HD Series · Service Manual

HD Series desiccant air dryers.

Installation, operation, and service procedures for HD Series continuous-regeneration desiccant air dryers, plus warranty terms and reference drawings.

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At a glance

Continuous regeneration

Less than 7% purge air
Continuous desiccant regeneration with minimal air loss.

–40 °F pressure dew point
Particulate filtration and dry air for delicate pneumatic controls.

Under 75 watts
Operating cost is less than a 75-watt light bulb.

3 HP and up
Scales from a single compressor to multiple-compressor systems.

In this manual

01

Why an air dryer

What moisture does to your air system, and what HD Series dryers deliver.

02

How it works

Dryer construction, port functions, and the charge and regeneration cycles.

03

Installation

Step-by-step instructions and requirements for HD2 and larger systems.

04

Service procedures

Replacing the inlet valve, purge valve, desiccant cartridge, control valve, and timer.

05

Testing the unit

Checks to run after installation or service.

06

Warranty and drawings

Warranty terms and the reference drawings supplied with this manual.

Air Dryer Stats

Why an air dryer

Moisture is the enemy of every air system.

All air systems trap and contain water moisture and contaminants. The chart illustrates water accumulation during a 12-hour period. Left unchecked, moisture in compressed air systems harms or destroys delicate pneumatic controls. Water and contamination shorten their life expectancy, reduce reservoir capacity, and affect compressor duty cycles.

Dry Air Systems offers air drying systems that improve the reliability of the overall system and its related pneumatic controls and devices. The HD Series air dryers are designed for continuous desiccant regeneration, with less than 7% of air required for regeneration. The operating cost of the air drying system is less than a 75-watt light bulb.

These drying systems offer designs with

01

Ease of installation

02

Expansion capabilities

03

Particulate filtration

04

Pressure dew point of –40 °F

What is a desiccant air dryer

Cool, dry, and filter before distribution.

HD dryers mount vertically after the compressor air reservoir and clean the air before it reaches your system.

General description

The MVP series of air dryers are models designed to mount vertically after the compressor air reservoir. HD air dryer systems receive warm compressed air, then cool, dry, and filter contaminants from it before distribution to air systems. Their designs reduce the buildup of dirt and moisture, protecting complete air systems, pneumatic tools, and spray paint booths.

HD air systems adapt to air compressors from 3 HP up to multiple-compressor systems. Each dryer within a system incorporates four pounds of desiccant. A precise continuous regeneration cycle runs without disrupting airflow, ensuring constant cleansing of both the desiccant drying bed and internal filtration.

All HD air dryers are built with a lightweight aluminum and steel design housing a unique spin-off cartridge. Below the cartridge are four ports, each with a specific function.

What-is-a-dessicant-air-dryer

PORT 1

Inlet

Receives contaminated air from the air compressor.

PORT 2

Outlet

Directs clean, dry air to the air system, with a dual function of controlling the regeneration flow rate.

PORT 3

Control

Receives an air signal from the MLT (Micro Logic Timer) to trigger regeneration.

PORT 4

Purge

Expels water and contaminants from the dryer.

Theory of desiccant operation

Two cycles, one continuous process.

Each dryer alternates between drying air and cleaning itself, without disrupting airflow to your system.

CYCLE 01

Charge cycle

Compressed air enters the air dryer through the inlet port. As the warm air enters the dryer, it expands; oil and water vapor condense and accumulate in the sump. The air is directed into a desiccant cartridge, passing through a series of internal filters and a cloth bag that remove contaminants. Water vapor continues to condense as the air travels to the desiccant bed, which holds water under pressure. The clean, dry air is then directed to the air system through the outlet port.

Air-Dryer-Charge-Cycle
Air-Dryer-Charge-Cycle
Air-Dryer-Regeneration-Cycle
Air-Dryer-Regeneration-Cycle

CYCLE 02

Regeneration cycle

Dryers regenerate systematically when they receive control signals from the MLT, which temporarily takes a single dryer off line to begin the regeneration process. An air pressure signal from the MLT opens the purge valve and closes the dryer’s inlet and regeneration valves.

This causes a sudden discharge of air through the dryer’s exhaust port. These valves react to air pressure when a dryer’s purge port opens. With the inlet valve closed, the regeneration valve controls a timed, pressurized backflow of filtered, dried air that reenters the desiccant cartridge.

During regeneration, the desiccant bed is depressurized. Accumulated moisture is removed from the bed, and the filters are back-flushed and cleaned, expelling contaminants out the dryer’s purge port. This completes the regeneration cycle.

At their specified time intervals, MLTs close the air dryer purge valve, which reacts to the evacuation of air pressure through the exhaust (EXH) port-controlling device.

Dry Air Systems, Inc. offers air drying systems for unique requirements, from complete plant operations to single units for small or isolated applications within an air system.

AIR-DRYER-SYSTEM-2
AIR-DRYER-SYSTEM-1

Installation instructions

Installing your HD system.

Follow the instructions for your system size. Dryers are installed in the vertical position only, canisters up.

HD2 · 10 HP COMPRESSORS OR LESS

HD2 installation

  1. Inspect air compressor lines and fittings for air leaks.
    1. Repair any air leaks. Replace any damaged lines or components.
  2. Drain all air system pressure.
  3. Locate the mounting position on the wall and mark the holes.
    1. Note: Desiccant canisters may be removed for easier installation.
    2. Note: Dryers are installed in the vertical position only (canisters up).
  4. Mount the air dryer system. Install mounting hardware as necessary.
  5. Connect the air line from the compressor reservoir to the manifold inlet (bottom) of the dryer system.
    1. It is recommended to install a bypass system for ease of servicing the air dryer system.
    2. Note: Two 3/4″ NPT ports are available for both inlet and outlet. Factory-installed plugs may be removed from the top and bottom of the manifold and moved to the front of the manifold for better pipe/hose routing.
  6. Connect the air line from the air dryer manifold (top) to the air system.
  7. Plug the MLT timer (6009X-010) into a grounded, surge-protected 110-volt receptacle.
  8. Restart the air compressor and check for leaks.

Installation requirements

  • Dryer system requires at least 80 psi to operate the MLT valve.
  • Thread sealant must be used on all air connections.
  • Dryers are installed in the vertical position only (canisters up).
  • Hoses may be attached to exhaust ports to direct water drainage.
  • Dryers cycle every 4 minutes.
Air-Dryer-Installation-Requirements

HD3 AND LARGER · ABOVE 10 HP COMPRESSORS

HD3 and larger installation

  1. Inspect air compressor lines and fittings for air leaks.
    1. Repair any air leaks. Replace any damaged lines or components.
  2. Drain all air system pressure.
  3. Locate the mounting position on the floor or wall and mark the holes.
    1. Note: Desiccant canisters may be removed for easier installation.
    2. Note: Limited left-to-right adjustment is available by loosening the 5/16 SHCS on the dryer manifold.
    3. Note: Brackets are shipped in the floor-mount position but may be moved to bolt to the bottom of the manifold (as shown) if a wall mount is desired.
    4. Note: Dryers are installed in the vertical position only (canisters up).
  4. Mount the air dryer system. Install mounting hardware as necessary.
  5. Connect the air line from the compressor reservoir to the manifold inlet (bottom).
    1. It is recommended to install a bypass system for ease of servicing the air dryer system.
  6. Connect the air line from the air dryer manifold outlet (top).
  7. Hook up electrical power.
    1. If the unit is supplied with a standard control box, a wall-mount DC transformer must be plugged into the wall and into the 5/16″ diameter female plug in the bottom of the control box.
    2. If the unit is shipped with an industrial power supply, a hole must be drilled into the control box and 120 VAC brought to the L1 and L2 terminal points. Use adequate protection from potentially live electrical circuits!
  8. Restart the air compressor and check for leaks.

Installation requirements

  • Dryer system requires at least 80 psi to operate the solenoid valves.
  • Thread sealant must be used on all air connections.
  • Dryers are installed in the vertical position only (canisters up).
  • Hoses may be attached to exhaust ports to direct water drainage.
  • Dryers cycle every 40 seconds.
Air-Dryer-Installation-Requirements-2

Replacement service components

Service procedures.

Read the precautions below before starting any procedure. They apply to every component on this page.

Installation precautions

  1. Stop the compressor when working on air systems. Never connect or disconnect a hose or line containing air pressure. Never remove a component or a pipe plug unless you are certain all system air pressure has been exhausted.
  2. Always wear safety glasses when working with air pressure. Never look directly into air dryer ports.
  3. Never exceed the recommended working air pressure.
  4. Never attempt to disassemble an air dryer until you have read and understood all recommended procedures. Use only proper tools and observe all precautions pertaining to the use of those tools.

Caution: Air dryers exhaust at high pressure. Protective eyewear should be worn while servicing.

Inlet-Valve

6002K-002

Inlet valve

  1. Exhaust/drain the air system to zero PSI. If an air dryer bypass was installed, open/close valves as necessary and drain the air dryer unit by removing the signal line from the dryer outlet manifold (1/4″ line).
  2. Disconnect the purge valve (PV-1) 1/4″ air line from the dryer to be serviced.
  3. Remove the air dryer (6002A-001) from the manifold by removing 4 5/16-18 SHCS.
  4. Remove the air dryer manifold mount plate (6003D-003) by removing 4 #10-32 SHCS.
  5. Remove the 8 bolts from the bottom cap assembly, remove the cap, and discard the gasket.
  6. Remove the inlet valve nut, valve stop, valve, and spring, and discard.
  7. Clean the cavity area thoroughly.
  8. Generously coat the 2 (small) O-ring surfaces with 6002X-005 silicone grease only, and install on the piston. Carefully install the valve and spring in the cavity with the tapered side up.
  9. Place the valve stop on top of the valve with the concave side down.
  10. Lube the large O-ring and place it on the nut. Install the flat seal into the nut.
  11. Install the nut and tighten to 50 ft-lb.
  12. Place the gasket on the bottom cap. Locate the bottom cap with the inlet port directly below the outlet port.
  13. Reassemble the unit by following steps 5 through 1 in reverse.
6002K-001-Purge-Valve-

6002K-001

Purge valve

  1. Exhaust/drain the air system to zero PSI. If an air dryer bypass was installed, open/close valves as necessary and drain the air dryer unit by removing the signal line from the dryer outlet manifold (1/4″ line).
  2. Disconnect the purge valve (PV-1) 1/4″ air line from the dryer to be serviced.
  3. Remove the air dryer (6002A-001) from the manifold by removing 4 5/16-18 SHCS.
  4. Remove the air dryer manifold mount plate (6003D-003) by removing 4 #10-32 SHCS.
  5. Remove 2 1/4-20 SHCS from the adapter (6003D-002).
  6. Remove the adapter and purge valve operator/seal retainer (6002X-020).
  7. Remove the seal retainer, purge valve assembly, 4 O-rings, and screen. Check that all components are removed and discarded.
  8. Clean the purge valve cavity.
  9. Remove all 3 old O-rings from the center portion of the bolt-on seal retainer. Apply a light coating of 6003X-005 grease to the first two new O-rings (1.362 x .103) and install them on the seal retainer. Apply a light coating of grease to the other new O-ring (1.174 x .103) and install it on the end of the seal retainer.
  10. Apply a light coating of grease to the threads of the 2 seal retainer bolts.
  11. Install the new filter screen in the purge valve cavity (closed end first).
  12. Apply a light coating of 6003X-005 grease to the O-ring seat on the new purge valve end (1/2 ball end) and install the new O-ring (1.364 x .070).
  13. Align the valve assembly exhaust port with the bottom cap exhaust port and install the valve assembly.
  14. Reassemble by following steps 6 through 1 in reverse.

Note: Excessive accumulation of oil in the air dryer purge valve indicates the compressor may require service. Disassemble the entire air dryer and check for blockage within the valve cavities, safety valve, and bottom cap cavity. Clean as necessary.

Note: When removing old O-rings, be careful not to damage the O-ring seats.

Note: Be careful not to dislodge the O-ring during valve installation.

Caution: Do not over-tighten the cartridge. Hand tighten until the gasket contacts the adaptor plate, then turn an additional 1/2 turn only!

6002K-003

Desiccant canister

  1. Whenever servicing the air dryer, clean and inspect the entire unit for any external damage.
  2. Remove the old cartridge (turn counter-clockwise).
  3. Clean dirt/oil from the top surface of the adaptor plate and threaded stud.
  4. Remove the old O-ring from the threaded adaptor.
  5. Lubricate the new O-ring and install it on the threaded adaptor.
  6. Lubricate the gasket on the new desiccant cartridge.
  7. Thread the new cartridge onto the adaptor (turn clockwise).

Note: Excessive accumulation of oil in the air dryer or air dryer cartridge indicates the compressor may require service. Disassemble the entire unit and check for blockage within the valve cavities, safety valve, and bottom cap cavity. Drain, clean, and replace worn components as necessary.

Note: When the gasket contacts the adaptor plate, tighten 1/2 turn. Do not over-tighten, or the cartridge could be extremely difficult to remove.

6009X-010-Control-Valve-(HD2-only)-

6009X-010 · HD2 ONLY

Control valve

  1. Exhaust/drain the air system to zero PSI. If an air dryer bypass was installed, open/close valves as necessary and drain the air dryer unit by removing the signal line from the dryer outlet manifold (1/4″ line).
  2. Remove the 1/4″ air line from 3 locations at the 6009X-010 control valve 6009X-005 tube fittings.
  3. Remove the 6009X-010C retaining nut from the control valve and drop the solenoid/timer from the unit. Remove the timer from the solenoid (1 screw).
  4. Remove the 6009X-007 #8-32 screws at 3 locations connecting the control valve to the HD2 manifold body, and drop the valve.
  5. Remove the fittings from the control valve and verify the serviceability of the fittings and exhaust mufflers. Replace as necessary. It is recommended that the (2) 6009X-006 exhaust mufflers be replaced with the valve.
  6. Install the fittings and mufflers on the valve and replace in reverse order.
6009X-011-Timer-(HD2-only)-

6009X-011 · HD2 ONLY

Timer

  1. Remove the 6009X-010C retaining nut from the control valve and drop the solenoid/timer from the unit. Remove the timer from the solenoid (1 screw).
  2. Replace the timer and install in reverse order.

After installation or service

Testing the unit.

  1. Check air tanks for accumulated moisture and drain as required.
  2. Start the air compressor and allow system pressure to build to cut-out pressure.
  3. Check all connections for air leaks.

Note: After the air dryer exhausts, air will continue to bleed out of the exhaust port until the timed regeneration cycle is complete.

Note: A soap solution works very well for locating leaks.

Warranty

One-year limited warranty.

For the period of one (1) year, Seller’s sole obligation and Buyer’s sole and exclusive remedy for any defect Product(s) shall be Seller’s reimbursement of the “Warranty Expense”. In addition Seller’s obligation for the Product(s) which are not in conformance with the Seller’s warranty shall be further limited to those product(s) which are promptly returned to Seller after discovery of any alleged defect with Freight prepaid to the warehouse designated by the Seller’s representative and which Product(s) are found by Seller (in the exercise of its sole and exclusive judgment made by Seller experienced and highly skilled personnel) to have been defective in accordance with the warranty. Seller will in no event be liable for any consequential special or contingent damages or expenses arising directly or indirectly from any defects in its goods or from the use thereof, nor is any other person authorized to assume for the seller any such liability or any contrary representations or warranty on behalf of the Seller. In no event shall the Seller be obligated under Seller’s agreement or otherwise in any manner whatsoever for normal wear and tear of any product(s) which in the seller’s sole and exclusive determination have been subjected to accident, abuse, misapplication, improper repair or alteration or maintenance, neglect, excessive operating conditions or for defects resulting from Buyer’s specifications or designs, or otherwise caused by the Buyer, including without limitation defects resulting from Buyer’s manufacture, distribution, sale or promotion of its own product. Seller expressly disclaims any implied or expressed warranty of fitness for a particular purpose. It is understood that such products are warranted to be fit for their ordinary intended use.

Drawings

Reference drawings.

Use these drawings alongside the maintenance procedures above, for system troubleshooting, and when ordering replacement parts.

Drawings supplied with this manual

6001A-001 thru –006 · 6002A-001, 002 · 6003A-001, 002 · 6005A-001 · 6007A-001, 002 · 6007E-001, 002 · 6007M-001 · 6009A-001, 002 · 6016A-001 · XL76

Service support

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