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Product Overview

 

Transformer valves manage insulating mineral oil, synthetic esters, and silicone fluids within high-voltage power and distribution transformers. Built to withstand continuous thermal expansion and contraction, these valves provide hermetic isolation for radiators, tap changers, and oil conservators during maintenance or transport. Each unit undergoes strict pressure testing to eliminate micro-leaks, protecting internal transformer windings from ambient moisture and oxidation.

 
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Product Types, Construction & Working Principle
 
01/

Transformer Butterfly Valves: Lug-type or wafer-type configurations installed between the transformer tank and cooling radiators. Features a positive locking mechanism and position indicator to prevent accidental closure during operation.

02/

Drain & Sampling Valves: Multi-turn globe or ball patterns forged from brass or stainless steel, engineered for periodic oil sampling and complete tank drainage under heavy operational loads.

03/

Pressure Relief Valves: Spring-loaded safety devices mounted on the transformer cover to instantly vent sudden internal overpressures caused by electrical faults.

04/

Working Principle: The valve obturator rotates or lifts against machined seats sealed with specialized elastomers. When open, full-bore flow paths minimize hydraulic pressure drop across cooling circuits. When closed, redundant O-ring seals isolate fluid compartments against vacuum filling (up to 0.1 MPa) and positive hydrostatic pressure.

Transformer Oil Shut-off Butterfly Valve

 

Key Features

Zero Leakage Seal Design: Dual-seal configurations utilizing nitrile or fluorocarbon elastomers resistant to transformer oil degradation and UV exposure.


Corrosion-Resistant Body: Cast aluminum bronze, ductile iron, or stainless steel bodies treated with multi-layer marine-grade epoxy paint systems (minimum 120-micron dry film thickness).


Mechanical Interlocking: Padlockable handles and clear open/closed position markers eliminate operator error on the substation floor.


Thermal Stability: Operates continuously in ambient temperatures ranging from -50 degrees C to +120 degrees C without elastomer hardening or torque binding.

 

Technical Specifications
 

Standard Sizes

DN25 to DN300 (1 inch to 12 inches); compatible with international grid and transformer tank configurations.

Operating Pressure

Vacuum up to 0.1 MPa; Working pressure up to 0.3 MPa (3 bar).

Test Pressure

Hydraulic body test at 0.6 MPa for 5 minutes; pneumatic seat test at 0.2 MPa.

Flange Connections

EN 50216-8, ASME B16.5, DIN 42560, and custom bolt patterns.

Seal Materials

Acrylonitrile-butadiene rubber (NBR), Fluorocarbon (Viton / FKM).

Body Materials

EN-GJS-400-15 ductile iron, ASTM A216 WCB cast steel, 304/316 stainless steel.

 

 

Applications

Power transmission substations (110 kV to 750 kV transformers)
Padmount and pole-mounted distribution transformers
On-load tap changer (OLTC) compartments
Transformer oil filtration and mobile processing rigs

Transformer Oil Inlet Butterfly Valve

 

Manufacturing & Quality Control

 

 

Production begins with spectrometer material analysis on incoming raw metal ingots to verify chemical composition conformity. Machining is performed on multi-axis CNC horizontal centers to maintain strict dimensional tolerances on flange faces and seat bores (plus or minus 0.02 mm).


Assembly occurs in a controlled environment. Every valve undergoes 100% factory acceptance testing (FAT):
Hydrostatic Shell Test: Verifies structural integrity of the valve body under elevated pressure.
Pneumatic Seat Leakage Test: Measures bubble-tight shutoff against strict industrial standards.
Torque Verification: Ensures operating force remains within standard ergonomic limits across the specified temperature band.

 

Customization

Special Flange Drilling

Custom bolt circle diameters matching legacy transformer footprints for retrofitting older units.

Extended Stems

Designed for transformers equipped with heavy external thermal insulation cladding.

Surface Finishes

Hot-dip galvanizing or marine-grade coatings for offshore, coastal, and corrosive industrial environments.

 

FAQ

 

Q: What seal materials are compatible with synthetic ester insulating fluids?

A: Fluorocarbon (Viton/FKM) seals are specified for synthetic and natural ester fluids (such as FR3) to prevent elastomer swelling and degradation over long-term operation. Standard NBR is reserved strictly for mineral oil applications.

Q: How do you prevent leakage during vacuum filling of the transformer?

A: Valves utilize a dual-O-ring stem seal design combined with a precision-machined back-seat arrangement. This prevents air ingress under full vacuum conditions (0.1 MPa absolute).

Q: What flange standards do your butterfly valves adhere to?

A: Production aligns primarily with EN 50216-8 specifications for transformer accessories, alongside ASME B16.5 and DIN 42560 standard requirements based on regional grid specifications.

Q: Can these valves remain in a partially open position for oil flow regulation?

A: Yes. Integrated locking quadrants and notched positioning plates allow secure throttling of cooling oil flow without vibration-induced position drift.

Q: What documentation is provided with each shipment?

A: Every delivery includes EN 10204 3.1 material test certificates, individual pressure test reports, dimensional inspection sheets, and surface coating thickness logs.

Q: What is the standard lead time for custom flange configurations?

A: Standard catalog sizes ship within 2 to 3 weeks. Custom face-to-face dimensions or specialized non-standard flange drillings require 4 to 6 weeks for pattern adjustment, CNC reprogramming, and testing.

Hebei Anmei Electrical Equipment Co., Ltd. is one of the most professional transformer valve manufacturers and suppliers in China, specialized in providing high quality products and service. Please feel free to buy customized transformer valve made in China here from our factory. Contact us for quotation.

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