Stainless steel fittings for fire pump sets, skids and suppression systems

Where are stainless steel fittings used in fire protection systems?

• Pump sets: auxiliary connections of electric and diesel fire pumps, test and circulation lines, and jockey pump connections.
• Pressure sensing lines: small-bore tubing and fittings connecting the pump controller to system pressure.
• Diesel engine auxiliary circuits: engine cooling water line, fuel and oil line connections.
• Control skids: trim lines, pressure gauge and drain connections on alarm valve, deluge valve and foam proportioner assemblies.
• Foam systems: lines between the foam concentrate tank, pump and proportioner.
• Marine and offshore fire systems: connections on fire pumps and distribution lines operating in saltwater environments.

Why stainless steel?

Most of a fire protection installation sits filled with stagnant water under system pressure. In carbon steel and galvanized fittings, internal corrosion can narrow the bore and cause blockages in small-bore lines. This risk is particularly critical in small-bore circuits such as pressure sensing lines, pressure gauge connections and trim lines: a blocked sensing line can prevent the pump from starting at the right moment. AISI 316/316L stainless steel fittings greatly reduce both internal and external corrosion and remain removable during maintenance years later.

In systems running on foam concentrates and seawater, choosing stainless steel becomes even more important, as these fluids accelerate corrosion in carbon steel. In seawater-fed marine, port and offshore fire systems, however, it should be remembered that 316L is also susceptible to crevice corrosion in stagnant seawater; flushing the lines with fresh water after use and testing is an important long-term maintenance step.

Auxiliary circuits of diesel pump sets

On diesel-driven fire pumps, the engine itself requires a number of auxiliary lines: the cooling line that cools the engine with water taken from the pump discharge, fuel supply and return lines, and oil and gauge connections. The connections between the strainer, valves and pressure-reducing components on the cooling line are among the points most prone to corrosion due to stagnant water. On fuel lines, vibration and sealing are the priorities; using a flexible hose between the engine and the fixed tank connection is common practice. The design requirements for these circuits are also determined by the standard adopted for the project.

Approvals, specifications and scope

Main components such as fire pumps, controllers, alarm valves and deluge valves are subject to approved or listed product requirements on most projects, and design follows the applicable fire protection standard. For these components, the project specification and the designer's approval govern. GÜNEYSS focuses on the auxiliary lines, in-skid connections, hose assemblies and custom adapter parts that connect these components to each other and to the installation. Stating at the quotation stage whether an item carries an approval requirement ensures that the right product is discussed from the start.

Size selection: from pump outlet to skid

In pump set and skid manufacturing, sourcing same-size fittings from a single supplier and to the same standard reduces mix-ups during assembly and field revisions. Once a fitting list tied to the skid drawing is established, every new order is prepared from that same list; non-standard adapter parts are dimensioned the first time and then produced to the same dimensions for subsequent skids.

Ease of service and periodic testing

Fire protection systems are tested and serviced at regular intervals. It is important to lay out the connections so that this work is made easier:

• Pressure gauge and pressure switch points should be fitted with isolation valves that allow replacement without draining the system.
• Fittings on test and drain lines should withstand frequent removal and be easily accessible.
• On diesel pump sets, which generate vibration, flexible hose connections isolate the fixed piping from vibration.
• Keeping hose assembly length and end type data in maintenance records ensures that the replacement assembly is built correctly.
• Drain and test line outlets should be directed so that discharged water does not splash onto equipment or electrical panels.
• A controlled leak check should be carried out after every intervention.

Lead times

Standard items are typically ready to ship within 1-3 business days, depending on stock availability. Hose assemblies and custom parts whose dimensions are predefined in the skid fitting list are scheduled within an average of 5-15 business days, while custom-size and project manufacturing produced for the first time from a technical drawing or sample is scheduled within an average of 10-20 business days after technical approval. For skid manufacturers' series requirements, same-size fittings are packed separately by order group, with threads and ports sealed by protective caps. On new facility projects, if the pump room fitting list is drawn up after the pump and skid selection has been finalized, sizes can be determined correctly in one go.