Pilot-operated DRP pressure regulators with inlet up to 40 bar

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DRP pilot-operated pressure regulators by KNOCKS FLUID-Technik maintain a constant pressure even at high air consumption – up to 50,000 l/min – and withstand an inlet pressure of up to 40 bar. You set the pressure with the knob of the small pilot regulator on the cover. The pilot then controls the large diaphragm of the main valve with air pressure, not with a strong spring. This is why the outlet pressure drops only slightly as air consumption rises – at a set pressure of 6 bar and full flow, by no more than 1 bar.

They are diaphragm regulators with secondary venting: when you reduce the pressure, they release the excess air from the outlet by themselves. Three body sizes cover flow rates of 15,000 to 50,000 l/min and threads from G 3/4" to G 2", each thread with a control range of 0.5–10 or 0.5–16 bar. A pressure gauge is included.

What the DRP regulators offer

• high flow rate at constant pressure – up to 50,000 l/min
• inlet pressure up to 40 bar, control range 0.5–10 or 0.5–16 bar
• the pressure is controlled by a pilot regulator – it drops only slightly as air consumption rises
• the adjusting knob of the pilot is locked by pushing it in
• secondary venting – excess pressure at the outlet is released automatically
• pressure gauge included, for size BG 8 also an inlet pressure gauge
• threads G 3/4" to G 2" in three body sizes
• aluminium body, NBR diaphragms and seals, operation from −10 to +60 °C

Three body sizes

The size determines the flow rate. Within one size, all threads and both control ranges have the same flow rate and dimensions.

Flow rate according to the manufacturer. Dimensions: body length (inlet–outlet) × overall height.

All DRP regulators

When to choose DRP and when another series

For an inlet pressure of up to 40 bar, we offer four series of regulators. They differ in how the pressure is set, what flow rate they handle and up to what pressure they control.

• Choose DRP when you need a high flow rate at constant pressure. With the same thread, roughly twice as much air flows through: G 1" 15,000 l/min (the manually adjusted regulator 280 with the same thread: 7,830 l/min), G 1 1/2" and G 2" up to 50,000 l/min (regulator 417: 25,000 l/min).
• Choose regulators 417 when you need an outlet pressure above 16 bar (up to 25 bar), operation above +60 °C, two pressure gauges or a setting secured with a lock.
• Regulators 286, 274 and 280 are for lower air consumption and smaller threads from G 1/4", with a brass body and control up to 25 bar.
• Choose DRI regulators when the regulator is to sit in an inaccessible place and the pressure is to be set remotely.

Flow rates according to the manufacturers at an inlet pressure of 8 bar and a set pressure of 6 bar: for the EWO series (417, 286, 274, 280) with a pressure drop of 1 bar, for DRP according to the flow curves with a pressure drop of no more than 1 bar. The DRP and DRI series are made by KNOCKS FLUID-Technik.

How to choose a DRP regulator

1. Size according to air consumption. Add up the air consumption of the machines downstream of the regulator. BG 5 handles 15,000 l/min, BG 7 31,500 l/min and BG 8 50,000 l/min. The flow curves below show how the pressure drops at high air consumption.
2. Control range. For a working pressure of up to 10 bar, choose the 0.5–10 bar range – the pressure can be set more finely in it. Choose the 0.5–16 bar range only if you need more than 10 bar at the outlet.
3. Inlet pressure. All DRP regulators withstand 40 bar, so they are also suitable downstream of high-pressure compressors and air receivers.
4. Thread according to the pipework. Within one size, both threads have the same flow rate.

Example: from an air receiver at 16 bar, you need to supply a line with 6 bar and an air consumption of up to 12,000 l/min; the pipework has a G 1" thread. Size BG 5 with the 0.5–10 bar range is sufficient – this is DRP5540. A manually adjusted regulator with the same thread would deliver only 7,830 l/min.

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How a pilot-operated regulator works

1. With the knob on the cover, you set the small pilot regulator. It feeds pilot pressure into the chamber above the main diaphragm – according to the setting.
2. The pilot pressure pushes on the large diaphragm from above and opens the main valve. Air flows from the inlet to the outlet, and the outlet pressure pushes on the diaphragm from below.
3. When the outlet pressure equals the pilot pressure, the valve partially closes and only as much air flows through as is being consumed.
4. The diaphragm is loaded by air, not by a strong spring. This is why the pressure drops only slightly at high air consumption – as the flow curves show.
5. When you reduce the pressure, the regulator releases the excess air from the outlet (secondary venting).

Flow curves

The manufacturer’s graphs show how the outlet pressure drops as the flow rate increases at an inlet pressure of 8 bar. The lines start at a set pressure of 2, 4 and 6 bar. The flatter the line, the more stable the pressure at high air consumption.

Dimensions

The manufacturer’s dimensional drawings for all three body sizes, dimensions in millimetres.

Installation and adjustment

• install a compressed air filter upstream of the regulator – dirt from the pipework would damage the valve seat
• connect the regulator with its inlet to the air network and its outlet to the consumers
• screw the supplied pressure gauge into the G 1/4" connection; size BG 8 has two connections – for the inlet and the outlet pressure
• set the pressure with the pilot knob and lock the setting by pushing the knob down; pull it up slightly before making another change
• set the pressure from below: if you overshoot, turn it down and slowly increase it again
• sizes BG 5 and BG 7 can be fixed to a wall with a bracket; size BG 8 is mounted directly in the pipework

Spare parts and accessories

The diaphragm in the regulator wears over time – replace it and the regulator will keep on working. Add a bracket when you mount a regulator of size BG 5 or BG 7 on a wall.

You will find all parts for the regulators in the category spare parts and accessories for pressure regulators.

Series specifications

What does “pilot-operated” mean?

The pressure is not set by a strong spring acting directly on the large diaphragm, but by a small pilot regulator on the cover. It feeds pilot air into the chamber above the diaphragm. The regulator then holds the pressure stably even at high air consumption: at a set pressure of 6 bar and full flow, it drops by no more than 1 bar.

When should I choose DRP instead of regulator 417?

When you need more air: a DRP with a G 1 1/2" or G 2" thread handles 50,000 l/min, regulator 417 25,000 l/min. Choose regulator 417 for an outlet pressure of up to 25 bar, operation up to +90 °C or if you want to secure the setting with a lock.

Is the pressure gauge included?

Yes. The ⌀ 50 mm pressure gauge has a 0–16 bar scale (range 0.5–10 bar) or a 0–25 bar scale (range 0.5–16 bar). Size BG 8 additionally has an inlet pressure gauge.

Can the set pressure be locked?

Yes. After setting, push the pilot knob down to lock it. Pull it up slightly before making another change.

Which control range should I choose?

For a normal working pressure of up to 10 bar, the 0.5–10 bar range – the pressure can be set more finely in it. Choose the 0.5–16 bar range only if you need more than 10 bar at the outlet.

Why does air escape from the regulator when the pressure is reduced?

That is secondary venting. When you reduce the pressure, the regulator releases the excess air from the outlet and the pressure drops immediately, not only once air is consumed. A short hiss is therefore normal.

Up to what temperature is the DRP regulator suitable?

The manufacturer specifies it for −10 to +60 °C, for compressed air and neutral gases. For higher temperatures (up to +90 °C), there are regulators 417 and 286.

Technical data according to the manufacturer KNOCKS FLUID-Technik. Flow curves at an inlet pressure of 8 bar.

You will find more regulators in the category air pressure regulators.