Model Boat Boiler Testing

DESIGN VERIFICATION

Before construction, the boiler examiner must see the proposed drawings to confirm that the design and materials are acceptable.


SHELL TEST

Boilers constructed by the owner will need to undergo a shell test. A new boiler has this initial test at twice the declared ‘working pressure’. It must be stripped of all cladding and fittings, and all but one of the bushes must be plugged. 

The test pressure will be increased in stages to prevent unnecessary distortion of the annealed copper. The test pressure will be maintained for a minimum of 10 minutes to allow thorough examination of all soldered joints.

Leaks from blanking plugs must be rectified and the test repeated, but any leak from a joint will constitute a fail. Minor distortion between stays will (at the tester’s discretion) be acceptable, but excessive bulging will constitute a fail. The boiler will then be drained into a jug to measure its capacity.

HYDRAULIC TEST (Every Four Years)

Brass fittings must be removed to check for dezincification, but cladding and bronze fittings may (if the owner prefers) be left in si’tu. All fittings except the safety valve are then to be attached.

The test pressure of 1.5 times the declared ‘working pressure’ will be applied in a single stage, and it will be maintained for a minimum of 10 minutes. The tester may require the cladding to be removed if the boiler fails to hold the test pressure.

Any leaks from the fittings must be rectified. 

STEAM TEST (Annually to a maximum of 14 months)

This is performed with the boiler installed in the model and fully operational. No stripping or preparation is required.

The test includes:
Cold examination to be performed prior to steaming the boilerPressure guage to be removed and calibrated against master gauge, then refitted if satisfactory

Boiler to be steamed at maximum firing rate. At maximum rate the working pressure must be maintained through the action of the safety valve.

Pressure must not rise beyond +10% of the working pressure with the engine stopped. Firing rate to be maintained to the examiners satisfaction Gauge glass operation to be verifiedIf fitted, water pump must be seen to be operating No evidence of leaks should be seen 

Refillable Gas TanksRefillable Gas Tanks up to 450cc capacity (tanks above this capacity are not acceptable).
Design Verification:

Before construction, the boiler examiner must see the proposed drawings to confirm that the design and materials are acceptable.

HYDRAULIC TEST  (Every Four Years)

Larger tanks require this periodic test.

The test pressure depends on the fuel mix being used, but is generally:
• 220 psig for plain butane (Blue Calor gas or lighter fuel).
• 380 psig for propane butane mixes up to 40% propane (Camping gas etc).

All but one of the bushes must be plugged, and the test pump, which has a 1/8” BSP male outlet, will be connected to the remaining bush. The boiler examiner must witness the tank being filled with water to ensure the minimum of air remains within.

The test pressure will be increased in stages to prevent unnecessary distortion of the annealed copper. The test pressure will be maintained for a minimum of 10 minutes to allow thorough examination of all soldered joints.

Leaks from blanking plugs must be rectified and the test repeated, but any leak from a joint will constitute a fail.

Minor distortion between stays will (at the tester’s discretion) be acceptable, but excessive bulging will constitute a fail.

Commercial tanks are supplied with a certificate that satisfies this test for the first four years.


GAS TEST (Every Year)

No preparation is required. The tank must have all fittings attached, and be filled with its normal fuel. It is immersed in slightly warm water to check for leaks.

If fitted, the pressure gauge should not be immersed. Any leaks must be rectified.

The owner should regularly check any stop valves to ensure they don’t leak when turned off. The tank must not be stored with gas in it if any leaks are detected (no matter how small they are).