting of handrail by drive equipment shall not be permitted. Handrail is pulled along its track by a chain that is connected to the main drive gear by a series of pulleys. Handrail Fig 1 - Handrail The handrail provides a convenient handhold for passengers while they are riding the escalator. Escalator Technology – Handrail 1 A-1 Handrail Construction Handrail shall be a composite of either vulcanized rubber or approved equal with a synthetic fabric slider and shall be constructed with a steel cable tension member providing a minimum strength of 25kN over the splice area. Cover stock Body Piles Bead Steel Cotton Slider Fig 2 – Handrail Construction It is constructed of four distinct sections. At the center of the railing is a "slider," also known as a "glider ply," which is a layer of a cotton or synthetic textile. The purpose of the slider layer is to allow the railing to move smoothly along its track. The next layer, known as the tension member, consists of either steel cable or flat steel tape. It provides the handrail with the necessary tensile strength and flexibility. On top of tension member are the inner construction components, which are made of chemically treated rubber designed to prevent the layers from separating. Finally, the outer layer, the only part that passengers actually see, is the rubber cover, which is a blend of synthetic polymers and rubber. This cover is designed to resist degradation from environmental conditions, mechanical wear and tear, and human vandalism. Handrail guides shall be continuous on exposed portion of handrails, constructed of 316 stainless steel which shall not subject to corrosion nor pitting, and shall have a polished or specially coated, permanent finish to minimize frictional wear to under surface of handrail. On the unexposed portion, guiding shall be by adjustable rollers having sealed bearings, and set in a way so as not to cause wear on the handrail. Escalator Technology – Handrail 2 A-2 Types of Handrail There are basically two main types of handrails: Standard and Vee-type. To function correctly a handrail depends heavily on the interplay with the guide element in the escalator or moving walkways and the drive. Standard Vee Fig 3 – Types of Handrail A-3 Types of Handrail Drive System The two common types of handrail drive system are:  Driving roller drive.  Traction pulley or Friction sheave drive. Drive Rolle Handrail rs Tensioner Truss Fig 4 – Driving Roller Drive Fig 5 – Front view of Handrail Escalator Technology – Handrail 3  Handrail Drive Middle Sprocket Friction Main Drive Sheave Sprocket Handrail Take-up Device Handrail Drive Chain Handrail Drive Chain Tension Adjust Tension Carriage Fig 6 – Friction Sheave Drive A set of drive rollers or friction sheave drives the handrail. A pair of sprockets fastened on the same shaft as the step chain drive shaft drives the drive rollers or friction sheave through chain links and sprockets. The handrail take-up device or tensioner remove slack in the handrail to provide the proper amount of slack in the handrail required to drive the handrail. Handrails are continuous vulcanized belts made of laminated rubber, canvas, and a stainless steel cord centre. The handrail serves as a safety device, giving passengers a hand-hold when entering, exiting, or riding an escalator. The system uses a drive wheel with an uphill and downhill side, an escalator handrail wrapped around a portion of the drive wheel, and two pressure rollers. One pressure roller is positioned adjacent to the downhill side of the drive wheel and forms a first nip (squeeze point) there between the drive wheel and the roller. The other pressure roller is positioned adjacent to the uphill side of the drive wheel, and there in between forms a second nip. The escalator handrail is driven by the drive wheel with the assistance of the uphill pressure roller and the downhill pressure roller applying pressure to the handrail as it passes through each of the first and second nips so as to ensure sufficient contact area between the drive wheel and the handrail. There are also guide rollers with at least one positioned adjacent to the downhill side of the drive wheel and at least one positioned adjacent to the uphill side of the drive wheel. The guide rollers provide for a smooth transition for the handrail as it travels around the drive wheel. A formed steel guide connected to the exterior of the balustrade guide the handrail over rollers at the newel ends and the escalator upper curve section. Escalator Technology – Handrail 4  Handrail Handrail Guide Handrail Base Newel Fig 7 – Installation of Handrail B Handrail Drive The handrail drive moves the handrail along the handrail tracking system through traction on the V-shaped handrail underside. The handrail drives consists of the handrail drive, and idler sheaves, handrail drive sprockets, and handrail drive chains. B-1 Handrail Drive and Idler Sheaves The Handrail Drive and Idler Sheaves are V grooved sheaves located in the upper and lower newel ends of the escalator. The handrail drive sheave drives the handrail in its journey around the escalator while the idler sheave reverses the direction of the handrail at the lower end. Drive Sheave Handrail Drive Chain Handrail Idler Sheave Handrail Support Rollers Fig 8 – Handrail Drive and Idler Sheaves Escalator Technology – Handrail 5  B-2 Handrail Drive Chain Sprockets Located on the handrail drive sheave and the outboard end of the bull gear shaft. Handrail drive sprockets are linked by the handrail drive chain and provide a direct link between the bull gear and handrail drive sheave. B-3 Handrail Drive Chains The handrail drive chains are double stranded chains and are the mechanical link between the dual toothed drive chain sprockets. The drive chain sprockets and handrail drive chain coming to transfer power from the bull gear shaft to the handrail drive sheave. The handrail drive chain has an adjustable take-up sprocket to keep the drive chain snug. The handrail drive chain receives lubrication from an enclosed bath system. C Handrail Take-Up System Traction required to drive the handrail is provided through the correct amount of slack in the handrail. The correct amount of slack is provided through the handrail take-up devices and handrail support rollers. C-1 Handrail Take-Up Devices The Handrail Take-Up Devices are located directly downhill from the handrail drive sheaves. The handrail take-up devices remove slack in the handrail to provide the proper amount of slack in the handrail required to drive the handrail. The short handrail take-up device can be adjusted to remove slack from the handrail. The long handrail take-up device can pivot from the center and be adjusted at the uphill end to remove slack from the handrail. The long handrail take-up device is always required. INCLINED TRUSS HANDRAIL TENSION DEVICE ROLLER ADJUSTABLE HANDRAIL Fig 9 – Handrail Take-Up Device Escalator Technology – Handrail 6  C-2 Handrail Support Rollers Located at various intervals down the incline. Their function are to support the handrail and protect it from coming into contact with the track brackets or any other truss components which may damage the handrail; and they help provide the correct loop of slack in the handrail at the lower end which proves the traction to drive the handrail. D Handrail Safety Devices Safety devices are built into escalator handrail system. Any one of the safety devices will immediately stop the escalator if a problem occurs. Escalator systems are provided with many safety devices that will automatically stop the escalator by cutting electrical power to the motor and applying the brake if a problem occurs. When a safety device stops the escalator, the problem must be corrected and the fault cleared before restarting the system. D-1 Handrail Inlet Safety Device The handrail inlet safety device is located at the handrail inlet port of each newel section. This device will cut power to the motor and apply the brake if an object is wedged between the handrail and the rubber entry guard. Any caught object will depress two switches behind the handrail guard. Handrail Inlet Split Door Arrangement Front Plate Front Plate Plunger Switch Fig 10 – Handrail Inlet Safety Device Escalator Technology – Handrail 7  Handrail Inlet Handrail Guard Switch Guide Handrail Switch Inlet Plate Plunger Fig 11 – Handrail Inlet Safety Device D-2 Broken Handrail Device A broken handrail device is located in the escalator incline section. The device consists of a hinged roller that is held up by handrail tension. If a handrail is stretched or broken, a limit switch is depressed by the roller bracket dropping. When the switch is pressed, it cuts power to the motor and applies the brake. The safety reset button in the controller must be pressed to restart the escalator. Incline Truss Frame Bracket Pivot Point Roller Handrail Switch Fig 12 – Broken Handrail Device Escalator Technology – Handrail 8  D-3 Handrail Speed Device The handrail speed device is a 1000 rpm tach generator wheel that rolls on the handrail. The weight of the tach generator and wheel pivots on a bracket to hold the wheel against the handrail. Contact of the tach wheel on the moving handrail turns the generator, which outputs a voltage of 6.72 volts. If the handrail speed drops below 80% or increases more that 110% over this voltage, then power to the escalator motor is cut and the brake is applied. HANDRAIL HANDRAIL SPEED DEVICE (TACHOMETER) ROLLERS Fig 13 – Handrail Speed Device E Handrail Maintenance E-1 Checking and Inspection All the checking and inspection shall be conducted with the power supply switched off. The following items shall be checked and inspected to ensure that they conform to the specifications:  Handrail tension and condition.  Handrail inlet safety guard.  Handrail guide rollers condition and lubrication.  Handrail drive and pressure rollers condition and lubrication. E-2 Operation and Safety Device Test The operation and safety device test shall be conducted with the escalator running continuously in the up and down direction. Inspect, observe and note any defects including abnormal noise and vibrations.  Ensure that the handrail and steps travel at substantially the same speed.  Measure the handrail speed in both directions using a tachometer.  Observe the smoothness of the handrail travel, noting any scratching of abnormal noise.  Check the handrail tension by pulling the handrail horizontally at the Check the handrail tension by pulling the handrail horizontally at the upper landing with the escalator moving in the down direction. Escalator Technology – Handrail 9