DM2® Series C Double Valves Installation Instructions — Basic Size 2, 4, 8, 12 & 30

Overview

The ROSS Controls DM2® Series C is a premium-quality control-reliable electropneumatic double valve featuring dynamic monitoring and inherent lockout capability for Category 3 and 4 safety applications. Unlike the DM1 Series C, which uses automatic reset, the DM2® Series C remembers a fault condition and requires an intentional reset signal before operation can resume — making it ideal for applications where any fault must be formally acknowledged by the control system.

The DM2® Series C is designed for base mounting in Basic Sizes 2, 4, 8, 12, and 30, covering a wide range of flow requirements. It is completely self-contained and does not require an external monitoring system. The crossflow passage design ensures that both valve elements must be fully shifted before Port 2 can be pressurized. The discordance detection time is approximately 125 milliseconds, preset by restricting orifices in the pilot air circuit.

The DM2® Series C is expressly not intended for press clutch/brake applications. ROSS Controls, with over 100 years of fluid power expertise since 1921, produces the DM2® Series D specifically for mechanical power press applications.

Key Features

Inherent Lockout with Memory — Intentional Reset Required

The DM2® Series C detects asynchronous valve element movement and locks out — preventing further operation until a dedicated reset signal is applied. This memory-based lockout ensures that faults cannot be cleared without operator intervention, meeting the requirements of Category 4 safety systems. The reset requires both main solenoids to be de-energized (anti-tie-down feature), and a 200 ms delay between reset completion and solenoid re-energization is recommended.

Crossflow Design for Redundant Flow Control

The DM2® Series C uses crossflow passages between both main valve elements. Air flows from Port 1 to Port 2 only when both valve elements have fully shifted, providing inherent double-protection against partial valve shifting. The pilot supply to each element is monitored through the position of inlet poppets, creating a fully self-contained monitoring architecture without the need for external sensors.

Wide Basic Size Range: BG 2 Through BG 30

Available in five basic sizes (BG 2, 4, 8, 12, 30), the DM2® Series C accommodates applications from small machine safety circuits to high-flow industrial systems. All sizes share the same installation, operation, and maintenance procedures, simplifying staff training and spare parts management.

Technical Specifications

Safety Category: Category 3 and 4 per ISO 13849-1
Construction Design: Dual poppet with crossflow passages
Basic Sizes: BG 2, BG 4, BG 8, BG 12, BG 30
Overall Function: 3/2 (three-port, two-position) normally closed
Actuation: Dual solenoid pilots — both must be energized simultaneously
Discordance Detection Time: Approximately 125 milliseconds
Reset Type: Inherent lockout with memory — intentional reset required
Reset Anti-Tie-Down: Both main solenoids must be de-energized during reset
Reset Duration: Momentary, 200 ms minimum recommended
Post-Reset Delay: 200 ms minimum before applying main solenoid power
Reset Solenoid: 3/2 normally closed solenoid valve supplied with valve
Status Indicator: Built-in pressure switch with 4 electrical contacts
Exhaust: Factory-equipped ROSS silencer (up to 25 dB noise reduction)
Electrical Connection: Plug-in connectors
Standard Voltages: 24 VDC; 110–120 VAC, 50/60 Hz
Air Filter Recommendation: 5-micron rated filter
Mounting: Base mounting
Monitoring: Completely self-contained — no external monitoring required
Application Limitation: Not for press clutch/brake applications

H2: Applications

Category 3 and 4 Industrial Safety Applications

The DM2® Series C is used in pneumatic safety circuits for Category 3 and 4 applications such as pneumatic clamping systems, automated assembly equipment, material handling, robotic cell safeguarding, light curtain interface pneumatic circuits, and two-hand control pneumatic outputs. Its inherent lockout ensures that control system faults are not automatically cleared without deliberate intervention.

Applications Requiring Fault Acknowledgment

In safety-critical processes where any valve fault must be formally acknowledged before restart — such as automated press rooms, stamping operations (non-press-clutch), and safety-critical assembly cells — the DM2® Series C's memory-based lockout provides the required level of control. The built-in status indicator allows the fault signal to be fed directly to a safety PLC or safety relay.

Safety and Compliance Standards

ISO 13849-1 — Category 3 and 4 compliance
Self-contained monitoring — no external monitoring required
Anti-tie-down reset feature prevents unintended actuation on reset
Constant fault detection — monitoring is active at all times
5-micron air filtration recommended for reliable operation
Not for mechanical power press clutch/brake applications

Installation and Setup Guide

Preparation and Air Line Cleaning

Before installation in any new or existing system, blow all air lines clean of contaminants. Install a 5-micron rated air filter in the inlet line close to the valve. Drain the filter bowl regularly and install an automatic drain if needed.

Base Mounting and Piping

Install the base first. For pipe threads, engage one turn, apply thread sealant (tape not recommended), then tighten. For parallel threads (SAE, ISO 228-G), no sealant is needed. After installing pipe in base ports, blow compressed air through the piping to clear debris, then install the valve onto the base.

Reset Solenoid and Electrical Connections

The DM2® Series C includes a 3/2 normally closed reset solenoid. The electrical supply for all solenoids must match the voltage and frequency ratings. Note: if the reset solenoid is mounted backwards, energizing it will release air through its exhaust port and no reset will occur.

Lockout Test Procedure

After installation and before normal use: (A) Energize both solenoids simultaneously, then de-energize one — valve should lock out. (B) Energize both solenoids — valve remains locked out. (C) De-energize both solenoids, reset valve. (D) Energize both solenoids simultaneously, de-energize the other solenoid — valve should lock out again. (E) Energize both solenoids — valve remains locked out. (F) De-energize both solenoids and reset. Normal operation may resume after passing all tests.

Why Choose ROSS Controls

ROSS Controls has been a leader in pneumatic safety valve technology since 1921. The DM2® Series C, protected by U.S. and worldwide patents, provides machine builders with a completely self-contained, base-mounted safety valve that requires no external monitoring system — simplifying machine design while achieving the highest safety performance. Contact ROSS at 1-800-GET-ROSS or www.rosscontrols.com.

Download This Document

The official DM2® Series C Double Valves Installation Instructions (document SS301) covers Basic Sizes 2, 4, 8, 12, and 30. Download the complete PDF for specifications, timing charts, and full test procedures.

Download PDF: https://ross-admin-global-us-east.s3.amazonaws.com/production/uploads/document_language_file/file/49/ROSS_DM2_Series_C_Double_Valves_Installation_Instructions_SS301.pdf.pdf

Frequently Asked Questions

Q: Why does the DM2® Series C require an intentional reset?

A: The DM2® Series C is designed with memory-based lockout: once a fault is detected, the valve remains locked out until a dedicated reset signal is applied. This ensures that any fault is formally acknowledged by the control system before operation resumes, meeting the requirements of Category 4 safety circuits.

Q: What are the most common reasons the DM2® Series C will not reset?

A: Common causes include: (1) main solenoids still energized during reset attempt; (2) insufficient pneumatic supply to Port 1; (3) supply pressure removed before de-energizing the valve (both elements in faulted condition); (4) reset solenoid mounted backwards. All four conditions can prevent successful reset.

Q: How does the crossflow design improve safety?

A: Crossflow passages between both main valve elements mean that Port 2 can only be pressurized when both valve elements have fully shifted. Even if one element partially shifts, the crossflow architecture prevents a pressure output from reaching Port 2, providing inherent redundant flow protection.

Q: What is the recommended filter rating for DM2® Series C?

A: A 5-micron rated air filter installed close to the valve inlet is strongly recommended. The filter bowl should be drained regularly, and an automatic drain should be installed if manual draining is difficult.

Q: Does the DM2® Series C require an external monitoring system?

A: No. The DM2® Series C is completely self-contained and does not need an external monitoring system. Its crossflow design and internal pilot monitoring provide all necessary fault detection.

Q: What is the anti-tie-down feature on the DM2® Series C?

A: The anti-tie-down feature requires both main valve solenoids to be de-energized before a reset can occur. This prevents an inadvertent pressure output at Port 2 when the valve resets. At least 200 ms should be allowed between removing power from the reset solenoid and applying power to the main solenoids.

Q: What basic sizes are available for DM2® Series C?

A: DM2® Series C is available in Basic Sizes 2, 4, 8, 12, and 30, spanning a wide range of flow capacities for different machine sizes and pneumatic circuit requirements.

Q: Can the DM2® Series C be used in press clutch/brake applications?

A: No. The DM2® Series C is expressly not intended for press clutch/brake applications. ROSS Controls produces the DM2® Series D specifically with the flow, exhaust, and lockout characteristics required for mechanical power press clutch/brake control.