Crosby OMNI-TRIM Series 900 and BP Pressure Relief Valves

Overview

The Crosby OMNI-TRIM range is a family of compact direct spring pressure relief valves designed for reliable and economical overpressure protection and thermal relief. Emerson describes it as a proven solution for air, gas, vapor, liquid and steam service, with a simple design that suits refineries, chemical and petrochemical plants, power plant auxiliary systems and pulp and paper mills. The Crosby OMNI-TRIM page covers two families: the Series 900 fixed blowdown valve and the Series BP balanced piston valve for variable back pressure.

Small-orifice relief valves look modest on a P&ID, yet they protect heat exchangers, trapped liquid lines, instrument headers, sample systems and small vessels in every plant. Seven Star LLC supplies the Crosby OMNI-TRIM range to maintenance and project teams in Oman and the GCC, with stock support and engineering assistance from Muscat. Because most orders are driven by an existing tag or nameplate, our team can cross-check the model number, orifice, connection type and soft seat material before an offer is prepared.

Direct Spring Operating Principle

The Crosby OMNI-TRIM relies on a calibrated compression spring that holds the disc against the nozzle. When the pressure at the inlet reaches the set pressure, the disc lifts and the valve discharges the excess fluid. In the Series 900 the maximum fixed blowdown is typically 20 percent or less, and a single trim design serves liquid, gas and vapor service, which keeps selection simple. For liquid thermal relief, where a blocked-in line expands as it heats, a very small flow is enough to prevent pressure from rising, and a compact valve of this type is the usual protection.

The Series BP of the Crosby OMNI-TRIM adds a balancing piston so that variable back pressure does not shift the set pressure of the valve. It is a piston, single trim design for gas, vapor and liquid applications, with a full nozzle and an O-ring seat as standard. The data sheet gives a maximum allowable back pressure of 70 percent of set pressure for liquid applications, and provides back pressure flow correction factors for capacity calculation, so the Crosby OMNI-TRIM BP can be sized for discharge headers where the downstream pressure changes.

Engineering Design of the Crosby OMNI-TRIM

The Series 900 of the Crosby OMNI-TRIM uses a full nozzle configuration with standardised components that make assembly, maintenance and inventory simple. Seat options include a flat metal-to-metal seat, an elastomer O-ring soft seat or a PTFE O-ring soft seat. Standard soft seat materials are NBR, FKM, EPR, FFKM, PTFE and silicone, with limits that depend on set pressure and inlet temperature: for example FKM can be used from 15 to 2500 psig at 0 to 400 degF, and FFKM up to 500 degF. The data sheet recommends metal-to-metal seats for steam service. Standard materials include a 316 stainless steel base, disc insert and disc holder, a 17-7PH stainless spring and a carbon steel cylinder, with Monel, Hastelloy C and 316 stainless variations.

Connections are screwed as standard, with optional flanged or male socket weld ends. A bolted cylinder version of the No. 5 orifice is available for installations that prefer it for maintenance. The valves are built to ASME Section VIII and XIII with the UV designator for pressures of 15 psig and above, and can be supplied to ASME Section III with the NV designator for nuclear-related applications. Additional approvals include Canadian registration, the China manufacturing licence, the Pressure Equipment Directive (ISO 4126-1) and USCG. Caps and lifting levers are available, and the catalog covers portable valve monitoring with a Rosemount 708 acoustic transmitter and position indication with GO Switch or wireless Rosemount 702.

Key Features

The Crosby OMNI-TRIM combines a compact footprint with the options that small-orifice duties usually demand:

• Series 900 sizes from 1/2 x 1 to 2 x 2 inch and 1 1/2 x 2 1/2 inch, with orifice areas of 0.074 to 0.503 square inch.
• Set pressures of 5 to 5000 psig and a steam limit of 1000 psig for the Series 900.
• Temperature range of -450 to +750 degF for the Series 900 and -20 to +400 degF for the Series BP.
• Single trim design for liquid, gas and vapor service in the Series 900.
• Series BP balanced piston construction for variable back pressure, with a 50 to 1500 psig set pressure range.
• Metal-to-metal, elastomer or PTFE O-ring soft seats for optimum seat tightness and minimal maintenance.
• Threaded, flanged or male socket weld connections to match existing installations.
• NACE MR0175 / ISO 15156 material supplement and special materials such as Monel and Hastelloy C on request.

Industrial Applications

The Crosby OMNI-TRIM is the typical choice for liquid thermal relief on exchangers, cooler shells, pipe sections between isolation valves and storage vessels, and for small gas or vapor relief points on air receivers, compressors, nitrogen skids and fuel gas lines. In oil and gas facilities, the compact bodies and threaded connections allow quick replacement during shutdowns, while the soft seat options help limit leakage on valuable or hazardous fluids. Power stations and desalination plants in Oman and across the GCC use similar valves on steam traps, chemical dosing systems and auxiliary boilers.

Because tag lists in operating plants often contain hundreds of small relief valves, standardising on the Crosby OMNI-TRIM family reduces inventory and training effort. Seven Star LLC can help consolidate part numbers and spares, and customers can compare the Crosby OMNI-TRIM with the LESER Type 437 small-capacity threaded safety valve, the LESER Type 462 soft-seal threaded safety valve or the LESER Type 483 clean service safety valve when a project calls for alternative approvals or sanitary design.

Technical Specifications

The table summarises published Crosby OMNI-TRIM Series 900 and Series BP data from the Emerson data sheet.

Request a Quote for Crosby OMNI-TRIM

Send your nameplate data or process conditions to Seven Star LLC to request a quotation for the Crosby OMNI-TRIM. Please include the model or figure number, set pressure, media, temperature, connection type and size, seat material and any NACE requirement. Our Muscat team will compare your request with the attached Crosby data sheet, confirm the correct Series 900 or Series BP configuration and respond with availability and lead time for your project in Oman and the GCC.