Piping Supplies has seen many changes in the industrial pipe, valve and fitting industry during our 60 years in business. One of the more current trends is the use of Monel 400 flanges for saltwater applications. Piping systems which have traditionally used stainless steel are being converted to Monel 400. Here is why.

Monel 400 is a copper and nickel alloy invented in the early 1900’s. It has been found to have excellent corrosion resistance and can withstand exposure to acids well. Monel 400 does well under pressure and is relatively easy to weld. All of these properties make it a great choice for underwater drilling and for the Navy.

The alloy, Monel 400, is composed of 28 to 34% copper and at least 63% nickel with traces of manganese, silicon, iron, sulfur and carbon. Nickel makes this alloy strong and resistant to corrosion while the copper allows for conductivity and ductility. Our machinists find the machinability of Monel 400 to be only slightly tougher than stainless steel grades.

The Navy has been converting some of their piping systems to Monel 400 in recent years. The volatility of the worldwide nickel market has made this metal harder to obtain. That has driven costs higher increasing the overall price of shipbuilding. Hopefully the the increase in lifetime of these piping systems will offset the higher costs.

Monel 400 is the most recent favored metal for flanges in saltwater applications. The only thing for sure is that newer more exotic materials will be developed in the future. The expert machinists at Piping Supplies will be ready for whatever happens.

As a flange manufacturer for over 50 years, we discuss Navy and commercial ANSI flange drilling all the time at Piping Supplies. We know when it comes to pipe flanges, it is all about the drilling. Other physical aspects of a pipe flange need to match the application, sure, but the main purpose of a flange is to connect two parts of a piping system together. The bolting pattern at the gasket surface accomplishes that.

Elements of a flange bolt pattern

Navy and commercial ANSI flanges bolt patterns are made up of three elements: the bolt hole size, the number of bolt holes and the bolt circle.

Bolt hole size

The bolt hole size is larger than the bolt which connects the flange to another part of the piping system. For ANSI flanges, the bolt hole size is 1/8″ larger than the bolt or stud. So, a flange having a 5/8″ bolt will have a 3/4″ bolt hole. Navy flanges generally have bolt hole sizes 1/16″ larger than the bolts used. A Navy flange using 5/8″ bolts will have an 11/16″ bolt hole.

Number of bolt hole

The number of bolt holes and the size of the bolts determine how much pressure the flanged union can hold at a given temperature. Pressure and temperature ratings of flanges are found in flange specifications like ANSI B16.5 and others. Generally, higher pressure class flanges will have more bolt holes and/or larger bolt hole diameters. A 2″ Class 150# flange has 4 holes and a 2″ Class 300# flange has 8 bolt holes. Both will attach to a 2″ pipe but will not bolt to the same outlet.

Bolt circle

The bolt circle is the distance from the center of one bolt hole to the center of the bolt hole directly across from it. This also changes between each pressure class which is another reason the 2″ 150# and 2″ 300# flange from the example above will not bolt up to the same outlet. ANSI flanges all have even number of holes, so measurements are easier. It is more challenging to measure bolt circles on some Navy flanges with an odd number of bolt holes like three, five and seven.

As flange manufacturing experts, we at Piping Supplies Inc try to make getting the flange you need easier. We have created two documents you can download. One will help you identify a flange or flanged outlet based on the drilling. The other gives you all the Navy and commercial drill patterns. Both are good resources.