SC20 sample cooler for safe boiler and steam sampling

The Spirax Sarco SC20 is a compact sample cooler for cooling boiler-water, steam and condensate samples before they are handled or analysed. Its stainless steel sample coil carries the sample while cooling water flows in the opposite direction through the stainless steel body. This counter-current arrangement uses the available temperature difference efficiently and helps produce a cooler, more representative sample at the outlet. For engineers looking for a Spirax Sarco SC20 sample cooler, the important selection question is the complete sampling arrangement: the source fluid, the expected flow, cooling-water availability, connection standard and the safe place where the cooled sample will be collected.

SC20 is a single-model product page. The documented construction is an austenitic 316L stainless steel body and 316L stainless steel coil. The standard water connections are 1/2 in BSP or 1/2 in NPT, while the sample side uses 6 mm outside-diameter tube. A version with a metal sanitary clamp connection is also documented. The cooler is supplied with mounting brackets at the top and bottom so it can be secured vertically. The body and coil are not internally polished or specially treated; clean-steam service that requires the separate hygienic specification should be assessed as a different product requirement.

How the SC20 arrangement works

Hot boiler water, saturated-steam condensate or another permitted water sample enters the sample coil. Cooling water enters the cooler body through the lower water connection and leaves at the upper connection, flowing counter to the sample. The sample outlet does not need to be hard-piped to a closed system: the installation guide describes a funnel below the outlet with enough room for a measuring cup or similar vessel. This open, visible arrangement can make sampling practical, but it also means the discharge point must be planned for hot water and any site-specific contamination risk.

The SC20 does not replace the upstream isolation and sampling valves. A sample inlet should be connected directly to the boiler or steam-line isolation valve, or to a blowdown sampling connection where a TDS control system provides one. The cooling-water line should be clean to limit scale. Piping should be corrosion-resistant for the sample, kept as short as practical and arranged without creating an air lock at the cooler outlet. These details are part of the performance of the complete sampling station, not optional accessories to be added after commissioning.

Applications and selection boundaries

Typical duties include checking boiler-water chemistry, collecting a saturated-steam sample and cooling condensate for laboratory or operator analysis. The technical information gives a worked example rather than a universal rating: at 10 barg boiler pressure, a 30 l/h sample flow and 0.3 l/s cooling-water flow, the stated approach is 4 °C. With 15 °C cooling water, the sample outlet is approximately 19 °C in that example. Actual outlet temperature depends on the installed flow rates, inlet temperatures, pressure and the condition of the cooling-water circuit, so the example must not be treated as a guaranteed capacity for every system.

Connection selection should identify BSP or NPT cooling-water threads and the sample-tube arrangement. The documents also list SCS20 assemblies with inlet valves and either carbon-steel or stainless-steel fittings, plus separate 1/4 in BSP or NPT male by 6 mm outside-diameter stainless fittings. Those are ordering options associated with the SC20 arrangement; they do not turn the SCS20 assembly into a second product model on this page. Clamp connections require the clamp manufacturer's pressure and temperature limits, which must be checked before ordering because the SC20 documents do not state one unconditional rating for every clamp configuration.

For broader system context, the sample cooler product category provides the available product route. The SC20 page itself remains focused on the exact model. SSC20 is not interchangeable by assumption: it is a separately documented clean-steam sample cooler with different internal treatment, so it should be specified only when the hygienic requirement has been established.

Installation and operation priorities

Mount the SC20 vertically using the holes in the top and bottom brackets. Connect cooling water to the lower 1/2 in connection and discharge the upper connection to a drain or funnel. Keep the thread engagement of the outlet elbow within the documented limit so that the fitting does not project into the body. Before opening the sample valve, open the cooling-water valve and confirm a full, steady flow. Then open the sample valve slowly and allow the cooler to bring the sample down to the required temperature before collecting it. Close the sample inlet first and the cooling water second. The sample line and cooler surface can be hot during normal service, so the outlet and collection point need protection from contact and splashing.

The installation and maintenance guide requires competent personnel, pressure isolation, cooling before work and verification that materials, pressure and temperature limits suit the intended service. SC20 is identified as a SEP product under the Pressure Equipment Directive and is specifically designed for steam and water in Group 2; other fluids require confirmation with the manufacturer. The unit has no routine maintenance requirement, but the documented spare parts include BSP and NPT sample inlet valves and several tube fittings. Isolation, safe venting and site permit procedures still apply before replacing any component.

Dimensions, ordering and enquiry checklist

The approximate SC20 envelope is A 410 mm, B 350 mm, C 300 mm, D 90 mm, E 27 mm, F 23.5 mm, G 13 mm, H 450 mm and J 55 mm. The approximate cooler weight is 3.1 kg. These values are useful for clearance and support planning, but the dimensional drawing and selected connection arrangement should be checked for the final order. When specifying a Spirax Sarco SC20 sample cooler, confirm the model, cooling-water connection standard, sample-tube or clamp arrangement, upstream valve configuration, sample fluid, expected sample flow, cooling-water flow and the discharge method. Confirm any site requirements for material compatibility, certification and safe sampling before release.