Vulkan LH25, LH40 and LH400: How to Choose the Right In-Line Regulator

The LH family at a glance

All three regulators share the same core job: reduce line pressure in a gas-carrying pipeline and hold the downstream pressure stable regardless of flow demand. Beyond that starting point, the design decisions diverge significantly — and the right choice depends entirely on the flow capacity required, the connection concept, the gas purity class and the installation environment.

Flow capacity: where the real differences lie

The most decisive selection criterion is usually flow. The LH series spans a wide range, and selecting the wrong model in either direction creates problems — too small means pressure droop under load, too large means unnecessary cost and installation complexity.

The LH25 covers applications where a compact, reliable pressure reduction is needed at flow rates typical of service connections, tapping point supply or single-machine connections. The LH40 extends well beyond that into high-flow industrial territory, rated up to 600 Nm³/h. The LH400 raises the ceiling further, up to 800 Nm³/h, without stepping up to a full pressure regulating station.

Construction: two philosophies

LH25 — classic separate-component approach

The LH25 is a single-function component: it regulates pressure. Inlet filtration, if required, is achieved by installing a separate filter upstream. This gives the planner flexibility in specifying filtration independently, but introduces intermediate piping — and with it, potential pressure loss, additional leak paths and maintenance points. For low to moderate flow rates, this is entirely adequate and cost-effective.

LH40 and LH400 — integration as the design principle

Both the LH40 and LH400 eliminate the gap between filter and regulator by placing both inside a single solid housing. The CuSn10 sintered filter element sits immediately upstream of the valve seat. There is no intermediate pipe run, no flanged joint, no added restriction. At high flow rates, this geometry makes a measurable difference: the pressure signal from downstream reaches the sensing diaphragm without a pneumatic buffer in the way, and the improved valve cone — with its enclosed, better-protected sealing zone — responds instantly to load changes while keeping mechanical stress on the sealing surface low.

On the LH40, the sintered filter is field-replaceable without removing the regulator from the pipeline, and is available in five filtration ratings — 8, 12, 20, 30 and 50 µm — selected to match the application. For sensitive packaging nozzles, the finer ratings are specified; for pipeline purging, coarser ratings maximise flow with minimal restriction. The LH400 uses the same integrated filter principle with a fixed 50 µm rating.

Connection size: not what you might expect

It would be intuitive to assume that connection size scales directly with flow capacity — bigger flow, bigger thread. In the LH series, this is not the case. The LH25 and LH400 both use G1 RH female connections at inlet and outlet. The LH40, despite its high flow rating, uses the smaller G½ RH female connection — a deliberate design choice that keeps the LH40’s footprint compact for installation into existing G½ pipework and machine connections, particularly in food and dairy processing environments where retrofitting is common.

This means connection size alone is not a reliable indicator of flow capacity in this series. Always check the actual flow rating against the application requirement rather than inferring capacity from thread size.

All three models in the series use classic thread sealing at the connection — a proven, well-understood approach for industrial gas pipework, compatible with standard sealing tape or sealing rings depending on installer preference and site standard.

Full technical comparison

Diaphragm choice: NBR elastomer vs stainless steel

The LH25 is available with an NBR elastomer diaphragm, which is adequate for the vast majority of industrial gas applications with technical gases and compressed air. The LH40 and LH400 both offer a stainless steel 1.4404 diaphragm as an option, and this opens access to applications where an elastomer would be unsuitable.

The practical differences matter in three scenarios:

• Gas purity class 5.0 (99.999%) — elastomer diaphragms have a finite diffusion rate; over time, molecules from the elastomer can permeate into the gas stream. At purity class 5.0 this becomes measurable. Stainless steel diaphragms have effectively zero permeation.
• Diffusion-aggressive media — hydrogen and helium, with their small molecular size, permeate elastomers at a rate that is technically relevant in analytical and semiconductor supply. Stainless steel diaphragms eliminate this entirely.
• Food-grade compliance — EC 1935/2004 restricts the materials that may contact food or food-contact gases. Both the LH40 and the LH400 carry full food-contact certification under EC 1935/2004 and LFGB when fitted with the stainless steel diaphragm version.

LH40 vs LH400: the specific choice between the two high-flow models

The LH40 and LH400 share the same integrated filter-and-regulator architecture, the same improved valve cone, the same NBR-standard / stainless-steel-optional diaphragm choice, and the same food-grade approval path. The decision between them comes down almost entirely to two factors: flow headroom and connection size.

Neither model is a universal replacement for the other. The LH40 fits naturally into existing G½ piping and machine connections where its flow ceiling of 600 Nm³/h is sufficient. The LH400 fills the gap above that ceiling, with the larger G1 connection suiting new-build installations or pipework already sized at G1.

Where each model fits: application mapping

What the LH400 does not replace

The LH400 is a high-capacity single-stage in-line regulator. It is not a pressure regulating station, a dome-loaded regulator or a multi-stage manifold regulator. For applications requiring pilot-operated pressure control, electro-pneumatic setpoint adjustment from a PLC, or inlet pressures above the LH400’s rated range, the correct solution steps up to the Vulkan LD1 or LDS1 series — dome-loaded in-line regulators capable of flows up to 2400 Nm³/h with pilot control.

The LH400 occupies the space between compact standard regulation and large regulating stations — precisely the segment where many industrial applications sit and where a well-specified in-line regulator avoids the cost and complexity of a full station.

Product in Action

The following videos show the Vulkan LH40 regulator in a real industrial installation.