Y42X Spring Diaphragm Pressure Reducing Valve
• Spring diaphragm type — smooth, chatter-free regulation
• Self-operated — no external power required
• 2 body materials: ductile iron (Y42X-16) or WCB cast steel (Y42X-16C)
• NBR diaphragm & seal rings for water/oil service ≤70°C
• Ideal for fire protection & building water supply systems
Gaoshan Valve — Y42X Spring Diaphragm Pressure Reducing Valve
Model: Y42X-16 / Y42X-16C | Pressure: PN16 | Connection: Flanged | Medium: Water, Oil
Product Overview
The Y42X Spring Diaphragm Pressure Reducing Valve is a self-operated, direct-acting pressure regulating valve designed for liquid pipelines carrying water, oil, and other non-corrosive fluids. The valve uses an adjustable spring-loaded diaphragm mechanism to reduce a higher upstream inlet pressure to a stable, set downstream outlet pressure. Unlike piston-type reducers, the Y42X features a flexible NBR (Buna-N) diaphragm that provides smooth, chatter-free regulation with fast response to flow demand changes. No external power source or control instrumentation is required — the valve operates entirely on the energy of the medium. With its compact design, reliable diaphragm sensing element, and two robust body material options, the Y42X is the preferred choice for building water supply systems, fire protection networks, and industrial water distribution where consistent low-pressure delivery is critical.
Key Advantages
Smooth Diaphragm Actuation — No Chatter
The NBR diaphragm provides smooth, progressive throttling action without the friction and stick-slip that can occur in piston-type regulators. This ensures stable outlet pressure even at low flow rates, making it ideal for residential and commercial water systems.
Self-Operated — Zero External Energy
The valve harnesses the pressure energy of the medium itself — no electricity, compressed air, or control wiring is needed. Install it and set the spring; the diaphragm mechanism handles the rest automatically.
Two Body Material Options
Y42X-16 features a ductile cast iron body for cost-effective general water service. Y42X-16C uses WCB cast steel for higher structural integrity. Both are internally trimmed with stainless steel stem and plunger for corrosion resistance.
Ideal for Fire Protection Systems
Specifically tested and recommended for fire-protection water supply in high-rise buildings. The diaphragm design delivers consistent low-pressure output required by fire hydrant and sprinkler networks, replacing outdated district water pipe regulators.
Durable Elastomer Diaphragm
The Buna-N (NBR) diaphragm and seal rings deliver excellent resilience for water and oil service up to 70°C. The wide-area diaphragm translates small pressure changes into precise valve position adjustments, leading to a tight outlet pressure deviation of ±15%.
Replace Conventional District Regulators
The Y42X directly replaces outdated conventional district water pipe pressure reducers, offering superior regulation accuracy, lighter weight, and lower maintenance requirements in municipal and building water distribution networks.
Technical Specifications
| Parameter | Y42X-16 | Y42X-16C |
|---|---|---|
| Nominal Pressure | PN16 | PN16 |
| Shell Test Pressure | 2.4 MPa | 2.4 MPa |
| Inlet Pressure Range | 0.25 – 1.6 MPa | 0.25 – 1.6 MPa |
| Outlet Pressure Range | 0.05 – 1.0 MPa | 0.05 – 1.0 MPa |
| Outlet Pressure Deviation | ±15% | ±15% |
| Nominal Diameter | DN40 – DN200 | DN40 – DN200 |
| Working Temperature | 0°C – 70°C | |
| Suitable Medium | Water, oil, and non-corrosive liquids | |
| Connection Type | Flanged (RF) | |
| Regulation Type | Self-operated spring diaphragm (no external power required) | |
Main Parts & Materials
| Part Name | Y42X-16 | Y42X-16C |
|---|---|---|
| Body, Upper Bonnet, Lower Bonnet | Ductile Cast Iron | WCB Cast Steel |
| Stem | Stainless Steel | Stainless Steel |
| Plunger | Stainless Steel | Stainless Steel |
| Main Valve Spring | Silicon-Manganese Steel | Silicon-Manganese Steel |
| Regulating Spring | Silicon-Manganese Steel | Silicon-Manganese Steel |
| Diaphragm | Buna-N Rubber (NBR) | Buna-N Rubber (NBR) |
| Seal Ring | Buna-N Rubber (NBR) | Buna-N Rubber (NBR) |
Model Selection
| Model | Body Material | Pressure Class | Temp. Range | Outlet Range | Size Range |
|---|---|---|---|---|---|
| Y42X-16 | Ductile Cast Iron | PN16 | 0°C – 70°C | 0.05 – 1.0 MPa | DN40 – DN200 |
| Y42X-16C | WCB Cast Steel | PN16 | 0°C – 70°C | 0.05 – 1.0 MPa | DN40 – DN200 |
How It Works
The Y42X spring diaphragm pressure reducing valve operates on a simple force-balance principle. The high-pressure medium enters the inlet and passes through the throttling gap between the main disc and seat, where its pressure energy is dissipated. The reduced downstream pressure acts on the large-area underside of the NBR diaphragm inside the lower bonnet chamber. An adjustable regulating spring above the diaphragm exerts an opposing downward force. When the downstream pressure force equals the spring set force, the valve settles into a balanced throttling position. If downstream pressure rises above the set point (e.g., due to reduced flow demand), the diaphragm is pushed upward, closing the main disc and reducing flow. If downstream pressure drops (increased demand), the spring pushes the diaphragm downward, opening the main disc to admit more flow. This continuous, proportional feedback loop maintains the outlet pressure within ±15% of the set point across the entire flow range — without any external power source or actuator.
Y42X Spring Diaphragm Pressure Reducing Valve — Structure & Working Principle Diagram
Dimensions (mm) & Weight (kg)
| DN | L (Face-to-Face) | H (Center Height) | H1 (Total Height) | Weight (kg) |
|---|---|---|---|---|
| 40 | 220 | 450 | 90 | 28 |
| 50 | 250 | 450 | 90 | 28 |
| 65 | 280 | 480 | 105 | 38 |
| 80 | 310 | 500 | 123 | 59 |
| 100 | 350 | 500 | 123 | 65 |
| 125 | 400 | 750 | 130 | 89 |
| 150 | 450 | 780 | 160 | 120 |
| 200 | 500 | 800 | 160 | 150 |
*Note: L = Face-to-face length, H = Center height from pipe centerline to top of valve, H1 = Overall valve height. Flange dimensions per GB/T 9113 / JB/T 79. Dimensions are identical for both Y42X-16 (ductile iron) and Y42X-16C (cast steel) models.
Installation Guidelines
- Install on a horizontal pipeline with the regulating spring housing in a vertical upright position. The diaphragm must remain horizontal for proper sensing accuracy
- Install a Y-type or T-type strainer upstream of the valve to protect the diaphragm, seat, and plunger from pipe debris, sediment, and scale
- Install pressure gauges on both the upstream (inlet) and downstream (outlet) sides for set-point adjustment and operational monitoring
- Provide a bypass line with a globe valve around the pressure reducing valve for maintenance or emergency operation without system shutdown
- Allow at least 5x pipe diameters of straight pipe run upstream and downstream for stable flow conditions and accurate pressure sensing
- During commissioning, back off the regulating spring completely (no preload), then slowly tighten while monitoring the downstream pressure gauge until the desired set point is reached
- For fire protection systems, secure the adjusting screw with a lock nut or tamper-proof cap after final set-point calibration
- Inspect the diaphragm every 12 months for signs of wear, fatigue cracking, or hardening. Replace if any degradation is found
- Avoid installing where freezing temperatures can occur — trapped water in the diaphragm chamber can cause ice damage
Application Fields
High-Rise Building Water Supply
Municipal Water Distribution
Residential Water Systems
Commercial Plumbing
Industrial Water Supply
Oil Transfer Pipelines
HVAC Chilled Water
Quality Standards & Certifications
- Design & Manufacture: GB/T 12244 (Pressure Reducing Valve)
- Face-to-Face Dimensions: GB/T 12221
- Flange Ends: GB/T 9113 / JB/T 79
- Test & Inspection: GB/T 13927 / GB/T 12245
- ISO 9001 Quality Management System Certified
- TS Special Equipment Manufacturing License
- 100% hydrostatic shell test at 1.5x rated pressure (2.4 MPa) before shipment
- 100% seat leakage test after hydrostatic shell test
Packaging & Shipping
Each Y42X pressure reducing valve is individually packed with protective end caps over the flange faces, sealed in a poly bag with desiccant, and secured in a plywood case or export-standard wooden crate. The spring housing and diaphragm assembly are packed with additional impact protection to prevent shipping damage to the sensitive regulating mechanism. All shipments include a packing list, material certificate, hydrostatic test report, and installation manual. We support FOB, CIF, DAP, and other Incoterms to suit your logistics requirements.
After-Sales Service
- 18-month warranty from date of delivery under normal operating conditions
- Technical support for set-point adjustment, commissioning, and system integration
- Spare parts supply for diaphragm, seal ring, plunger, springs, and trim components
- Replacement diaphragm kits available for routine maintenance
- On-site inspection, troubleshooting, and repair service available upon request
Request a Quote
Need a specific outlet pressure range or a custom material option? Contact Gaoshan Valve today for competitive pricing, sizing support, and expert technical guidance on your water pressure regulation project.