Sealing NPT Ports

Aeroquip sells a special quick disconnect designed for reading pressures on equipment. Look for FD90-1045-02-04 (1/8-27 MALE PIPE). And FD90-1012-04-04 (1/4-18 MALE PIPE). Good luck.

Last time I did this I built a clamping device with plastic dust plugs installed the clamp held the pressure in for testing. No change of cross threading or getting dirt in the product.

use M-seal . Or else clear whether you want to close it permanently or wants to spare the option of NPT plug .

Normally the nipple have flat side under the hexagon you must put downthere or a common aluminum washer or some kind of washer some people calls tredoring and others bond-seal,those are common washer with an internal ruber lip but normally those conectors for measures are rubered on its flat side.If you are using your stocked fittings try with the washers.-

NPT tapping is based on a conical shape. It is thought, the fitting of NPT becomes self-locking and self-sealing without any need for a qualified spot surface machined at housing. First aim does work - but to condition the fittings position in depth can't be determined exactly, and therefore flat seals can't be used with NPT!

Self-sealing of NPT usually doesn't work. Therefore the tapping itself need to be sealed by liquid sealing fluid (e.g. LOCTITE products) or using the old fashion hemp fibres or PTFE-tape. All recommendations given before in this discussion do not work with sufficient reliabilty because of the conical shapes of NPT.

In case you need a temporary and quick connection the advise for an quick-relase fitting is the right one. Most makers of hydraulic fitting components will provide those connections, not Aeroquip only.

As an alternative you may install an inverter-fitting, connecting the housing with male NPT, but providing female G-tapping (cylindrical tapping and sealing spot face) for fitting plugs or other things with flat sealing elements (sealing shoulder).

Are you worried about damaging the zinc body?

You could have some plugs made in a rigid plastic like Delrin or Noryl so they would still seal on the thread but not cause any damage.

Alternatively, make a blanking plate with face seals incorporated & clamp it in place.

Nylon pipe plugs are readily available with hex, square or Allen (flush fitting) heads. Silicone plugs might be available through a powder coat supplier.

I want to minimally affect the threads.

I've heard of using BSP oring seal lightly threaded into NPT but I still believe it will affect the threads.

It looks like a fixture will be required to clamp plug the ports.

Thanks all for the input.

Very nice! I think this will work very well.

Thank you Morgan 23.

Another great option.

Thanks!