MANPADS coolant. Rechargeable in five minutes.

Introduction

A shoulder-fired air-defence missile only sees its target through a cooled infrared seeker. The seeker stares at a hot target against a cool background; for that contrast to be detectable, the seeker's detector element must itself be held cold. In the operational round, that cooling is provided by a small, high-pressure argon Coolant Reservoir Assembly (CRA) bolted to the launcher grip stock. The CRA is a finite resource: each launch consumes one charge, and stored CRAs can drift below the acceptable charge window over months in magazine.

The Coolant Recharging Unit (CRU) is the maintenance-bay tool that puts argon back into a CRA on-spec. Neometrix's CRU is an indigenous build under the Make-in-India programme, designed to the operating envelope of the canonical TM FMS-CRU-MAINT-13 reference and qualified for the Indian operating environment. It is a self-contained argon booster station: source bottle in, filtered + boosted argon out, with three independent layers of overpressure protection and a single-operator front panel.

What this machine is designed to recharge

The Coolant Reservoir Assembly (CRA)

• 30-inch length, 3-inch diameter, 122 cubic-inch internal volume
• Filled charge weight ~ 4.8 kg; empty ~ 3.9 kg
• Working charge: 6,000 ± 200 psig argon at 99.998% purity
• Blow-out plug setting: 9,000 ± 1,000 psig at 21–24 °C

The CRA presents a Schrader-style fill-and-bleed port at one end. The CRU's fill-and-bleed valve mates to that port through the diffusion-chamber access hole; the bleed action allows operators to relieve residual pressure before removing the cover. Cover-torque (36 ± 12 in-lb) and vent-screw torque (7 ± 1 in-lb) are both specified by the SOP — under or over-tightening either is a known cause of seal failure in service.

Source-bottle compatibility

The CRU works from any clean, dry argon source within the 1,000–6,000 psig input range. Two adapters ship in the storage compartment to cover the global base of source bottles: a CGA-677 adapter for high-pressure bottles rated to 7,500 psig (519 bar) per Compressed Gas Association practice, and a BS3-341 adapter for standard-pressure bottles rated to 3,300 psig (230 bar) per the British Standard most common in Indian-defence stock. Either adapter mates source-side with no thread-sealant and no field-fitting.

Core operating capability

The unit is not a multi-mode test stand — it is a single-purpose argon booster. The recharge cycle is six phases: purge (briefly vent the inlet hose), charge (boosted ramp to 6,000 psig with auto-shutoff), cool (mandatory five-minute hold for thermal equalisation), top-off if needed, drain (controlled section-by-section depressurisation), and shutdown. A trained operator completes a full cycle in roughly five minutes per CRA — the rate-limiter is the cool-down hold, not the booster.

System architecture

1. Pneumatic booster & fluid path

At the heart of the unit is a 3D Instruments twin-piston reciprocating booster, V-belt driven from a Leeson 230 V single-phase motor. Two opposed pistons compress the inlet argon up to 6,200 psig with smooth, balanced reciprocation; stainless steel check valves in the upper and lower cylinder heads prevent backflow. Two Swagelok 2-µm inline filters bracket the flow path — one immediately after the inlet check valve, one before the outlet port — with a molecular sieve in series for moisture and hydrocarbon polish.

2. Diffusion chamber & CRA fixturing

The diffusion chamber is welded aluminium plate. The CRA sits on two saddles and is locked by rotary draw latches in the chamber base; two over-centre pull clamps secure the chamber door during operation. Vent holes in the internal-facing wall allow rapid dissipation of any sudden gas release inside the chamber, isolating the operator from a pressure event.

3. Three-tier overpressure stack

The system never operates above its design pressure even with a single failure in the primary cut-off chain. A Barksdale pressure switch is the primary cut-off: it auto-cuts power to the motor at 6,000 psig, with an adjustable sleeve and a roughly 10% deadband — so once cut-off occurs, the switch will not reset until pressure drops about 10% below set-point. If that switch fails closed, an Aqua Environment relief valve opens and vents to atmosphere at 6,500 ± 325 psig, with a poppet that blows fully open at approximately 8,500 psig as a backstop. If both fail, a Zook rupture disk bursts within a 7,200 +6%/-3% psig window — a single-use element that must be replaced before next operation.

4. Operator interface

Five gauges and four levers across one front panel. Three pressure gauges read Inlet, Boosted, and Outlet line states. An hour meter logs run-time for the filter, V-belt, and pressure-switch service intervals. A rotary START/STOP switch drives the motor through the integrated circuit breaker. Four ball valves — INLET CONTROL, OUTLET CONTROL, UNLOADER VENT, OUTLET DRAIN — click into labelled hard-stop positions with no ambiguity about state. No software, no SCADA, no firmware updates — nothing to patch.

Depot, school, and forward-bay use

Ideal where simple, robust, single-operator operation matters more than throughput. A depot-level workshop can recharge a steady stream of returned CRAs against archived inspection cards. A training school can recharge after live exercises so the next intake works with on-spec rounds. A forward maintenance bay can position a single unit and a source bottle inside a 20-foot ISO container for mobile deployment. The unit's reusable shipping & storage container (62.6 kg empty) is sized for transit on a standard aviation pallet.

Target users

Competitive advantages

• Indigenous — complete Make-in-India build; no ITAR or end-use-certificate exposure
• Field-deployable — 111 kg dry, single-phase 230 V, no SCADA, no network
• Triple safety stack — pressure switch + relief valve + rupture disk, three independent layers
• Standard interfaces — CGA-677 + BS3-341 cover the global source-bottle base
• Five-minute cycle time — cool-down hold is the rate-limiter, not the booster
• Aligned to MIL-PRF-27415 — 99.998% argon purity, 6,000 ± 200 psig charge window
• Built to TM FMS-CRU-MAINT-13 envelope — reverse-engineered, indigenous, qualified for Indian climate
• 20+ years defence domain expertise — DGAQA-aligned design, manufacturing, and acceptance
• Turnkey — design, manufacture, FAT, commissioning, operator training, AMC under one vendor