Watson McDaniel HD Regulator- Main Valve
The HD-Series Pilot-Operated Regulators is for pressure reduction or temperature control in steam service applications. These valves require the use of a pressure or temperature pilot which attaches to the main valve to perform the desired function. Back pressure and differential pressure pilots are also available. When both a pressure and temperature pilot are used together an additional pilot adapter is required.
- Select the appropriate main valve size to handle the required capacity. The flow capacity is determined by Inlet pressure, Outlet pressure and valve size.
- When sizing valves for temperature control application assume that outlet pressure in the heat exchanger is 50% of inlet pressure to the valve. For example: If inlet pressure is 50 PSI outlet pressure is assumed to be 25 PSI.
- If inlet pressure is under 15 PSI the LP (Low Pressure) option for main valve must be used. Example: HD-12-N-LP
- Select the appropriate pilot for pressure reduction or temperature control from pilot section.
Example Model Codes for Main Valve:
(HD Series Valve with 1-1/4: Threaded, NPT connections)
(HD Series Valve, Reduced Port with 1-1/2” 150# Flanged connections)
(HD Series valve with 4” 300# Flanged connections & SS External tubing)
Stainless Diaphragm Option:
The HD regulator is supplied standard with a high tensile strength Phosphor Bronze diaphragm which has been determined thru experience and testing to be the absolute best diaphragm material choice for steam applications. Stainless Steel diaphragms are offered as an option because certain industry specifications have been written requiring stainless steel. Note: Stainless steel is prone to work hardening and will not last as long as phosphor bronze; only use if required by the specification to do so.
Stainless Tubing Option:
Copper tubing is supplied as standard. Copper tubing offers excellent corrosion resistance and is easy to bend and manipulate and normally outlasts the life span of the valve. Stainless Steel tubing is offered as an option.
Reduced port trim Option:
Regulators should be sized to meet the application not to fit the pipe size. Over sizing a regulator may cause overshoot which leads to erratic pressure or temperature control often referred to as “hunting.” A valve with reduced port trim has a reduced seat and disc size for a given pipe size, (refer to capacity charts)
Low Pressure (Differential and inlet) Option:
Regulators require a minimum Inlet pressure as well as a minimum pressure drop across the valve to operate properly. The HD Standard Main valve requires a minimum inlet pressure of 15 PSIG and minimum differential pressure of 10 PSI. The Low Pressure Main valve requires 5 PSIG minimum inlet pressure and 3 PSI minimum differential pressure. Low pressure main valve uses a EPDM diaphragm.
PDF Download: HD Series Spec Sheet
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