PRODUCT FEATURES
Union Flat Ptfe Ff — Product Features
Food & beverage equipment, water treatment, pharmaceutical piping, chemical industry, machinery, cooling & heating systems, marine plumbing, pump and valve connections, process lines requiring frequent disassembly.
Product Feature
Buyer Notes
Product Feature
EN 10204 3.1 material test certificate can be provided for bulk orders. OEM marking is acceptable. Samples available for dimensional and leak test verification before mass production. Please confirm thread type and size before order. PTFE gasket spare parts can be supplied separately upon request.
OPERATING PRINCIPLE
How Union Flat Ptfe Ff Works
1. Flat-face sealing design (FF, female-to-female): Features female threads at both ends with a flat-face sealing structure, equipped with a replaceable PTFE (polytetrafluoroethylene) gasket.
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2. PTFE flat gasket
Offers excellent chemical resistance, heat resistance, and non-stick properties; suitable for acids, alkalis, oils, and high-temperature media. Easily replaceable when worn.
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3. Three-piece union design
Comprises two main body components and a hex nut, facilitating easy installation and disassembly.
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4. AISI 304 stainless steel
Provides good rust resistance in freshwater, mildly corrosive environments, and outdoor installations.
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5. Precision-machined threads
Available with BSPP, BSPT, or NPT thread options, compliant with ISO 7-1, DIN 2999, or ANSI B1.20.1 standards.
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Operation 5
6. Compliant with ISO 4144; pressure ratings include PN16 (150LB) and 3000LB. Ensures stable performance under rated pressure and a leak-free seal when properly tightened.
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7. Pickled and passivated surface
Provides a clean finish and enhanced corrosion resistance; custom marking options available.
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8. Comprehensive size range
Covers all sizes from 1/8″ to 4″ (DN6 to DN100).
ENGINEERING DATA
Technical Specifications
Technical data supplied for Union Flat PTFE FF. Ratings and material combinations should be confirmed for the selected configuration.
| PARAMETER | SPECIFICATION |
|---|---|
| – Material | AISI 304 (1.4301 / ASTM A182 F304) |
| – Type | Flat-seat union with PTFE gasket (female-to-female thread) |
| – Standard | ISO 4144 |
| – Thread | BSPP / BSPT / NPT |
| – Pressure Rating | PN20 (150LB, 20 bar) |
| – Sealing | Pure PTFE flat gasket |
| – Surface Treatment | Pickled and passivated |
| – Operating Temperature | -20°C to +120°C |
MECHANICAL DIMENSIONS
Dimensions & drawings.
Compare connection size with the corresponding overall length, bore and handle clearance dimensions from the supplied drawing.
Dimension chart
| SIZE | H | D | D1 | W |
|---|---|---|---|---|
| 1/4 | 31 | 9 | 14 | 12 |
| 3/8 | 33 | 12 | 17 | 13 |
| 1/2 | 39 | 16 | 21 | 14 |
| 3/4 | 42 | 21 | 27 | 16 |
| 1″ | 44 | 28 | 34 | 17 |
| 1-1/4 | 53 | 36 | 42 | 19 |
| 1-1/2 | 55 | 42 | 48 | 20 |
| 2″ | 60 | 53 | 60 | 21 |
| 2-1/2 | 62 | 73 | 83 | 26 |
| 3″ | 67 | 85 | 95 | 27 |
| 4″ | 120 | 110 | 122 | 28 |
Refer to the supplied dimension chart.
APPLICATIONS
Applications
Applicable media: the supplied document lists the following fluids. Actual compatibility depends on selected materials, concentration, temperature, pressure and the specific service conditions.
Application – Water Circulation
Cooling water, circulating water, drinking water and neutral purified water.
Application – Steam Piping
Clean, low-temperature saturated steam, subject to the product’s confirmed temperature and pressure limits.
Application – Compressed Air
Compressed air and nitrogen; verify compatibility for each system.
PURCHASING SUPPORT
Frequently Asked Questions
Find answers to common questions about sizing, materials, threaded connections and operating conditions.
What does “Union Flat PTFE FF” mean exactly?
FF means **Female × Female threads on both ends**. Flat = flat sealing seat (not conical seat). PTFE is the removable PTFE gasket between the two flat faces for sealing. It is a 3-piece demountable union: two female thread bodies + one hex coupling nut + one PTFE gasket. The seal relies on the flat face compressing the PTFE gasket, not thread taper seal.
What thread standards are available for this FF flat union?
Standard: **BSPP (G / ISO228-1 parallel thread)** (most common for this flat PTFE FF type). Optional: BSPT (Rc), NPT.
Important note: Flat seat PTFE FF is mostly designed for parallel BSPP; tapered thread version is less common. Please confirm thread type before order. Threads are NOT interchangeable.
What stainless steel grades do you supply?
Standard grades:
– 304 / CF8
– 316 / 316L / CF8M (1.4408, preferred for marine, chemical, chloride environment)
Special duplex or alloy material available by custom inquiry.
What standard and pressure-temperature rating?
Normally manufactured to ISO 4144, 150LB .
Max working pressure: 20 bar at ambient temp. Pressure derates at higher temperature, approx. 13 bar .
Temperature range for PTFE gasket: -20°C ~ +120°C.
If you need higher temperature, we can offer alternative sealing materials (e.g. RPTFE).
Which thread standards are supported?
BSPT, BSPP (G), or NPT standards are supported. Please specify the required thread type when placing an order.
What is the difference between Flat Seat PTFE Union and Conical Seat Union?
Flat seat union: seal by PTFE gasket clamped between flat faces. Easier alignment, less sensitive to torque, easy to disassemble & replace gasket.
Conical seat union: metal-to-metal taper contact seal, NO PTFE gasket inside. Cannot swap these two types. Do not mix flat union and conical union parts.
Do I need PTFE tape on the flat mating face during installation?
NO PTFE tape / sealant on the flat sealing face. Only the end female threads connecting to pipe can use PTFE tape. Putting tape on the flat seat will cause uneven sealing and leak risk. Just tighten the hex nut evenly to compress the PTFE gasket.
What surface finishes are available?
Answer: The standard finish is a pickled matte surface. Other options include a satin finish or a mirror-polished finish suitable for sanitary/hygienic applications.
Why might a leak occur after installation? A: Primary causes:
1. Mismatched thread standards (e.g., mixing NPT and BSP standards).
2. Damaged threads or the presence of burrs.
3. Insufficient application of PTFE sealing tape (thread seal tape).
4. Overtightening, leading to thread galling (seizing).
It is recommended to wrap 2–3 layers of PTFE sealing tape before installation.
What is the Minimum Order Quantity (MOQ)?
Small-batch orders are accepted, and a single order may include products of different specifications.
What is the lead time?
Typically, shipments are dispatched within 7–15 days of receiving the deposit, depending on the order quantity.
How is quality controlled?
Raw material inspection → CNC machining → Thread inspection → Hydrostatic testing → Visual inspection → Final dimensional verification before packaging.
Which Incoterms are available for overseas buyers?
We offer FOB (Free On Board) terms, with the shipment originating from a Chinese port. We will provide a commercial invoice, packing list, and bill of lading for import customs clearance.
Which Incoterms are available for buyers?
We offer FOB (Free On Board) or CIF (Cost, Insurance, and Freight) terms, with shipments originating from a Chinese port. We will provide a commercial invoice, packing list, and bill of lading for customs clearance.
What should be done if the threads are found to be defective or do not meet requirements upon arrival?
Please provide photos, videos, and inspection records. We will assess the root cause; depending on the contractual terms, solutions may include product replacement, a partial refund, or a reshipment.
Union Flat PTFE FF
304 Stainless Steel Union Flat PTFE FF, Flat Seat Female x Female Union with PTFE Gasket, PN16 150LB, ISO4144
3-piece flat face F/F union with PTFE flat gasket for reliable non-metal sealing. Easy disassembly for process piping. 304 stainless steel, chemical & high temperature resistant. BSP/NPT thread options. MTC certificate available.
Type: Union Flat PTFE FF
Material: 304/316L stainless steel
Nominal diameter: 1/4”–4” (D8–DN100)
Rated pressure: 150LB/3000LB
Connection type: Threaded connection (BSPT / BSPP / NPT)
