Compression & Storage
Raising the gas to the pressure the storage or the customer needs, and holding it - heavy rotating machinery on stiff bases, vessel banks in a compound that is deliberately open and deliberately half empty, because the spacing is the control measure.
Last updated 2026-08-25
Typical duration
Typically 4-8 months for the compression and storage package, running alongside the rest of the plant. Delivery of the compression packages usually governs the start, and the alignment, grouting and joint records usually govern the finish.
What is Compression & Storage?
Gas leaves production at a modest pressure and generally has to be raised before it can be stored, loaded onto a vehicle or sent out. That job belongs to compression packages, which arrive as skids complete with their drivers, coolers, separators, controls and acoustic enclosures. They are heavy, they rotate, they are noisy, and they are almost always the most maintenance-hungry item on the site. Plant availability tends to be decided by them rather than by the process, which is why the design usually provides more than one and why the space around them for maintenance access looks generous until the first overhaul.
Storage is the other half, and it is what makes the business case work. Production follows the power available, demand follows the customer, and the two rarely line up, so a buffer sits between them. Above ground that means vessel banks or tube modules in an open compound. The compound looks empty on purpose. Spacing, orientation, the absence of a roof and the natural ventilation that comes with being outdoors are all design decisions taken by the designer, and they are the reason the storage area occupies more ground than its contents would suggest. At larger scale, storage can move underground into suitable geology, which is a specialist scope with its own disciplines entirely.
Two things dominate the quality story here, and neither is glamorous. The first is materials. Metals do not all behave the same way in this service over long periods, so the designer selects them deliberately and specifies the certification that must come with them. The site's obligation is traceability - the vessel, the pipe, the fitting, the fastener and the gasket installed must be the one specified, with a documented chain back to its origin. Substitution to keep a programme moving is not a site decision, ever. The second is joints. A small gas finds paths that other gases do not, so the design keeps the number of joints down and puts the remaining ones where they can be seen and reached. The site's contribution is to make those joints properly and to leave them accessible.
Compare the methods at a glance
When and why is Compression & Storage used?
Compression and storage follow production because there is nothing to compress until the plant runs, and they precede export because there is nothing to send out until the gas is at the pressure the offtake needs. They also sit on the critical path for a reason that has nothing to do with construction: the compression packages are long-lead items, frequently the longest on the site after the transformers, and the delivery date drives the phase far more than the installation work does. Commercially, this is the part of the plant that turns an intermittent producer into a reliable supplier. A plant running on variable renewable power produces when the power is cheap and available, while the customer wants a steady flow, and the buffer between them is often the entire justification for the investment. That is why the storage volume is sized by the commercial case as much as by the process. There is a strong technical argument for building this phase slowly. Rotating machinery installed on a base that is not stiff enough, or aligned in a hurry, or grouted with voids underneath, will vibrate for the rest of its life, and vibration is what turns sound joints into leaking ones over time. Storage installed without proper attention to how the vessels are supported and restrained will fight thermal movement instead of accommodating it. Both faults are cheap to avoid at installation and extremely expensive to correct once the compound is live and the plant is earning.
Types of Compression & Storage
Explore each method in depth - benefits, limitations, plant and quality control on its own page.
Packaged compression skids
Factory-built and factory-tested units delivered complete with driver, cooling, separation, controls and acoustic enclosure, landed on a prepared base and connected. The common solution because the package supplier carries the performance risk and the site work reduces to setting, aligning, grouting and connecting. The trade-off is weight, craneage, and a maintenance footprint that has to be respected in the layout rather than borrowed later.
Above-ground vessel banks in an open compound
Groups of vessels set out to the designer's spacing and orientation in an area kept open to the weather on purpose. Simple to install, straightforward to inspect and easy to expand, which is why most sites start here. The land take is the cost, and the layout is not adjustable - the arrangement is a control measure and the compound will not be allowed to fill up with anything else later.
Modular tube storage and trailer-based buffer
Storage arranged as transportable modules or as the vehicles themselves standing in a designated area, so capacity can be added, relocated or dispatched. Useful on sites where demand is uncertain, where the offtake is by road, or where storage needs to grow in steps. It brings vehicle movements into a classified part of the site, so the loading arrangements and the traffic layout have to be designed with as much care as the storage itself.
Large-scale underground storage
Where the geology allows and the volumes justify it, storage moves below ground and becomes a specialist scope with its own investigation, its own construction disciplines and its own long timescales. The surface works still belong to this phase - the compound, the compression, the pipework and the controls - but the store itself is designed and delivered by people who do nothing else, and it is not comparable to building a vessel bank.
Best suited for
- Plants running on variable power, where storage is what turns intermittent production into steady supply
- Sites exporting by road, where loading demands a buffer and a predictable stock on hand
- Schemes whose availability is governed by rotating machinery and therefore by how well it was installed
- Layouts where an open, generously spaced compound is the design solution rather than wasted land
Compression & Storage: step by step
- 1
Step 1: Set the compound out to the designer's layout
The compound is set out from the civils as-built survey, and the first job is to confirm that what was cast matches what the equipment expects. Spacing, orientation, the position of any barrier or separation structure, the access routes and the areas that must stay clear are all taken from the design and marked on the ground. This is the point to catch a discrepancy, because everything installed afterwards makes it harder to fix. It is worth being blunt with everyone joining the phase about why the compound looks the way it does: the empty ground between items is not spare land, the open sides are not an unfinished building, and the access routes are not just for deliveries. Storing materials, parking plant or erecting a temporary cabin inside the compound because it happens to be flat and empty is one of the most common and most serious mistakes made on this kind of site.
- 2
Step 2: Receive, place and secure the compression packages
The packages are the heaviest single items in this phase and often on the whole plant, so the lift runs to a written plan built on the supplier's confirmed weights, lifting points and centres of gravity rather than on the general arrangement. Each unit is inspected on arrival for transit damage and for the condition of its preservation before it leaves the trailer. Landing is done onto a base that has been surveyed and prepared, with the shimming, packing or soleplate arrangement the supplier specifies rather than an improvised one. Once down, the unit is set to line and level, checked, and secured before the crane is released. Everything about this step is recorded, because a compression package that ends up in dispute later - and they do - is defended by the installation record. Preservation is then re-established, and someone is named as responsible for maintaining it until the machine is commissioned.
- 3
Step 3: Align, grout and prove the rotating equipment
This is where rotating machinery is made or ruined. Alignment is carried out to the supplier's tolerance with proper instruments, checked for soft foot, corrected by shimming rather than by pulling the machine into place with its holding-down bolts, and recorded. Grouting under the baseplate is a controlled operation - the right product, mixed and placed to the manufacturer's instructions, with the forms, venting and placing sequence arranged so that no voids are left, because a void under a baseplate is a soft spot that will show up as vibration for the life of the machine. Holding-down bolts are tightened in the specified pattern to the specified value with calibrated tools. Alignment is then rechecked after grouting and again once the pipework is connected, because pipework pulling on a machine is one of the most common causes of persistent vibration, and it is far easier to prove now than to argue about later.
- 4
Step 4: Set the storage vessels and their supports
Vessels are lifted into position to the designer's layout using the lifting points provided and not improvised ones, with any protective coating and any internal preservation intact and checked. Supports, saddles and restraints are installed exactly as detailed, and the detail matters more than it looks: the design allows the vessel to move as it changes temperature while restraining it against everything else, and a support installed hard where it was meant to slide converts free movement into stress. Each vessel is identified against its certification on arrival and that identity is recorded against its position in the compound, so that years later the operator can point at a vessel and produce its paperwork. Levels and positions are surveyed once the bank is complete, because the interconnecting pipework is fabricated to the drawing and the bank has to match it rather than the other way round.
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Step 5: Install the interconnecting pipework, valves and connections
The pipework inside the compound is short but it carries a disproportionate amount of the risk, because it is nearly all joints. Materials, fittings, gaskets and fasteners are the specified ones, verified against their certification at the point of installation and not just at the gate. Valves and other in-line items are checked for identity, rating and orientation before they go in, and they are positioned where the design puts them so that they can be operated and maintained from where the operator will actually stand. Connections are made by qualified people to the designer's detail, and every one is recorded. Where a joint has to be bolted rather than welded, it is made square and aligned before it is tightened rather than pulled together by the fasteners, which is a habit that produces joints that pass on the day and leak six months later. Internal cleanliness is protected throughout, since debris left inside ends up in a valve seat.
- 6
Step 6: Route the relief, vent and blowdown systems as designed
Every pressure system needs somewhere for gas to go safely when the design says it should, and the arrangements for that are engineered rather than assembled. Relief devices, vent lines, blowdown routes and their discharge points are all specified by the designer, and their positions, orientations, heights, supports and terminations are part of the safety case for the plant. The site builds them precisely as drawn. This is the last part of a plant anyone should be tempted to adjust for convenience, and it is unfortunately the part most often shortened, redirected or resupported on the day because something else got in the way. Relief devices are identified and verified against the schedule before installation, their settings and certification are collected into the record, and the discharge routes are left clear, supported and protected. Where anything genuinely cannot be built as drawn, it goes back to the designer, because the discharge point was chosen for reasons that are not visible from the ground.
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Step 7: Complete the electrical, earthing, bonding and detection
The compound has its own electrical and instrumentation scope and every part of it is governed by the classification. Equipment installed here is checked against the classification drawing for its rating before it is fitted, cable entries and glands are made to the requirement rather than to habit, and any penetration is sealed as specified. Earthing and bonding are connected to the grid the civils installed, with continuity tested and recorded - bonding in a compound like this is not an electrical formality, it is a control measure, and it is checked as one. Detection devices are installed where the designer places them, with tag, type and position recorded, and their calibration certificates collected as they go in. Lighting, small power, control cabling and the connections to the shutdown system complete the picture. All of it is documented as installed, because the commissioning team will prove this compound function by function and they need to know what is actually there.
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Step 8: Preserve, protect and prepare for commissioning
Months can pass between a compound being mechanically complete and gas arriving, and machinery does not like waiting. Supplier preservation regimes are followed and signed for, with shafts turned, heaters energised, desiccants replaced and results recorded by a named person rather than assumed. Open ends stay capped, temporary protection stays on, and the compound stays clear. The installation record is assembled while the people who made it are still on site: alignment sheets, grout records, torque records, vessel identities against certification, weld and joint records, earthing test results, instrument calibrations and the as-built layout. Mechanical completion is declared honestly, against a punch list that separates work which must be cleared before anything is introduced from work that can wait. Handing over a compound with an optimistic list does not shorten the programme - it simply moves the work into the commissioning window, which is the most expensive place on the project to do it.
Plant & equipment
- Crawler and mobile cranes sized from confirmed package and vessel weights and lifting points
- Transporters, jacking systems and skidding equipment for moving packages within a congested compound
- Laser and dial alignment equipment for setting rotating machinery to the supplier's tolerance
- Grouting equipment, mixers, forms and sampling kit for baseplate and machinery grouting
- Calibrated torque and tensioning tools for holding-down bolts and bolted joints
- Welding plant and non-destructive testing equipment for interconnecting pipework
- Rigging, slings, spreader beams and specialist lifting frames for vessels and skids
- Preservation equipment and the means to record that preservation actually happened
Quality control & testing
- Package and vessel receipt inspection, with transit damage and preservation status recorded on arrival
- Machinery alignment carried out to the supplier's tolerance, recorded, and rechecked after grouting and piping
- Grout products, mixing and placing controlled and sampled, with the placing sequence planned to avoid voids
- Holding-down and joint fasteners tightened with calibrated tools in the specified pattern and recorded
- Vessel and component identity traced to certification at installation, with position recorded in the compound
- Pipework joints inspected to the regime the designer specified, with every joint numbered and recorded
- Earthing and bonding continuity tested and recorded, and detection devices verified against the schedule
Safety watchpoints
- Heavy lifting of packages and vessels within a compound whose layout restricts where a crane can stand
- Stored energy in rotating machinery, drives and control systems during installation and testing
- Noise from compression plant during any running, with hearing protection zones established early
- Hot work in a compound that will later be classified, controlled under a permit system without exception
- Simultaneous operations with pipework, electrical and instrumentation trades in a tight, congested area
- Manual handling and pinch points around vessels, saddles, restraints and heavy in-line components
- A compound layout that is a control measure, so storing, parking or erecting anything inside it is prohibited
- The transition of the area to the operator's permit system, after which the construction rules no longer apply
Common defects to hunt
- Misalignment and soft foot left uncorrected, giving vibration that shortens the life of every joint nearby
- Voids under a machinery baseplate because the grout was placed without a planned sequence or venting
- Fasteners tightened by feel rather than to a recorded value, leaving joints that pass today and pass gas later
- Vessel supports installed rigid where the design intended movement, so thermal expansion becomes stress
- Components fitted without traceable certification, discovered when the operator asks for the records
- Joints positioned where they cannot be inspected, reached or remade without dismantling something else
- Relief and vent routes shortened, redirected or resupported on site to suit access rather than the design
- Preservation signed for but never carried out, so machinery is worn before it has ever run in service
How long does Compression & Storage take?
Typical duration: Typically 4-8 months for the compression and storage package, running alongside the rest of the plant. Delivery of the compression packages usually governs the start, and the alignment, grouting and joint records usually govern the finish..