1,800-Bar Bomb Shell Hydraulic Pressure Testing Machine

1. The challenge: replacing an imported proof-testing capability

Every artillery shell that leaves an Indian ordnance production line has to prove, before it ever reaches a gun, that its body will hold the firing pressures it was designed for — and will hold them with a large safety margin after storage, temperature cycling, and transport. That proof is not a document. It is a physical test, applied shell by shell, at pressures substantially higher than service pressure, under conditions that are unambiguously traceable years after the fact. For 155 mm and 105 mm shell bodies, the proof-pressure target sits at the ultra-high-pressure end of hydraulic testing: up to 1,800 bar, held long enough to detect microstructural yield, with pressure accuracy tight enough that a passing shell truly is within spec and a rejected shell truly is not.

Until recently, the Indian ordnance industry met this requirement with imported test benches. Those systems worked — but they came with the standard imported-equipment tax. Long lead times on commissioning, 6 to 16 week spare-part replenishment, foreign-currency exposure, and OEM engineers on flights whenever anything needed intervention. More fundamentally, the imported benches available on the market were either configured for lower throughput at research-grade accuracy or for higher throughput at lower pressure. Very few combined the three things an Indian production line actually needed: 1,800 bar peak, 50 shells per hour sustained, and full MIL-STD-1522 / DGAQA documentation out of the gate.

The customer — an Indian ordnance manufacturer supplying artillery ammunition under DGAQA oversight — came to Neometrix with a single-page brief: build a turnkey proof and burst station that clears every shell off the upstream machining line without becoming the bottleneck, meets the full compliance chain on day one, and does it with a bill of materials that satisfies the Make-in-India content threshold. The brief assumed what most imported-bench vendors could not deliver: that the supplier would own the mechanical design, the hydraulics, the PLC firmware, the SCADA layer, the robot integration, and the certification package, end to end, from one engineering team.

2. Four engineering constraints that drove the design

Every interesting engineering project comes down to three or four constraints that, taken together, eliminate every off-the-shelf answer. The bomb-shell proof station had four.

Ultra-high pressure with laboratory accuracy

The bench had to reach 1,800 bar and hold it within 0.1 percent of full scale — about ±1.8 bar at peak — for the duration of the proof dwell. That accuracy class is routine at 200 bar. At 1,800 bar it is not. Pump pulsation, fluid compressibility, temperature drift, and transducer hysteresis all scale unfavourably with pressure, and every one of them has to be engineered out rather than tolerated. The pressure-generation architecture had to be servo-hydraulic with closed-loop PLC control from the first design iteration; there was no path forward using stroke-controlled conventional pumps.

Fully automated test cycle — no operator in the cell

At 1,800 bar, the energy stored in a pressurised shell is not small. A containment failure at that pressure releases fragments at ballistic velocity. The only responsible configuration is one where the operator is outside the cell, behind reinforced-concrete and interlocked doors, throughout the pressurised portion of the cycle. That meant every operation inside the cell — loading, sealing, pressurising, unloading — had to be machine-executed. No manual intervention during pressure hold was a non-negotiable line.

Production-line throughput

50 shells per hour translates to approximately 72 seconds per shell cycle, start to finish. That includes robot pick, placement into the chamber, sealing, pressurisation ramp, hold, decay evaluation, depressurisation, unsealing, and robot unload. A cycle that runs 20 seconds long every time turns a 50/hour spec into a 40/hour actual, and the bench instantly becomes the production bottleneck. Every sub-operation had a budget, and those budgets were tight.

Full certification chain from first article

The bench could not be commissioned, tweaked, and then put forward for approval. It had to arrive at its DGAQA acceptance test already compliant. That meant NABL-traceable calibration for every pressure transducer, MIL-STD-1522 design compliance for the pressurised boundaries, documentation traceable all the way back to the Indian Association for the Accreditation of Laboratories and NPL reference standards, and a full Factory Acceptance Test (FAT) completed at Neometrix's Noida facility before the bench ever saw the customer site.

3. The Neometrix solution — technical anatomy

The finished machine is a single-cell installation with a reinforced-concrete footing, a layered-steel containment chamber, and a robot island that integrates with the upstream conveyor from the machining line. Walking through it sub-system by sub-system:

Layered-steel blast containment chamber

The chamber is the single most consequential mechanical element on the bench. It has to contain a full-shell rupture at 1,800 bar without deforming and without secondary fragmentation. The design uses a layered-steel construction — multiple concentric shells, each heat-treated to a specific hardness profile, assembled with interference fits — rather than a single monolithic forging. Layered construction was chosen for three reasons: it delivers superior fragment-arrest behaviour (each layer absorbs and redirects spall), it simplifies non-destructive examination during fabrication, and it can be built in India from domestically-available forging stock rather than depending on a single foreign source for a high-integrity single-piece forging.

Around the steel containment, a reinforced-concrete outer shell adds redundant protection for the operator station and for adjacent equipment. The door is interlocked with the pressure system: the chamber cannot be pressurised unless the door confirms locked, and the door cannot release unless the chamber confirms vented.

Servo-hydraulic pressure generation with closed-loop PLC control

Pressure is generated by a servo-hydraulic circuit rather than by a stroke-controlled reciprocating pump. The servo valve modulates flow to a high-pressure intensifier, and the intensifier's output connects via rigid stainless-steel manifold to the chamber. The PLC closes the loop on output pressure, comparing measurement to setpoint at 1 kHz and adjusting the servo valve command accordingly. The result is smooth, pulsation-free pressure ramping at the programmed rate — typically 20 bar per second during production cycles, adjustable under recipe control.

ABB six-axis pick-and-place robot

An ABB six-axis robot sits at the robot island, reach-optimised for the three working points: the in-feed conveyor station, the chamber, and the accept/reject stacking area. The gripper was designed in-house by the Neometrix mechanical team to handle the range of shell calibres (155 mm and 105 mm shell bodies and mortar variants) without tool change. Grip pressure is servo-controlled so the same gripper passes delicately between calibres without dropping a heavier shell or crushing a lighter one. The robot's motion programme is integrated into the master PLC; the PLC, not the robot controller, owns the interlocks that govern when a pick or place is permitted.

Automated shell sealing and de-sealing system

The single most novel piece of intellectual property on the machine is the automated shell sealing system. Sealing a shell at 1,800 bar is not a commodity operation. The seal has to conform to shell geometry, close against an internal pressure that ramps to nearly 26,000 psi, hold that pressure without leakage for the duration of the dwell, then retract cleanly without damaging the shell body. There were no off-the-shelf seal cartridges available at these pressures in a form factor compatible with automated pick-and-place loading, so Neometrix developed the sealing architecture from first principles. Upper and lower sealing heads engage the shell ends hydraulically under PLC command; the design is patent-pending and is reused across the 155 mm, 105 mm, and mortar variants of the product family.

12-inch HMI with SCADA and test traceability

The operator station is outside the blast cell behind a reinforced window. The primary interface is a 12-inch industrial HMI running Neometrix's in-house SCADA on a Siemens PLC platform. The HMI exposes three working screens: recipe selection (shell type, target pressure, dwell, leak threshold); live trend (pressure, flow, decay rate at 100 Hz rendering); and batch management (operator ID, lot number, shell serial, pass/fail verdict). Everything the operator does or the machine decides is logged to a tamper-evident database with synchronised timestamps.

Emergency pressure dump

Above the normal control-loop depressurisation path, the bench carries a dedicated dump valve capable of discharging the chamber from 1,800 bar to zero in under two seconds. The dump is triggered by any one of five conditions: operator emergency stop, door interlock failure, pressure exceeding 105 percent of working limit, redundant transducer disagreement beyond the voted-threshold, or loss of PLC heartbeat. The dump line is sized per API 520 principles adapted to hydraulic service, with a direct routing to a shielded discharge reservoir.

4. Automation deep-dive: the 72-second cycle

The 50-shells-per-hour spec becomes real only because every sub-operation inside the cycle has been engineered to its time budget. Here is the sequence from the moment a shell reaches the loading station:

1. Arrival. The machined shell arrives on the upstream conveyor. A presence sensor and barcode reader notify the PLC, which cross-references the shell against the active recipe and validates that the shell type matches the loaded programme.
2. Robot pick. The ABB arm moves to pick, centres on the shell using a short camera sample, closes the servo-controlled gripper to calibre-specific grip force, and lifts. Budget: 8 seconds.
3. Place into chamber. The robot rotates to the chamber, drops the shell vertically onto its locating seat, and signals "placed" to the PLC. The door closes and confirms locked. Budget: 10 seconds.
4. Auto-seal. Upper and lower sealing heads drive against the shell ends under hydraulic command. Seal-force sensors confirm engagement within tolerance. Budget: 6 seconds.
5. Pressurisation ramp. The servo-hydraulic generator ramps pressure at 20 bar per second under closed-loop PLC control. For an 1,800 bar target this is 90 seconds nominal — but the cell runs shorter dwell cycles for production-rate sampling, and the 72-second production cycle uses a specified intermediate proof pressure and dwell as defined by the customer's acceptance protocol.
6. Hold. The PLC holds pressure at setpoint with 0.1 percent of full-scale accuracy. Two redundant NABL-calibrated pressure transducers sample at 1 kHz; the controller votes on their readings and flags any disagreement beyond threshold for immediate dump.
7. Decay monitoring. During the hold, the controller evaluates pressure decay against the pass/fail leak threshold specified in the recipe. A decay rate greater than the threshold flags the shell as a reject.
8. Depressurisation. Pressure is released in a controlled ramp through the main control path. The emergency dump path stays armed throughout the depressurisation and only disarms once the chamber confirms vented.
9. Unseal and unload. The sealing heads retract, the door unlocks, and the robot re-enters to remove the shell. Based on the PLC's verdict, the robot routes the shell to the accept stack or the reject bin. Budget: 10 seconds.

Total cycle, end to end, holds inside the 72-second production budget with margin. The margin matters — it absorbs the inevitable sub-second variability from conveyor arrivals, barcode reads, and network chatter without degrading the overall 50/hour rate.

5. Safety engineering at 1,800 bar

Ultra-high-pressure hydraulic testing has exactly one rule that matters more than any other: design as if the component will rupture, and make sure the operator survives. Every other decision flows from that rule.

The bench's safety architecture rests on five layers. First, the layered-steel chamber itself, sized for the worst-case fragment pattern from a shell rupture at design pressure. Second, reinforced concrete around the chamber, shielding adjacent equipment and the operator station even in the unlikely event the chamber sheds a fragment. Third, interlocked doors and barriers, with no path from operator-accessible space into the cell while pressure is above an arming threshold. Fourth, redundant pressure sensing: two NABL-calibrated transducers reading into separate PLC channels, with the voted controller going to dump if they disagree beyond tolerance. Fifth, the emergency dump, capable of the sub-two-second discharge described above, triggered by any one of five independent conditions.

An over-pressure hard stop sits above the dump logic as the final arbiter. If measured pressure exceeds 105 percent of the working limit the PLC commands dump unconditionally — no recipe override, no operator acknowledgement, no software retry. The hard stop exists because the expensive lesson in ultra-high-pressure testing is always the same: the controller you rely on to protect you has to have exactly one behaviour when the pressure is out of bounds, and that behaviour has to be immediate depressurisation.

The dump valve itself is sized using principles adapted from API 520 relief-sizing methodology — built originally for process gas and fluid systems, re-derived here for the rapid blowdown of a compressible hydraulic charge through a short, rigid line to a shielded reservoir. The sizing calculation had to account for fluid compressibility at 1,800 bar and for entrained air behaviour during the transient; neither term is in the standard relief-sizing template, and both had to be verified experimentally during FAT.

6. Data, certification, and audit trail

Every shell that goes through the bench generates a test record. The record carries the timestamped pressure-versus-time curve at 100 Hz, the pass/fail verdict with the decay value that produced it, the operator ID, the batch number, the shell serial, and the NABL calibration serial of the transducers in use at the time of the test. Records are written to a tamper-evident local database and exported in two formats for customer archival: CSV for machine-readable audit, and PDF for the DGAQA-format signed certificate.

The pressure transducers are NABL-calibrated at installation and re-certified on a scheduled annual basis — the calibration certificates are stored against the transducer serials and propagate automatically into every test record generated during that calibration window. When a transducer is replaced, the old unit's final calibration and the new unit's incoming calibration are both captured, and the database records the exact shell serial at which the changeover took place. The chain of custody from IAS-accredited laboratory through NPL reference standards to the test record against an individual shell is unbroken and verifiable.

The documentation package delivered with the bench included the full FAT record (every functional test run at Noida before shipment), the SAT record (the equivalent set after commissioning at the customer site), electrical and hydraulic schematics to customer document-control standards, PLC firmware listings with revision control, the SCADA configuration backup, operator manuals in English and Hindi, and the complete bill of materials with country-of-origin for every line item.

7. The Make-in-India bill of materials

The machine replaced a previously-imported capability. What follows is not an abstraction — it is a specific, auditable bill of materials in which domestic Indian content exceeds 85 percent by value. The breakdown reads:

The only imported element of significance is the ABB robot arm itself, sourced from ABB's global robotics supply. Even there, integration engineering, programming, calibration, and commissioning are all performed by Neometrix's automation team in Noida, and spare parts are stocked in India through ABB's domestic channel.

8. Results and lessons learned

The bench was commissioned on the customer's scheduled window and cleared DGAQA acceptance inside the originally-planned FAT + SAT period. The figures below reflect a full twelve months of production-line operation after acceptance:

Beyond the headline numbers, four engineering lessons came out of the project that shaped later Neometrix designs.

Servo-hydraulic beats stroke-controlled at ultra-high pressure, without exception

Stroke-controlled reciprocating pumps are the pragmatic choice up to roughly 700 bar. Above that, their pulsation envelope and dead-band behaviour make 0.1 percent accuracy unreliable even with downstream accumulation. Servo-hydraulic architecture — servo valve modulating an intensifier under closed-loop PLC control — is the only configuration that produces pulsation-free, setpoint-accurate pressure at 1,800 bar over thousands of cycles. The cost premium is real but the accuracy improvement is decisive. Every subsequent Neometrix design above 1,000 bar has adopted the same topology.

Auto-sealing IP had to be developed from first principles

No off-the-shelf seal cartridge existed in 2024 that combined 1,800 bar pressure rating, automated engagement and retraction, tolerance for the shell-end geometry variation that production machining actually produces, and a service life compatible with production-line running. Developing the seal in-house, patent-pending, became both a project risk that had to be retired early and an asset that now differentiates every subsequent high-pressure shell-testing machine in the Neometrix product family.

Layered containment beats single-piece forgings

Single-piece forgings at this chamber size are available only from a narrow set of suppliers, mostly outside India, with lead times that dominate the project schedule and prices that dominate the bill of materials. Layered-steel construction, correctly designed, delivers equivalent or better fragment-arrest performance; is easier to NDE during fabrication; scales more predictably; and sources entirely from Indian forging stock. On every subsequent ultra-high-pressure chamber Neometrix has built, layered construction has been the default choice.

PLC firmware revision control is a quality-system element, not a convenience

The DGAQA audit trail extends not only to the hardware that did the test but to the firmware that ran the hardware when the test was conducted. If the firmware was updated between shell 100,000 and shell 100,001, that fact has to be traceable, signed, dated, and recoverable decades later. Neometrix's firmware revision-control practice was strengthened materially during this project, with signed binaries, immutable version records in the test database, and full regression-test logs retained for every release. It is now a standard element of the delivery package on every regulated-sector bench we ship.