TECTULby IMR

Fluid conveyance · 2/2 solenoid valves

TECHNICAL DATA SHEET

FT-TC-VAL-SOL-001

Issue date: August 4, 2026 · Rev. 001

Check the current version

2/2 solenoid valves in the TECTUL catalog — bronze and carbon steel, stainless steel and steam bronze, direct-acting or diaphragm servo-assisted

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The three 2/2 solenoid valves in the TECTUL catalog: Generic Bronze Solenoid (bronze and carbon steel body, 1/4″ to 1″, 110/220 V), Stainless Solenoid (stainless steel body, 1″, declared working pressure 0.15-0.85 MPa) and Steam Solenoid Series 2L (bronze body, piston-pilot operated, minimum opening pressure 0.5 to 15 kgf/cm²). The number one cause of returns in this family is not a factory defect: it is confusing a direct-acting solenoid (the magnetic field moves the plunger with no need for line pressure) with a diaphragm or piston servo-assisted one, which needs a minimum differential pressure to open. This sheet publishes that distinction with the real figures for each reference, how to correctly specify a solenoid valve (Cv, orifice, elastomer by fluid, coil, 100% ED duty cycle), why a water solenoid is unfit for steam, water hammer from fast closure in a long line, and the NC versus NO criterion.

SKU VT-59224 (Generic Bronze Solenoid) · line of 3 2/2 solenoid valve references in the TECTUL catalog, from 1/4″ to 2″

1. Technical specifications

References, mechanism and construction

The "direct acting" or "servo-assisted" construction of each reference is taken from the manufacturer's description on its product page (direct plunger on the Generic Bronze; piston pilot expressly declared on the Steam one). The Stainless one is declared 2/2 NC without specifying the exact internal mechanism; its working pressure range, which does not start at zero (section 2), is consistent with a servo-assisted design.

Reference framework and supply conditions

Pressure, fluids and temperature declared per reference

The pressure, fluid and temperature values are data published by the manufacturer on each product page, not an independent TECTUL test. Where the manufacturer does not declare a datum, the cell states so explicitly rather than assuming another reference's value. The steam reference's kgf/cm² is converted using 1 kgf/cm² = 0.9807 bar = 14.22 psi.

2. Why it does not open (or close): direct acting versus servo-assisted

The number one cause of returning a solenoid valve that "does not work" is not a factory defect: it is having installed the wrong actuation type for the actual installation.

Direct acting: zero minimum ΔP

In a direct-acting solenoid, the coil alone, with its own magnetic force, moves the plunger that opens the port — it needs no line pressure to operate. That is why it can open at zero differential pressure, even under partial vacuum: it is the type suited to gravity feed, low-head tanks or lines where inlet pressure can drop to almost nothing. The trade-off is that, for large orifices, the required magnetic force grows a great deal, so direct action is typically reserved for small to medium sizes and orifices.

Diaphragm or piston servo-assisted: needs pressure to open

In a servo-assisted solenoid (diaphragm or piston-pilot type), the coil does not move the main closure member directly: it opens a small pilot orifice, and it is the line pressure itself, unbalanced through that pilot, that lifts the diaphragm or main piston and opens the large port. That mechanism allows much larger orifices with a small coil — and it is the construction of this catalog's Stainless Solenoid and Steam Solenoid — but it requires a minimum differential pressure between inlet and outlet for the line pressure to do its part of the work. Below that minimum, the diaphragm or piston does not fully lift: the coil may hum (energised) while the valve still fails to open, or it opens only partially and drips when closed.

The field selection criterion is simple: if the installation does not guarantee a permanent minimum differential pressure, direct acting is needed, not servo-assisted, no matter how appealing the large orifice of the servo-assisted option looks. It is the criterion that prevents the most returns in this family.

3. How a solenoid valve is really specified

A diameter and a voltage do not specify a solenoid valve. The seven data points below do, and none can be omitted without leaving an engineering gap.

Function, orifice and Cv/Kv

• Function: 2/2 normally closed (NC) or normally open (NO) — see the fail-safe criterion in section 4.
• Orifice diameter: the actual internal port, which does not always match the connection thread; on servo-assisted valves a larger orifice requires more minimum differential pressure to lift the diaphragm, not less.
• Cv (or Kv in metric): the flow coefficient — the water flow rate in gallons per minute (or m³/h with Kv) passing through the fully open valve with a 1 psi (or 1 bar) drop. It is the datum that truly predicts the actual installation flow rate; the thread's nominal diameter does not. None of the three references in this catalog publishes its Cv: it is confirmed on quotation with the actual manufacturer.

Minimum and maximum ΔP by fluid, not a generic psi

The correct pressure rating for a solenoid valve is not a single psi number: it is a pair of values, minimum and maximum, declared per fluid (water, air, oil, steam), because the fluid's viscosity and density change the force line pressure can exert on the diaphragm or piston pilot. This sheet already declared those pairs for the Stainless one (1.5-8.5 bar) and the Steam one (0.49-14.7 bar) in section 1; for the Generic Bronze one, the manufacturer does not publish the pair and it is confirmed on quotation.

Elastomer and its temperature

This table is a general industry elastomer reference, not the actual elastomer data sheet of each TECTUL reference. The temperature range declared by the manufacturer for the Stainless one, -5 °C to 80 °C, is compatible with an NBR-type elastomer; the Steam one declares neither elastomer nor service temperature, and being a steam service its actual elastomer is confirmed on quotation (section 4).

Coil: voltage, power, insulation class and duty cycle

Voltage (110 V, 220 V) is only half the datum: the coil power in watts and its insulation class (usual pattern class F at 155 °C or class H at 180 °C) determine how much it heats up in continuous service. 100% ED duty cycle (continuous duty) means the coil can remain energised indefinitely at its rated voltage without overheating by design: the housing being hot to the touch under those conditions is normal, not a fault. The IP rating of the electrical enclosure defines its resistance to dust and water from the installation environment (outdoor, weather, washdown) and none of the three references declares it on its commercial sheet.

4. Steam, water hammer and the NC versus NO criterion

Why a water solenoid dies in steam

A solenoid specified for water or air almost always carries an NBR-type elastomer, with a temperature ceiling on the order of 80 °C (section 3). Saturated steam, even at moderate pressures, comfortably exceeds that temperature — at 7 bar, saturated steam is above 165 °C —, so the NBR degrades, loses elasticity and ends up failing within weeks where it would have lasted years in water. In addition, the condensate that forms inside a poorly drained steam line hits the seat with high-velocity droplets and carries scale particles, wear a clean fluid like treated water does not produce. That is why this catalog's Steam Solenoid is a distinct reference, in bronze, piston-pilot operated — and not a Generic Bronze Solenoid put to work with steam.

The Steam Solenoid's manufacturer does not declare the elastomer or the service temperature on its commercial sheet: for steam, the expected elastomer on engineering grounds is PTFE or an equivalent high-temperature elastomer, consistent with the section 3 table, but this is confirmed on quotation and is not published as a certified datum in this sheet.

Water hammer from fast closure on a long line

A solenoid valve closes in fractions of a second — it is part of its usefulness —, but that same fast closure, on a long line with a considerable liquid column, stops the flow abruptly and generates an over-pressure wave: water hammer. The longer the line and the higher the fluid velocity, the more severe the wave. Two practical mitigations: install a cushioned check valve downstream (from the catalog's special check valve line) to absorb the return, or specify, when the manufacturer offers it, a slow-closing solenoid (with a pilot circuit that delays closure, analogous to this catalog's hydraulic pilot control valves) instead of forcing an instantaneous closure on a line that cannot tolerate it.

NC versus NO: the fail-safe criterion

The choice between normally closed (NC) and normally open (NO) is not one of electrical convenience, it is one of what must happen if power is cut:

• Normally closed (NC): with no power, the valve is closed; it is energised to let the fluid through. It is the default choice when a power cut must stop flow — most safety, dosing and process control applications.
• Normally open (NO): with no power, the valve is open; it is energised to close the port. It is used when a power cut must allow flow to continue — for example, emergency cooling lines that must not run dry if the controller's power fails.

All three references in this catalog are declared normally closed (NC); an NO configuration is confirmed on quotation as a special order if the manufacturer offers it for that reference.

5. Frequently asked questions

Why doesn't my solenoid valve open if the coil hums?

Almost always insufficient differential pressure on a servo-assisted valve. The Stainless Solenoid needs a minimum 1.5 bar (21.8 psi) and the Steam one a minimum 0.49 bar (7.1 psi) between inlet and outlet for line pressure to lift the diaphragm or piston pilot; the energised coil hums, but without that minimum differential the port does not fully open (section 2). The Generic Bronze Solenoid, direct acting, does not depend on that differential.

What does Cv mean on a solenoid valve?

It is the flow coefficient: the water flow rate, in gallons per minute, passing through the fully open valve with a 1 psi pressure drop. It predicts the installation's actual flow rate better than the thread's nominal diameter. None of the three references in this catalog publishes it; it is confirmed on quotation with the actual manufacturer (section 3).

Why does a water solenoid get damaged if I use it in steam?

Because of the elastomer and the condensate. The typical seal of a water solenoid is NBR, with a temperature ceiling of about 80 °C; saturated steam comfortably exceeds that temperature and degrades the elastomer within weeks. Condensate in a steam line also hits the seat with high-velocity droplets. That is why the specific steam reference exists, in bronze and with a piston pilot (section 4).

Should I choose NC or NO?

It depends on what must happen if power is cut. Normally closed (NC) if a power cut must stop the flow — the most common case. Normally open (NO) if a power cut must let the fluid through, for example on an emergency cooling line. All three references in this catalog are NC; an NO version is confirmed on quotation (section 4).

Is it normal for the coil to feel hot to the touch?

Yes, if the coil is designed for 100% ED duty cycle (continuous duty): it can stay energised indefinitely at its rated voltage without overheating by design, and a high temperature to the touch under those conditions is expected, not a fault (section 3).

How do I avoid water hammer when the solenoid closes?

By installing a cushioned check valve downstream to absorb the return, or by specifying a slow-closing solenoid when the manufacturer offers one, instead of forcing an instantaneous closure on a long line that cannot tolerate it (section 4).

6. Application notes

7. Technical notice and limitation of liability