When a customer requests a seal selection guide, he is most likely considering point solutions for his specific services, especially if his plant is small. As a result, particular services such as vacuum bottoms pumps, crude oil pipelines, propane pipelines, ethylene product pumps, cooling water pumps, and so on may be requested. Such service-based options are available in several application guidelines. For example, an API 682 Type-A De salter Effluent pump in a crude oil distillation plant with carbon/silicon carbide faces, peroxide cured per fluoroelastomer, Super Duplex metallurgy, and Plan 53A.
The Service-Based Selection approach has the benefit of being able to be done in great detail with minimal inputs and based on current application requirements. The downside is that there are a limitless number of point solutions.
Instead of considering the service, a version of Service Based Selection examines solely the fluid. For example, whether the process service was a reflux pump in a refinery light ends unit or a propane pipeline, propane would always be sealed in the same way. Obviously, more information is required, particularly pressure and temperature, in order to make consistent decisions based merely on the fluid.
In a sense, machine-based seal selection is similar to service-based seal selection. A heavy-duty pump will most likely need a heavy-duty seal and vice versa. All API pumps use API seals. A "Pipeline" pump uses a "Pipeline" seal. Several different fluids can be handled with small, general-purpose pumps that do not require modification and are inexpensive.
According to API 682, seal selection is organized by fluid groups and subgroups for typical services and variations. API 682 fluid groups include:
1. Water
2. Sour water
3. Caustics
4. Amines
5. Acids
6. Hydrocarbons
This approach may also be taken by certain end-users, but may also include additional groups or considerations. Some users extend API 682's pressure range to account for variations in hydrogen sulfide content.
Seal selection by Fluid/Service Group is probably the most common method.