The coding rules for mechanical seals are as follows:

The first letter indicates whether the seal is balanced (B) or unbalanced (U).

The second letter denotes the type of seal face: single-ended (S); double seal without pressure (also known as "tandem seal" in the seventh edition) (T); or double seal with pressure (also known as "double-ended seal" in the seventh edition) (D).

The third letter represents the type of gland (i.e., the seal cover): plain without throttle bushing (P); with throttle bushing and equipped with quenching, leakage, and/or drain connections (T); or with auxiliary sealing device, the type of which needs to be specified (A).

The fourth letter indicates the material of the gasket (seal ring) (see Table 1).

The fifth letter denotes the material of the seal face (see Table 2).

For example, a seal with the code BSTFM is a balanced, single-ended mechanical seal with a gland equipped with a throttle bushing. The material of the static seal ring gasket is fluoroelastomer (FKM), and the material between the rotating seal ring and the shaft sleeve gasket is also fluoroelastomer (FKM). The material pair for the rotating and static seal faces is carbon versus tungsten carbide type 2. For sealing materials other than those listed above, they should be coded as X and clearly specified on the data sheet.

Table 1: Fourth Letter of the Classification Code for Mechanical Seals

表2 机械密封分类编码的第五位字母

表3 机械密封垫和波纹管的温度极限

Notes for Mechanical Seals:

a: Please consult the manufacturer for the minimum and maximum ambient or pumping temperatures.

b: For non-oxidizing atmospheres, the maximum temperature is 870°C (1600°F); consult the manufacturer.

Formula for converting Celsius (°C) to Fahrenheit (°F) and vice versa:

Celsius (°C) = (Fahrenheit - 32) × 5/9

Fahrenheit (°F) = Celsius × 9/5 - 32

Annotations for Mechanical Seals:

Unless otherwise specified, the spring material for multi-spring seals must be Hastelloy C. The spring material for single-spring seals must be austenitic stainless steel (AISI Type 316 or equivalent). Other metallic parts must also be made of austenitic stainless steel (AISI Type 316 or equivalent) or other corrosion-resistant materials suitable for the operating conditions, except for metal bellows. If metal bellows are used, the material must be recommended by the seal manufacturer based on the operating conditions. The corrosion rate of metal bellows should be less than 50 μm (2 mils) per year.

Unless otherwise specified, the seal between the seal plate (gland) and the seal chamber should be an O-ring made of fluoroelastomer, with an operating temperature below 150°C. If the temperature exceeds 150°C or if specified, a graphite-filled austenitic stainless steel spiral wound gasket must be used. This spiral wound gasket must be able to withstand the full temperature of the pumped liquid (i.e., without cooling).

Metal seal rings should not have sprayed coatings instead of integrated sealing faces.

If the pumping temperature exceeds 175°C, the pump manufacturer and seal manufacturer should consult together to implement cooling flush fluid for the sealing faces or maintain a continuously circulating cooling water chamber for a seal chamber with one end blocked.

The temperature limits for mechanical seal gaskets (gasket seals) should be as specified in Table 3.