Relief Valves

Relief valves should be rated for the full flow of the pump. The set pressure or cracking pressure must be sufficiently above the operating pressure to prevent normal pressure pulsations from activating the relief valve. The following values can be used as guidelines, but the final selection should be made only in agreement with the pump supplier and system designer:

• Duplex double-acting: 25 percent

• Triplex and above: 10 percent

Bypass Relief Starting a power pump under a full load requires a high starting torque. Also, a pump with sleeve-bearing construction when starting under a full load may not have adequate bearing lubrication to reach the operating speed.

The starting torque on the driver and plunger load on the bearings may be reduced by performing one of two steps:

• Install a bypass line from the discharge back to the source or to a drain (see Figure 25). This line is located between the pump discharge and a check valve before the discharge piping system. The bypass valve is operated manually or automatically. The bypass line

Ammonia service Carbamate service Chemicals Crude-oil pipeline Cryogenic service Fertilizer plants High-pressure water cutting Hydro forming Hydrostatic testing

Liquid petroleum gas Liquid pipeline Power oil Power press

Salt-water injection for water flood

Slurry pipeline (up to 70 percent by weight)

Slush ash service

Steel mill descaling

Water blast service

Cryogenic service

Low-speed operation Slurry pipeline Special fluid-end materials Viscosities over 500 SSU

Highly compressible liquids Liquids over 250°F (121°C) Liquids with entrained gas

Survival Treasure

Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

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