11.125.120 Valves – Generally.
(a) Pumping Units. The normal valve arrangement for pumping units shall be as follows:
(1) Inlet Side.
(i) Butterfly valve, Class 150B, rubber seated, flanged and conforming to the latest revision of AWWA C504 with handwheel, for isolation (with gear operators for valves sized eight inches and larger).
(ii) Acceptable manufacturers: CMB Industries, DeZurik, Henry Pratt, or Olson Technologies.
(2) Discharge Side.
(i) Swing check valve of the outside lever and weight type.
Acceptable manufacturers: American Flow Control, Apco-Willamette, GA Industries, Val-Matic.
(ii) Automatic Pump Control Valve. The function of this valve is for waterhammer control. For criteria for including such a valve on the pump discharge side, see WSSC 11.125.140, Surge analysis.
This valve shall be a hydraulically operated, flanged eccentric plug valve consisting essentially of a semi-steel body, nonlubricated type with rubber faced eccentric plugs, nickel alloy steel seat, permanently lubricated stainless steel upper and lower stem bushings, plug operating mechanism consisting of an enclosed gear quadrant attached to the plug shaft, a toothed steel rack, hydraulic cylinder with piston and three limit switches (one for fully open, one for fully closed, and one momentary break on valve closure). The design of the valve shall be such that it can be repacked without removing the valve bonnet.
The hydraulic operating cylinder shall be of the size required to permit opening and closing the valve under the worst condition maximum unbalanced differential pressure across the valve and with available pressure to the cylinder at only 40 psi. Metallic parts to be in contact with water shall be stainless steel or bronze. The cylinder shall be vertical and the plug stem horizontal.
Acceptable manufacturers: DeZurik, Val-Matic, Victaulic.
The valve is to operate in conjunction with its respective pump motor and a complete control system especially designed to perform the control and operating functions described below shall be provided. All control valves and other devices associated with a particular valve (except certain remotely located devices) shall be located adjacent to the valve on a floor mounted panel.
For discharge valve control schematic and details, see Drawing DG-02-2.
Water for the operation of the valve is to be taken from the discharge side of the pump ahead of the check valve and also from the system side of the pump control valve. Pressure piping complete with check valves, ball valves, strainers and unions shall be provided from the two sources to the pump discharge valve control panel.
For normal opening and closing, the hydraulically operated plug valve shall be controlled by means of a three-quarter-inch four-way valve, suitable for unlubricated water service and piped exhaust, Valvair No. M110-646-19 or equal. The four-way valve shall be positioned by means of two three-way solenoid pilot valves, Skinner V53 DB 2150, one being normally closed. Operating coils shall be heavy duty molded (water-tight) for continuous operation on 120V 60-cycle current.
The solenoids shall be connected by moisture-, heat- and oil-resistant flexible cords that plug into a duplex receptacle wired to the pump control system and located on the valve control panel.
The timing for opening and closing of each plug valve shall be readily adjustable and independent. During the entire time that a pump unit is running, its plug valve shall be held in the full open position by the normal hydraulic control.
The speed of opening and closing of the plug valve shall be readily adjustable over a wide range by means of Pneutrol needle valves at the output side of the four-way control valve, so that the most satisfactory speed can be determined by trial.
The control system of the discharge valve shall be sufficiently complete and capable of performing the following functions:
1. For operating during the starting period of the pump, the valve shall open slowly, starting its cycle only after a time delay relay has allowed the pump motor to reach its running speed. The timer shall be so set that the valve does not begin its opening cycle until approximately 15 seconds after the pump motor starts. For each of the valves this time delay shall be readily adjustable over a range of zero to one minute to permit changing of the initial time delay setting to secure the most satisfactory performance of this function.
2. Also, during the starting period, in the event that the valve has not reached the fully open position within a preset time after the pump motor has started, the pump motor control circuit shall be interrupted to cause the pump to stop and remain locked out until the abnormal condition (incomplete sequence) is corrected and the controls manually reset. This timer shall be adjustable over a range of zero to 10 minutes.
3. For pump shutdown, the valve control circuit shall be first actuated causing the valve to move toward the closed position. When the valve has reached the practically closed position, the pump motor circuit shall be interrupted by a momentary break limit switch (furnished with and mounted on the valve) and the pump motor shall stop. In the event the valve has not reached the fully enclosed position within a preset time after initiation of the close signal, the motor shall be stopped and locked out similar to the incomplete sequence shutdown during starting.
The equipment furnished shall be such that when a pump starts the two three-way solenoids are energized to position the four-way valve. The equipment furnished shall include limit switches, solenoids, and all control devices (except the electrical time delay relays). Limit switches shall function as described under Article VII, Controls and Instrumentation.
Manual control of the hydraulic valve shall be provided as indicated on the piping schematic. It shall consist of a four-way manual valve for open/close control in the circuit bypassing the solenoid controlled four-way main control valve. Isolating valves (normally kept closed ball valves) shall be provided in this circuit, as shown on the schematic.
(iii) Butterfly valve for isolation (with gear operators for valves eight inches and larger).
(b) Venturi Meter, Influent Line, Reservoir, Etc. Butterfly valves at appropriate locations shall be used for isolation of the Venturi meter, influent line, and/or reservoir.
(c) Reservoir Fill Valve. In the case of booster stations with pumped storage, a reservoir fill valve is needed in the fill line to open and refill the reservoir when the water level drops and to close when the reservoir is full and prevent overflow.
This valve shall be a motorized cone valve complete with limit switches for open and closed indications as well as pump start permissives. For control schematic, see Drawing DG-02-14. In general, the functional requirements of the reservoir fill valve control system shall be as follows:
(1) Local open-close.
(2) Remote manual open-close from WSSC Control Room when the selector switch is in the Auto mode.
(3) In the auto position, it shall be possible to open the valve remotely only if the reservoir is not full, there is no overflow, the valve has not closed because of low pressure at control points, and pumps are not called to run automatically.
(4) Once opened, the valve shall continue to fill the tank and automatically close only if the center frequency is lost (after a time delay), if low pressure exists at any control point (after a time delay), when the tank is full, if the reservoir overflows, or if pumps are called to run.
The amount of opening of the valve and thus the filling rate will be set by adjustment of the “open” limit switch position, based on operating experience.
If cavitation in the fill line is a potential predictable problem, cavitation control measures shall be adopted. See WSSC 11.125.130, Cavitation. The control of the reservoir fill valve, however, shall remain essentially the same.
(d) Other. Other isolating valves, pressure control valves, etc., shall be provided, as required, with all necessary accessories, depending upon the function of the pumping station in the system and the connection to the system. Requirement of such valves shall be decided on a case-by-case basis. (Amended during 2019 codification; 28-ME-DG-02 § 8.2)