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The stack is a fifth of the plant. We build the rest.

Pressure equipment, process skids and balance of plant for green hydrogen. Built and lined in Bockenem, Lower Saxony.

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Ø5.5 m
Max diameter, Bockenem
25 t
Max weight, Bockenem
300 t
Single equipment, group works
Why balance of plant

Most of a hydrogen plant is pipework, vessels and steel.

The electrolyser stack is 14 to 24% of what a hydrogen plant costs to install. Balance of plant, utilities and construction take 60 to 76%. (Source: European Hydrogen Observatory.)

The rest of the plant is separator vessels, KOH circulation skids, demineralisation packages, coolers, dryers, buffer storage, pipe spools and racks. Much of it is Category III and IV pressure equipment. Most of it needs corrosion protection that survives hot caustic.

HAW has built this kind of equipment in Bockenem since 1899, for the chemical and power industries, under the codes German buyers specify.

Keep your stack vendor. Let us quote the other three-quarters.

Range of supply

What we would like to quote

Mapped to the hydrogen train, and to the commodity groups your buyers purchase against.

Gas–lye separation

Separator vessels, demisters, knock-out drums and lye receivers. Lined or alloy.

KOH circulation

Circulation skids, pumps and manifolds, heat exchangers and filtration. Lined carbon steel for hot caustic.

Water treatment

Demineralisation packages, feed tanks, dosing skids and containment.

Gas cooling & drying

Coolers, condensate separators, dryer vessels and adsorber pairs.

Buffer & storage

Buffer vessels, receivers and low-stage compression bottles.

Piping & interconnect

Pipe spooling, manifolds, jacketed lines and expansion joints. Shop-fabricated, NDT documented.

Structural & modular

Skid frames, pipe racks, platforms and containerised modules.

Corrosion protection

Rubber, PVDF, PP, PE, PTFE, glass flake, FRP, brick and tile. 13 rubber compounds mixed in house.

We are strongest where a pressure boundary meets an aggressive medium. Hot KOH eats carbon steel, and solid alloy prices the vessel out of the job. A lined vessel solves both. If your separator or lye circuit is priced in exotic alloy, let us price it lined.

A separator or lye circuit to price?

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Related Pages

Brochure

The works · Bockenem, Lower Saxony

What fits through the door

Werkstraße 30–33, 31167 Bockenem. Steel, lining, machining and testing on one site, under one quality system. The site covers 120,000 m². Its 30,000 m² covered lining shop floor is the largest in the world.

5,500
mm
Max outside diameter
15,000
mm
Max length
3–22
mm
Wall thickness
25
tonnes
Max weight

Above that, we engineer and build at the group works, then inspect here. The group rolls plate to 95 mm thick and 3 m wide, presses dished ends to Ø5.5 m and 65 mm on 600 t presses, and builds single pieces of equipment to 300 tonnes. It has delivered equipment to more than 40 countries.

The HAW advantage

We build it, then we line it

The steel shop and the lining bays share a roof. Europe's largest vulcanising autoclave cures linings at the same site, to 150 °C. HAW is the only works that builds and lines equipment under one roof.

German codes

The codes German buyers specify

We issue calculations to AD 2000-Regelwerk or EN 13445, or build to your drawings. Material certificates come to EN 10204 3.1 as standard, and 3.2 where you specify it.

Technology partnership

A stack from India. Everything around it, from here.

HAW works in technology partnership with Greenzo Energy India Limited, which develops and manufactures alkaline electrolysers. Greenzo builds the stack. HAW builds the pressure equipment, skids, water treatment and lining that turn a stack into a plant, in Germany. Already have a stack vendor? The fabrication offer stands on its own.

A

Complete hydrogen system

Stack, balance of plant, water treatment, lining, installation and commissioning on one European contract.

B

Balance of plant only

You keep your stack vendor and your process guarantee. We build the fabricated scope to your specification and your ITP, as your subcontractor or a nominated supplier to your EPC.

Reference projects

Comparable work, at scale

None of our references are hydrogen projects. These show the same problems: lined circuits carrying aggressive media, and heavy equipment to fixed dates. We do not name customers. Named references are released on request, subject to customer consent.

Coal-fired power station

Flue gas desulphurisation circulation, re-lined

We modernised the circulation system of two flue gas desulphurisation trains: eight pumps, and the suction and delivery mains that feed them. GBT Bücolit, our sister company, was main contractor for the whole job. The 300 tonnes of large-bore pipe were lined with HAW W06 butyl at 4 mm at Bockenem, autoclave cured, with HAW H94 on the flange faces. An alkaline electrolyser circulates hot KOH through pumps, exchangers and large-bore pipe. It is the same problem.

300 t
Large-bore pipe
8
Pumps
HAW W06
Lining, 4 mm
14 months
Duration
Chemical plant, Germany

Flue gas ducting, engineered from a scan

We laser-scanned the existing duct and re-engineered it through detailed design, static calculation and 3D modelling. We built and coated more than a hundred components at Bockenem, erected them, welded and examined the joints, and air-tightness tested the finished assembly. One party answered for it from survey to tested assembly.

1,200 t
Ducting
>100
Assemblies
10 months
Scan to test

Trade fairMeet us at Hydrogen Technology Expo Europe, Hamburg, 20–22 October 2026.

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Common questions

Green hydrogen, answered

Do you make electrolysers?

No. HAW works in technology partnership with Greenzo Energy India Limited, which develops and manufactures alkaline electrolysers. We build the balance of plant around the stack, and we will serve whichever stack you chose.

Have you built a hydrogen plant before?

No. None of our references are hydrogen projects. They are comparable pressure and process work: lined circuits in aggressive media, heavy equipment and site erection against fixed dates.

Which design codes do you work to?

We issue calculations to AD 2000-Regelwerk or EN 13445, or build to your drawings. Material certificates come to EN 10204 3.1 as standard, and 3.2 where you specify it.

How do you handle hot KOH service?

Concentrated KOH at temperature attacks carbon steel, and solid alloy prices the vessel out of the job. Lined carbon steel answers both. HAW patented the bonding of vulcanised rubber to steel in 1920 and mixes 13 rubber compounds in house.

Can we audit the works?

Yes. We open Bockenem for supplier qualification audits at reasonable notice: shop floor, quality laboratory, autoclave bay and document control. Bockenem is two hours from Hamburg by train.

One scope to quote

Send us a live enquiry, however small. Separator vessels, a lye skid, pipe spools or a structural package. We would rather earn the Category IV work than ask for it.

+49 (5067) 990-0