Hydac SK350-10/3218S-210ACM-KCH-18H Piston Accumulator, 10 L

A versatile ASME piston accumulator with a 180 mm bore

The Hydac SK350-10/3218S-210ACM-KCH-18H (HYDAC part number 2800037) is a 10 litre model from the SK350 series, which HYDAC calls its most versatile piston accumulator range. The series covers sizes from 1 quart to 200 gallons, bore diameters from 2.4 to 19.3 inches, standard and low-friction pistons and many port and sensor options. This code is the ASME-certified 3000 psi version, with a 180 mm bore, a 711 mm height, an SAE-24 female fluid port and a catalogue weight of 106 kg (235 lb).

Technical specifications

What this code selects

SK 350 – 10 / 3218 S – 210 ACM – KCH – 18 H: SK350 is the series, 10 the size in litres, 3218 the general-duty piston with a machined carbon steel piston and cylinder and PUR seals, S the USA code, 210 the working pressure in bar, ACM the female threaded SAE-24 fluid port, KCH the two-piece gas valve with cover, 18 the 180 mm piston and H made in the USA. Its larger bore than the SK210 gives a shorter body for the same volume.

Options in the series

The SK350 series offers supplementary equipment that the SK210 does not: limit switches with 35, 200 or 500 mm stroke, linear position measurement, ultrasonic and cable measurement systems, magnetic flapper indication, a protruding piston rod, and safety devices such as a burst disc, gas safety valve and thermal fuse cap. HYDAC says ASME, CRN and PED/CE certifications are available in the series. None of these options is part of this order code, so request them separately if needed.

If you need to monitor the piston stroke, discuss the position sensor options at the enquiry stage because they change the cylinder and end cap. For high-flow service, ask HYDAC about the low-friction piston option, listed in the datasheet as piston type 2, as the quoted code uses the general-duty type.

The datasheet describes bore diameters from 2.4 inches up to 19.3 inches across the SK350 and SK600 families, with sizes from 1 quart to 200 gallons, so a 10 litre unit with a 180 mm bore is a mid-range choice. Select the piston and seal materials against the fluid, since the PUR seal is not suited to water or water-glycol fluids, and ask for stainless steel or special seals if your medium requires them. State the precharge pressure and the temperature range when you order, because piston accumulators are normally supplied empty or precharged on request.

Related Hydac products: Hydac SK280-0.5/3218U-280ACF-VB-05 Piston Accumulator, Hydac SB330TR-10A1/112S1-210A Bladder Accumulator, 10 L, Hydac SBO200-1E1/112S-210AB Diaphragm Accumulator, 1 L, Hydac SB600-10A1/112S-345C Bladder Accumulator, 345 bar, Hydac SB330 Bladder Accumulator and Hydac SK210-10/3218S-210ACM-KCH-15H Piston Accumulator, 10 L.

Documents and quotation

The piston accumulator catalogue section is attached. Please state the precharge, fluid and approval. See also our hydraulic valves and components category.

How the SK350-10/3218S-210ACM-KCH-18H works

Inside the SK350-10/3218S-210ACM-KCH-18H a lightweight piston separates the fluid section from the gas section and acts as a gas-proof screen. The gas side is precharged with dry nitrogen. As system pressure rises above the precharge, oil flows in, drives the piston towards the gas end and compresses the nitrogen; when pressure drops, the gas expands and pushes the stored oil back into the circuit. The cylinder has a finely finished bore, and both end caps are sealed with O-rings. HYDAC notes that auxiliary gas bottles are frequently used with piston accumulators when more gas volume is needed than the cylinder itself provides.

Because the piston is a solid barrier, the design delivers high flow rates, high ratios between precharge and maximum working pressure and, according to HYDAC, no sudden discharge of gas when a seal wears – wear shows up gradually as gas bypass instead of a burst element.

Piston type and fluid cleanliness

"3" in the material block selects the general-duty piston. For this type the HYDAC catalogue gives a maximum continuous velocity of 3 ft/sec and requires filtration of 10 µm absolute (ISO 17/15/12). If the duty involves fast, frequent strokes or very low pressure differentials, the type 2 low-friction piston is the alternative, rated up to 12 ft/sec continuous with short bursts to 15 ft/sec and no stick-slip effect.

SK350 ASME 3000 psi size range (180 mm bore)

Values as printed in the HYDAC catalogue for the type 2 dimension sheet; HYDAC states that dimensions are for general information only and all critical dimensions should be verified with the factory before you design brackets or pipework.

Selection & ordering guide

• Seals: code 8 is PUR (–22 to 180°F). Alternatives are 2 NBR (–4 to 180°F), 5 low-temperature NBR (–50 to 180°F) and 6 FPM (5 to 320°F). PUR suits mineral oils (HL, HLP) and HFA fluids.
• Materials: the piston can also be aluminum, stainless steel or protected carbon steel, and the cylinder can be specified with external surface protection or in stainless steel for corrosive environments, a useful option near the coast.
• Gas side: KCH needs an FPO charging unit. The catalogue also lists gas valve versions such as VA (M28×1.5, charged with an FPK unit) and VE (7/8-14 UNF).
• Approval: the country code "S" is for the USA; U is PED/CE and S1 is Canada (CRN). State your country of installation so the correct pressure-code version is quoted.

Installation & maintenance

HYDAC piston accumulators may operate in any position, but vertical mounting with the gas side up is preferred, and HYDAC recommends its own clamps and supports to minimise failures caused by vibration. Charge only with dry nitrogen. Check the precharge at regular intervals and at a known temperature, since gas pressure rises and falls with ambient temperature – significant for outdoor skids in the Gulf summer.

For repair, HYDAC supplies seal kits and complete replacement pistons for each bore, and stresses that a seal assembly tool and a piston insertion tool must be used to avoid seal damage during reassembly. Only qualified persons should maintain accumulators, and the gas side must be fully discharged before any end cap is opened.

Typical applications in Oman & the GCC

• Energy storage for industrial hydraulic power units, presses and test benches
• Emergency stroke and fail-safe functions for valve actuators
• Heavy mobile hydraulics on mining, quarry and port equipment
• Pulsation damping and leakage compensation in high-flow circuits

Why source from Seven Star LLC

Seven Star LLC supplies HYDAC piston accumulators across Oman and the GCC. Share your fluid, pressure range, usable volume, precharge and approval requirement, and our team can help confirm the correct ordering code for the SK350-10/3218S-210ACM-KCH-18H or a better-suited variant. Request a quote with your project details.