Steam traps

The Hoffman FT015H‑3 is the float and thermostatic trap I’d put on a low-pressure steam drip. It scores 9.0, tied for the top of this page, because Hoffman publishes everything from capacity to sizing steps.

It’s a Series H trap. Hoffman’s catalog lists it as part 404200: 3/4 in. NPT, a 15 psi seat differential rating, a 250 psi body design rating and 11.7 lb. The same body comes in 1 in. and 1-1/4 in. with the same ratings.

Capacity is in Hoffman’s table: 390 lb/h of condensate at 1/4 psi differential, 680 lb/h at 1 psi, 1,100 lb/h at 5 psi and 1,600 lb/h at 15 psi, through a 0.253 in. orifice.

The feature I value most is the four-port body. Hoffman says the second inlet is a place for a vacuum breaker or a separate air vent, and the second outlet takes a test valve, which saves a trap test chamber. Hoffman adds that vacuum breakers are required with a modulating temperature valve, and external air vents when the trap discharges into a wet return.

Service is simple. Hoffman says the cover assembly can be replaced without disturbing the piping. The internals are stainless: valve pin and seat, float, lever and the thermostatic air vent, which Hoffman says prevents air binding.

Hoffman lists the Series H as resistant to water hammer and corrosion, with a seat below the condensate level to stop steam leaking through, and as meeting military spec WW-T-696-E.

One listing note: the Amazon title calls the trap plastic. Hoffman’s catalog lists a cast iron body and cover, so I take half a point off the listing match. The part number, 404200, matches Hoffman.

Hoffman’s sizing steps are worth following: find the differential across the trap, use 1/2 psi where a modulating valve controls the steam, then multiply the load by 1.5 as a safety factor. The sizer below uses that rule.

The Barnes & Jones FT2015‑4 also scores 9.0. It’s the 1 in. size of Barnes & Jones’s Series 2000 float and thermostatic trap, rated 15 psi and built for steam heating, unit heaters, coils and low-pressure mains and risers.

The repair story is the reason to choose it. Barnes & Jones says all working parts mount on the cover casting, and its repair kit is a complete factory-assembled head that bolts on. No pipe connections need to be broken except on 2 in. models.

The body is an H-pattern: two inlet and two outlet connections, which Barnes & Jones says permit multiple piping options. That gives the same flexibility as Hoffman’s four ports.

Barnes & Jones publishes two capacity tables. The gross table, in line with ANSI/ASME PTC 39.1, gives the FT2015‑4 1,050 lb/h at 10 psi and 1,129 lb/h at 15 psi. The SHEMA table, which Barnes & Jones says needs no safety factor, rates it at 550 lb/h at 10 psi and 575 lb/h at 15 psi.

Use the right one. SHEMA ratings come from the Steam Heating Manufacturers Association standard for low-pressure F&T traps, which Barnes & Jones says provides for continuous air elimination at maximum rating. Gross ratings need your own safety factor.

Materials are listed: cast iron ASTM A278 Class 30 body, grade 5 bolting, stainless float, valve plug and seat, and a phosphor bronze and Monel thermostatic element in the air vent. The 3/4 in. and 1 in. body weighs 11 lb.

Barnes & Jones lists the Series 2000 as meeting MIL spec WW-T-696, with a PMO of 15 psi at 250°F and a PMA of 250 psi at 450°F for the 15 psi model.

It misses one check: the sheet gives no install steps. The Amazon listing carries the FT2015‑4 part number, which matches Barnes & Jones’s table.

The Spirax Sarco FT‑15 scores 8.3. Spirax is one of the biggest names in steam, and its data sheet for the FT series is the clearest on how to install the trap.

Spirax describes how it works: a float valve modulates to discharge condensate continuously at steam temperature, while a separate balanced-pressure thermostatic air vent releases air and other non-condensable gases.

The ratings: 15 psi maximum operating pressure for the FT‑15, a pressure shell rated 125 psi at 450°F, and a cast iron ASTM A126 Class B body and cover with stainless internals. The 3/4 in. and 1 in. sizes weigh about 9 lb.

Spirax’s capacity sheet gives the 3/4 in. FT‑15 279 lb/h of hot condensate at 1/4 psi, 489 lb/h at 1 psi, 785 lb/h at 5 psi and 1,075 lb/h at 15 psi, through a 0.218 in. orifice.

The install rules are the best part. Spirax says to put a strainer ahead of any steam trap, full-port isolating valves for servicing, and to mount the trap below the drainage point with a collecting leg before it. The float arm must be horizontal so the float rises and falls vertically, and flow must follow the arrow on the body.

Maintenance doesn’t disturb the piping. Spirax says to isolate the supply and return, then disassemble the trap periodically to clean the valve head and seat, mechanism and air vent. It sells a replacement module with the air vent and float mechanism on a new cover.

Spirax lists typical uses as process equipment with modulating valves, unit heaters, air heating coils, heat exchangers and steam main drip stations. Its spec text says the air vent withstands up to 450°F and resists water hammer.

It scores lower than the other two because the body has only the two main ports, no military spec is listed and the capacity basis is described only as hot condensate, without a named test standard.