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Brand: GESTRA
GESTRA MK 45 Thermostatic Steam Trap PN 40, DN 15-25
Description
A thermostatic steam trap for process and tracing lines up to PN 40
The GESTRA MK 45 is a thermostatic steam trap with a corrosion-resistant membrane capsule, a built-in Y-type strainer and integrated water hammer protection. It opens as soon as condensate cools below the saturation temperature and closes again against live steam, so it drains condensate with a controlled amount of undercooling instead of passing steam. The family is rated PN 40 / Class 300 in nominal sizes DN 15, 20 and 25 (1/2, 3/4 and 1 inch), which makes it a common choice for steam tracing, heaters, process equipment and drip points where the load is small to moderate.
Four variants share the same body. MK 45-1 and MK 45A-1 use a tandem seat (double sealing) for low condensate flows, while MK 45-2 and MK 45A-2 use a single seat for larger flows. The MK 45 body is carbon steel; the MK 45A body is stainless steel.
Technical specifications
| Parameter | Specification |
|---|---|
| Types | MK 45-1, MK 45-2 (carbon steel); MK 45A-1, MK 45A-2 (stainless steel) |
| Nominal sizes | DN 15, 20, 25 (1/2, 3/4, 1 inch) |
| Pressure rating | PN 40 / Class 300 |
| Max. differential pressure | 32 bar (465 psi) for PN 40 and Class 300 flanged; 19.6 bar (284 psi) for Class 150 (MK 45), 15.9 bar for MK 45A Class 150 |
| Admissible service temperature | Saturated steam temperature |
| MK 45 PN 40 flanged, EN 1092-1 | 40.0 barg at -10/20 C, 33.3 barg at 200 C, 27.6 barg at 300 C, 17.1 barg at 420 C |
| MK 45A PN 40 flanged, EN 1092-1 | 40 barg at -10/20 C, 31.8 barg at 200 C, 27.6 barg at 300 C, 25.7 barg at 400 C |
| Body and cover | MK 45: 1.0460 / SA 105; MK 45A: 1.4404 / SA 182 F316L |
| Gasket; capsule; internals | Graphite/CrNi; Hastelloy membrane regulator capsule; high-grade steel internals |
| Capsule codes (undercooling) | N: approx. 10 K (standard); U: approx. 30 K; H: approx. 5 K. Tandem seat 5N1, 5U1, 5H1; single seat 5N2, 5U2, 5H2 |
| Condensate capacity (manual) | Tandem seat: hot approx. 10-600 kg/h, cold 20 C approx. 0-1000 kg/h; single seat: hot approx. 15-1100 kg/h, cold approx. 0-2800 kg/h |
| End connections | Flanges EN 1092-1 B1 PN 40; ASME B16.5 Class 150 RF and 300 RF; screwed sockets G (ISO 228-1) or NPT; socket-weld EN 12760 and ASME B16.11 Class 3000; butt-weld via transition pieces (EN 12627, ASME B16.25) |
| Face-to-face length L (flanged) | 150 mm (DN 15, 20) and 160 mm (DN 25); 95 mm for socket-weld and screwed; 200 mm butt-weld |
| Weight, flanged PN 40 | 3.7 kg (DN 15), 4.3 kg (DN 20), 4.8 kg (DN 25); screwed or socket-weld approx. 2.0-2.2 kg |
The data sheet warns that the membrane capsule must not be exposed to superheat above 5 C, and that above 300 C intercrystalline corrosion may occur unless it can be ruled out.
Choosing the capsule, seat and body
Pick the tandem-seat versions for tracing lines and other small loads, and the single-seat versions where the condensate flow is higher. Capsule N suits most duties; capsule U discharges with more undercooling and uses the sensible heat of the condensate, which suits tracing and heaters that tolerate cooler condensate; capsule H discharges nearly at steam temperature for duties that must not back up. The stainless MK 45A is the choice where the carbon steel body is not acceptable for the condensate or the surroundings. Use the capacity charts in the data sheet at your actual differential pressure rather than the single flow figures above.
Install the trap with the strainer insert hanging downwards, remove the capsule before welding because heat can damage it, and do not insulate the trap or the condensate line in a way that stops it dissipating heat, since insulation can cause malfunction. Related steam equipment is listed under steam and clean steam equipment, for example the GESTRA UNA 16 ball float steam trap for larger loads.
How the GESTRA MK 45 works
A capsule inside the trap senses the temperature of the fluid. Cold condensate keeps the valve open and it drains out. When steam arrives, the capsule expands and closes the valve against the steam.
Where the MK 45 is used
- Steam tracing
- Heaters
- Process equipment
- Drip points
- Small to moderate condensate loads
Selection checklist for the MK 45
- Nominal size
- Body material
- Tandem or single seat
- Differential pressure
- Undercooling code
- Condensate flow
- End connection
- Steam temperature
Installation, commissioning and maintenance notes for the MK 45
Fit the trap in a clean line with the flow arrow correct and the strainer cap accessible. Blow the line clean before the trap goes in. Check the strainer and the discharge at regular intervals.
Requesting a quotation for the GESTRA MK 45
Please send the size, the steam pressure, the condensate flow and the end connection. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.
MK 45 trap type
It is a thermostatic steam trap.
MK 45 capsule
It has a corrosion-resistant membrane capsule.
MK 45 strainer
A Y-type strainer is built in.
MK 45 water hammer protection
Water hammer protection is integrated.
MK 45 opening
It opens as soon as condensate cools below the saturation temperature.
MK 45 closing
It closes again against live steam.
MK 45 undercooling
It drains with a controlled amount of undercooling instead of passing steam.
MK 45 pressure rating
The family is rated PN 40.
MK 45 nominal sizes
Sizes are DN 15, 20 and 25.
MK 45 variants
Four variants share the same body.
MK 45 tandem seat
The MK 45-1 and MK 45A-1 use a tandem seat for low condensate flows.
MK 45 single seat
The MK 45-2 and MK 45A-2 use a single seat for larger flows.
MK 45 carbon steel body
The MK 45 body is carbon steel.
MK 45 stainless steel body
The MK 45A body is stainless steel.
MK 45 differential pressure
The maximum differential pressure is 32 bar on the PN 40 version.
MK 45 service temperature
The admissible temperature is the saturated steam temperature.
MK 45 internals
It has a Hastelloy membrane capsule and high-grade steel internals.
MK 45 gasket
The gasket is graphite with CrNi.
MK 45 capsule N
Capsule N gives about 10 K of undercooling and is the standard.
MK 45 capsule U
Capsule U gives about 30 K of undercooling.
MK 45 capsule H
Capsule H gives about 5 K of undercooling.
MK 45 tandem capacity
A tandem seat drains about 10 to 600 kg/h hot.
MK 45 single seat capacity
A single seat drains about 15 to 1100 kg/h hot.
MK 45 end connections
Flanges, screwed sockets, socket-weld and butt-weld connections are listed.
Trap records for the MK 45
Record the capsule code, the line pressure and the date of each strainer cleaning.
Choosing the right MK 45 variant
Choose the seat type from the condensate flow and the body material from the service.
Documents and quotation
The attached GESTRA data sheet 810317 covers MK 45-1, MK 45-2, MK 45A-1 and MK 45A-2 with ratings, dimensions, spare part numbers and capacity charts. Send the steam pressure, differential pressure, condensate load, end connection standard and capsule type for a quotation. Confirm the exact variant, end connections and test certificate requirements before ordering, as inspection certificates must be stated with the order.
Datasheets & Documents
- Datasheet GESTRA MK 45 steam trap data sheet 810317-09 (08-2026) Download
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About brand
Steam and condensate equipment has been GESTRA's field since 1902, when the company started in Bremen, Germany. Its steam traps, non-return valves and boiler control electronics are found in boiler houses worldwide. Seven Star LLC lists the GESTRA LRGT 16-1 conductivity transmitter, the NRGT 26-2 level transmitter and UNA series ball float steam traps, and supplies GESTRA boiler control parts, valves and steam trap spares to plants in Oman as an independent supplier.
GESTRA LRGT 16-1 and GESTRA boiler control
The LRGT 16-1 is a conductivity transmitter screwed into the boiler shell or blowdown line. It measures the electrical conductivity of the boiler water, which indicates the dissolved solids content, and sends a 4-20 mA signal to a conductivity controller that operates a continuous blowdown valve. The manufacturer also names condensate and feedwater monitoring as uses. The transmitter belongs with the GESTRA level electrodes, limiters and controllers fitted to steam boilers in the GCC, which is why searches for GESTRA boiler control and GESTRA boiler spare parts often end at this type of component.
Ordering GESTRA parts: what we need
Send the type designation and the data from the name plate: pressure rating, connection thread, measuring length, supply voltage and serial number. Tell us which controller and blowdown valve the transmitter works with, and the boiler pressure.
Browse GESTRA products by category: Liquid Analysis Sensors.
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Frequently Asked Questions
What pressure rating does the GESTRA MK 45 have?
The MK 45 family is rated PN 40 / Class 300 in DN 15, 20 and 25, with a maximum differential pressure of 32 bar for PN 40 and Class 300 flanged versions.
What is the difference between MK 45-1 and MK 45-2?
MK 45-1 has a tandem seat (double sealing) for low condensate flows; MK 45-2 has a single seat for larger flows.
What do the capsule codes N, U and H mean?
They set the undercooling at discharge: N approx. 10 K (standard), U approx. 30 K and H approx. 5 K below boiling temperature.
What is the difference between MK 45 and MK 45A?
MK 45 has a carbon steel body (1.0460 / SA 105); MK 45A has a stainless steel body (1.4404 / SA 182 F316L).
Does the MK 45 include a strainer?
Yes. It has an integral Y-type strainer and water hammer protection; install it with the strainer hanging downwards.
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