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Large-diameter pipework running along the outside of a UK industrial building on steel supports, pale cladding behind, soft daylight along the run.

Application

Pipework, insulated as one continuous sleeve: no joints, no gaps at the bends, cut back cleanly at every support.

Runs, bends, tees and the awkward lengths between them: closed-cell foam is sprayed around the pipe as a continuous sleeve, then coated where it is exposed to the weather. It is the same system as a tank jacket, applied to the pipes that serve it.

Start a project brief What it costs: the cost guide
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01The build-up

The pipe stays. The sleeve goes on around it, bends included.

A cold pipe sweats along its whole length and drips from its underside; a hot pipe loses heat from every metre. Pre-formed sections leave a joint every metre and a gap at every bend. Switch the drawing between the bare run and the sleeved run.

Two states. Switch between them; the marks and the reading follow.

Swipe across to see the whole section.

BARE PIPE · CONDENSATION ALONG THE RUNSection, schematic, not to scale. Three marks in each state; the cards beneath read them.

Cold pipe · below the dew pointThe dew point · water formsAbove the dew point · dry

1The pipe

Thin wall, whole length exposed.

Steel or plastic a few millimetres thick between the contents and the air. A chilled or cold-water pipe sits below the dew point along its whole run; a heated pipe loses heat from all of it.

2Condensation and drips

The drip line under a cold pipe.

Water forms on the underside and falls in a line beneath the run, onto whatever is below. Corrosion starts at the supports, where the water collects. Sectional insulation with open joints puts the dew point at the joints.

3The pipe, in section

One thin wall, no resistance.

In section the problem is obvious: the whole circumference is exposed, and any insulation that does not close around it completely leaves a cold path.

The short version: pipework is the tank jacket's smaller cousin: a shape, sprayed around, then coated and cut back. Where pre-formed sections leave a joint every metre, the sleeve has none. The rest of this page is how it goes on properly.

02The order of work

Five steps, along the run.

The work is done along the pipe run in place, with the plant normally kept running. Each step is checked before the next begins. Pipework is a smaller and less common job than a roof, so the survey settles more of it up front.

  1. Pipe and supports

    Diameter, material, operating temperature, the supports and everything on the run (valves, flanges, gauges, trace heating) are recorded. Leaks at joints are repaired first, by someone else.

    HOLVEM checksSound run, no leaks; every fitting and support listed.

  2. Preparation and protection

    Old insulation and cladding come off. Corrosion product, oil and loose coating come off the pipe. Valves, gauges, supports and the area beneath the run are masked and protected.

    HOLVEM checksClean, dry pipe; everything that must stay accessible protected.

  3. Passes and depth

    Closed-cell foam is sprayed around the pipe in passes, working along the run and around bends and tees, to the specified depth. The sleeve is built up evenly around the circumference.

    HOLVEM checksApplied thickness measured and recorded along the run.

  4. Protective coating

    Once cured, exposed external runs are coated with a protective elastomeric coating to the specified thickness. Plant-room runs are coated where a cleanable or classified face is specified.

    HOLVEM checksCoverage and film thickness logged.

  5. Cut back and finish

    The sleeve is cut back cleanly at supports, valves, flanges and instruments, the edges closed and the coating carried over them. Anything that has to move or be maintained is left accessible.

    HOLVEM checksEvery fitting closed and finished.

A close detail of a bare steel pipe on a support bracket, condensation beaded along its underside and a rust stain spreading on the bracket beneath.
BeforeThe bare pipe at a support
The substrate as it is inspected: the pipe, the support, and the drip line that says what the contents do to it.

Every step is checked before the next. Thickness measured, coverage logged, compiled into a QA record at completion.

03Preparation

Before the first pass: what the run has to be.

Pipework carries the plant's working conditions along its whole length. Three things HOLVEM establishes first.

Sound and sealed

No weeping joints.

Foam over a weeping flange hides the fault and traps the product. Leaks are repaired first; the sleeve goes on a run that is doing its job.

Within range

Temperature, material and diameter.

The operating temperature of the contents has to be within the foam's service range: −40 °C to 82 °C, with intermittent peaks to 104 °C, on the NexSeal LE data sheet. Very hot process lines are a different insulation; HOLVEM says so at survey rather than spraying them.

Mapped

What stays accessible.

Valves, flanges, instruments, supports and trace heating are listed and the cut-backs agreed before the first pass. Nothing that has to move or be maintained is buried.

Survey, or photographs?How HOLVEM works: we understand your project before we price it

04Thickness and objective

The depth is set by what the run has to do.

Three objectives, three directions for the depth, each confirmed for your pipes and their contents. What it costs is on the cost guide, not here.

25 mmCondensation control

Stop the drip line.

Enough on most chilled and cold-water runs to keep the sleeve's outer face above the dew point of the surrounding air, so the pipe stays dry and the supports stop rusting.

50 mmHeat retention

Keep the contents at temperature.

Cuts the heat lost from heated runs or gained by chilled runs along their whole length, so the plant works less. The depth is calculated from the temperature of the contents and the loss you want to cut.

75 mm and aboveA specified heat loss

A figure to meet, for the process.

Set by the heat-loss figure the process needs, calculated for the pipe diameter, the contents and the site conditions. Specified per project and confirmed by the calculation.

A run of pipework wrapped in a smooth, continuous cream closed-cell sleeve finished in a pale protective coating, cut back neatly at a support bracket and a bend.
AfterThe sleeve, coated and cut back
The finished face: a continuous sleeve, the coating over it, the supports and fittings cut back and closed.

Thickness and objectiveWhat it costs: the cost guide

05Where it suits

Where the pipework is.

External pipe runs and plant-room services belong to process plant, agriculture and the buildings that serve them. Three building pages where this application is common.

Building

Industrial units and factories

Process and service pipework on working sites, sleeved in place without stopping the line.

Read the building page

Building

Grain stores and silos

The conveying and service runs around silos and bins, insulated with the vessels they serve.

Read the building page

Building

Cold stores and chill rooms

Chilled lines and refrigerant runs that sweat and drip wherever the insulation is broken.

Read the building page

Every building type HOLVEM works on

06What HOLVEM checks

Three things checked before anyone talks about depth.

HOLVEM does not quote a depth from a photograph. The run is understood first: what its contents do to it, what the coating has to withstand, and what heat loss the process can accept.

Condensation risk analysis

Will the sleeve's outer face stay above the dew point?

For a cold run, the operating temperature of the contents and the humidity around the pipe set the dew point the sleeve has to clear. HOLVEM calculates the depth that clears it, rather than assuming one.

The coating

What the weather and the site will do to it.

UV, rain, temperature cycling and the site's own hazards: the protective coating is chosen for them and its film thickness specified. Exposed external foam is never left as the finished face.

Heat loss

What the process can accept.

For a heated or chilled run, the heat lost through the sleeve at the specified depth is calculated for the pipe diameter and the site conditions, so the depth is a number the process can check, not a guess.

Condensation risk analysisU-values and Approved Document LFire performance and coatings

07Straight answers

Ask us the hard ones.

The questions people with cold or hot pipework actually ask on the call, answered the way the specialist answers them.

Why spray foam rather than pre-formed pipe sections?
Sections leave a joint every metre and a gap at every bend, tee and reducer, and the dew point moves to the joints. A sprayed sleeve is continuous around the whole run, fittings included, and bonds to the pipe so it cannot slip or open up.
Can you insulate pipes while the plant is running?
Normally yes, along the run in place, with the area sheeted and protected. The operating temperature of the contents is part of the specification; very hot lines are a different insulation and HOLVEM will say so.
What happens at valves, flanges and supports?
The sleeve is cut back and closed at anything that has to move, be read or be maintained, and the coating is carried over the edge. Supports stay supports; valves stay reachable.
Does the sleeve need a coating?
Outdoors, yes: exposed foam degrades under UV, so a protective elastomeric coating over the sleeve is part of the system. In a plant room the sleeve may be left as applied or coated for a cleanable face.
How do you prove it was done properly?
Applied thickness is measured and recorded along the run, coating coverage is logged, and the evidence is compiled into a QA record handed over at completion.

The next step

Your pipework.
Your brief.
A specialist.

If you already know the thickness or U-value you need, we price to it and confirm it is right; if not, we work it out with you. Tell us what the pipes carry, at what temperature, roughly how long the runs are and where they go. Photographs of the run and its supports are the most useful thing you can send.

Start a project brief Send photographs first

Or call . Enquiries received before 3pm on a working day are contacted the same day. After 3pm, the next working day. We understand your project before we price it.