| Application Overview
The DYS10A is the smallest-footprint member of DJ's cryogenic pressure-building regulator portfolio, scaled to DN10 for low-flow LNG tank applications and distinguished by a dedicated four-port body architecture that separates the main inlet/outlet flow path from the pressure-building (PB) circuit.
Where the larger DYS15F and DYS15FM variants route both functions through a shared M27×2 inlet/outlet pair, the DYS10A physically partitions the tank-to-regulator connection (IN / OUT) from the regulator-to-vaporizer pressure-building loop (PB IN / PB OUT). This topology eliminates the need for an external tee or manifold to split the pressure-building circuit from the tank supply line—a valuable simplification in the confined under-chassis mounting environments typical of light-duty LNG trucks and small stationary vessels.
With a body envelope of just 52 mm wide and 83 mm tall (A1 variant), the DYS10A fits into installation clearances where the 68 mm DYS15F or 96 mm DYS15FM cannot. The 3/8NPT port sizing aligns with the smaller-bore tubing and hose assemblies used in DN10 cryogenic systems, reducing adapter count and potential leak paths.
Internally, the seven-component architecture mirrors the proven DYS family design: brass body and bonnet, bronze diaphragm for pressure sensing, PTFE dynamic seal, and dual stainless steel springs. Three factory-calibrated models cover the full 30–450 PSIG pressure spectrum, with the A1 variant uniquely starting at a lower 125 PSIG factory set point for low-pressure tank applications. All units are CGA G-4.1 cleaned and degreased for oxygen service and comply with TSG23 and GB/T34530.1.
| Working Principle
The DYS10A operates on the same diaphragm-referenced force-balance principle as the DYS family, but its four-port body architecture materially changes the hydraulic circuit topology compared to the two-port DYS15F/FM siblings.
Four-Port Circuit Partitioning:
The DYS10A body contains two distinct flow paths that do not intermix internally:
Sensing Path:The tank bottom liquid port connects to the valve IN port. The OUT port returns to the tank vapor space or supply manifold. This path is always open—it serves as the sense line that transmits tank pressure to the diaphragm cavity and, when the poppet lifts, as the supplemental return path for vaporized gas.
Pressure-Building Circuit (PB IN → PB OUT): PB IN draws liquid from the tank sump. When the poppet opens, liquid flows from PB IN across the disc/seat orifice to PB OUT, which is piped to the ambient vaporizer inlet. The vaporized gas then returns to the tank ullage via a separate line. The critical advantage of this partitioned architecture is that the pressure-building flow is hydraulically independent of the main tank supply line: the engine can draw fuel through IN→OUT while the pressure-building circuit simultaneously operates through PB IN→PB OUT without flow interference or pressure coupling.
Regulation Sequence:
Sensing: Tank vapor pressure is continuously transmitted through the OUT port into the diaphragm cavity beneath the bronze membrane. The diaphragm converts this pressure into an upward force.
Set-Point Comparison: The upper control spring exerts a calibrated downward force. When tank pressure ≥ set point, the diaphragm overcomes the spring, lifting the stem assembly. The lower return spring seats the disc, blocking flow through the PB IN→PB OUT orifice. The pressure-building circuit is quiescent.
Build Cycle: When tank pressure falls below the set point (due to engine fuel consumption), the spring force dominates, driving the stem and disc downward. PB IN is now connected to PB OUT through the open orifice. Liquid cryogen flows to the vaporizer, undergoes phase change, and the resulting gas streams back into the tank, raising vessel pressure.
Proportional Throttling: As tank pressure approaches the set point, the diaphragm-spring balance enters a proportional band. The disc assumes a partially open position, throttling PB flow to match the pressure decay rate. This modulation prevents overshoot and eliminates the hunting behavior common in on-off pressure switches.
Four-Port Advantage in Practice:
On a two-port regulator (DYS15F/FM), the pressure-building circuit must be teed off the main tank-to-engine supply line. During high-engine-demand periods, the supply line pressure drop can cause the regulator to misread tank pressure as lower than actual, triggering unnecessary PB cycles and wasting liquid cryogen. The DYS10A's dedicated PB IN port taps the tank directly, isolated from supply-line pressure fluctuations, ensuring that PB actuation is driven solely by true tank pressure—not by downstream hydraulic noise.
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Factory Shoot
1: When should I choose DYS10A over DYS15F or DYS15FM?
A: The selection hierarchy follows three criteria in descending priority:
① Space constraint: If the available installation clearance is less than 68 mm wide, DYS10A (52 mm) is the only option. This is common in light-duty LNG trucks, compact stationary tanks, and retrofit installations where the original bracket was designed for DN10 regulators.
② Flow demand: DYS10A is optimized for small-bore DN10 systems with lower liquid withdrawal rates. If the tank serves an engine above approximately 200 kW or a vaporizer with rated capacity exceeding 50 Nm³/h, the larger DN15 porting of DYS15F/FM is recommended to avoid PB flow restriction during rapid pressure recovery.
③ Circuit architecture: If the installation calls for independent PB and supply circuits (engine fuel draw must not perturb the pressure-building logic), DYS10A's four-port architecture is inherently superior. If the system already has a dedicated PB line teed off the tank and only needs a two-port regulator, DYS15F/FM is simpler to pipe.
2. Why is A1 factory set at 125 PSIG instead of 145 PSIG like F1?
A: The 125 PSIG set point addresses low-pressure LNG tank applications where the tank's maximum allowable working pressure (MAWP) is below 200 PSIG—common in older or lightweight aluminum-alloy tank designs. Setting F1's 145 PSIG on such a tank would leave only a 55 PSI margin to the MAWP before the safety relief valve (typically set at MAWP × 1.1) lifts, resulting in excessive venting during normal thermal pressure rise. The 125 PSIG A1 provides an additional 20 PSI of operating headroom, reducing relief-valve cycling and methane slip. The A1 adjustment range still extends to 320 PSIG, so it can be field-adjusted upward if the tank is later recertified for higher pressure.
3. What is the flow capacity difference between 3/8NPT (DYS10A) and 1/2-14NPT (DYS15F)?
A: The 3/8NPT port has a nominal bore of approximately 11 mm versus 1/2-14NPT's approximately 15 mm. By cross-sectional area ratio, the DYS15F port offers roughly 86% more flow area. However, in pressure-building service, the limiting flow element is rarely the port diameter—it is the disc/seat orifice inside the valve body and the downstream vaporizer capacity. The DYS10A's internal orifice is sized proportionally to its DN10 designation, typically yielding a Cv of approximately 0.8–1.2 versus the DYS15F's estimated 1.5–2.5. For a 200-liter LNG tank with a 30 PSI pressure deficit, the DYS10A restores pressure in approximately 45–60 seconds of PB flow; the DYS15F achieves the same in 25–35 seconds. Both are well within the pressure recovery window between engine fuel drawdown cycles.
4. Does the four-port architecture add internal leakage risk?
A: No. The IN/OUT and PB IN/PB OUT flow paths are separated by solid brass webbing cast integrally into the valve body—there is no gasket, O-ring, or seal between these cavities. Internal cross-port leakage would require a casting porosity pathway through the brass web, which is eliminated by the 100% factory pressure test at 1.5× maximum rated pressure (760 PSIG). The only potential internal leakage mode is past the PTFE disc seal when the poppet is seated, which would manifest as continuous low-rate flow through PB OUT—this is detectable during commissioning by disconnecting the PB OUT line and checking for frost formation with the tank at steady-state pressure above the set point.
5. Why does DYS10A have a D0 of Φ57 mm but DYS15F/FM have much smaller bonnet ODs?
A: D0 = Φ57 mm on the DYS10A specification table refers to the body diameter, not the bonnet diameter. The DYS10A body is a cylindrical brass forging with a uniform OD of 57 mm that houses all four ports. In contrast, DYS15F has a bonnet OD (D) of Φ17 mm and DYS15FM has D0 = Φ14 mm—these are bonnet cap dimensions, not body dimensions. The DYS10A does not list a separate bonnet OD because the body and bonnet form a continuous cylindrical profile with the bonnet recessed into the body cavity, unlike the DYS15 series where the bonnet sits atop the body as a distinct external component. This integrated body-bonnet geometry contributes to the DYS10A's compactness and eliminates the bonnet-to-body gasket joint that exists in the DYS15F, reducing one potential cryogenic leak path.
6.Does DYS10A share internal components with the DYS15 series?
A: Only the material specifications are shared—the physical components are scaled down. The seven parts (body, two springs, disc, PTFE seal, bronze diaphragm, bonnet) use the identical material grades (C37700 brass, 304SS springs, virgin PTFE, C51000 bronze diaphragm), ensuring the same cryogenic compatibility and corrosion resistance. However, the disc diameter, spring wire gauge, diaphragm effective area, and bonnet thread pitch are all reduced proportionally to the DN10 scale. This means spare parts are not interchangeable between DYS10A and DYS15F/FM—each family requires its own service kit. The common material specification simplifies raw material procurement and QC testing across the product line, but field mechanics must stock separate spares for each DN size.
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