Valve Safety Issues In The Workplace

A valve is a mechanical device whose purpose is to open, close, and regulate the flow of liquids or gasses within pipes and vessels.  Valves are very important to workplace safety, and thus they are important in OSHA trainings to increase awareness and safety protocol in the workplace. The names of valves give some idea of their variety – ball, butterfly, control, flow limiter, needle, safety shutoff – an almost endless array, from simple to highly complex, each with its specific function and purpose.  Three of the most common types are

Gate Valve:   Also known as sluice valves, gate valves open by lifting a gate or wedge out of the path of the fluid.  Gate valves are frequently used where minimum restriction is needed, and are typically constructed from cast iron, carbon steel, or stainless steel.  Typical gate valves are designed to be fully opened or closed; and when fully open, the typical gate valve has no obstruction in the flow path, resulting in very little friction loss.

Globe Valve:   Globe valves are designed to regulate flow in a pipeline, are often spherical in shape, and have a movable disk-style element and a non-movable ring seat.  The two halves of the sphere are separated by a baffle which provides an opening and a seat onto which a movable plug can be screwed in to shut the valve off.  Globe valves can be automated, or manually operated by using a handwheel.

Plug Valves:  Plug valves have cylinder or cone-shaped plugs inside the body of the valve which can be rotated to control flow from inside.  The plugs have sideways hollow passages, allowing fluid to go through the plug when the valve is open; and have two positions – open, to allow flow, and shut, to stop flow.  Plug valves are not complex, and therefore are often quite economical to use.

Safety regulations mandate that hazard analysis be made before actual use of the equipment containing the valve takes place; both to determine any hazards and to decide how to control exposure to risk.  If the valve is used in processing corrosive gases or liquids, for example, hazard control would indicate protective eyewear and clothing for the operator.  Flammable liquids require fire-retardant protection for both site and operators.  If steam is flowing through the pipes under pressure, there may risk of explosion .  In all situations, hazard assessment of the gas or liquid and of the piping and process system itself are as vital as hazard assessment of the valves within the system.

Since many valves are controlled manually, operators should be trained to work with such valves.  When  bending or reaching below waist level to operate a valve, for example, bend at the knees and keep the spine upright to avoid injury.  The operator should be able to move around enough to avoid long periods of standing or sitting in one position; he should be able to take a moment to shift position and to stretch at least every few minutes.  Operators should always be trained to understand the process flow and fluids they are working with so that they have the background for making split-second decisions if necessary.  Operators also need to have the best tools at hand to help them.  Wrenches can provide extra leverage, so they need to know which wrench to use; the wrong size can cause the wrench to slip and possibly cause harm.  

Operators should also know enough to replace a broken valve with another of the same type and rating; if not, all affected personnel must be made aware of any system changes.  Valves may look like a small part of the overall system, but they function much like the rudder of a ship – such a small part to produce such large results.