Correct installation procedures are further promoted by providing dimensional information associated with a variety of Parker Autoclave Engineers tube connections as well as the torque required to properly seat numerous Parker Autoclave Engineers components. Several tools developed by Parker Autoclave Engineers are presented to help accomplish proper valve, fitting and tubing installation and maintenance.

Autoclave Engineers is the leader in the field and provides a great combination of connections, but like all connections, special attention is required to make reliable and safe connections.

First of all: Identification of the connection types

Autoclave Engineers offers several connections divided by pressure rating; let's see which ones

• Low Pressure (LP - 10,000psi)
• Medium Pressure (MP - 20,000psi)
• High pressure (HP 60,000psi)
• Ultra High Pressure (Up to 150,000 psi)
• QS Series (not included in this guide)
• SpeedBite (not included in this guide)

As an example, let's compare two different plugs with different ratings, MP and HP (medium pressure and High pressure)

The two plugs look the same; change the conic part only. The OD HP cone is smaller than the MP cone. This is the fundamental basis of an autoclave connection

Note: Improper installation can cause a high-pressure leak (Never attempt to secure something that doesn't fit). Improper installation risks damage, such as leaks or component failure, between the tubing and fitting (scratch the cone during installation). When damage occurs to a fitting, will be solved by replacing the fitting or making up new cone and thread of tubing with Autoclave machine. When it occurs on some device like a high-pressure valve where it is impossible to change the internal cone (like the fitting), and requires replacement with result that wasted money, time, and non-production

For this reason, before starting any activity, It is mandatory to clarify which type of connection is in place (MP, HP,or LP)

Installation procedure

The conical seal fittings are for Ultra High Pressure and can reach pressure up to 150,000 psi (10500 bar). This kind of technology was invented by Autoclave Engineers over 90 years ago in the United States. This design set the precedence of quality and reliability found in all Parker Autoclave Engineers products to this day. All-metal sealing and working temperatures from 0° to 600°F (-18° to 315°C), along with a variety of different material options make this connection one of the most versatile ever.

Working Pinciple

The principle/design of Autoclave connections is based on a metal-to-metal line contact seal between tubing and the fitting surface (cone to cone). A smaller sealing surface (like a cone) often results in a higher pressure rating for a given clamping force because the force is concentrated over a smaller area. A larger surface involves a more significant force, which means the pressure rating will reduce
(the law of the Kgcm²).

Figure 3 shows a hydraulic lift/jack using a small piston/area to lift a car with a large piston/area, demonstrating Pascal's Principle

Figure 3 Hydraulic lift bridge

The Weep Holes

Figure 4 below shows a standard connection between the tubing and autoclave fitting.

Figure 4 Autoclave Connection

As you can see from Figure 4, the sealing part is only between the tubing cone and the fitting cone. On both sides of any fitting, there are two holes called “Weep Holes”.

These holes serve for drainage and visual inspection during installation, allowing immediate identification of leaks (gas or liquid escaping before target pressure is reached) if issues arise, making fault location easier.

Normally, weep holes are in most fittings, but sometimes they are missing.Figure 5 shows a grease fitting applied to the injector body valve.

For your information, some valve suppliers include a weep hole at the connection point, while others don't, which is a crucial detail to note (Pay attention because this is very important).

Figure 5 Injector Grease

Note:  The thread of the fitting cannot withstand a pressure of 20,000 psi. The pressure must be only between the fitting cone and the tubing cone, as shown in figure 4

Unfortunately, several types of valves don't have the weep hole, this means that in case the cone gets damaged (metal seal), the Gas or liquid will exit from thread connection. This is one of the reasons for never using any type of seal (teflon, loctite,etc.) on the thread connections. The threads shall always be free from any type of seal to prevent thread pressurization if cone seals fail and no weep holes are available. See Figures 6 and 7.

Fitting Working Principle

Autoclave Engineering (Parker) is the reference in this guide. Many reliable companies provide the same technology, it all depends on what you have available, but the principle of operation remains the same.

Figure 6 below shows a standard Autoclave Engineering connection

 Figure 8 Tubing and fitting installation

As you can see from Figure 8 above, the seal for this connection is only cone-to-cone (metal-to-metal).

Figure 9 below shows all components that are included in a Fitting

Figure 9 Autoclave Fitting

Each of these components has a detailed code which is very important for the correct installation.

Tubing's Diameter

There are many tubing sizes; the most common lines have diameters of 1", 3/4", 9/16", 3/8", and 1/4" (with 5/16" for ultra-high pressure)

Autoclave high-pressure tubing uses a unique metal-to-metal seal where the tube end is coned (shaped) to a specific angle, typically around 59 degrees, to mate perfectly with the fitting's 60-degree cone, the connection creates an incredibly strong, leak-proof seal for extreme pressures (up to 150,000 psi), unlike standard fittings that rely on ferrules or NPT threads.The sealing happens when the precisely angled tube tip presses into the fitting's cone, forming a line contact seal for reliable performance in harsh environments. Tubing ratings are divided into three types

Low Pressure Cone

An autoclave low pressure cone refers to Parker Autoclave Engineers' SpeedBite fittings, a single-ferrule compression system for tubing (up to 15,000 psi) that provides reliable, Bubble-tight seals for moderate-to-high pressure fluid for oil & gas, and chemical industries, ideal for high-pressure fluid handling in research, oil & gas, and chemical industries, featuring a bite-type action for strong, easy connections.

Key Features & Function:

• SpeedBite Connection: A single ferrule bites into the tubing upon tightening, creating strong mechanical support and a seal.
• Pressure Range: Handles pressures up to 15,000 psi (1034 bar), bridging the gap between standard compression fittings and higher-pressure cone & thread systems.
• Application: Used for liquid and gas service in demanding environments, common in labs, petrochemicals, and oil & gas.
• Materials: Typically made from 316 Stainless Steel (UNS S31600).
• Components: Includes valves (like the 10V series), fittings, and tubing designed for compatibility.

How it Works (Simplified):

• Tube Preparation: Annealed instrument tubing (like ASTM A269 316 SS) is used.
• Installation: The ferrule is placed on the tube, inserted into the fitting body, and tightened with the gland nut.
• Bite Action: The leading edge of the ferrule bites into the tube wall, creating a shoulder that prevents blow-out, even at high pressures. 

Medium Pressure Cone

• In the context of Autoclave Engineers (a brand by Parker) and similar high-pressure systems, a medium pressure cone typically requires a specific angle to create a metal-to-metal line contact seal:

• Tubing Cone Angle: The end of the tube is coned to 57° to 59°.
• Mating Seat Angle: The connection (female port) has a 60° cone angle.

For more details see Figure 10 below

Figure 10 - Cone Angle

This 1° to 3° mismatch (the "dissimilar angle") ensures the seal is formed at the tip of the cone, creating a reliable, high-pressure, metal-to-metal line seal.

• MP tubing: (medium pressure) typically rated up to 20,000 psi (1,379 bar - Depende from tubing size)
• Operating Temperatures: Standard stainless steel components can operate from -423°F to 1,200°F (-252°C to 650°C).
• Sealing Type: Coned-and-threaded connection, which does not use ferrules or pipe tape for the primary seal.

High Pressure Cone

High-pressure Autoclave fittings use a metal-to-metal seal from a 59° tube cone fitting into a 60° fitting cone, creating a leak-proof line seal for extreme pressures (up to 60,000 PSI or more) and temperatures (-423°F to 1200°F), relying on precise angles, not degrees of heat for sealing, though they handle high heat.

1. Understanding the "Cone" in High-Pressure Autoclaves:

• Design: The sealing mechanism isn't about a degree setting for the cone itself, but the specific angles used: the tubing has a 59° cone, and the fitting has a 60° cone.
• Sealing Action: When tightened, these slight differences create a precise metal-to-metal line contact, forming a strong seal that withstands immense pressure

2. Temperature & Pressure Ratings

• Temperature Range: These fittings are built for extreme conditions, often working from cryogenic temperatures (around -423°F / -252°C) up to very high heat (around 1200°F / 650°C).
• Pressure Ratings: Depending on the series, they can handle massive pressures, from medium (20,000 PSI) to ultra-high (60,000 PSI or even more), notes Parker Autoclave Engineers, Fluid Controls Ltd, and Parker US.

In Summary: The "degrees" in an Autoclave high-pressure cone refer to the precise 59° and 60° angles for sealing, allowing operation across a wide range of extreme temperatures and pressures, crucial for heavy-duty industrial applications. 

Up to today, no other methods can withstand high pressure with tubing diameters greater than 1/4 " except this type of connection

When a line is built, the rating depends on the thickness and materials of the tubing. Based on the tubing, it will be applied the proper fitting, valve, etc.(Medium, High, or ultra-pressure). Any line modification, such as a different fitting rating or tubing thickness, even an installation of a pressure gauge with a lower range, entire line will be downgraded.

Fittings and Valves

• Special Material Fittings are supplied with CW 316 SS Glands and Collars, as these parts do not touch flowing (wetted) media. To match the same material as selected for the body, use either “-SOG” (Sour Oil or Gas - NACE) or “-AP” ("All Parts" (does not get hard-ness check typical of -SOG option)) suffix. Special material glands and adapter bodies usually are supplied with four flats (square) in place of a standard hex. Include option suffix “- H” if the hex is required (see photos below)
• All metal seal fittings and valves have two holes on the body near the thread. The utility of these two holes called by Autoclave Engineering "Weep holes" are to prevent overpressure on gland thread and also easy identification of leak if the conic seal gets damaged. See Figures 6 and 7 above.
• Light gases such as hydrogen and helium are more difficult to seal than liquids. When selecting a valve series, consideration should be given to the fluid application and not just pressure and temperature requirements. The higher the valve rating or fitting, the less the likelihood of weepage problems with light gases. Tubing selections should also consider the service requirements, since the thicker wall. Smaller outside diameter tube sizes will produce a more reliable connection seal. 

Classic issue when internal cone gets damaged (Possible causes):

1. The tubing was improperly prepared, possibly during the cone preparation phase
2. Used the wrong tools
3. Damage occurs between the tubing and fitting during installation. This can happen when the tubing and fitting are not aligned, requiring more force to screw the nut into the fitting (tubing bended,short,long,etc.). This can happen when internal cone gets damage or scratched.

If the cone is damaged and a leak appears, never try to solve the issue by applying sealing (Teflon, Loctite) on the thread. The cone and fitting surface are totally different (much bigger). The fitting surface cannot support a pressure of 10K, 20K or more or more. The diameter of injector grease fitting is 9/16" HP (look like 3/4" NPT - see Figure 5 above). Applying sealant like loctite on the fitting, such as Loctite, etc., will result in high clamping force, but could cause excessive stress on the fitting surface, and also on the threads, with the serious risk that the fitting may tear away from the connection. If consider that a 3/4 plug the max pressure is 300/400bar only (depende from materials). Always thinking about KgCm2 and never apply any seal on the Autoclave connections (mandatory).

Advantages

• Metal-to-metal seals (conic) are safe systems for high and very high pressures.
• If the internal cone of the fitting is scratched, special tools can remake the cone without replacing the fitting.  Figure 10 below shows this (each size is available the special tool).

Figure 10 Special cleaning tools

• For each size of fittings and valves, there is a tool. The gland connection can be from 1",3/4", 9/6", 5/16",3/8", and 1/4". According to the cone, it also changes the size of the Reamer. The pipe cone can be make-up with sandpaper, like when lapping the internal ball of a valve (Sizes 1000 and 2000).
  
• 1/2" TEFC motor, capacitor start (220Volts)
• Pop open die prevents thread damage. No reversing is necessary on threading.
• Supplied with oil pump and reservoir.
• Optional reservoir heater for operation below 65°F.
• Stand mount with locking casters.
• Complete range of tooling available by separate order.
• Possibility to use the electric machine (for very long jobs) or the manual one for regular routine.

Disadvantages

Even if metal to metal seal of the fitting and tubing is very reliable in terms of high pressure, they also have problems which should not be underestimated. Below are the considerations:

• All the Parker/autoclave (including other company) valves shall be fixed by proper support (mandatory). See Figure 11 below. Is easy to unscre the gland uncer pressure

Figure 11 autoclave valve

For safety systems, including maintenance, the Autoclave valve must be fixed to support by bolts. The support is mandatory if the valve like in Figure 11 above, is classified as a full seal valve. The problem appears when the valve is closed and under pressure (upstream side only).

Let's say the valve supports are missing. In that case, there is a serious possibility that operating the valve could unscrew the upstream gland, causing uncontrolled leakage of liquid or gas. In this case, the best solution is to close everything upstream of the valve. Consider all reccomandation below:

1. Always fix the valves with the appropriate supports (see figure 11 above)
2. Never tighten the gland while it is leaking (under pressure), especially if the valves are not fixed with support

Unfortunately, in some projects, the support is not installed during construction (maybe to save time), but this is very important for the safety system (autoclave Engineering recommendation). For any metal-to-metal fittings, if the fitting gland unscrews due to valve missing the support, even if the gland moving few millimetres can cause a catastrophe.

Figure 12 below shows some hydraulic accumulators under high pressure without the supports on the valve. (an essential thing).

Figure 12 Autoclave valve without support

Our suggestion: Do not try to unscrew or operate (open or close) an autoclave valve under pressure without support.

• Preparing a line takes a lot of time because every connection must be made with maximum accuracy (cone and thread, see procedure above).
• Two keys must be used when tightening a fitting, one to keep the fitting or valve and the other to tighten the nut.
  
• The fittings must be tightened with the manufacturer's dynamometric key (for all sizes of fittings, there are different torque ranges). See table torque from the autoclave. See table torque in Figure 13 below.
• When preparing a connection between the fitting and the tube, ensure the tube is aligned with the fitting, and tighten the nut by hand until it is secure, and the last action tight it with dynamometric key. This procedure shows that the pipe is perfectly linear with the fitting.
• If a fitting opens and closes continuously, it can easily scratch the cones and cause a leak

Figure 13- Torque wrench Key

Recommendations

• Never mixing collars or glands with different companies
• Experience does not mean modifying the connection system or internal parts of the fittings; knowing all the procedures written in the manual is mandatory.
• You must be very careful to correctly identify whether fittings or valves are medium or high pressure. The high-pressure cone surface exposed to the fluid is smaller than the medium-pressure surface. See Figures 1 and 2 above.
• Never apply any seal on the thread gland is strictly forbidden
• During tubing cutter, do not overheat it; it could lose its properties
• Bend the tubing according to the degrees recommended in the manual
• Always before the installation of a connection, lubricate the conical parts with grease
• Never install an Autoclave valve without support
• Always following manual instructions is the basis of all things.
• Always use the torque wrench to tight the glands

Note:  FAILURE, IMPROPER SELECTION OR IMPROPER USE OF THE PRODUCTS AND/OR SYSTEMS DESCRIBED HEREIN, OR RELATED ITEMS CAN CAUSE DEATH, PERSONAL INJURY AND PROPERTY DAMAGE. Due to the variety of operating conditions and applications for these products or systems, the user, through its own analysis and testing must identify which is the correct fittings, valves, tubings, etc. If you are not sure always please contact qualified people.