Armstrong JD and KD Ultra-Capacity Ductile Iron F&T Steam Trap

Very large condensate loads from one ductile iron trap

The Armstrong JD and KD Series are ultra-capacity float and thermostatic steam traps in ASTM A395 ductile iron, made for horizontal installation with an integral thermostatic air vent. They are the large end of the F&T range: Armstrong quotes capacities to 64,400 kg/h and pressures to 21 bar, from a single body with all floats, valves, seats and lever mechanisms in stainless steel. In general engineering terms that is the duty of very large heat exchangers and air heaters, where condensate quantities overwhelm a standard F&T trap.

Air is handled by a balanced-pressure phosphor bronze bellows caged in stainless steel. Armstrong says this vent responds to the pressure-temperature curve of steam at any pressure from zero to 21 bar, so air leaves at slightly below steam temperature. The data sheet notes the design is meant for heavy-duty industrial applications where uninterrupted service is essential, and lists a maximum back pressure of 99% of inlet pressure.

Technical specification

Maximum operating pressure by model (saturated steam)

Dimensions and weights (mm and kg)

Model codes, options and special configurations

The model code combines the pressure rating, the series and the connection size, for example 75 JD 8 VB: the leading 75 is the pressure model (5 bar for the 75-JD), JD the series, 8 means DN50, and VB adds the vacuum breaker. The KD size codes are 8 (DN50), 10 (DN65) and 12 (DN80). Option suffixes are VB for an integral vacuum breaker (10 bar maximum), LD for a liquid drainer without the thermostatic vent, CC for a condensate controller and GG for an armored gauge glass rated 17 bar at 217 C.

The CC configuration adds a fixed, restricted orifice near the top of the body to bleed off flash steam and air. It was developed for syphon drainage and cascade service, where condensate is lifted from the drain point to the trap and part of it flashes; an ordinary trap cannot tell flash steam from live steam and closes. The LD liquid drainer uses the access port in the top of the body as a back vent connection to prevent air or gas binding, for draining water and other liquids from air or other gases under pressure. The vacuum breaker (1/2 in NPT, 3/8 in connection, 30 mm high, 22 mm hex) is useful where vacuum can hold back condensate.

Where ultra-capacity traps are specified

Large heat exchangers, multi-bank heating coils, dryer cylinders and similar equipment in refineries, petrochemical and fertiliser complexes, power stations and desalination plants are the natural homes for a JD or KD trap. A single trap that handles up to 64,400 kg/h avoids ganging several small traps, and ductile iron gives a robust body for the 21 bar rating.

Because ductile iron and a phosphor bronze bellows are limited by temperature, keep to the 217 C bellows limit and the flange derating noted in the data sheet. For steam above that, ask the manufacturer for another trap type. Capacity curves for the JD, the 30-K8, the 50-KD10 and 300-KD10 and the 300-KD12 are printed as graphs in the data sheet and should be read at the actual differential pressure.

Selection and installation notes

Specify a steam trap from the steam pressure, the condensate load and the connection size, and check the body material and the pressure rating against the system. Fit a strainer upstream, a union or flange for easy removal and isolation valves either side, prime the trap with condensate before start-up where the type requires it, and protect it from freezing. Inspect traps on a regular schedule to find failures early, because a failed trap wastes steam or floods the line.

Information needed for a quotation

Send the full model code, the quantity, the delivery location in Oman or the GCC, the intended use and any accessories needed, so that the complete package can be quoted together.

Documents and supply information

The manufacturer data sheet is attached to this page and should be read together with the project specification and the site risk assessment before a purchase is confirmed. Ratings, standards and dimensions are quoted as printed on that sheet. Lead time, stock position and certificates available with the shipment are confirmed in the quotation, and we supply to Oman and the wider GCC region for industrial, utility and building services projects.

Documents and quotation

The official EMEA data sheet is attached. Armstrong also publishes a cast iron L and M Series ultra-capacity F&T trap for pressures to 17 bar. Related steam fittings are in pipes and fittings. Seven Star LLC is an independent supplier in Muscat; send the model, connection size, flange standard and any option suffix and we will confirm the configuration against manufacturer data before we quote.