NPT Thread Archives - RYCO Hydraulics
The three types of hydraulic connectors and their two key functions

This article is an overview of the theory of hydraulic connectors, the three main types of connectors and the two key functions that all hydraulic connectors must fulfil. Three Main Types of Hydraulic Connectors It provides basic information about the three main classes of hydraulic connectors: Tapered Threads Metal seal connectors Soft seal connectors Two Key Functions of Hydraulic Connectors It’s important to understand that there are two functions that a hydraulic connector must fulfil: Holding Sealing Sometimes the holding and sealing functions are provided by the same mechanism, and sometimes by two different parts. Hose connectors may seem very confusing because of the many different types available. However, when looking objectively, connectors will always simply do two things. Hold, and seal under pressure. Development of Hydraulic Connectors Hydraulic connectors were developed in this order: Tapered threads Metal seal connectors Soft seal connectors Tapered Threads Tapered pipe threads were one of the first ways to connect pipes together. They involve cutting the pipe thread in a tapered manner, so that the diameter of the pipe changes over the length of ...

Tapered Pipe Threads – The earliest hydraulic connectors

Pipe threads were invented to join pipes together. Pipe threads are cut into a tapered form, which means that the diameter changes over its length. The taper is usually a gain of ¾” diameter or 12” of length (or 1 degree 47 minutes). Tapered threads were among the first methods of sealing a threaded connector. The threads pull and hold the parts together, and also provide the method of sealing. The thread is cut to a taper. In this way, the threads will “take up” the gap between the male and female components as they are screwed together. Sealing on a thread is an older method, and as a consequence, has become less preferred. Problems with Tapered Pipe Threads Some of the problems that pipe threads create are: Leaks The sealant may cause blockages Orientation is sometimes difficult Pipe threads cannot accept tube Let’s look at each of these points more closely. Leaks with Pipe Threads Once the threads are screwed together, the thread will bind and seal on the flanks. However, even though there is a close assembly of ...

Metal Seal Connectors – A better alternative to tapered threads

Machined faces were added to tapered pipe threads in an effort to address some of the shortcomings of pipe threads. A deep 30 degrees chamfer was added to the face of thread to form a seat. This is a modification that is only really seen in hydraulic products due to the high pressures involved. While a tapered pipe thread is still used, the thread no longer provides the sealing function. The thread now only provides the holding function, which is a fundamental change in its use. The machined face provides the following benefits: Easier orientation Better sealing No need for sealant The 30 degree machined face was first developed for the British pipe thread, BSP. That way the advantages of the sealing on the machine seat are available in the America thread also. Metal Seal Pipe Thread Types British Pipe Threads: British Standard Pipe Taper (BSPT) British Standard Pipe Parallel (BSPP) American Pipe Threads: National Pipe Taper (NPT) Advantages of Metal Seal Pipe Threads These connectors have a greatly reduced leakage when compared with simple pipe threads. Disadvantages of Metal ...

Tapered pipe thread hydraulic connectors – BSPT and NPTF

Tapered pipe thread hydraulic connectors have an outside diameter that is cut on a cone. This results in sides that are not parallel. Two common types of tapered thread connectors are BSPT and NPTF. BSPT British Standard Pipe Taper Country of origin: Britain Thread angle: 55 degrees (Whitworth) Seat angle: 30 degrees BSPT is a tapered thread. This means that the outside diameter of the thread is cut on a cone. The sides are not parallel. The taper angle is a rise of 3/4" for every 12" in length. This is approximately 1 degree, 47 minutes. Male BSPT threads mate with female BSPT threads in adaptors. BSPT female threads are also used in port applications. As BSPT ports seal directly on the thread, the only machining required is drilling the hole and tapping the thread. BSPT threads can also be used as a machined seat connector. The thread used in the female swivel is parallel, BSPP. This is so that the connector bottoms out onto the sealing face. The female swivel is made as a two part assembly. The majority ...