The effects of valve wheel size, operation position and in‐line pressures on required torque for gate valves

Abstract

Some of the hazards encountered by process plant operators involve the operation of in-line valves to control, start, and to stopflow. Torque required to operate valves may vary according to valve wheel size, in-line pressure, and valve flange position (open/closed). This study determined how valve wheel size, in-line pressure and valve position (open/closed) affect torque required to actuate a valve. Data were gathered with each combination of size, pressure and position for 336 valves in an operating petrochemical process facility. The results indicate that the main effects of valve wheel size, the in-line pressure, and open/closed valve position significantly affect operational torque requirements. I n addition, the interaction between position and pressure was significant for operational torque. The implication of these results is that operators are eqosed to operational torque requirements that exceed maximum acceptable capabilities that have been determined in previous studies. PROCESS OPERATOR INJURY TRENDSData searches were conducted for downstream facilities (refining and petrochemical) for Phillips Petroleum Com-

Height of Industrial Hand Wheel Valves Affects Torque Exertion

“…However, anecdotal reports from workers reveal that the torque required to open valves (CCW) is much greater than closing them. These reports are corroborated by data from Parks and Schulze (1998) in a study of the required closing and opening torque of industrial valves. They found that the torque to open a valve (CCW) was much greater than the torque required to close a valve (CW) (means of 149 N⋅m vs. 109 N⋅m, respectively).…”

“…Field studies have shown that the required tangential force to "crack" open a hand wheel valve of 40.6 cm (16 in.) diameter at a petroleum refinery averaged 788 N (160 N⋅m; Parks & Schulze, 1998). Although the 788-N force as measured in the field study is lower than the level approved by MSSVFI (1,000 N), many workers are not able to exert almost 800 N of shear force on a hand wheel without the use of a hand wheel extension arm.…”

“…hand wheel was 305 N, which is less than half of the 800-N force that Parks and Schulze (1998) measured in the field. In a study of 250 college students (125 men and 125 women) using two types of grip (rim grip and spoke grip), the average maximum tangential forces exerted on a 56-cm (22-in.)…”

“…Field studies have shown that workers have to exert 788 N of tangential force to crack open valves at a petroleum refinery (Parks & Schulze, 1998). Industrial workers in the present study were not able to exert an average tangential force of 788 N. Given a mean of 678 N and standard deviation of 130 N of the tangential force exerted at the condition of greatest torque (CCW and at the overhead height), less than 20% of industrial male workers would be able to exert 788 N of tangential force on a hand wheel (z score = 0.85).…”

“…During a 3-year period, Parks and Schulze (1998) performed a data search within five facilities of the Phillips Petroleum Company to determine the relationship between the number of operators with back injuries and those with valve operation as the activity associated with the injury. The results of their search found that 56%, more than half, of the back injuries acquired by operators were associated with valve tasks.…”