Air Compressor Unloader Valves - Auxiliary Machinery and Engine Room
Air compressor unloader valves relieve cylinder or discharge pressure during startup and control unloaded running in marine reciprocating air compressors. They reduce starting torque, prevent motor overload, and support automatic starting-air or service-air compressor operation.
ProShipWorks provides end-to-end support to source and supply Air Compressor Unloader Valves for marine vessels, ship operators, industrial facilities, maintenance teams and procurement departments.
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Product Information
| Product Name | Air Compressor Unloader Valves |
|---|---|
| Product Category | Auxiliary Machinery and Engine Room |
| Product Reference | 366 |
| Brands / Manufacturers | Sperre, J.P. Sauer & Sohn, Tanabe |
| Unit of Measure | Piece |
Key Features
| Key Feature |
|---|
| 1. Automatically relieves compression pressure during startup |
| 2. Reduces starting torque and motor current |
| 3. Available in mechanical, pneumatic, solenoid, or pressure-actuated designs |
| 4. Designed for compressed-air service and repeated cycling |
| 5. Typically supplied as an OEM-specific compressor spare |
Applications of Air Compressor Unloader Valves
| Application |
|---|
| 1. Main and emergency starting-air compressors |
| 2. Engine-room service and control-air compressors |
| 3. Marine reciprocating compressor capacity-control systems |
Models & Manufacturers
| Model | Manufacturer |
|---|---|
| HL2/77 OEM unloader valve | Sperre |
| WP121L OEM unloader valve | J.P. Sauer & Sohn |
| H-74 OEM unloader valve | Tanabe Pneumatic Machinery |
Technical Specifications
| Model | Specification | Value | Unit |
|---|---|---|---|
| HL2/77 OEM unloader valve | Compatible compressor | HL2/77 marine reciprocating air compressor | — |
| WP121L OEM unloader valve | Compatible compressor | WP121L high-pressure reciprocating air compressor | — |
| H-74 OEM unloader valve | Compatible compressor | H-74 marine air compressor | — |
| Marine compressor unloader valve | Service medium | Compressed air | — |
Standards, Certifications & Class Approval
Review the available standards and approval information relevant to the product. Actual certification, material traceability, inspection and classification requirements depend on the product type, intended application and purchasing specification.
| Applicable Standards & Certification | Compressor performance may be tested to ISO 1217, while installation must follow the compressor OEM manual, applicable pressure-equipment requirements, and vessel flag-state rules. Unloader valve dimensions, materials, pressure ratings, and connections are normally OEM-specific. |
|---|---|
| Class Approval | Acceptance may fall under the compressor package or starting-air system approval by DNV, ABS, Lloyd's Register, Bureau Veritas, or ClassNK. Confirm the exact valve part number and any required OEM or class certificate for the vessel. |
Installation, Maintenance & Safety Information
| Installation Notes | Isolate, depressurize, drain, and lock out the compressor before replacement. Match the OEM part number, port arrangement, pressure rating, actuation method, seals, and flow direction. Use approved sealing materials and test unloading and reload operation after installation. |
|---|---|
| Maintenance Tips | Inspect periodically for air leakage, carbon or oil deposits, sticking pistons, weak springs, damaged seats, and blocked pilot passages. Clean using OEM-approved methods, renew seals and worn internals, and verify correct unloading during every compressor start. |
| Safety Notes | Never remove the valve while the compressor or receiver is pressurized. Isolate electrical and pneumatic energy, allow hot components to cool, and wear eye and hand protection. A failed unloader can cause high starting current, compressor damage, overheating, or unsafe pressure conditions. |
Request a Quote for Air Compressor Unloader Valves
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