PRODUCT FEATURES
Negative Bushing — Product Features
Instrument piping, machinery manifolds, hydraulic & pneumatic systems, water treatment, light chemical, food & beverage equipment, confined space threaded port reduction.
Product Feature
Buyer Notes
Product Feature
EN 10204 3.1 material test certificate available for bulk orders. OEM marking is acceptable. Samples can be arranged for dimension & thread verification before mass production. Please confirm thread type and size combination before order to prevent fitting mismatch on site.
OPERATING PRINCIPLE
How Negative Bushing Works
1. Male and Female Threads (Same Specification): Features a male thread on one end and a female thread on the other, with identical nominal diameters; ideal for extending and connecting piping systems.
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2. Precision-Cast Body
Compact and robust construction, free from porosity or sand holes, offering stable pressure resistance.
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3. AISI 304 Stainless Steel
Provides excellent rust and corrosion resistance; suitable for use with fresh water, mildly corrosive media, and outdoor installations.
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4. Precision-Machined Threads
Available in various thread standards, including NPT, BSPT, and BSPP. Thread tolerances comply with ISO 7-1, DIN 2999, and ANSI B1.20.1 standards, ensuring a leak-free assembly.
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5. 150LB Pressure Rating
Complies with the ISO 4144 standard; suitable for general industrial piping systems.
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6. Pickled and Passivated Surface
Features a clean, metallic luster and enhanced corrosion resistance; supports custom product marking/engraving.
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7. Comprehensive Range
Available in sizes from 1/8″ to 2″ (DN6 to DN50), with options for customized marking.
ENGINEERING DATA
Technical Specifications
Technical data supplied for Negative Bushing. Ratings and material combinations should be confirmed for the selected configuration.
| PARAMETER | SPECIFICATION |
|---|---|
| – Material | AISI 304 (1.4301 / ASTM A182 F304) |
| – Type | Male/Female Threaded Fitting (Equal) |
| – Thread Standard | NPT (ANSI B1.20.1) / BSPT / BSPP (ISO 7/1, DIN 2999) |
| – Pressure Rating | 150LB |
| – Standard | ISO 4144 |
| – Surface Treatment | Pickled and Passivated |
| – Operating Temperature | -20°C to +200°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 | T1 | D2 |
|---|---|---|---|
| 1/4 | 30 | 13 | 17 |
| 3/8 | 34 | 16 | 20 |
| 1/2 | 37 | 20 | 26 |
| 3/4 | 43 | 25 | 31 |
| 1 | 45 | 32 | 39 |
| 11/4 | 50 | 41 | 47 |
| 11/2 | 52 | 46 | 54 |
| 2 | 61 | 58 | 66 |
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.
1、What is Negative coupling?
Negative coupling is a threaded fitting with **male external thread on one end and female internal thread on the other end**. It is a plain round body design without hexagonal wrench flats. It screws into a larger female port to reduce down to a smaller female thread connection.
Important distinction:
✅ Negative coupling: round smooth body, NO hex flats (usually you grip by thread or use pipe wrench)
✅ Negative coupling: built-in hex flats for spanner tightening
They have the same M×F reducing function but different outer shape, cannot be mixed up.
2、What stainless steel grades can you supply?
Standard grades:
– 304 / CF8 for water, air and general low-corrosion service
– 316 / 316L / CF8M for coastal, brine, chemical and chloride-containing media
3、What stainless steel grades can you supply?
Standard grades:
– 304 / CF8 for water, air and general low-corrosion applications
4、Manufacturing process: casting or bar stock machined?
Standard stock items: lost wax investment casting.
High-pressure, high-precision requirement: solid bar CNC machined, higher cost.
7、Can you provide MTC material certificate?
Yes, EN10204 3.1 MTC with heat number is available. EN10204 3.2 third-party certificate can be arranged at buyer’s extra cost.
8、Surface finish options?
Standard: pickled matte finish.
9、Can you do laser marking?
Yes. We can mark size, grade, heat number, customer logo or brand on the flats.
10、Packaging for sea shipment?
Male threads are protected by plastic thread caps. Packed into export cartons, then loaded on fumigated wooden pallets with waterproof stretch film to avoid scratch and thread damage.
11、What is the lead time?
Typically, shipments are dispatched within 7–15 days of receiving the deposit, depending on the order quantity.
12、How is quality controlled?
Raw material inspection → CNC machining → Thread inspection → Hydrostatic testing → Visual inspection → Final dimensional verification before packaging.
13、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.
14、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.
15、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.
Negative Bushing
304 Stainless Steel Forged/Cast Hexagon Reducing Bushings, 3000 lb / 150 lb Class, Available with NPT/BSP Threads
These reducing bushings are forged or cast from 304 stainless steel and feature an external (male) thread paired with a smaller internal (female) thread, designed for transitioning between different pipe sizes. The compact, internal-bore design saves installation space, making them ideal for use in space-constrained industrial piping systems. They offer excellent corrosion resistance. Material Test Certificates (MTC) are available upon request.
Type: Negative Bushing
Material: 304/316L stainless steel
Nominal diameter: 1/2”–2” (D15–DN50)
Rated pressure: 150LB
Connection type: Threaded connection (BSPT / BSPP / NPT)
