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D&M Automatic Restarting Injectors


D&M Inline Steam Injectors

We are one of the original developers of the steam injector with patents dating back to the 1870s and an extensive history in the steam locomotive and traction engine world. Our injectors have been fitted to some of the most famous steam engines in the world and are renowned as being second to none in their quality and performance. Indeed, one of the other well-known injectors previously on the market by Penberthy were originally made under licence based on our design.

Fittings & Sizes

Our injectors come as standard with NPT bodies and BSP threads on the nuts and tails. Our latest developments allow them to operate effectively from low pressures right upto 250psi.

We currently make Brand New Inline injectors in sizes 3/8", 1/2", 3/4" and 1" as standard with other sizes available on request.
Injector internal copy.jpg
Operating Principles

1. Steam Valve is opened releasing steam through a series of jets building to a speed of around 2500 ft per second and creating a vacuum in the suction chamber.

2. The vacuum created draws water through from the tender/water supply. A mixture of water and steam pass through the injector and out of the overflow.

3. When the mixture of steam and water reach correct proportion the steam condenses as the mixture draws though the injector.

4. This builds up a pressure as it passes through the delivery jet into the boiler. When this delivery is established the overflow valve automatically closes.


As well as Brand New Davies & Metcalfe injectors we also overhaul and recondition virtually all types of steam injector including Penberthy. This includes injectors for traction engines both full size and scale model, sentinal steam wagon injectors, injectors for steam boats and stationary engines, model locomotives and right upto the biggest injectors for the World's largest locomotives.

This is subject to a free inspection of the body to ensure it is fit for purpose.

Capacity Table 

​Deliveries, Approximate deliveries in imperial gallons per hour.

Feed water at 74 degrees F. 3 foot lift.

Steam Injector Capacities
Deciding the correct size injector to install
This requires careful consideration with regards to the max and min steam pressure, the position and temperature of the feed water, and the evaporation of the boiler when steaming at full capacity.
The injector selected should be capable of passing approximately 75 per cent more water per hour than will actually be required by the boiler. For example, by referring to the capacity chart that for a boiler working at 100 lbs with an evaporation of 2,000 lbs per hour, feed water 3ft below the injector at a temperature of approx 74 degrees F, an injector capable of passing 3.55lbs or 300 gallons should be fitted. Therefore the correct size would be a 1" size CC. The fact this injector will deliver more is a definite advantage, and under no circumstances should the next smaller size be chosen.
Injectors must be fixed in a vertical position and the injector should work equally well with the water feed water supply either above or below.
Steam Injectors
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