EN 12845 Sprinkler Guards, Water Shields, Escutcheons and Corrosion Protection

Guards, the 75 mm water shield, the escutcheon rule and selecting a compliant coating — how the accessory clauses are applied on site.

Stripping bronze sprinklers fitted seven years earlier from the ceiling of a coastal hotel's indoor pool building, the picture was bad: deflectors under a green oxide layer, orifices blocked, bulbs weeping. When pressure dropped during the annual flow test, we understood that half the heads would probably not distribute water properly even if they opened. This article is about that scene: four small clauses in EN 12845 — guards, water shields, escutcheons and corrosion protection — that determine whether your project still works in ten years.

Where they sit

The accessory and protection clauses are collected in section 14:

• Sprinkler guards
• Sprinkler water shields
• Sprinkler escutcheons
• Corrosion protection of sprinklers

For coating compliance, the standard refers to EN 12259-1, the automatic sprinkler product standard. Galvanic corrosion measures appear again in the pipework clauses.

Guards — protection against mechanical damage

The clause is clear: sprinklers other than ceiling or recessed types, installed in positions at risk of accidental mechanical damage, must be protected by a suitable metal guard. So not every projecting upright or pendent head — but wherever there is a risk, a guard is mandatory.

The risky areas on site:

• Warehouse forklift aisles — where the pendent drop sits at 2.5 m, the risk of contact with forklift forks is high.
• Sports halls — basketballs and volleyballs strike routinely, and a bent deflector destroys the spray pattern.
• Beneath car parks — upright heads at the level of van and lorry bodies must be caged.
• Stages and performance spaces — frequently struck during set construction.
• Production lines with cranes — anywhere pallet lifting takes place.

Guards must be metal; plastic and wire mesh are not accepted. Use the specific listed sprinkler with its own listed guard; a random cage can change the spray distribution unpredictably. The listing must state that the spray density test was passed with the guard fitted.

Water shields — mandatory in racks and on intermediate levels

This is the most commonly mishandled part of in-rack sprinkler design. The standard states that sprinklers installed in racks, or beneath perforated shelves, platforms or floors — where water from a sprinkler above could wet the bulb of one below — must be fitted with a metal water shield of at least 0.075 m (75 mm) diameter.

The mechanical logic is simple: when the upper head operates, cold water falls. The 3 mm glass bulb below takes a thermal shock and either opens late or does not open at all — the cold soldering effect. The shield cuts that dripping so the head below senses its own fire gases.

Configuration	Water shield	Diameter
In-rack, multi-level	Mandatory	≥ 75 mm
Beneath a perforated intermediate platform	Mandatory	≥ 75 mm
Pendent beneath a mezzanine	Generally mandatory	≥ 75 mm
Single-level ceiling sprinklers	Not required	—
ESFR (high-bay K200/K320)	Design specific	Per EN 12845-2

A further detail: on upright heads, the water shield is not attached directly to the deflector or the yoke. Any bracket must be shaped so as not to obstruct the spray. In practice the manufacturer's certified accessory set must be used; a plate welded up on site falls outside the listing.

Escutcheons — simple but rule-bound

The escutcheon is often treated as an architectural request, but the clause sets three concrete rules:

1. The material must be metal or thermosetting plastic. Thermoplastics — soft PVC and plastics that go brittle in the cold — are outside the standard.
2. The escutcheon may not be used to support the ceiling or any part of the structure. Hanging a net from the sprinkler body is prohibited; the escutcheon is aesthetic and closes the gap, nothing more.
3. The escutcheon may not extend below the visible top of the heat-sensitive element. This is the rule most often ignored: a deep recessed escutcheon can delay fire gases reaching the bulb.

Where a concealed sprinkler is used, the cover plate's thermal performance comes from the manufacturer's listing; you cannot add an arbitrary cover for appearance. Plate and sprinkler must come from the same listed set.

Corrosion protection

The clause is short but comprehensive: sprinklers installed in premises where corrosive vapours predominate must be protected by a corrosion-resistant coating applied by the supplier in accordance with EN 12259-1, or manufactured from a corrosion-resistant material. Corrosion-inhibiting treatment is not applied to the bulb.

Three details matter here:

• The coating must be applied by the supplier — painting on site voids the listing.
• The coating must have passed the K-factor and activation time tests under EN 12259-1.
• The bulb is never coated — it destroys thermal sensitivity. Bulb operation is delayed by 5–10 seconds under a coating.

Corrosive environments

Environment	Corrosive agent	Recommended protection
Coastal hotels and piers	Salt vapour (chloride)	Wax or PTFE coating; stainless steel body
Chlorinated pool halls	Chlorine gas, condensate	Wax coating (most common); stainless
Cold stores at −20 °C	Condensate, freeze-thaw	Wax plus dry pendent; stainless
Chemical plants (acid)	HCl and H₂SO₄ vapour	PTFE or ETFE coating; full stainless
Galvanising plants	Ammonia, acid fumes	PTFE
Wastewater treatment	H₂S	PTFE or stainless
High humidity (pools, spas)	Chlorine plus condensate	Wax coating

Coating types

• Wax coating: the cheapest, common on coastal sites and pools. Wax softens above about 60 °C, so read the manufacturer's temperature range.
• PTFE: the most robust against acid and alkali vapours. Expensive but with a twenty-year life; white or yellow in appearance.
• Polyester epoxy: moderate resistance with better impact tolerance, and available in colours. Less durable than PTFE in chlorinated environments.
• Stainless steel body: the whole body in 304 or 316L rather than a coating. The most durable and the most expensive; the bulb is still glass.

Galvanic corrosion between pipe and sprinkler

Galvanised steel pipe with a bronze sprinkler forms a galvanic couple; with wetting and humidity, white oxide appears outside and corrosion products build up inside. The standard requires measures against galvanic corrosion. The practical steps:

• A stainless or PTFE-taped intermediate connection on galvanised runs.
• Avoid a bronze sprinkler directly into a hot-dip galvanised fitting; use a galvanised nipple or stainless adaptor between them.
• In cold store wet pipe systems, freeze-thaw condensate seriously attacks the internal surface of black steel; mixing black and galvanised pipe is never recommended.

Field case: a system dead in five years

On a holiday resort's indoor pool building (50 × 18 m, with high chlorine levels), standard bronze K80 pendent heads had been used. When we tripped three heads at the mandatory annual flow test five years later:

• Seven orifices were blocked with green-blue copper oxide.
• Two bulbs had taken chlorinated water through a crack and changed colour, destroying thermal sensitivity.
• Salt crystals on the deflectors made the spray pattern unpredictable.

One cause: the designer had skipped the corrosion clause, treating the pool hall as a comfort space rather than a hazard classification. The fix was replacing every head with a wax-coated pendent and adding a five-year inspection plan. The unit cost difference was about €4 per sprinkler — €720 across 180 heads. The replacement operation cost around €18 000, twenty-five times more.

Certification and listing

EN 12845 does not approve the sprinkler product itself; that is EN 12259-1's role. The documents to require from the supplier:

• An EN 12259-1 declaration of conformity, with mandatory CE marking.
• Independent approval — LPCB, VdS, FM Approvals or UL listing. Most insurers in Turkey ask for LPCB or VdS.
• For coated sprinklers, the corrosion-resistant coating sub-listing must be shown separately; a single-line note is not enough, and the coating type should appear in the product code (W for wax, T for PTFE, S for stainless).

Comparison with NFPA 13

Item	EN 12845	NFPA 13
Guards	Metal, where risk exists	Listed guard required
Minimum water shield diameter	75 mm	76 mm (3 in) — effectively identical
Escutcheons	Metal or thermoset	Listed escutcheon
Corrosion coating	EN 12259-1, supplier applied	Listed corrosion-resistant
Site painting	Prohibited (voids the listing)	Prohibited

In practice an LPCB-approved wax-coated sprinkler is often also FM Approved, and selection generally comes from the same catalogue. The one difference: NFPA 13 does not treat dry pendents as corrosive-duty items, while EN 12845 is more sensitive to corrosion risk.

Turkish context

BYKHY requires sprinkler systems to be built to TS EN 12845. It does not name accessories explicitly, but the phrase "the conditions specified in the standard" brings the accessory clauses in automatically. At site inspection, the fire inspector asks three things:

• Where there is a chlorinated pool hall: what coating type, certified by which laboratory?
• Where there are in-rack sprinklers: is there a 75 mm water shield, and has the diameter been checked?
• In car parks and similar areas: are guards fitted, and has the manufacturer's listing been shown?

Insurance requirements specifically look for LPCB or VdS listing; FM Approvals is also accepted, but domestic approvals alone are not sufficient.

Common errors

• Spray painting bronze sprinklers on site. Lengthens activation time and voids the listing.
• Using thermoplastic (PVC) escutcheons. The standard requires thermoset or metal; PVC yellows and cracks with time.
• Cutting a water shield from plate outside the manufacturer's set. The geometry disrupts the spray pattern and voids the listing.
• Screwing a bronze sprinkler directly into galvanised pipe. Galvanic corrosion starts within two to three years.
• Using a standard upright in a cold store. A wax-coated dry pendent is required.
• Buying the cover plate for a concealed sprinkler from a different manufacturer. The thermal response is then unlisted.

Frequently Asked Questions

When is a sprinkler guard required?

Wherever a non-recessed head is at risk of accidental mechanical damage — forklift aisles, sports halls, car parks, stages. The guard must be metal and listed with that sprinkler.

Why is a water shield mandatory in racks?

Because water from an upper head cools the bulb below, delaying or preventing its operation. A metal shield of at least 75 mm diameter cuts that dripping.

Can a sprinkler be painted on site?

No. Corrosion-resistant coating must be applied by the supplier and tested under EN 12259-1. Site painting delays activation and voids the listing.

Which coating suits a chlorinated pool hall?

Wax coating is the most common and economical; PTFE is used where acid or alkali vapours predominate, and a stainless body is the most durable option.

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