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Summary of Contents for Danfoss LDT 21
- Page 1 Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission www.danfoss.com...
- Page 2 Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Revision history Table of revisions Date Changed June 2022 First edition 0101 © Danfoss | June 2022 AX417167456877en-000101...
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Page 3: Table Of Contents
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Contents Introduction Overview......................................5 Warranty......................................5 General Instructions..................................5 Remove the unit..................................5 Keep it clean....................................5 Lubricate moving parts................................5 Replace all O-rings and gaskets............................. 5 Secure the unit..................................... 5 Safety Precautions....................................5 Unintended machine movement............................6 Flammable cleaning solvents.............................. - Page 4 Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Contents Required Tools and Standard Procedures Required Tools....................................21 Standard Procedures..................................21 Charge Check/HPRV Adjustments............................21 Checking for proper charge check/HPRV operation....................21 Minor Repair Shaft Seals......................................22 Removal......................................22 Inspection....................................22 Assembly......................................22 Charge Check/HPRV..................................23 Removal......................................23...
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Page 5: Overview
A worldwide network of Danfoss Authorized Service Centers is available for major repairs. Danfoss trains and certifies Authorized Service Centers on a regular basis. You can locate your nearest Authorized Service Center using the distributor locator at www.danfoss.com. -
Page 6: Unintended Machine Movement
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Introduction Unintended machine movement Warning Unintended movement of the machine or mechanism may cause injury to the technician or bystanders. To protect against unintended movement, secure the machine or disable/disconnect the mechanism while servicing. -
Page 7: General Description
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission General Description Basic Design LDT21/24/32 is a U-style hydrostatic transmission with a Z-shaft configuration, including a closed circuit variable displacement piston pump with DDC (Direct displacement control) and a fixed motor. - Page 8 Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission General Description LDT24 hydraulic schematic LDT32 hydraulic schematic © Danfoss | June 2022 AX417167456877en-000101...
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Page 9: Operations
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Operations Check / High Pressure Relief Valve LDT21/24/32 is equipped with a combination high pressure relief and charge check valve. The high- pressure relief function is a dissipative (with heat generation) pressure control valve for the purpose of limiting excessive system pressures. -
Page 10: Cprv (Charge Pressure Relief Valve)
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Operations CPRV (Charge Pressure Relief Valve) The charge pressure relief valve maintains charge pressure at a designated level above case pressure. The charge pressure relief valve is a direct acting poppet valve which opens and discharges fluid to the hydrostatic transmission case when pressure exceeds a designated level. -
Page 11: Control
LDT. This applies to both directions of the trunnion rotation. The LDT24 features two threaded (M10) holes near the trunnion. Contact Danfoss for proper application guidelines if these holes are intended to be used for a neutral return mechanism. -
Page 12: Operating Parameters
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Operating Parameters Overview This section defines the operating parameters and limitations for LDT21/24/32 with regard to input speeds and pressures. For actual parameter data, refer to the operating parameters table in the Technical Specifications section. -
Page 13: Case Pressure
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Operating Parameters Case pressure Under normal operating conditions, the rated case pressure must not be exceeded. During cold start case pressure must be kept below maximum intermittent case pressure. Size drain plumbing accordingly. -
Page 14: Technical Specifications
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Technical Specifications General Specifications Features Description Design U-style HST with variable displacement piston pump and fixed motor Direction of Rotation Clockwise / Counterclockwise Pipe Connections Main Pressure ports: SAE O-Ring Boss... -
Page 15: Fluid Specifications
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Technical Specifications LDT Fluid Specification Features Units LDT21 LDT24/32 Viscosity Minimum /sec. [ SUS] 7 [49] Recommended range 12-60 [66-280] Maximum 1600 [7500] Temperature Minimum °C [°F] -40 [-40] Rated 82 [180]... -
Page 16: Fluid And Filter Maintenance
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Fluid and Filter Maintenance Fluid and Filter Recommendations To ensure optimum life, perform regular maintenance of the fluid and filter. Contaminated fluid is the main cause of unit failure. Take care to maintain fluid cleanliness when servicing. -
Page 17: Pressure Measurements
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Pressure Measurements LDT24 Port Locations and Gauge Installation The following table and drawing show the port locations and gauge sizes needed. When testing system pressures, calibrate pressure gauges frequently to ensure accuracy. Use snubbers to protect gauges. -
Page 18: Startup Procedures
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Startup procedures Startup Procedure Always follow this procedure when starting up a new LDT21/24/32 installation or when the transmission has been removed and reinstalled on a machine. If the unit was torn down and reassembled before reinstalling on a machine, the product should be tested on a test stand and pass the necessary quality checks according to the test specification for LDT transmissions. -
Page 19: Troubleshooting
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Troubleshooting Overview This section provides general steps to follow if you observe undesirable system conditions. Follow the steps listed until you solve the problem. Some of the items are system specific. We reference the section in this manual of more information is available. -
Page 20: Sluggish System Response
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Troubleshooting Sluggish System Response Item Description Action Oil level in reservoir Low oil level causes sluggish response. Fill reservoir. Charge check/HPRVs Incorrect pressure settings affects system reaction time. Replace charge check/HPRVs... -
Page 21: Required Tools And Standard Procedures
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Required Tools and Standard Procedures Required Tools The service procedures described in this manual can be performed using common mechanic's hand tools. Special tools, if required, are shown. When testing system pressure, calibrate pressure gauges frequently to ensure accuracy. -
Page 22: Minor Repair
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Minor Repair Shaft Seals Removal 1. Using a snap ring pliers, remove retaining ring (J150/K250/G130/G230). 2. Use a slide-hammer style puller to remove seal (J140/K240/G120/G220). Be careful not to damage the shaft or seal bore when removing the seal. -
Page 23: Charge Check/Hprv
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Minor Repair Charge Check/HPRV The high pressure relief and charge check valve assembly may be removed for cleaning and replacement of the O-rings. These valves are factory set and are not field adjustable. Refer to the transmission model code for the factory setting when ordering replacements. -
Page 24: Torque Chart
Service Manual LDT 21/24/32 Closed Circuit Axial Piston Transmission Torque Chart LDT24 Plug Size and Torque Chart Item O-Ring Plug Wrench Size Torque Nm [lbf-ft] G010 ½-20 UNF 17mm External Hex 27.1 [16.6] G020 ¾-16 UNF 5/16" Internal Hex 39.2 [58] G030 ¾-16 UNF... - Page 25 Phone: +86 21 2080 6201 Danfoss can accept no responsibility for possible errors in catalogues, brochures and other printed material. Danfoss reserves the right to alter its products without notice. This also applies to products already on order provided that such alterations can be made without subsequent changes being necessary in specifications already agreed.
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