EKINSUN LTD is a custom parts manufacturer that machines check valve adapters and bodies to drawing: a threaded body with a metric-fine port on one side and G on the other holding a series check-valve cartridge, a stud check valve with a thread the series lacks, an elbow check body in 316L, a manifold block with a check valve in each port, from 1 piece; standard pneumatic check valves in the common thread and tube sizes are catalogue parts. Opening pressures, maximum pressures and temperature ranges belong to each valve maker’s data and are not quoted here.
A typical request: a non-return valve that screws into an M14 x 1.5 port and takes an 8 mm push-in line, in stainless, flow into the port — a thread nothing in the pneumatic catalogue has.
The valve is a series cartridge; the body around it is the custom part.
Check valve forms
| Form | Ports | Direction | Series range | Where it is used |
|---|---|---|---|---|
| Threaded inline check valve, M × F | male in, female out (or the reverse) | arrow on the body | G1/8–G1/2; NPT 1/8–1/2 | between a port and a line; the general-purpose form |
| Threaded inline check valve, F × F | female both ends | arrow | G1/8–G1/2; NPT | inline on a pipe between two nipples |
| Threaded inline check valve, M × M | male both ends | arrow | G1/8–G3/8 | between two female ports |
| Push-in check valve, union | tube × tube | arrow | 4, 6, 8, 10, 12 mm; 1/4, 3/8 in | inline on a tube run |
| Male stud push-in check valve | tube × male thread | flow into or out of the port, per part number | 4–12 mm tube; M5, G1/8–G1/2, R, NPT | on a cylinder or valve port |
| Female push-in check valve | tube × female thread | per part number | 4–10 mm; G1/8–G3/8 | on a male port or nipple |
| Elbow check valve | tube × thread at 90°, or thread × thread | arrow | 4–10 mm; G1/8–G3/8 | tight spaces on equipment ports |
| Mini check valve | M3, M5 or 3–4 mm tube | arrow | M5; 3–4 mm | instrument and small actuator lines |
| Ball check valve, threaded | F × F, larger sizes | arrow | G1/2–G2 | water and low-viscosity liquids |
| Check valve cartridge | press-in or screw-in insert | arrow on the insert | to the series | inside a machined adapter or manifold |
Need a check-valve connection on a thread or size no catalogue lists? EKINSUN is a custom parts manufacturer: we make the adapter or connector around the check valve to your drawing, sketch or sample — brass, 304 or 316L stainless steel — from 1 piece, quoted in 12 hours and shipped duties paid. Standard sizes can often be supplied from stock; the more pieces, the lower the unit price. All custom adapters and fittings →
Reading a check valve: direction, spring, seat
| Feature | Options | What it decides |
|---|---|---|
| Flow direction | arrow on the body; for stud valves, flow into the port or out of it | the part number changes with direction on stud valves; always state which |
| Spring | spring-loaded poppet, or no spring (gravity or back-pressure) | a spring closes the valve in any orientation and sets the opening pressure; no spring needs a vertical line or back-pressure |
| Seat | elastomer seal (NBR, FKM, EPDM) or metal-to-metal | elastomer seals tight at low pressure; metal seats take heat and chemicals |
| Poppet or ball | poppet for air and gas; ball for liquids | a ball tolerates dirt; a poppet closes cleaner |
| Body | nickel-plated brass, 304 / 316L, plastic, aluminium | medium and corrosion |
| Opening and maximum pressure | per the maker's data sheet | quoted from the maker for the series valve chosen; not stated for a machined body |
Which check valve where
| Where | Form | Why |
|---|---|---|
| Holding a cylinder against leak-back | male stud push-in check valve on the cylinder port | one part on the port; direction per the actuator |
| Compressor or pump outlet | threaded inline check valve, M × F | prevents back-flow into the pump when it stops |
| Vacuum circuit holding vacuum on a gripper | inline push-in check valve | keeps the gripper holding when the pump cycles |
| Two supplies feeding one line | two inline check valves as an OR function | each supply is isolated from the other |
| A port with a thread the series skips | series cartridge in a machined body | the cartridge is proven; the body is made for the port |
| A water or chemical line | 304 / 316L body with FKM or EPDM seal, or a ball check valve | medium and corrosion |
What to send for a check valve that is not in the series
- Each port: thread standard, size and pitch, or tube outside diameter; male or female.
- Flow direction relative to the ports, and whether the valve must close in any orientation (spring).
- Medium: compressed air, vacuum, water, oil, chemical; and the working pressure and temperature if known, so the cartridge and seal are chosen inside their maker's rating.
- Body material and form: straight, elbow, stud, manifold.
- Quantity: from 1 piece.
Identify the thread before you order the check valve. Measure the outside diameter of a male thread, or the inside diameter at the mouth of a female one, with a caliper, and count the threads in 25 mm or in one inch. A G1/4 male measures about 13.2 mm across and has 19 threads per inch; a 1/4 NPT male measures about 13.7 mm and has 18; an M14×1.5 measures 14.0 mm with 1.5 mm between crests. Those three are the ones most often confused on a fitting, and only the metric one is not tapered. Then check whether the thread is parallel or tapered by measuring the diameter at the first and the fifth turn. The fitting thread identification chart lists every common pipe, port and tube thread with its diameter, pitch and seal, and the BSPP vs BSPT note explains the parallel and taper forms of the same BSP size.
Series check valves, and the bodies we machine
| What you need | In the catalogue? | What we make |
|---|---|---|
| Threaded inline check valve G1/8–G1/2 or NPT, push-in check valve 4–12 mm, stud check valve in a series thread | Yes | Buy it from stock, or have the body made to order around a series cartridge from 1 piece; the maker's data sheet gives the pressures. Standard parts: ask us too — we may have them in stock. |
| Elbow, mini and ball check valves in series sizes | Yes | Standard sizes: buy it off the shelf, or have it made to order from 1 piece. Standard parts: ask us too — we may have them in stock. |
| A check valve body with a port the series skips — metric fine, UNF, 3/8 NPT on a 4 mm line, a mixed pair | No | Machined in brass, 304 or 316L around a series cartridge; from 1 piece. |
| A check valve adapter: thread conversion on each side with the valve in the middle | No | Machined; cartridge and seal chosen for the medium. |
| A manifold block with a check valve in each port | No | Machined from aluminium 6061 / 7075, brass or stainless with cartridges fitted — see fittings and manifolds. |
| A check valve body in 316L, titanium or PEEK | No | Machined; seal chosen for the medium. |
| A check valve with a published opening pressure, flow or maximum pressure for the machined body | No | Not offered: those numbers belong to the series cartridge and its maker's data; the body is quoted for the medium and pressure you state, and the cartridge data is passed on as it is. |
| A valve with a special cracking pressure or a custom spring | Partly | Series cartridges come in a few spring rates; outside them we say so rather than invent one. |
Materials
| Material | Designation | Where it fits here |
|---|---|---|
| Nickel-plated brass | CW614N / C36000 | standard check valve bodies; machined bodies for air and water |
| Stainless 304 | 1.4301 | standard stainless check valves in the common sizes |
| Stainless 316L | 1.4404 | machined bodies for chemical and marine lines |
| Free-machining stainless | 303 / 1.4305 | custom turned bodies where corrosion duty allows |
| Engineering plastic | POM, PA, PP | series push-in check valve bodies |
| Aluminium 6061 | AlMg1SiCu | machined manifold blocks with check cartridges |
| Aluminium 7075 | AlZn5.5MgCu | high-strength manifold blocks |
| Seals | NBR standard; FKM, EPDM; PTFE seats | chosen for the medium |
Related pages
- every fitting by port combination — every fitting form by ports and standard
- one-touch pneumatic fittings — the tube ends on push-in check valves
- valve fittings — adapters for valve ports
- pump inlet and outlet adapters — check valves on pump outlets
- street elbows and 90° adapters — elbows without a valve
- Liquid cooling fittings and manifolds — manifolds with valves
- fitting thread identification chart — G, R, NPT and metric by diameter and pitch
Frequently asked questions
None: three names for a valve that passes flow in one direction and closes against the other. Pneumatic catalogues say check valve, European pipework says non-return valve, and one-way valve is the plain description.
The arrow on the body points in the free-flow direction. On stud push-in check valves the direction is part of the part number, flow into the port or out of it, so the direction has to be stated when ordering and checked on the old valve when replacing one.
It is set by the spring and published by the valve maker for each series; light springs open at a fraction of a bar. The figure is quoted from the maker's data for the series valve chosen and is not invented for a machined body.
Yes. A series check-valve cartridge is fitted into a body machined with the port threads you need, in brass, 304 or 316L, from 1 piece; the cartridge keeps its maker's rating and the body is cut for the port.
EKINSUN LTD is a custom parts manufacturer that machines check valve adapters, stud bodies, elbows and manifolds around series cartridges in brass, 304 / 316L stainless, aluminium and PEEK, from 1 piece, with a quote within 12 hours.
No list price. The series cartridge is a standard part; the body is priced by material, the port threads, any milling and quantity. A brass stud body in a metric fine thread is a short lathe job; a 316L manifold with four check valves is priced as the machined block it is. The quote separates cartridge and body.
Send the ports, the direction and the medium
Each port (thread or tube OD, male or female), flow direction, medium, pressure and temperature if known, body material, form, quantity. A photo of the old valve with its arrow works. From 1 piece, quote within 12 hours.
Not sure of the thread? Tell us four things: what the fitting connects to (pump, valve, gauge, cylinder, tube or hose); whether the port is the inlet or the outlet; which way the flow must go; and the tube outside diameter, not the hose bore, unless it is a barb. A photo with a caliper across the thread answers most of it.