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Brand: Flowserve
Flowserve DHTW and UHTW High-Energy Mechanical Seal
Description
Flowserve DHTW and UHTW balanced cartridge seals
The Flowserve DHTW and its sister model UHTW are custom-engineered mechanical seals for high-energy, critical pumping duties. Both are balanced, flexible-stator cartridge seals offered in single or dual configurations, and the datasheet names boiler feed, boiler circulation, oil-field injection and pipeline services as typical uses. The seals are listed for pressures to 207 bar, temperatures to 371 °C and speeds to 76 m/s.
Because each seal is configured for a specific application, this page describes the DHTW/UHTW range rather than a single ordering code. Seven Star LLC is an independent supplier in Muscat and supports Flowserve seal enquiries in Oman and the GCC, including seals for the high-pressure barrel pumps used in the region.
DHTW and UHTW technical specifications
| Parameter | Specification |
|---|---|
| Manufacturer / part number | Flowserve / DHTW and UHTW |
| Seal type | Balanced, flexible-stator cartridge seal, single or dual |
| Pressure | Up to 207 bar (3,000 psi) |
| Temperature | -40 to 371 °C (700 °F) |
| Shaft speed | Up to 76 m/s (250 fps) |
| Shaft size | 25.4 to 228.6 mm (1.000 to 9.000 inch) |
| Metal components | Stainless steel |
| Rotating face | Silicon carbide or tungsten carbide |
| Stationary face | Carbon or silicon carbide |
| Gaskets | Fluoroelastomer, perfluoroelastomer, EPDM or nitrile |
| Drive | T-drive with multiple drive pins engaged in the faces; split ring or shrink disc high-pressure drives available |
| Special options | Anti-electro-corrosion package; Precision Face Topography; GSLW containment seal |
How the DHTW and UHTW seals work
Both seals hold a thin fluid film between a rotating and a stationary face. The balance ratio, which decides how much closing force the faces see, is set behind the stationary face in a flexible-stator design. The manufacturer explains that this arrangement helps manage thermal effects and equipment dynamics, and that the face geometry is optimised with finite element analysis to give zero net deflection under pressure, temperature and centrifugal loads.
The key difference is the pumping feature. In the DHTW, a pumping geometry around the rotating face moves fluid through a seal cooler at high flow rates, so plans 23, 52 and 53 work at all speeds including slow roll and hot standby. In dual seals the DHTW circulates enough barrier fluid to meet cooling needs. The UHTW omits this feature and is used where circulation is provided otherwise.
A T-drive with multiple pins deeply engaged in the faces lowers stress on the face material and resists damage from vibration and from high start-up torque, for example with viscous fluids.
Where DHTW and UHTW fit with pumps and auxiliary systems
These seals belong to the high-end of the Flowserve seal range and are intended for pumps such as boiler feed and circulation pumps, injection pumps and pipeline pumps, including high-pressure barrel pumps like the WIK. The seal works together with a support system: a seal cooler such as the Flowserve 682 cooler, a reservoir for plan 52 or 53 and instrumentation. Atmospheric bushings or a GSL containment seal can be added to restrict leakage and give an access point for seal condition monitoring. A lighter-duty hot-water option from the same manufacturer is the QBU pusher seal, which is limited to moderate pressure.
DHTW and UHTW selection and ordering checklist
- Pump make and model, shaft diameter and seal chamber dimensions
- Single or dual arrangement; face-to-back or face-to-face
- Process fluid, including phase behavior near flashing or supercritical conditions
- Seal chamber pressure, temperature, speed and viscosity
- Face and elastomer materials suited to the fluid
- Piping plan (23, 52, 53) and available barrier fluid system
- Need for the anti-electro-corrosion package on low-conductivity water
- Containment option: atmospheric bushing or GSLW / GSL seal
- Drive type: standard, split ring or shrink disc
- Applicable standard and required documentation
Installation, commissioning and maintenance
Cartridge seals are delivered pre-assembled with setting devices, which lowers the chance of assembly error. Check shaft runout, shaft end play, seal chamber face squareness and bore concentricity before fitting, and keep the setting clips in place until the gland is tightened. Piping plan lines should be flushed and vented before start-up so that the faces never run dry.
On hot services follow the heat-up procedure of the pump to avoid thermal shock to the seal faces. Monitor the barrier or flush system, seal cooler temperatures and any leakage indications. Typical spares are stationary and rotating face sets, elastomers, springs and the drive hardware; when a pump is overhauled the whole cartridge is often replaced by a rebuilt spare to shorten downtime.
Typical DHTW and UHTW applications in Oman and the GCC
In Oman and the GCC, the natural applications are boiler feed and circulation pumps in power and desalination plants, water injection pumps in oil fields and pipeline pumps on export lines. Plants with ultra-pure feed water can use the anti-electro-corrosion package, while gas processing and CO2 handling duties use the dual UHTW/GSLW arrangement. High ambient temperatures and cooling-water limits in the region make a pumping feature and good seal cooler design especially valuable.
DHTW and UHTW configurations
| Configuration | Features | Typical use |
|---|---|---|
| Single DHTW | Isolation bushing inboard, fixed throttle bushing outboard; plan 23 with seal cooler | Boiler feed and circulation pumps |
| Dual DHTW/DHTW face-to-back | Pumping ring circulates barrier fluid | High-pressure boiler circulation pumps |
| Dual DHTW/DHTW face-to-face | Redundant sealing with zero process emissions | Heavy-duty services needing no process leakage |
| Dual UHTW/GSLW face-to-back | Non-contacting GSLW containment seal, Precision Face Topography | Flashing and supercritical fluids: CO2, ethane, ethylene, LPG |
Information to send with a DHTW RFQ
- Pump data sheet or seal chamber drawing and shaft diameter
- Process and barrier fluid, temperature, pressure and speed
- Required arrangement and piping plan
- Existing seal nameplate or serial number if replacing
- Standard, material and emission requirements
Documents and quotation
A datasheet for the DHTW and UHTW series is attached on this page. Send the pump details and operating conditions and we will review the seal configuration and arrange a quotation.
Seven Star LLC is an independent supplier and does not claim any official status with the manufacturer.
Datasheets & Documents
- Datasheet Flowserve DHTW/UHTW Datasheet Download
Reviews (0)
About brand
Flowserve is the American flow control company for pumps, valves, mechanical seals and valve automation, known through brands such as Durco, Worthington, Byron Jackson, Valtek, Limitorque, Worcester, Logix and Argus. It was formed on 22 July 1997 by the merger of equals of Durco International and BW/IP, whose heritage reaches back to Simpson & Thompson (1790) and Byron Jackson (1872). Flowserve Corporation is headquartered in Irving, Texas, and listed on the New York Stock Exchange.
Seven Star LLC sources and supplies Flowserve pumps, seals, control valves, ball valves, actuators and positioners for process plants in Oman, working from the nameplate data and the manufacturer's documentation.
Flowserve company profile
| Formed | 22 July 1997, merger of Durco International and BW/IP |
|---|---|
| Heritage companies | Simpson & Thompson, later Worthington Simpson (1790); Byron Jackson (1872); Duriron foundry, later Durco (1912) |
| Headquarters | Irving, Texas, USA |
| Ownership | Flowserve Corporation, public company (NYSE: FLS) |
| Product families | API and ANSI process pumps, Durco and Worcester ball and plug valves, Durco TX3 triple-offset and Valtek butterfly and globe control valves, Limitorque electric actuators, Logix positioners, mechanical seals |
Milestones
- 1790: Thomas Simpson founds Simpson & Thompson, a predecessor of Worthington Simpson pumps.
- 1872: Byron Jackson is founded, a root of BW/IP.
- 1912: The Duriron foundry, later Durco, is launched.
- 1997: Durco International and BW/IP merge on 22 July to form Flowserve, listed on the NYSE as FLS.
Flowserve product families listed here
Flowserve pumps on this page are the Durco Mark 3 ANSI process pump and the ECPJ vertical sump pump built to API 610 type VS4. Sealing products are the ISC2 cartridge mechanical seal to API 682 and DuraClear barrier fluid for dual seal systems. Flowserve valves include the Valtek Mark One globe control valve, Argus floating and trunnion-mounted ball valves (EK71, FK79, FK76M) and Durco Microfinish ball valves. Automation is covered by Limitorque MX and L120 multi-turn electric actuators, the Rotadisk RD and RDF pneumatic actuator and the Logix 3800 digital positioner.
Where Flowserve equipment is used
Mark 3 pumps handle acids, caustic, solvents and utilities in chemical and petrochemical units. VS4 sump pumps drain pits and collection tanks. Valtek control valves and Argus ball valves are found in refining, gas processing, power and desalination, and Limitorque actuators operate gate and globe valves on pipelines, tank farms and water networks across the GCC.
Flowserve products we list
Ordering Flowserve parts: what we need
The serial number on the nameplate is the key to Flowserve records for a pump, valve or actuator. Please add the following by product type:
- Pumps: size and model, impeller diameter, materials, seal arrangement, and the part name and item number from the sectional drawing
- Mechanical seals: seal type and size, drawing or part number, materials code, pumped fluid and flush plan
- Valves: size, pressure class, body and trim materials, end connections, and the actuator and positioner model
- Limitorque actuators: unit size, order and serial number, supply voltage, wiring diagram number
Facts checked against Flowserve's SEC filings and published company histories, October 2026.
Browse Flowserve products by category: Control Valves, Pumps, Valve Actuator, Valve Positioner.
FAQ
Questions about the Flowserve DHTW and UHTW High-Energy Mechanical Seal
Answers from our engineering team on installation, compatibility and integration.
01What is the difference between DHTW and UHTW?
The two seals share the same core components. According to the datasheet, the DHTW has a high-performance pumping feature integrated around the rotating face, which circulates fluid through a seal cooler and satisfies cooling needs in dual arrangements. The UHTW does not include that pumping feature.
02What operating limits are published?
Pressure up to 207 bar (3,000 psi), temperature from -40 to 371 °C (700 °F), speed up to 76 m/s (250 fps) and shaft sizes from 25.4 to 228.6 mm (1.000 to 9.000 inch).
03Which piping plans suit the DHTW?
The pumping feature is engineered to deliver cooling through piping plans 23, 52 and 53 at all operating speeds, and the datasheet shows a single DHTW with plan 23 and a Flowserve 682 seal cooler.
04How does the seal handle ultra-pure boiler feed water?
For low-conductivity water that promotes electrically induced corrosion, the DHTW can include an anti-electro-corrosion package with face treatments and materials, face isolation rings and a grounding throttle bushing.
05Can the seal handle flashing or supercritical fluids?
A dual UHTW/GSLW arrangement with a non-contacting GSLW containment seal is described for fluids such as CO2, ethane, ethylene and LPG, using Precision Face Topography to reduce heat and emissions.
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